Help with a simple three LEDs lamp - Page 1
Forum section: electronics / beginners

author: razrook
author_rank: Contributor
timestamp: November 17, 2024, 07:37:42 am
content: Hi all, I'm new here and an absolute beginner - needing help, of course.I need to make a lamp circuit with three LEDs powered with two AAA 1.5v batteries. I've tried to figure it out myself, reading about how to connect the LEDs, series or parallel, use Ohm's law to calculate the resistor value depending on the LED and power specs, but couldn't quite get it.I've got these two LED types to choose from (local store):1)12000mcd,55deg,20mA,3.2V9000k, Size 5.0mm Wavelenght 9000K Color White Lens Type Water Clear Viewing angle 55deg Luminous Intensity 5860mcd Forward voltage typ. 3.2V Test forward current 20mA Maximum forward current 100mA LED Mounting TH2)7000mcd,15deg,30mA,3V5000K, Size 5.0mm Wavelenght 5000K Color Pure White Lens Type Water Clear Viewing angle 15Ã¸ Luminous Intensity 7000mcd Forward voltage typ. 3.1V Test forward current 30mA Maximum forward current 30mA LED Mounting THSo, to sum it up: should I connect LEDs in series or in parallel? What are the correct resistor values for the circuit (one with series, three with parallel)? Is it best to use batteries in series, getting 3v, or in parallel maybe?Thanks in advance, cheers!

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 07:45:10 am
content: First of probably many replies here.You're not going to get anything out of a 3.2 volt LED with 3 volts of battery. Nada.If you're intent on powering this with 2 AAA cells--which is doable--my suggestion, since I've done this many times, is to build what's called a "Joule thief" circuit. This is a very simple circuit, using one transistor and a few other parts, which will light a high-brightness LED from just a single 1.5 volt cell. It's a crude but effective boost power supply that raises the voltage to a level that will illuminate the LED. If interested I'll be happy to post details. Construction is well within almost anyone's means.Or you could use 3 AAA cells plus a current-limiting resistor.

author: pcprogrammer
author_rank: Super Contributor
timestamp: November 17, 2024, 08:09:00 am
content: Analog Kid already wrote that it won't simply work with two 1.5V batteries.Here is as to why. A LED is a component that just like a diode needs a certain voltage before it starts conducting. It depends on the way the diode or LED (light emitting diode) is made. The types you mentioned have a typical forward voltage of 3.1 or 3.2V. This means that you need to supply at least this voltage to have it produce light. But the diode also tries to hold this voltage as stable as possible, so when you apply more the current will rise very fast.There is an explanation on stack exchange:https://electronics.stackexchange.com/questions/618606/led-forward-current-vs-forward-voltageThis means that when you connect the LED's in series you would need at least 9.3 or 9.6V to light up the string of LED's. When you connect them in parallel the voltage needed would be 3.1 or 3.2V, but with the spread between components this could lead to differences in illumination of the LED's.In parallel it is common to use a current limiting resistor per LED. This way they will all settle on their own specific forward voltage for the set current.The option Analog Kid described of using a joule thief or boost converter to raise the voltage does mean that the current drawn from the battery is higher then what flows through the LED, and as such drains the battery faster.For the resistor values Ohm's law does apply. The way to do the calculation is to take the input voltage minus the LED forward voltage and divide this new voltage by the current you want to flow through the LED. The more current the brighter the LED will shine. But stay below the absolute maximum because it will destroy the LED otherwise.

author: brucehoult
author_rank: Super Contributor
timestamp: November 17, 2024, 08:34:42 am
content: In addition to the others, we should ask what the aim is here.If you simply want some kind of pretty lights and be able to see that the LEDs are on, then even 1-2 mA of current can be enough.But you said "lamp", so are you trying to get as much brightness as possible out of them? In that case you'll want to keep them as close to their rated current as you can. But with a small difference between the supply voltage and the turn on voltage for the LEDs the resistor value needed becomes both more critical and less stable as the battery voltage changes, or with manufacturing tolerances in various things.You're going to need at least three 1.5V cells (or a voltage booster circuit), but four cells with bigger resistors might be safer -- though that will get into dissipating more energy in the limiting resistors.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 08:35:25 am
content: OK, 1st circuit here.This is not the only way to do this!Just trying to get things started here.This is assuming you want to light all 3 LEDs from a battery source. The LED and resistor strings are all in parallel here.How to figure the resistor values? OK, let's apply Ohm's Law:For each LED, we know the following:The LED's "forward voltage", which is the voltage across the LED when it's litThe current (in amps) the LED drawsThe total supply voltage across the resistor and the LEDThe first thing to do, since we know the total supply voltage and the LED voltage, is to determine the voltageacross the resistor. That's easy: Vresistor= Vtotal- VLED, in this case 4.5 - 3.2 = 2.3 volts.Now comes the Ohm's Law part. One form of the law states thatR = E/Imeaning that resistance equals voltage (E is used here by convention) divided by current (I). So put the numbers in and turn the crank: 2.3 volts / 0.02 A (20 mA) = 115 ohms.115 ohms isn't a standard resistor value, but 120 ohms is, so use that. (Best to go with slightly higher than lower resistance, because as pointed out otherwise you risk letting the "magic smoke" out of the LED.)(This is for your first type, the 3.2V/20mA one. For the other one, 3V/30mA, a 100Ω resistor would be appropriate.)

author: razrook
author_rank: Contributor
timestamp: November 17, 2024, 08:53:10 am
content: Hey, thanks for a quick reply! And for taking time to draw and calculate the values, much appreciated.However, I wasn't clear enough - I'm limited to use only two AAA batteries for the circuit, as this is actually an attempt to revive a bicycle lamp that I ruined with accidentally testing it with higher voltage (7 instead of 3v). So, I want to use the same housing, making a new circuit on perf board stripe, replacing the one I burnt. Old one had a few programs and a momentary switch, which I don't need - just to turn it on and off, using a new latching switch.I guess that I need a different kind of diodes? Or a voltage step up circuit part? Cheers.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 09:02:23 am
content: 3 volts just won't work for what you want to do. There are LEDs that will operate on that voltage but they're not bright at all.Here's my Joule thief circuit (I was going to make a post on this anyway):It's a circuit known as a "blocking oscillator" that produces high-ish voltage spikes (about 7 volts) that actually overdrive the LED and make it light up really brightly. But because the spikes are so short, it doesn't hurt the LED. At all. I know, because I've built and used dozens of these over the last decade or so, and I've never had one fail. One of these converters can easily drive 4 high-brightness LEDs in series-parallel (2 strings of LEDs in series in parallel). The other nice thing is that this will work even on a battery that's almost dead, which is why they call it a "Joule thief": it seems to suck every last electron out of the cell.The only somewhat tricky part here is winding that transformer, but even that isn't rocket surgery. Basically just coiling some magnet wire around a small ferrite (iron) rod.If you're interested I can go into detail on this.

author: razrook
author_rank: Contributor
timestamp: November 17, 2024, 09:10:13 am
content: Thanks! Yes, I'm interested, as I want to solve this (may seem ridiculous, as I could just buy a new lamp, but there you go).The lamps original circuit has one transistor, four resistors, one cap and what seems to me is an inductor, not sure, and one black blob which I believe is a IC for programing the LEDs. This is all unnecessary and I'd like to make it using the circuit you described, or step up the voltage if I'm not able to make the transformer. I have some guitar pickup thin wire...

author: razrook
author_rank: Contributor
timestamp: November 17, 2024, 09:30:03 am
content: I just checked, and I already have some 2n222a transistors that I can maybe use instead of bc337 (but I can buy that one anyway, when I go get the LEDs). Plus, to fit the housing and what I have is a 3x21 holes perf board piece - guess it should be enough to accommodate all the parts. I intent to use the same connectors and solder them to this perf board stripe, and I can go from there.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 09:32:28 am
content: I'm assuming you know how to solder stuff together.I'd suggest mocking the circuit up first to make sure it works, either on a "breadboard" or just soldered connections.The transformer is wound on a ferrite rod about 3mm in diameter by 12mm long (not critical). For my first flashlights I didn't have any ferrite, so I ended up salvaging it from inductors (coils) and transformers that I cannibalized from discarded electronics. I broke these into pieces and took square sections that were about the size of the ferrite rod.You need thin magnet wire for the windings. I used 32 gauge wire that I bought; you might be able to use your guitar-pickup wire if it's thin enough.I wind the primary (the 40 turns) first, taking care to make the turns nice and tight and neat. Tie each end in a knot to keep it tight, and mark the ends of the wires somehow (tie a know, nail polish, whatever). Then wind the 60-turn secondary on top of this, tying off the ends as before.After it's done I paint it with nail polish to keep the windings in place; later it'll be epoxied over.To make connections with magnet wire you need to scrape off the insulation first, otherwise you won't get any electrical connection. Use an Xacto knife or a razor blade to get down to shiny copper. Then you can solder it just like any other wire.Put the circuit together and test it. If it doesn't work, the transformer is probably connected out-of-phase, so just reverse either the primary or secondary wires (doesn't matter which) and re-test it. When it works, label the wires so you know how to connect them in the working light.Parts list:o BC337 NPN transistor (much better than a 2222)o Homemade transformero 1KΩ resistoro 0.01μF ceramic capacitorSince the circuit runs on 1.5 volts, and you have 2 cells, you could wire them in parallel for longer run time.You can wire the LEDs either in series or in parallel; you might want to experiment to see which is brighter. (Observe polarity, of course.)That's all I can think of at the moment. I'll be happy to answer any questions.

author: Zero999
author_rank: Super Contributor
timestamp: November 17, 2024, 09:39:25 am
content: Have you tried just connecting the two AA cells in series to an LED?In my experience, white LEDs will run off two AA cells. It's not the "correct" way to do it, but it does work. Normally the internal resistance of the batters and bond wires inside the LED limits the current to a safe level, because the battery voltage is very close to the forward voltage of the LED.If you want to use a Joule Thief, then I would recommend connecting the two LEDs in series.

author: brucehoult
author_rank: Super Contributor
timestamp: November 17, 2024, 09:44:24 am
content: Ok, so this is not actually a lamp (e.g. LED headlight), but just a "Please don't run over me" thing. You actually don't WANT that to be too bright -- there are even probably laws limiting the brightness.The programmed patterns are actually quite valuable with one of these. I'd look into a small microcontroller that can run from 3V. The CH32V003 can run on 2.8V, but that's cutting it a bit fine. The ATTiny85 can run on 1.8V if you don't need the highest clock speeds (which you don't). Get some lower voltage LEDs and run them off the GPIOs of the microcontroller and you can program whatever fancy patterns you want. Even with an 8 pin package you'v got a couple of pins spare to connect switches to do something like choose the pattern you want.Small strips or panels of WS2818 RGB LEDs are even more fun. He's me running some off an ATTiny85 on a breadboard:https://x.com/BruceHoult/status/1734341688515276975/video/1https://www.aliexpress.com/w/wholesale-ws2812.html

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 09:52:03 am
content: Here's a recent JT I made, attached to a loupe driving 4 HB LEDs:The thing on top is the front part of a cheap-ass dollar store 1-AA flashlight. Just enough room for the parts.Here's one of my early transformers made from a salvaged chunk of ferrite. Note wire stubs for connecting to breadboard and labels:

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 09:54:18 am
content: Quote from: brucehoult on November 17, 2024, 09:44:24 amCouldn't disagree more with that.I'm a bicycle rider, and I want that thing to be as fucking bright as can be. When I used to ride at night (don't do much anymore), I had a wickedly powerful FLASHING bright light. Almost blinding. I want to be seen.I don't know what the laws are and I don't fucking care anyhow: I've been hit and knocked off my bike twice already.

author: razrook
author_rank: Contributor
timestamp: November 17, 2024, 09:58:47 am
content: Yeah, I'm not too excited to be making it blinking and making patterns - just straight up shine (and yes, bright as can be, but not too much drain on the batteries). But I appreciate the note about the programing the thing too.The thing is, I do want it to work, but I do want the simplest solution. If making a transformer is that, so be it. If it can run three LEDs, one of those I described, and on two AAAs. That's it.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 09:59:18 am
content: Quote from: Zero999 on November 17, 2024, 09:39:25 amThat might well be true, with fresh cells. But as soon as the battery voltage drops a few tenths of a volt, it won't be able to forward bias the LED any more.

author: brucehoult
author_rank: Super Contributor
timestamp: November 17, 2024, 10:26:52 am
content: Quote from: Analog Kid on November 17, 2024, 09:54:18 amI'm also a bicycle rider. I bicycled extensively around Wellington NZ for the 30 years I lived there, Seattle half a year I lived there, all over central Moscow for three years (not in winter!), and the Fremont CA area the year I lived there.It is important to be seen, but it's also important to not piss people off.

author: razrook
author_rank: Contributor
timestamp: November 17, 2024, 10:38:09 am
content: Hey guys, it doesn't really matter how each of us feel about the bike lights - use whatever you want. I'm also against too bright ones, that some riders use, coming from the opposite direction they can blind you for a moment. But, I'm also not a fan of blinking, pattern changing thingies - just plain light is fine by me. As a matter of fact, for the most part, I've been using bottle dynamo, with an old type bulb that's not so bright and it's kind of warm colored white.That being said, let's keep focus - I'm already into making the transformer, found a ferrite, wire and I have a question - do I wind a secondary in the opposite direction? Thanks!

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 10:46:46 am
content: I wound all mine in the same direction, but it probably doesn't matter (although it may reverse the polarity: you'll find out when you test it and it either works or needs to be switched around).Regarding flashing vs. steady: another big advantage of flashing LEDs is that the run time is greatly increased.Let us know when you get this working!I want to point out that this is in no way "my" circuit: it comes from the Joule Thief meister himself, Colin Mitchell. Here'shis page on these amazing little devices. I did modify it a little; I found that changing the resistor to 1K made it even a little brighter.

author: razrook
author_rank: Contributor
timestamp: November 17, 2024, 10:54:12 am
content: Will do, cheers!

author: Zero999
author_rank: Super Contributor
timestamp: November 17, 2024, 11:06:19 am
content: Quote from: Analog Kid on November 17, 2024, 09:59:18 amI have a set of Christmas lights which work off two AA cells, with no Joule Thief or boost converter. The light output doesn't drop off as quickly as you think. It's not ideal, but it works.Quote from: brucehoult on November 17, 2024, 10:26:52 amIt's also important to be able to see where you're going. One of the cycle tracks I regularly use is shared with pedestrians. Having a bright light is very important to see people walking, especially those dressed head to toe in black, walking a black dog and not paying attention.

author: brucehoult
author_rank: Super Contributor
timestamp: November 17, 2024, 11:28:25 am
content: Quote from: Zero999 on November 17, 2024, 11:06:19 amThe CATEYE Omni 3 shown in the photo from OP is a rear light, not a headlight.

author: Zero999
author_rank: Super Contributor
timestamp: November 17, 2024, 11:57:09 am
content: Quote from: brucehoult on November 17, 2024, 11:28:25 amWhat the one in this post?https://www.eevblog.com/forum/beginners/help-with-a-simple-three-leds-lamp/msg5716953/#msg5716953It doesn't matter. Given in his first post, he wants to use white LEDs, indicates he wants to use it as a headlight. If he wants to use it as a rear light, then he should use red LEDs, which will work well with two AA cells and a suitable resistor.https://www.eevblog.com/forum/beginners/help-with-a-simple-three-leds-lamp/msg5716909/#msg5716909

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 12:13:27 pm
content: Quote from: Zero999 on November 17, 2024, 11:57:09 amWhich will be about as bright as birthday candles.

author: Xena E
author_rank: Frequent Contributor
timestamp: November 17, 2024, 01:14:34 pm
content: Just some notes.If you want to use two cells to power this lamp, use them in series, the extra voltage will make the circuit forward bias losses less prominent, and further will allow the circuit to start up at ≈ 400mV for each cell and the use of both cells down to around 200mV each.Also, if you do this you can use the three LEDs in series which will stop the tendency for parallel LEDs to have one of them 'current hog'. (Not often really an issue with LEDs from the same production batch.)As the topology makes for a very efficient way to drive LEDs one thing you will notice with any battery power source, is the dimming of the LEDs over the useful voltage range of the battery. This drawback can be mitigated by regulation of the circuit by sensing LED current, it's adding a little complication, but is worthwhile as an improvement if the LEDs are required to be run at highest output at all levels of battery health.The inductors in these circuits will work with just about any core, however for serious light output you would have to use an efficient design, some students that I mentor have studied these neat circuits and have found that 'binocular ferrite cores" in plain ferrite suitable for HF use are the best performers.If you're not restricted to the number of LEDs that can be used, it may be worth remembering that although light output drops with forward current, the efficiency of LEDs improves in an approximately exponential manner, so for example an LED that gives a specific lumen output can be only half the brightness of four similar devices at quarter the current.Regards,X

author: Zero999
author_rank: Super Contributor
timestamp: November 17, 2024, 03:00:56 pm
content: Quote from: Analog Kid on November 17, 2024, 12:13:27 pmWhat gives you that idea?There are some very bright red LEDs available, which have a better efficiency in terms of optical power out vs electrical power in, than any white LED, because there are no phosphor losses.

author: razrook
author_rank: Contributor
timestamp: November 17, 2024, 03:49:29 pm
content: Ok. So I breadboarded the circuit as per diagram, replacing a few components with the ones I had in hand (it's Sunday, no electrics store is open till tomorrow). There's a .022 cap in stead of .01, and the LED is the one saved from the original lamp, so I'm not sure of its specs. And it does lit up, but very faint. Not sure if my transformer is doing it's work as it should, how the cap value makes difference and about the LEDs voltages and whatnot...

author: Zero999
author_rank: Super Contributor
timestamp: November 17, 2024, 04:25:55 pm
content: Here's a Joule Thief circuit which uses a single inductor, rather than a transformer. It does have more parts, but being able to use an off the shelf inductor, rather than a custom wound transformer can make it easier to mass produce.

author: razrook
author_rank: Contributor
timestamp: November 17, 2024, 04:35:10 pm
content: Thanks, will consider it as well. You reminded me - I did use 2n2222a instead of bc337, as it's the one I have at hand. Not sure, however, if I can fit more parts into the housing, as I'm not going to use SMDs, and this is one off and it's tight as it is already. I think I may have to make a smaller transformer too, to fit in between the batteries...

author: Xena E
author_rank: Frequent Contributor
timestamp: November 17, 2024, 05:22:40 pm
content: 2n2222 isn't a great choice, it's probably not saturating.Re: transformer between the batteries, beware the steel jackets found on most AA cells.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 17, 2024, 08:46:33 pm
content: Yes, a BC337 should work much better than a 2222 (which BTW is probably actually a PN2222, not a 2N2222, as I recently discovered: they're not the same thing). The 337 should be available over there in Yurp.And@Zero999, I recognize that circuit: a standard boost converter driven by an astable multivibrator. Certainly a respectable circuit; I've used it to make a 3-volt to 9-volt boost converter that works well. But in this case I much favor the JT; they're so so simple and work so well.

author: razrook
author_rank: Contributor
timestamp: November 18, 2024, 05:45:41 am
content: Sure, I'll get the right transistor today, cap, and the LEDs. I took a risk and hook it up with both batteries at 3v - it's blinding bright and no magic smoke!

author: Xena E
author_rank: Frequent Contributor
timestamp: November 18, 2024, 10:15:50 am
content: Quote from: razrook on November 18, 2024, 05:45:41 amAlso have a play with the bias resistor and capacitor values, getting nice fast switching edges will help the efficiency.(It's all to do with making the circuit live happily with your transformer)X

author: razrook
author_rank: Contributor
timestamp: November 18, 2024, 11:49:56 am
content: How do I go about that? I have a cheap multimeter, but not sure how can I fine tune the efficiency and all...

author: Xena E
author_rank: Frequent Contributor
timestamp: November 18, 2024, 12:36:11 pm
content: Quote from: razrook on November 18, 2024, 11:49:56 amDifficult without an oscilloscope.What you can do is measure the current the circuit is drawing at different values of the component, I'd be inclined to start with a lower capacitor value and check the current drawn against the apparent brightness of the LEDs with each change. Obviously looking for lowest current/maximum brightnessOf course, the resistor is easy just select one of a couple of hundred ohms or so, and put say a 5k potentiometer in series with it. That is also a method of including a brightness control, otherwise if that feature is not required then just measure the total resistance with your meter and replace with the nearest fixed value component for the results you like.X

author: razrook
author_rank: Contributor
timestamp: November 18, 2024, 01:44:03 pm
content: Yeah, no oscilloscope is available to me and I certainly would have to learn how to use one at first. I can just try out caps and resistors, as you described. I did find some bc546 that I have, from my guitar pedal days (which was just like painting by numbers) and I have much higher brightness, it's practically the same like with 2n2222 on 3v. But, as I understand that one has higher current gain than bc337 - how does this reflect to the battery drain?

author: Xena E
author_rank: Frequent Contributor
timestamp: November 18, 2024, 05:35:38 pm
content: If the transistor has a higher gain the battery drain will be very slightly less given everything else being equal. It may be just switching more efficiently as being the most likely reason for better performance.The thing to remember is the current pulses in the transistor will be proportionately higher than that in the LEDs , if the circuit is switching cleanly this won't matter up to a greater proportion of the transistor Ic but be aware of that if you want to drive the LEDs at maximum possible brightness.Also don't remove the LED from the working circuit, it could over volt the transistor with voltage spikes when the transistor switches off!Having re read your replies please be aware that if you are using two cells in series and only one LED to test the circuit, then it is most likely that the LED is lighting on DC from the battery, not stepped up voltage from the circuit. For this to work the forward volt drop of the LEDs has to be higher than the supply voltage.If you do a few experiments you will soon get a feel for what works well.It's a shame you don't have an oscilloscope, it would be a very useful tool in assessing your circuit. As you understand music and waveforms it would be easy to learn the basic operation of a simple scope.X

author: tooki
author_rank: Super Contributor
timestamp: November 18, 2024, 09:32:16 pm
content: Quote from: Analog Kid on November 17, 2024, 09:54:18 amNo, you don’t want to be as bright as possible: if you blind others, they will be aware of your existence, but they will not be able to actually see you, which means they can’t accurately judge your distance (which is already harder with cyclists because there’s only one light.)I experience this problem (as a pedestrian) now and then when a cyclist has a super bright headlamp, aimed too high.

author: tooki
author_rank: Super Contributor
timestamp: November 18, 2024, 09:39:57 pm
content: Quote from: Analog Kid on November 17, 2024, 12:13:27 pmHave you, like, not bought a high efficiency red LED in a while? While it certainly is true that blue LEDs are where most of the action has been (since they are the light sources in white LEDs), the other colors haven’t stood still. Modern red LEDs are capable of being visible in daylight (like in the LED video walls that we now use as billboards), which requires tremendous brightness.I have a ~150W red LED at work waiting to be hooked up. (It’s intended for video projectors.) It uses just 6 LED dice for all that output. And yes, it requires massive cooling.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 18, 2024, 09:48:20 pm
content: Quote from: tooki on November 18, 2024, 09:39:57 pmYes, but in that case he'll have the same problem as with any other "high-efficiency" (i.e., 3.2V) LED: itmightlight directly from a 3-volt supply but will probably go out after the batteries droop a few tenths of a volt.I was referring to the older, less bright, lower-voltage red LEDs which, as you pointed out, have been eclipsed by the newer-fangled ones.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 18, 2024, 10:17:49 pm
content: Quote from: tooki on November 18, 2024, 09:32:16 pmDon't try to tell me what I want.I wrote that I want my bicycle headlamp to be as bright as possible, and that's what I meant.I seriously doubt the OP's lamp will be anywhere near as bright as the one super-bright one I currently use: I'm pretty sure it uses a COB LED (+ lithium battery), plus it has a very aggressive flash (like 3 short flashes, pause, 3 short flashes ...), so it definitely gets one's attention.

author: Zero999
author_rank: Super Contributor
timestamp: November 18, 2024, 10:34:50 pm
content: Quote from: Analog Kid on November 18, 2024, 09:48:20 pmNo it won't, because modern high efficiency red LEDs have a much lower voltage drop than white LEDs.

author: brucehoult
author_rank: Super Contributor
timestamp: November 18, 2024, 10:36:01 pm
content: Quote from: tooki on November 18, 2024, 09:32:16 pmThat's a thing about LED strips. You can make yourself look bigger, not only brighter. You can put them across your shoulders, your back, your pus^H^H^H rear carrier, up both legs of your front or rear forks, to the tips of your handlebars ...

author: tooki
author_rank: Super Contributor
timestamp: November 18, 2024, 10:43:43 pm
content: Quote from: Analog Kid on November 18, 2024, 09:48:20 pmYou are misinformed. High-efficiency red LEDs aren’t 3.2V (other than the comparatively rare ones that are actually phosphor-converted blue).If you look at DigiKey, for example, in the indicator LED category (where normal LEDs are), filter by in stock, active-status, red, and then sort by brightness, the among the top 50 brightest not one is higher than 2.2V. Among the top 100, a small handful are 2.4 and 2.5V. The brightest one, at 65000mcd, is 2.2V at just 50mA. The single one listed as 3V is actually a typo, it’s 2.2V. Every single one above 3V is a low-brightness indicator with integrated resistor.If we look in the COB light engine category, it’s the same thing: up to 2.5V per LED die (some modules have multiple in series).So the upshot is that driving red LEDs from 3V batteries is super easy since the forward voltage is well below the battery voltage, even when the battery is nearly dead.

author: tooki
author_rank: Super Contributor
timestamp: November 18, 2024, 10:55:08 pm
content: Quote from: Analog Kid on November 18, 2024, 10:17:49 pmI cantryto tell you what you actually need. I doubt you’ll listen, but here goes nothing:Your ultimate goal is not to be as flashy and bright as possible, it is to avoid being hit. This means you want the driver to a) know you exist, and more importantly b) know where you are.If you blind the driver with a poorly-designed bright light, the driver will certainly know you’re there, but will be less able to judge your distance, and the distraction you cause by blinding them can pose a serious hazard. You can also cause the blinded driver to be unable to see other things on the road. All of that makes it more dangerous for everyone on the road,including yourself. If you blind a driver such that they can’t make out the lane markings, you could easily cause them to crash into you. As I understand it, that’s something you’d like to avoid.If your goal isnotyour personal safety, nor the safety of others, but rather to just make a statement, then yes, going as bright as possible is the best approach. But if safety is your goal, then you want just the right amount of light to optimize others seeing you, no less, andno more.Use non-headlight lights to make yourself more visible. (See brucehoult’s reply above.)

author: Analog Kid
author_rank: Super Contributor
timestamp: November 18, 2024, 11:28:27 pm
content: Quote from: Zero999 on November 18, 2024, 10:34:50 pmThanks for that; obviously my knowledge of LEDs is a bit out of date. I didn't realize that one could now get high-brightness LEDs at <3V Vf.

author: tooki
author_rank: Super Contributor
timestamp: November 18, 2024, 11:41:11 pm
content: Quote from: Analog Kid on November 18, 2024, 11:28:27 pmI assume you mean “<3V” (less than 3 volts), and not the “greater than 3V” you just wrote.High-efficiency red LEDs have always been below 3V, and often under 2V. They’ve just gotten a lot brighter over the years.

author: Xena E
author_rank: Frequent Contributor
timestamp: November 18, 2024, 11:45:44 pm
content: A single lithium cell driving white LEDs is a good method.Charge with a good regime to protect the cell butDO NOTuse a low voltage cut off for cycle lighting, as long as it gets charged as soon as the lamp dims is sufficient to prevent bricking the cell.A good beam pattern well adjusted, pointing at the tarmac not oncoming drivers eyes is essential. I think my cycle lights are 2W and are more than enough to see to ride and easily be seen. Theres a local lycra clad twat that cycles our local lanes at night with such bright badly adjusted headlamps that driving towards him in the dark you are unable to see either kerb: he thinks it's funny that car drivers normally have to stop, but I wouldn't mind betting he's not going to be laughing much after a collision with the front of a car when it happens.A good bright tail light is on the other hand often neglected, however these also have to be adjusted not to dazzle.X

author: Analog Kid
author_rank: Super Contributor
timestamp: November 18, 2024, 11:58:16 pm
content: Quote from: razrook on November 18, 2024, 05:45:41 amI just breadboarded my JT and tried different transistors: the specified BC337, a 2N3904, a PN2222 and a BC547.All of them worked. The 2222 was noticeably less bright than the 337, which is still the preferred part here.

author: Zero999
author_rank: Super Contributor
timestamp: November 19, 2024, 08:19:47 am
content: Quote from: tooki on November 18, 2024, 10:55:08 pmYou appear to be speaking from a driver's perspective, not a cyclist's. You are right that it is important not to blind other road users but, don't forget cyclists also need to see where they're going. I have had accident because I didn't see a curb which protruded out into the road. I've had near misses because I couldn't see pedestrians on a shared cycle/footpath. The solution was to get a very bright headlamp. Since then I've not and problems with not seeing things.

author: brucehoult
author_rank: Super Contributor
timestamp: November 19, 2024, 09:50:17 am
content: Quote from: Zero999 on November 19, 2024, 08:19:47 amCyclists don't need very bright headlights, as they are not travelling very fast.My little 250cc dirt bike has a LED headlight that is wimpy compared to my car or BMW 1100cc motorcycle headlights, but it's still enough to see a couple of hundred meters and ride safely at night at 80 or 100 km/h on no-lines, no-reflectors, pitch-black countryside gravel roads.Cyclists have no need of such a headlight. I know. I am one too.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 19, 2024, 10:11:48 am
content: Since we've taken a little trip down a side road here, my 2¢ worth:I'm a bicyclist, not a motorcyclist. As I've stated before, to the displeasure of some, I want a really really fucking bright headlamp (and even a bright taillight) when I'm riding at night.It's not to see the road ahead of me, nor the curb or anything else:it's so drivers can see me. It's that simple.Since I put my super-bright headlamp on flashing, it's really not much good as a headlight, as in a light to illuminate the road in front of me. That would be nice, sure, but it's not the reason for my using a bright headlamp.I've been hit and knocked off of my bike--by cars--twice so far. It's not gonna fucking happen again (because the next time I'll probably wind up dead). (Neither of those incidents happened at night, btw.)Of course, YMMV ...

author: brucehoult
author_rank: Super Contributor
timestamp: November 19, 2024, 10:34:40 am
content: Quote from: Analog Kid on November 19, 2024, 10:11:48 amFlashing at least a couple of times a second works fine as a headlight, in my experience.I'm starting to get the impression your idea of a "super fucking bright headlight" is a long way short of my idea of bright. Which would be fortunate for other road users.QuoteOnly twice?I think I was knocked off twice in 1983 alone. One of them, for example, was drafting a car at 50 km/h (I could do that in those days) down Clyde St in Hamilton East, heading away from the university, when a Ute coming the other way wanted to turn right into probably Fox St. They waited for the car in front of me to pass, then turned across the centerline right into me. I went over the handlebars, did a couple of forward rolls, and ended on my feet. My bicycle was under the front of the ute, fortunately not damaged.Another incident I remember well was in maybe 2008, going south on Main Rd Tawa (Wellington), when while going uphill around the roundabout at Linden Ave, a small milk delivery truck behind me was impatient to pass me and did so exiting the roundabout, squeezing me into the gutter and against the curb. I ended up lying on the footpath.Another time was on Paremata Rd, opn the south side of the Pauatahanui inlet, also circa 2021 ± a couple of years. Someone towing a boat misjudged the width of the trailer and clipped me as they passed, also resulting in a crash, this time onto the road itself. Fortunately no one was immediately behind them.That was when I finally got wise and if there is not enough of a shoulder to allow me to get entirely off the road, I ride in the center of the lane until there is a place where it is safe for me to move fully onto a shoulder and let people past. If they have to drive a few hundred meters at 30 km/h (or less if it's uphill) that's too bad.Visibility was not an issue in any of these (all were in daylight), but judging the necessary clearance to safely pass me was the biggest factor in both the latter two incidents. Anything that makes it harder for the vehicle driver to do that is bad.

author: Zero999
author_rank: Super Contributor
timestamp: November 19, 2024, 11:25:09 am
content: Quote from: Analog Kid on November 19, 2024, 10:11:48 amI don't like flashing lights. The only time when I have my headlight on flashing mode is during the day, when it's a bit cloudy or raining, otherwise it's on continuous. Flashing is good for attracting attention of other road users, but it can also be distracting and make it difficult for tracking your position. Ideally you want both a continuous light and a flashing one, to give you both.Quote from: brucehoult on November 19, 2024, 09:50:17 amYou don't need to be travelling very fast to cause significant injury to either yourself or a pedestrian.I was probably doing 35km/h (just over 20mph), when I hit the curb I didn't see in the dark. I was flung through the air about 10m and got a nasty graze when I hit the ground. Fortunately I didn't hit anything, or it would have been worse.

author: brucehoult
author_rank: Super Contributor
timestamp: November 19, 2024, 01:26:01 pm
content: Quote from: Zero999 on November 19, 2024, 11:25:09 amI am sorry that I failed to make myself sufficiently clear.It is not question of whether you can hurt yourself if you don't see something. It is a question of what is required in order that you DO see an obstacle, and in time to avoid it.35km/h is just under 10m/s. I expect that a bicycle can very comfortably stop from that speed in 10m. That's only half a G. Road bikes on tarseal with modern brakes can actually brake at 1G or even a bit more, so this is conservative, and we can take reaction time as being included.Anyway, let's assume you need to be able to see 10m.A motorcycle travelling at 100km/h is doing almost 30m/s. With the same deceleration as the bicycle it will require 6 seconds to stop, in which time it will travel 90m. So the motorcyclist needs to be able to see 90m.Light intensity drops off with the square of the distance, so lighting an object up at 90m requires 81 times more light intensity than lighting up an object at 10m range.

author: Zero999
author_rank: Super Contributor
timestamp: November 19, 2024, 02:39:07 pm
content: Quote from: brucehoult on November 19, 2024, 01:26:01 pmIt's not just the illumination distance, but also angle. I've found that low powered lamps tend to have too narrrower beam to be usefull. It's easy to see road markings and reflectors with dim lamps, but not people dressed in black, when there's wind and rain. We also have to take into account the worst case: a person on another bicyle, with no lights, dressed in black, speeding towards you: illegal ebikes are the worst.I've found I need about the same amout of light on my motorcycle as my pedal bike. My motorbike can stop quicker, has ABS and the helmet has a visor, which protects my eyes better from wind and rain. On my pedal bike, I get wind and rain in my eyes which makes it difficult to see. A visor/goggles are no good because they steam up.

author: Grandchuck
author_rank: Super Contributor
timestamp: November 19, 2024, 03:31:29 pm
content: This works well. It is a simple step up converter and works down to 0.9 volts, but barely so. It is useable at 1 volt. I have some LEDs on order that might be brighter.I have remote controls and such that stop working at a cell voltage of 1.3 or so and built this to get some additional use from the cells. I live in hurricane alleyEmergency lighting is a priority.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 19, 2024, 10:37:12 pm
content: Quote from: Grandchuck on November 19, 2024, 03:31:29 pmSchematic? Looks like a 2-transistor Joule Thief (or similar) to me, although I don't see any inductive element there.The "super bright" LEDs I was using (this is about 10 years ago or so) were, if I remember correctly, something in the range of 50,000 mcd or so; how bright are yours?(These are definitelynotsuper-bright compared to today's LEDs like COBs and such!)

author: Grandchuck
author_rank: Super Contributor
timestamp: November 20, 2024, 12:14:18 pm
content: Here is the schematic. I will report back if the new LEDs make any appreciable difference (my guess is that they will not).

author: tooki
author_rank: Super Contributor
timestamp: November 20, 2024, 01:04:27 pm
content: Quote from: Zero999 on November 19, 2024, 08:19:47 amWell, I was responding to Analog Kid‘s stated concern of being visible to cars.But as for my perspective: I am a pedestrian, cyclist, and car driver. As someone who does all three, I am familiar with all three perspectives, which is why I tend to take a more nuanced take on traffic issues, compared to hardliners who typically represent one of those viewpoints only.Anyhow, as I see it, a headlight optimized for actually illuminating the street is different from visibility lights. And indeed, this is something humans have known for ages, which is why car headlamps have such complex, and legally mandated, light patterns, and requirements for tail lights. Laws haven’t kept up with bicycle headlamp technology, in that until fairly recently, bicycle headlamps were fairly dim incandescent affairs, with the neat characteristic that brightness scaled with speed. Now everyone has bright-as-hell battery powered LED headlamps, often aimed way too high.

author: razrook
author_rank: Contributor
timestamp: November 20, 2024, 01:42:50 pm
content: Hi all - thanks for all of the replies, considering the circuit and the notes about your preferences of road lights as cyclists.To further complicate things, I have a note about cycling with low visibility due to fog - these days we have some almost London fogy days. It's what I found to be useful actually. I bought a winter cap while ago, thinking that it's a simple (and cheap) orange shade, but when it arrived and I opened the package, it was as if it's radioactive - it was actually a high visibility accessory from this company that specializes in those things - Vizwell. I have one that is shown on the right, orange, with no stripe.As I'm mostly cycling in city environment, and where I'm at, I'm almost always at a separate track (there's a stripe of grass or rows of parking spots between the road and my track), and I found that when it's a situation like this, with much fog or other circumstances of low visibility, this cap rules - by the reactions of the drivers, I can see that they see me at cross sections and when I'm down there with them (track is missing here and there). I'm not wearing helmet, as I'm not going at very high speeds and it's not a requirement over here, but I have nothing against them. The city authorities sometime mention that they may be passing the law where the use of high visibility vest is required - which all of the cyclists here find ridiculous.As for the circuit, I have a question - how can I know for sure that the "thief" is actually working? Someone said that there's possibility of the LEDs just shining from the batteries directly - how can this be? When I disconnect one of the transformer posts, the circuit does not work. Is that a proof of it working correctly?Another thing that I find useful with this circuit, rather than the original, is that the original didn't want to lit up with rechargeable batteries, and I can use this one with them, getting a nice brightness at 1.2v+1.2v=2.4vThis new circuit without the transformer intrigues me, as it may be a bit simpler for me to build and maybe more stable - can someone explain what's happening there and is it worth while? Thanks!

author: Analog Kid
author_rank: Super Contributor
timestamp: November 20, 2024, 06:41:28 pm
content: Quote from: razrook on November 20, 2024, 01:42:50 pmYes, pretty much; the JT can't work without the transformer, so if you get a bright light with everything wired up correcctly and nothing without the xfmr, then it's working.BTW, are you powering the JT from 1.5 volts (one cell) or two (3 volts)? It only needs 1.5V, and 3V may be excessive. I suppose it might be brighter at the higher voltage, but I've never tried that, so I don't know how long things will last, as you may be exceeding the maximum operating conditions for the LED (or maybe even the transistor).QuoteWithout transformer meaning just driving the LEDs directly from batteries, correct? (Directly through a current-limiting resistor, of course, to avoid blowing them up.)What would be happening there is that the Vfof the LEDs (the forward voltage necessary to light them) is less than the battery voltage, so they'll always light directly and don't need the voltage to be boosted, which is what the JT does.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 20, 2024, 06:45:38 pm
content: Quote from: razrook on November 20, 2024, 01:42:50 pmDropping back into tangent mode here: While I usually don't take absolute positions on matters such as this, here is one exception:You really need to wear a helmet!Now, I really don't like helmets, in fact I kind of hate them: they're uncomfortable, they don't let you put anything warm over your head in winter, and they're easy to lose.But they can save your life. As I wrote, I've been knocked off my bike by cars twice. (Someone else here apparently has had this happen even more times.) Luckily I never hit my head on the pavement, but if I had, I might not be able to type out this reply. So please get a helmet and wear it.That's the last of the scolding you'll hear from me on this subject. Back to LED circuits!

author: Xena E
author_rank: Frequent Contributor
timestamp: November 20, 2024, 07:05:24 pm
content: Quote from: razrook on November 20, 2024, 01:42:50 pmIf the votage of the battery is higher than the forward voltage drop of the LED then the current will have a path through the inductor, the LED and back to the battery.It is only when the voltage across the LED is higher than the battery votage, is the circuit 'working'.Quote from: razrook on November 20, 2024, 01:42:50 pmOnly in the conjunction that the transformer connection disconnected are one or other on the transistor base drive winding.It would be useful if you could post a schematic of the exact circuit you are using.X

author: Zero999
author_rank: Super Contributor
timestamp: November 20, 2024, 07:06:33 pm
content: Quote from: Analog Kid on November 20, 2024, 06:45:38 pmThe speed you're travelling at has nothing to do with it.You still have the same distance to fall and cars travelling fast, which is why it's a good idea to wear a helmet.

author: Analog Kid
author_rank: Super Contributor
timestamp: November 20, 2024, 07:08:41 pm
content: Quote from: Xena E on November 20, 2024, 07:05:24 pmKeep in mind that the circuit I gave the OP (somewhere up above in this thread) runs on a 1.5V cell, which is too low to light most LEDs directly.

author: Xena E
author_rank: Frequent Contributor
timestamp: November 20, 2024, 07:21:50 pm
content: Quote from: Analog Kid on November 20, 2024, 07:08:41 pmYes.However, they suggested they had tried the circuit on 3Volts so unless they were explicity saying what voltage and what arrangement of LEDs we cannot make assumptions.X

author: cosmicray
author_rank: Frequent Contributor
timestamp: November 20, 2024, 08:16:38 pm
content: Quote from: tooki on November 18, 2024, 09:32:16 pmWhen I leave the house at 30-60 minutes before sunrise, get on the bike path (which runs parallel to the main highway and about 50-meters from it), most of the drivers on the main highway are blinding me with their high-beams. I need something that will illuminate my path sufficiently that I can tune out the distraction(s) off to my left. The morning after the last hurricane came thru, there were so many trees, limbs, and clutter all over the trail, after the first mile I gave up and turned around. I need a seriously good light source, for my own safety, and I'm working on it. My light source will be mounted on the outriggers, about 12-inches off the surface.

author: tooki
author_rank: Super Contributor
timestamp: November 20, 2024, 08:38:25 pm
content: Quote from: cosmicray on November 20, 2024, 08:16:38 pmAgain, I was responding only to Analog Kid’s discussion of headlights as visibility devices.I was not addressing illuminating the road surface. I addressed that in a subsequent reply:Quote from: tooki on November 20, 2024, 01:04:27 pm

author: razrook
author_rank: Contributor
timestamp: November 20, 2024, 08:53:08 pm
content: Ok, firstly, I'll try and wear a helmet - today the traffic and wind were crazy and it felt like a couple of times there could be a problem (more for me than for the drivers, of course).Secondly, I am using the first JT diagram AnalogKid posted (slightly different with cap that's 0.022, bc546 and using two of the remaining LEDs from the original lamp - I don't have their specs, but originally there were three with two AAA batteries, which may have been connected in parallel).Yes, I tried it with 3v (two cells in series) and that was the best result, also at 2.4v from the rechargeables did great.Still, I'm unclear on what to do - please understand that I don't speak "electric" and while I can understand the meanings, theoretically, I'm still very inexperienced with this things and can't make out all of it.Perhaps, if I can measure the voltage at the LEDs, and if it's higher than what I'm hooking up, than we can say the JT is boosting? I do like the setting where I have bigger brightness, at 2.4 or 3v, but will this drain the cells too fast? Should I be looking to find a best brightness with cells in parallel, to have a longer cycle before replacement/charging is needed?Remember, the project is limited within two AAA sized batteries (1.5 or 1.2v) and three 5mm LEDs that I posted the specs before (they go at 3.2v if I remember correctly). Cheers!Update: Here are the specs again, for those 5mm LEDs I can get for this. They don't have any that go lower than 3v... I'm also not sure which one of these would perform better:1)12000mcd,55deg,20mA,3.2V9000k, Size 5.0mm Wavelenght 9000K Color White Lens Type Water Clear Viewing angle 55deg Luminous Intensity 5860mcd Forward voltage typ. 3.2V Test forward current 20mA Maximum forward current 100mA LED Mounting TH2)7000mcd,15deg,30mA,3V5000K, Size 5.0mm Wavelenght 5000K Color Pure White Lens Type Water Clear Viewing angle 15Ã¸ Luminous Intensity 7000mcd Forward voltage typ. 3.1V Test forward current 30mA Maximum forward current 30mA LED Mounting TH

author: Analog Kid
author_rank: Super Contributor
timestamp: November 20, 2024, 10:43:37 pm
content: Since you're getting the LEDs to shine brightly from 3V (2 X AAA), I'd just go ahead and leave the test JT (on your breadboard) and see how long the cells last; my guess™ is that they'll run for a good long while; the JT just sips current from the cells.If you're satisfied with how the circuit works, then you can solder it up into your headlight case.

author: razrook
author_rank: Contributor
timestamp: November 26, 2024, 01:53:03 pm
content: Hey guys, it's a success! Not quite perfect, as I didn't anticipate the size differences between the components, so the casing turned out to be too loaded to properly close. But the circuit works, giving a strong light that can keep being solid for at least 24h (I'm not riding longer than an hour or two). It would be better if I have drawn the circuit before transfer to the perf board, as I got a ridiculous amount of jumpers on the back, adding to it's height a bit.For now I'm keeping it closed with a black insulation tape - holds good, until I add 3-4mm in height with a strip of metal bent to the shape of the casing. Those diodes I've used are at least double the height of the original ones... Also, I had to add a switch on the back, since I couldn't find any that are pressed on the side that are that small.In any case, thank you all, especially to you AnalogKid - much appreciated help! Cheers!

author: Analog Kid
author_rank: Super Contributor
timestamp: November 26, 2024, 08:30:02 pm
content: So is that a JT? Is that yellow tape-wrapped thing your transformer? And I don't see a cap, but it must be there somewhere.In any case, as they say, mazeltov!

author: razrook
author_rank: Contributor
timestamp: November 27, 2024, 05:05:54 am
content: Yes, yes, it's the same circuit you sent, with a correct cap .01 (it's under the resistor, pretty small ceramic), and bc337 (it seemed that it worked better than the bc546 I had at hand), and it's with LEDs in series and two cells in series (two rechargeables 1.2v, so it's 2.4v). LEDs are those 12000mcd, 20mA, 3.2v, 5mmAnd yes, the transformer is under the tape (made one that's smaller than the first one, to make it fit, but it's the same number of winds and it's ferrite I took out of a inductor).Thanks again! I just might make another lamp, to use the parts - old LEDs and transformer. Can't hurt to have one at hand...

author: armandine2
author_rank: Frequent Contributor
timestamp: December 01, 2024, 11:34:44 am
content: Quote from: Grandchuck on November 19, 2024, 03:31:29 pm,,,built this with 100uH inductor and 1N5819 diode otherwise same - found a youtube theory of operation video for single inductor joule thief difficult to follow.seems to work on low voltage as described - except on one battery with an open circuit voltage of 1.4V

author: razrook
author_rank: Contributor
timestamp: December 02, 2024, 06:41:57 am
content: Looking cool to me, but what's the circuit here? I've used the one in the attachment - no inductor, but a transformer around the inductor core, one transistor (not two), one resistor (not three), three LEDs in series (can't figure your connection choice)...

author: Analog Kid
author_rank: Super Contributor
timestamp: December 02, 2024, 07:20:31 am
content: ^^^^^ Izzat ... spam?

author: Halcyon
author_rank: Unknown
timestamp: December 02, 2024, 07:45:47 am
content: Quote from: Analog Kid on December 02, 2024, 07:20:31 amRemoved/Banned.

author: Grandchuck
author_rank: Super Contributor
timestamp: January 13, 2025, 04:47:08 pm
content: The new LEDs did not make any difference (see replies #56 and #58). Some new inductors arrived and a new version was built. The new inductors are a tad better. Increasing the LEDs from 3 to 7 made the biggest improvement. A version with 9 LEDs was constructed but the performance was worse. A bypass capacitor was added to allow better measurement of the input current to allow efficiency to be calculated. This capacitor is not necessary and is not shown on the schematic.The LTspice LED model used is a bit off. The voltage across the string is 22.3 volts in the simulation and 19 volts in the actual circuit. Also, the efficiency of the actual circuit is quite a bit higher.

author: Zero999
author_rank: Super Contributor
timestamp: January 13, 2025, 10:44:34 pm
content: Thank you for posting an update. It's good you got it working.What's the battery life?

author: SteveThackery
author_rank: Super Contributor
timestamp: January 14, 2025, 09:57:55 am
content: Just as an aside, a comment on the see/be seen issue that has been mentioned earlier.As a car driver I find a flashing light much more noticeable (attention grabbing) than a continuous light. On the other hand, a continuous light is much easier to locate in space compared with a flashing light - especially one with very brief flashes. As a cyclist I find a continuous light much more suitable for seeing where I'm going. To resolve this I use two lamps at each end, one flashing and the other steady. I space them apart as far as reasonably possible, and ensure that one of the rear lamps is close to the outside of the bike so it acts as a "guard".It seems to work well.

author: Analog Kid
author_rank: Super Contributor
timestamp: January 14, 2025, 10:01:23 am
content: Keep in mind that batteries driving a flashing light will last alotlonger than a steady one.

author: Grandchuck
author_rank: Super Contributor
timestamp: January 14, 2025, 01:34:37 pm
content: Quote from: Zero999 on January 13, 2025, 10:44:34 pmFrom 8 hours (cell already down to 1.3 volts) to 20 hours (fresh cell) depending on the initial state and quality of the AA alkaline cell.