hybridfree/eevblog-posts huggingface dataset:
555 + comparator Boost supply - Page 1
Forum section: electronics / projects

author: BiOzZ
author_rank: Regular Contributor
timestamp: April 03, 2013, 04:46:47 am
content: Well i needed awhile ago a simple 35V supply for a random number generator inside my computer so i whipped this upi just needed 35V so i did no calculations and detuned the hell out of this and still got well over 80v out of this damn thing!works quite simply! the 555 generates the boost and the 393 drives the reset pin low when you get above the set voltage!the knob i put on for kicks i could have used a simple threw hole pot but than i could not fiddle with it!NOTE: I HAVE NO IDEA HOW R9 GOT IN THERE! DONT USE IT!!!it goes inside an all metal snus container and probably is loaded with noise and im not sure on the output ... its not driving any real load in its purposeim a huge fan of the 555 and the 393 ... yes i have some SMPS controllers but why? i have a 555 and a 393! you can go to the moon with a 555 and a 393!!!hope this was useful for yall!PS: i use a small 160W PSU inside my computer just for lights, fans and the little addons so its separated from the rest of the PC PSUs ... im not sure how well this would work on the main supply ...

author: Kaptein QK
author_rank: Regular Contributor
timestamp: April 03, 2013, 01:01:29 pm
content: How about using the other comparator in the 393 to make a controllable oscillator to replace the 555?

author: Rerouter
author_rank: Super Contributor
timestamp: April 03, 2013, 01:09:20 pm
content: not the first time i've seen this done, a bit of lab gear i have uses a 556 using the second 555 in a similar fashion to drive and regulate pretty much all the voltage rails,

author: c4757p
author_rank: Super Contributor
timestamp: April 03, 2013, 01:17:31 pm
content: If you're going do to regulated boost with a 555, the CV pin is your friend. Don't even need the 393, just a transistor and a few resistors.Also, have you stuck a scope on the output? $5 says it's unstable.

author: SeanB
author_rank: Super Contributor
timestamp: April 03, 2013, 03:33:28 pm
content: I have done clock ( the ticking kind) oscillators using a 555. Was at least accurate to make an hour meter that turned over on the hour.

author: BiOzZ
author_rank: Regular Contributor
timestamp: April 03, 2013, 05:11:55 pm
content: too answer many of your questions at once i wanted to whip this up quickly and space was not a concern so i did not take time to calculate out a relaxation occ or calculate out what i would need to send in to the CV or other workarounds like a vref and stuff ... just pulled my 2 favorite parts from the parts bin and had at it right on the perf!@Rerouter, i would not doubt this was done before but using the 555s built in comparator + latch on the 556 is quite smart!@SeanB, its a wonderful little thing!

author: SeanB
author_rank: Super Contributor
timestamp: April 03, 2013, 06:31:50 pm
content: It worked well, though the little audio transformer i used did not really like running at 400Hz to make a 26VAC rail to drive the clock mechanism. Those clock mechs were nice, still have one around somewhere.
555, EEPROM, PWM assortment kit project? - Page 1
Forum section: electronics / projects

author: NightMoth
author_rank: Contributor
timestamp: July 13, 2024, 01:29:42 am
content: Hello allI bought anIC assortment kitwhich includes:- NE555 timers,- UC3842/43/45 Current-mode PWM Controllers,- 24C04/08/16/32/64 EEPROMsNow I'm wonder is it just a random set of IC's, or these parts usually utilised together for some purpose?Can anyubody advice some project in which these parts to be used together?

author: Ian.M
author_rank: Super Contributor
timestamp: July 13, 2024, 02:44:31 am
content: Random as ****!* NE555 is old-skool analog timing/cycling that can also be abused as a relay driver or even as a latch.* UCx84x is a family of SMPS controllers - typically for the primary side of off-line PSUs, or transformer coupled DC-DC applications. They are also pretty long in the tooth but nowhere near as ancient as the 555. There are probably some fringe hobby applications, but otherwise they are pretty much repair parts.* The 24Cxx I2C EEPROMs are useless without a processor to read them. Sometimes its a MCU you are writing code for, sometimes its OEM firmware or a hardware state machine in some application specific USB IC, or various other applications where storing a tiny amount of data is worth the cost of an extra IC (e.g. monitor EDID).While you *COULD* (if you are a masochist) use UCx84x if you were designing your own SMPS to power circuits containing the other two, anything with a 555 is *VERY* unlikely to have an I2C EEPROM and visa versa!

author: Andy Chee
author_rank: Super Contributor
timestamp: July 14, 2024, 04:29:40 pm
content: I must admit that my junkbox salvaged parts bin is also fully stocked up with 555s, PWM controllers, and EPROMs, which don't really go together!Out of the three, the EPROMs are the most useless.

author: Ian.M
author_rank: Super Contributor
timestamp: July 14, 2024, 04:58:06 pm
content: ... or the most useful if you do a lot of development with microcontroller families that don't have on-chip EEPROM.I'd vote for the UCx84x ICs to be the most useless - even if you *ARE* into SMPS design, there are much better choices for driver chips nowadays, and if someone is paying me to repair a SMPS that uses one, I'd prefer to use one from a reputable distributer rather than risking a fake chip blowing up all the other parts I've just replaced and anything connected to the power supply output(s)!

author: Gyro
author_rank: Super Contributor
timestamp: July 14, 2024, 06:02:50 pm
content: It is a really good idea to look at and understand the datasheets of all ICs before you buy them. I assumed that it was a random selection (lucky bag), but all the part numbers are stated in the listing. I guess this is advice for next time though.As a beginner, you will probably get most use out of the 555s. There are lots of simple projects and explanations on the web. As for the others, probably no use to you.
555 Nonsense Engine - Page 1
Forum section: electronics / projects

author: jonovid
author_rank: Super Contributor
timestamp: December 05, 2021, 05:47:47 pm
content: 555 Nonsense Enginea 555 oscillator input a 4017 chiplong string of 555 timers in monostable mode liked When triggered by a 4017so output states of all 10 monostable 555 timers go to a common audio output .all 555 timers have two potentiometers one for timing other for output level.the 4017 can be stopped by the monostable 555 timers the 4017 clock inputthis may need a nand gate or two so the ten 555 timers take turns with the 4017 stopping or interrupted when a monostable 555 timer is timing out.then the 4017 chip gets oscillator input so moving on to the next monostable 555 timer in the 10 step loop.the Hz of the output wave is made up of all ten output levels one at a time as set by the potentiometers.so the 4017 stops then a monostable 555 timer is running.up-date-clock inhibit NOT clock re-setthe 4017 job is to advance loop one count one monostable at a timeif no inhibit is used then all the ten 555's can overlap in there own cycles.monostable 555 timers trigger one at a time so the output wave is made up of all ten 555 timers outputs end to end.circuit can have up to 21 potentiometers with one 4017 and up to 41 potentiometers with a 2nd 4017 with its own ten more 555,sif two or more 4017's or 20 or more 555's then the output Hz is low enough to feed back into the master oscillator as FM on pin 5 of the 555.the Nonsense Engine is a Analog Synthesizer. similar to theAtari Punksynth.do not have time to set-up circuit nowtry and dig up 21 potentiometers in a hurrythis circuit art shown is missing most of its details that are common to the 555 in its modes of operationalso output audio buffer op-amp and Vss Vdd bus'sjust found out about a 555 timer contesthave nowhere it post this onlineback of the napkin circuit and made up a name for it ! Nonsense Engine

author: Terry Bites
author_rank: Super Contributor
timestamp: December 06, 2021, 04:51:19 pm
content: It might be interesting.more bonkers stuff from ancient timeshttps://makingcircuits.com/blog/burp-sound-simulator-circuit/greathttps://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiH2OTEz8_0AhWGZMAKHdnaAHcQFnoECAQQAQ&url=https%3A%2F%2Farchive.org%2Fdownload%2FElektorMagazine%2FElektor%255Bnonlinear.ir%255D%25201978-07_08_text.pdf&usg=AOvVaw2LO0BWez7oge4MNOjuvioOpage 39.
555 PWM simple fan controller - Page 1
Forum section: electronics / projects

author: FlevasGR
author_rank: Regular Contributor
timestamp: May 02, 2015, 08:10:03 pm
content: Hello, i'm having a 12V 240mm computer fan which i want to drive in different speeds. Currently i'm using a 12V wall adaptor and it works fine but full speed. I tried to put a simple pot on the circuit and most of you know what will happen if you connect a pot into 12VI found out from YouTube a trick which uses a 555 timer chip few caps and a masfet in order to create a PWM controller, however none of the videos showed a schematic. Where can i find a simple schematic?PSFor mosfet i only have 1 TIP120. Is it what we want?

author: Zero999
author_rank: Super Contributor
timestamp: May 02, 2015, 08:30:53 pm
content: The TIP120 is not a MOSFET.You need to learn how to use Google.https://www.google.co.uk/search?q=PWM+controller&source=lnms&tbm=isch&sa=X&ei=sTNFVcjoJNbeapbagYgD&ved=0CAgQ_AUoAg&biw=1760&bih=876#tbm=isch&q=555+PWM+controller

author: Whales
author_rank: Super Contributor
timestamp: May 03, 2015, 05:17:36 am
content: QuoteNot at all. Your pot would have died from the power (heat) dissipating in it. This is controlled by a combination of how you wired your pot, what value the pot is and the voltage (amongst other things). It's possible to use a pot to vary fan speed but you would need a much bigger one to handle the power dissipation (heat). I presume that your fan draws a lot of power given its dimensions.For circuits: search up "555 PWM fan" in your favourite search engine.
555 relay switch that triggers when it's not suppose to - Page 1
Forum section: electronics / projects

author: gore
author_rank: Regular Contributor
timestamp: January 29, 2016, 08:52:25 pm
content: Howdy, folks of the engineering community! I'm having some trouble with this little circuit. It's a simple 555 based relay switch. There's a momentary SPSP switch (*JP1) to trigger the on/off mechanism. SPDT switch (*SW) to set the ON or OFF state of the relay on power on. And a power supply terminal block (*JP2) with a polarity protection diode. It's all there in the schematic bellow.So here's the problem. Basically it works, but it often triggers with a mere touch of a screwdriver on the contacts of *JP1, for example. Or touching some of the relay outputs does the same thing. It's trigger happy! I need to tone it down a little. It's only suppose to be doing the switching when I press down the momentary switch (*JP1). Why is it so sensitive?

author: w2aew
author_rank: Super Contributor
timestamp: January 29, 2016, 10:37:56 pm
content: Possibly small static charge or noise injection when touching those various nodes. Consider the following:Add power supply decoupling.Consider lowering the value to the two 10K resistors on the THR/TRG line.Consider adding a small cap 0.1uF or so to the THR/TRG line.

author: gore
author_rank: Regular Contributor
timestamp: February 01, 2016, 10:01:00 pm
content: QuoteThank you for suggesting that. That seems to do the trick. I've also tried an isolated power supply (a battery), as opposed to a bench power supply. That works too.

author: Gyro
author_rank: Super Contributor
timestamp: February 01, 2016, 10:11:45 pm
content: Yes, definitely a 100n capacitor to ground on the THR/TRG line, and maybe a series resistor before it too (1k?), otherwise it's effectively an open antenna for spikes.Edit: Does that capacitor on the CON pin work reliably for defining the power-up state? It might be rather sensitive to slow power supply rise time. The more usual method would be an RC network on the Reset pin.

author: gore
author_rank: Regular Contributor
timestamp: February 01, 2016, 10:41:03 pm
content: Quote from: Gyro on February 01, 2016, 10:11:45 pmYou are correct. It's not reliable. I've tested it on a bench power supply by switching the channel on and off. It won't define the power up state. Physically removing and reattaching a wire works.

author: Pjotr
author_rank: Frequent Contributor
timestamp: February 01, 2016, 11:01:29 pm
content: Have build numerous of this circuit reliably. It's by itself quite elegant. For a normal bipolar NE555 youmustdecouple the power with at least a 100nF ceramic close to the pins. When switching the thing draws a large cross over current shortly. For the switch use simply screened cable with the screen grounded. Rising R4 to 220K gives a larger debounce/noise margin.I wouldn't use this reset mechanism with relay contacts. The cont input is noise sensitive and it can also be triggered from noise from the relay then. Better hold the trh/trig input high at power on this way:
555 Super-Regenerative IF HF Spectrum Analyser - Page 1
Forum section: electronics / projects

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 21, 2018, 10:38:05 am
content: I've have all the main parts (I think) and time to make this.http://www.vk2zay.net/article/256About the 4 filter inductors used in the input stage. I have some green ferrite core and some yellow ones, they are both bigger than used. IDK the material, they are just generic ones off ebay. They are about 3mm x 8mm, inner diameter is about 4-5mm.I have 24, 26, 30AGW magnet I think. I made 1 and it was around the right inductance according to my LCR meter. I'm wondering what's more important here.If I can get the same inductance, with the different wire's and turn numbers, what would make more sense to use ? I should just experiment and see the difference.Any thoughts? Not much of a question, I'm off to breakfast

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 21, 2018, 12:18:39 pm
content: If they're actually ferrite, I doubt you'll get low enough inductance from a single turn.Presumably they're powdered iron of some sort (alloy or otherwise). There are powders good enough here (like the mix #6 used in the original), but not just any will work. The problem is if you have the wrong type, you end up with more of an RC filter than an LC filter, and your response is drooping off above a few MHz.So, that also suggests how to test it: apply RF to a few turns and measure the Q. You've no shortage of RF sources in such a circuit, so you can leave that 'til later and check.Tim
555-SWG-KiCad - Page 1
Forum section: electronics / projects

author: Kilroywashere
author_rank: Regular Contributor
timestamp: November 02, 2017, 04:36:09 am
content: Hey I just wanted to see what you guys think for a first attempt on KiCad , I spent a bit over an hour with this so it cant be that good. but i wanted some feedback... I archived the files so i hope you can check it out that way....I want to really build this so any feedback is welcome ... Especially negative
555 Timer "No Resistors" - Page 1
Forum section: electronics / projects

author: Thewafflication
author_rank: Contributor
timestamp: February 03, 2018, 12:13:02 am
content: I was wondering if its feasible to replace the two resistors in the 555 astable multivibrator configuration with BJTs? Such that the duty cycle is constant and the frequency is controlled by a variable resistor.Has anyone done this?Because the 555 time is so old, we did not talk about it much in school. I want to use it because its cheap and so am I!

author: Insatman
author_rank: Frequent Contributor
timestamp: February 03, 2018, 12:34:26 am
content: Published in FreeElectronicCircuits on Feb 18 2011 // 555 based Oscillator circuits

author: Datman
author_rank: Regular Contributor
timestamp: February 07, 2018, 02:52:56 pm
content: For a fixed 50% duty cycle:https://www.electronics-tutorials.ws/waveforms/555_oscillator.html50% Duty Cycle Astable Oscillator

author: macboy
author_rank: Super Contributor
timestamp: February 07, 2018, 06:49:28 pm
content: Have a look at this old post:https://www.eevblog.com/forum/projects/555-timer-continuously-variable-duty-cycle/msg290749/#msg290749It requires adding two jellybean BJT transistors, but seems to answer both of the very frequently requestedconstant duty cycle, variable frequency, andconstant frequency, variable duty cycle.

author: Zero999
author_rank: Super Contributor
timestamp: February 07, 2018, 07:37:30 pm
content: The easiest way to get a fixed 50% duty cycle, is to make Ra as small as possible and vary Rb. For example, if Ra is 470R and Rb variable between 100k and 1M, the duty cycle will barely change, as the frequency is adjusted.

author: moffy
author_rank: Super Contributor
timestamp: February 08, 2018, 01:13:47 am
content: Multiply the frequency of the '555' by 2 then divide it by a flipflop to get your guaranteed %50 duty cycle.

author: Zero999
author_rank: Super Contributor
timestamp: February 08, 2018, 09:23:50 am
content: Another way is to use a CMOS 555 timer, such as the ICM7555 or TS555.Quote from: moffy on February 08, 2018, 01:13:47 amFlip-flops normally come in dual packages, so rather than using the 555, configure one of the flip-flops as an astable. Make one of the RC circuits small, say R2 = 1k and C2 = 100pF and vary R1. The duty cycle will be very low/high (depending on whether you look at Q or Q') but it will be 50% once put through a divide by two counter.

author: Thewafflication
author_rank: Contributor
timestamp: February 14, 2018, 02:54:44 am
content: This one looks awesome. I will try this one out! I like this one because I can still set my duty cycle to what I need, but vary the frequency.Thanks for the responses guys.
555 Timer Calculator (Backwards) - Page 1
Forum section: electronics / projects

author: German_EE
author_rank: Super Contributor
timestamp: July 20, 2019, 08:17:32 am
content: There are plenty of 555 calculators on the Internet but for what I want they are all operating the wrong way around! All of them let you input the two astable resistor values and the capacitor then they show you the resulting frequency, mark/space ratio and pulse width.I want it the other way, start with mark/space ratio and frequency then give me the component values. Does anyone know of a web site that can calculate this?

author: soldar
author_rank: Super Contributor
timestamp: July 20, 2019, 10:18:07 am
content: So you know time on and time off. Andyou have the formulas. And you know algebra. What's the problem?

author: patrick1
author_rank: Contributor
timestamp: July 20, 2019, 03:39:19 pm
content: depending on what your doing with the output, i recommend using a 1uF cap. and pin 8-7 100k pot, and pin 7-6 2ohm resistori have not had any problems with burnt pots. and it will give you 45hz too about 2.1khz, convenient range for what i do...however it comes with the proviso of the pin 3 output pulses are on average 95% duty on, good for driving a 4017,and the pin 2 out is perfect for driving opamps because its a very straight up sawtooth.
555 timer circuit triggered by drill? - Page 1
Forum section: electronics / projects

author: themacman33
author_rank: Contributor
timestamp: March 03, 2014, 05:11:59 pm
content: I have built a 555 based timer for my analog soldering iron. When I used my drill on the same power strip as the circuit and power through the relay to the outlet, the circuit triggered. I can't seem to figure out how this happened. Can anyone explain how this works, and how to fix it without changing the drill to another outlet?Thanks, Mac

author: uwezi
author_rank: Unknown
timestamp: March 03, 2014, 06:09:29 pm
content: Where does the Vcc of your NE555 come from? A power drill is a nasty device when it comes to introducing spikes on the mains - if your Vcc is not properly filtered it can do anything with your timer.Place some decent electrolytic (probably 1000 µF or more) and some 100 nF or bigger ceramics capacitor between Vcc and Gnd. Additionally you might want to use a net filter on the primary side of your power supply.

author: themacman33
author_rank: Contributor
timestamp: March 03, 2014, 06:18:49 pm
content: The power comes from a 12v DC wall wart on the power strip. I will add the filter cap, thanks!What is a net filter? I've never heard of that...Thanks!

author: uwezi
author_rank: Unknown
timestamp: March 03, 2014, 06:27:47 pm
content: Quote from: themacman33 on March 03, 2014, 06:18:49 pmI probably used the wrong term, what I meant is aline filter

author: themacman33
author_rank: Contributor
timestamp: April 07, 2014, 12:04:39 am
content: The resistor did in fact work. Thanks!

author: calexanian
author_rank: Super Contributor
timestamp: April 07, 2014, 02:42:32 am
content: 8 meg ohm resistor and a 470uf cap? Does it ever time out? I would thing the leakage of the cap alone wound keep the thing going for ever. Also are you using the CMOS version? Much more susceptible to noise.
555 Timer continuously variable duty cycle - Page 1
Forum section: electronics / projects

author: dodad_guy
author_rank: Contributor
timestamp: September 09, 2013, 07:06:53 pm
content: Having struggled with the typical duty cycle problems of a 555 timer, I overcame them several years ago, however never published my circuit. One configuration will give a <99% to > 99% duty cycle change using only one potentiometer (the frequency remains essentially unchanged). Another configuration has independently variable high and low duty cycles.Someone wanted a constant duty cycle with variable frequency. I haven't tried that one yet, but I am confident this circuit will also do that. "Impossible" you say?I use mine for a light or motor speed controller. I also works great to pulse a transformer (great zap from an ignition coil!)If anyone is interested, which of the three mentioned configurations do you prefer?

author: CalG
author_rank: Contributor
timestamp: September 09, 2013, 11:33:30 pm
content: I would be interested in a variable freq. constant amplitude, fixed duty cycle circuit.TIACal

author: JoeO
author_rank: Frequent Contributor
timestamp: September 09, 2013, 11:36:15 pm
content: Why don't you just post all 3?

author: TerminalJack505
author_rank: Super Contributor
timestamp: September 10, 2013, 12:51:41 am
content: A fixed-frequency, true 0% to 100% duty cycle 555 timer circuit would be handy. That's basically what the guy inthis threadwould need.

author: dodad_guy
author_rank: Contributor
timestamp: September 12, 2013, 09:16:31 pm
content: Here is how I handled a 12v light dimmer / motor speed controller using option #1. The frequency should run around 100 Hz.I used option #2 to pulse a transformer. The on pulse is typically 0.1 to 15 msec. For my ignition coil, I connected the coil's condenser (it came with the ignition coil) across the MOSFET. If the pulse width is too long, the transistor gets too hot because the transformer reaches saturation.

author: dodad_guy
author_rank: Contributor
timestamp: September 12, 2013, 10:41:29 pm
content: I see that my other post for the basic layout didn't post. Here is another try...

author: dannyf
author_rank: Super Contributor
timestamp: September 12, 2013, 10:46:23 pm
content: QuoteBut it is not possible.QuoteYou could have replaced those two bjts with two diodes.

author: dodad_guy
author_rank: Contributor
timestamp: September 13, 2013, 10:01:21 am
content: Almost as stated, <99% <. There is a pulse in the microsecond range at reset when on either end of the duty cycle. In one of my dimmers, the MOSFET speed was slower than the reset blip so that it did not show up at the output.
555 timer output not going low when reset pulled down - Page 1
Forum section: electronics / projects

author: bji900
author_rank: Contributor
timestamp: April 03, 2019, 12:39:32 pm
content: I am working on a project that needs to generate a single pulse, and then delay until the reset line is pulled high to re-generate a single pulse. I have this working on a bread board, with a Fairchild 555 dip 8 package. However when I moved to a pcb, and a soic 8 TI 555 timer, the pcba still works, however the output is sitting around .3V vs 0.06V. This is causing my output transistor to leak. My question is this, is there significant enough difference between multiple 555 timers and packages that could cause this? I will upload actual part numbers and schematic screen shots later today.I think I may have a CMOS timer on the PCBA and a Standard timer on the bread board, and I think this may cause this issue.My next try, will be to mount a dip8 onto my PCBA and see if that fixes the problem.

author: iMo
author_rank: Super Contributor
timestamp: April 03, 2019, 12:57:56 pm
content: Show us your schematics including the transistor.

author: bji900
author_rank: Contributor
timestamp: April 06, 2019, 12:31:52 pm
content: So long story short. I was seeing oscillation on my 5V supply, because I did not install output capacitance on the linear regulator. Which is why I was seeing 9V out of my 5V linear regulator. When I finally probed with a scope, it was obvious. This was causing my 555 timer to oscillate and not drive its output correctly.This behavior was happening even with out any output drive on the 555, so a basic 555 in astable mode does not like noisy linear regulator outputs.
555 timer, pin 5, control voltage, capacitor 10 or 100 nF? - Page 1
Forum section: electronics / projects

author: AndersJ
author_rank: Frequent Contributor
timestamp: March 01, 2018, 06:50:18 am
content: The CV capacitor is ”always” 10 nF?I want to use 100 nF, to avoid a single 10 nF cap in the BOM.MUST it be 10 nF?

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 01, 2018, 09:02:33 am
content: no. it can be left open.

author: Audioguru
author_rank: Super Contributor
timestamp: March 01, 2018, 05:12:06 pm
content: Pin 5 on a 555 is a simple resistor voltage divider for its voltage reference. 100nF is fine as a filter if you want it filtered. Use thousands of microfarads if you want but it will take all day to turn on.

author: danadak
author_rank: Super Contributor
timestamp: March 02, 2018, 11:22:42 am
content: Look in data sheet and you will see control voltage pin, if unused, bypassedby .01 uF. That's to avoid having output modulated by stray coupling to thatpin. Note it has to be AC bypassed, you can't connect pin to either rail becauseits part of an internal biasing network.Note the pin is relatively low Z, that's why I think community has been able toget away without bypassing, eg. coupling has to be pretty significant to affectthe pin. But best practice bypass it.Regards, Dana.
555 timer project? - Page 1
Forum section: electronics / projects

author: greencardigan
author_rank: Contributor
timestamp: November 06, 2011, 06:10:02 am
content: HiI have a little project I'm working on and I'm thinking a 555 timer or 2 might be able to help.I have a switch connected to a clock that is open for 5 minutes then closed for the remainder of the hour. As the switch closes I want to generate a 1/2 second high pulse.Is this something I can use a 555 for? I've had a bit of a play and couldn't work it out. In monostable mode the trigger has to be shorter than the output pulse.Any ideas??

author: IanB
author_rank: Super Contributor
timestamp: November 06, 2011, 07:11:31 am
content: You can use a capacitor and a resistor to generate a short trigger pulse from the switch closing event. You use the property of a capacitor that the voltage on one side will try to follow a changing voltage on the other side. So you connect the switch on the upstream side of the capacitor and the 555 input trigger downstream. Then you ground the downstream side of the capacitor with a suitable value resistor so it is normally pulled low.When the switch closes it will momentarily raise the capacitor voltage and trigger the timer. However, the resistor will then discharge the capacitor back to ground taking the trigger signal away again.

author: IanB
author_rank: Super Contributor
timestamp: November 06, 2011, 07:41:08 am
content: I guess you need a resistor to ground on the upstream side of the capacitor as well to reset it after the switch opens.

author: Simon
author_rank: Unknown
timestamp: November 06, 2011, 11:27:11 am
content: you could possibly do this also with a comparator
555 timer with two outputs? - Page 1
Forum section: electronics / projects

author: geobee
author_rank: Contributor
timestamp: June 20, 2019, 08:41:36 pm
content: Hi all, trying to perform a function on a model rail layout. I need to have a setup where a single trigger input, be it a simple momentary button switch, or a signal from an infrared sensor, or even a reed switch, it doesn't matter, but I require two outputs that switch from one to the other when the input is triggered. The outputs can be latching on, or just a momentary signal to drive a relay. Probably a momentary would be best. I am trying to set up a system where a train is sent down one direction, then reverse and be sent down the other track after it reverses back over the sensor trigger. I have the automatic reversing all worked out, jut the A/B output to switch the direction points of the track.I thought maybe something around a 555, or similar might do the job. Any help would be much appreciated.

author: larsdenmark
author_rank: Regular Contributor
timestamp: June 21, 2019, 07:38:57 am
content: I'm not sure that I fully understand what you are aiming at, but it sounds as if you can use a shift register:https://en.wikipedia.org/wiki/Shift_register#Serial-in_parallel-out_(SIPO)You would then only use the first two outputs.Shift registers are cheap and can be used for many things so it doesn't hurt to have some of these lying around.Alternatively you could use a (very) small microcontroller.

author: Zero999
author_rank: Super Contributor
timestamp: June 21, 2019, 07:50:16 am
content: The 555 timer only has one output. Another 555 timer could be added, to invert the output, but there are other monostable IC which provide both inverting and non-inverting outputs. Try the CD4538 or 74HC221.http://www.mouser.com/ds/2/149/cd4538bc-294672.pdfhttps://www.ti.com/lit/ds/symlink/cd54hc221.pdf

author: geobee
author_rank: Contributor
timestamp: June 21, 2019, 08:25:03 am
content: Thanks for the help. Think I have found a very cheap solution on the old Ebay. A little flip flop relay module that changes state when it is triggered. It cycles through contacts open/closed whenever a trigger signal is sent to it. Perfect solution, neat and dirt cheap. A little more than $1AUD each.
555 with differentiated input - Page 1
Forum section: electronics / projects

author: reyntjensm
author_rank: Regular Contributor
timestamp: July 11, 2022, 01:25:09 am
content: I'm trying to make short timed pulses with a 555 timer. I have found a schematic online using a 555 timer with a differentiated input. But i don't understand how this exactly works. I know how the 555 timer works but i can't figure out why the capacitor gets charged when the switch is still connected to ground? Could somebody explain me how this differentiated input exactly works?" alt="" class="bbc_img" />

author: MikeK
author_rank: Super Contributor
timestamp: July 11, 2022, 02:41:39 am
content: Do you mean how C3 charges up through R2, because the other side of it is connected to ground?

author: reyntjensm
author_rank: Regular Contributor
timestamp: July 11, 2022, 02:59:55 am
content: Quote from: MikeK on July 11, 2022, 02:41:39 amyes, exactly. From what i understand, the capacitor is discharged trough the switch briefly but why would it ever charge again when the switch is still connected to ground? What do i miss here?

author: ledtester
author_rank: Super Contributor
timestamp: July 11, 2022, 05:22:31 am
content: Perhaps this explanation will help...Let's assume Vcc is 5V.While the switch connects the cap to ground the cap charges up through R2 like any RC circuit. Eventually the voltage across the cap will reach 5V (Vcc).When the switch disconnects the cap the voltage across the cap is still 5V but the voltage at the left end of the cap will jump to 2.5V and at the right end to 7.5V (ignoring the diode for the moment). It will then discharge through R2 and R4. As the cap discharges both ends will tend towards 5V.Here's a Falstad simulation of just the switch, cap and R2, R4:https://tinyurl.com/2jmg7c7bThe graphs and meters show the voltages at each end of the cap.

author: MikeK
author_rank: Super Contributor
timestamp: July 11, 2022, 06:49:51 pm
content: The Falstad simulation ledtester posted is good, and should help. If you're confused about C3, there are four states to be aware of:1. Initial condition and charging. Assuming C3 starts with no charge, when the switch first goes to ground C3 will charge up. This is because the right side of C3 is connected to Vcc through R2 and the left side of C3 is connected to ground.2. Steady state. C3 will get charged up to 12V (your Vcc voltage) and stay there. After that, current will only flow through R4 to ground.3. Initial change of switch. When the switch disconnects the ground you now have C3 acting like a 12V battery. The Vcc power supply is no longer acting here, because its return path (the ground) has been removed. This is a simple voltage divider calculation: 12V (from C3) across two resistors (R2 and R4) in series. You can then see that this puts the left side of C3 at 6V and the right side of C3 at 18V (6V + 12V).4. Discharging. C3 will then discharge until both sides of it are equal, so 12V on each side, no voltage across it.
5730 / 5630 LED Availability  - Page 1
Forum section: electronics / projects

author: Factotum
author_rank: Contributor
timestamp: January 28, 2021, 12:41:07 pm
content: I built a large sculpture a couple of years ago - seehttps://whispertree.factotumindustries.com/It's getting upgrades and I'm looking for high brightness single colour SMD LEDS.I saw info on 5730 (5630) LEDs but don't see them from reputable suppliers like Mouser, RS, etc. (and if I do only in white).Anyone suggest where else I should look or an alternate package?I've tried some Chinesium ones from the usual places and they are unsurprisingly rubbish.Cheers!
5859 nixie tube clock circuit wanted! - Page 1
Forum section: electronics / projects

author: xwarp
author_rank: Frequent Contributor
timestamp: September 28, 2016, 08:57:02 pm
content: I've got this old Systron Donner freq counter that I have been very unsuccessful in finding any information on. It's apparently a custom build for Motorola. Maybe that is why.....In any case, it has issues and I want to build a clock out of it, but I've not found schematics for a clock circuit that uses the 5859.Caveat is that I do not want a PIC type circuit.Any suggestions would be appreciated.

author: Ian.M
author_rank: Super Contributor
timestamp: September 28, 2016, 09:46:48 pm
content: Is that an objection specifically to PICs or to MCUs in general? Over inhttps://www.eevblog.com/forum/projects/hv5812-driving-nixies/I suggested SN75468N transistor arrays which have a 100V Vce rating as alternative drivers. With its outputs clamped by a 90V Zener there appears to be a sweet spot between 170 and 190V B+ where it will drive your Nixies comfortably (based on the5859 datasheetfigures). As its input is individual 5V logic level pins, you can then use any 'classic' SSI logic digital clock circuit you like.
5A quasi darlington driven by bq24450 - Page 1
Forum section: electronics / projects

author: rastislav
author_rank: Newbie
timestamp: October 10, 2014, 01:14:18 pm
content: hello,I'm designing currently bq24450 for 12V Ah car yellow Optima battery.Charging current 5A, which basically mandates quasi darlington driver.Since this configuration uses NPN and PNP transistor and NPN should handle 5A I've chosen MJE2955T for NPN and since Ib for this NPN is 6A I was going to use MJE3099T as complementary pair.Will this be correctly working with BQ2455 driving those?I see that it is capable of putting 80mA into base of PNP (MJE3099T)On this PNP again base current is 6A, which I have no idea whether is required. If it is, I think I'll need PNP darlington driving MJE2955T, but I'm not sure on this.Is it possible to replace quasi-darlington with FET? How will driver part of the circuit change?
5D Optical Storage Technology  - Page 1
Forum section: electronics / projects

author: quarks
author_rank: Frequent Contributor
timestamp: February 17, 2016, 05:02:25 pm
content: Hello all,just read this very interesting article"5D Optical Storage Technology Can Store up to 360 TB On A Single Disk, Last Billions of Years"http://deliddedtech.com/2016/02/17/new-5d-optical-storage-technology-can-permanently-store-up-to-360-tb-on-a-single-disk/byequarks
5eBoard solderless breadboarding system - Page 1
Forum section: electronics / projects

author: Kalvin
author_rank: Super Contributor
timestamp: February 26, 2015, 02:12:08 pm
content: Hi breadboarders,While browsing eBay for the solderless breadboards, I stumbeled on to this new player:http://www.5eboard.com/Looks pretty usable prototyping system. Compared to the current breadboarding systems, if some of the connectorblocks break and wear out during use, they can be simply replaced instead of replacing the whole breadboard. Also,routing the power lines becomes more flexible in this system. The price seems to be quite good as well. However,I have no idea how reliable these blocks are in practice and how well the jumper wires stay in place. Just wantedto share this if someone finds this interesting.Does anybody have any hands-on experience using this new breadboarding system?

author: Kalvin
author_rank: Super Contributor
timestamp: February 26, 2015, 02:21:15 pm
content: Possibly this system could be used while construction a prototype in manhattan style. The copper plated base board will provide good ground plane, and some parts of the design could be implemented using these blocks by glueing a strip here and there for component holders and wiring.

author: BlueBill
author_rank: Regular Contributor
timestamp: February 26, 2015, 03:03:07 pm
content: Looks more fidgety than a breadboard, seems a lot more wiring is necessary too. Hard to follow the layout. Floating IC pins and no current limiting resistors on the LEDs (unless I can't see them). I'm guessing it costs more than a common breadboard.

author: eggen
author_rank: Newbie
timestamp: February 27, 2015, 10:54:49 pm
content: Actually this is a very reliable, much easy to use board than any breadboard. My son's high school (Montgomery High School at NJ) is using the boards for their STEM programs. It is easy not only for young kids but also professionals. I don't think any breadboard can do the staff you posted.I also found many cool videos from YouTube using this board:Eric
5GHz wifi band signal source - Page 1
Forum section: electronics / projects

author: BFX
author_rank: Frequent Contributor
timestamp: April 10, 2015, 02:38:56 pm
content: Hi all,I working on testing environment and I need something like XL24017(2.4GHz) for 5Ghz Wi-Fi band with about 20dBm output power.Any suggestion's?

author: BFX
author_rank: Frequent Contributor
timestamp: April 10, 2015, 08:02:22 pm
content: I think it's difficult question

author: LaserSteve
author_rank: Super Contributor
timestamp: April 10, 2015, 11:22:54 pm
content: What bandwidth do you need to simulate?Steve

author: Marco
author_rank: Super Contributor
timestamp: April 10, 2015, 11:59:40 pm
content: There are 5.8 GHz video transmitters with analog modulation, you can probably trash the entire band with them as easily as with the 2.4 GHz modules.

author: hendorog
author_rank: Super Contributor
timestamp: April 11, 2015, 05:55:54 am
content: Cheapest option: I have hacked these to sweep above about 5.6GHz, they use the Richwave chipset, there is a doc floating around:http://www.aliexpress.com/item/Boscam-FPV-5-8Ghz-200mW-Wireless-Audio-Video-Transmitter-Module-TX5823/2040265101.htmlAnother option is a old YIG, this one is about 10dBm:http://www.ebay.com/itm/YTO-40-Micro-Lambda-Yig-Tuned-Oscillator-3-5-7-4-GHz-Tested-w-plot-NOS-TINY-/381021711462?pt=LH_DefaultDomain_0&hash=item58b6a9ec66Or perhaps an eval board e.g. MAX2870/2871 but you will need an amp (~5dBm):http://www.maximintegrated.com/en/products/comms/wireless-rf/MAX2870EVKIT.html/tb_tab0

author: BFX
author_rank: Frequent Contributor
timestamp: April 11, 2015, 09:14:28 am
content: Quote from: hendorog on April 11, 2015, 05:55:54 amThank youThe first one looks very good.
5hz (min) GPS Module without built in antena - uk source - Page 1
Forum section: electronics / projects

author: max_torque
author_rank: Super Contributor
timestamp: August 17, 2015, 06:22:38 pm
content: Hive mind i have a question!I'm looking for a GPS module, with serial output (USART or SPI) that can do 5Hz updates, but that doesn't have a built in antenna. It also needs to be easily available in the UK, and ideally at least semi guaranteed not to go obsolete in the next year or so as a minimum?Anyone got any suggestions as which to use? (plenty available from a quick "Google", but i'd like a secure source, like Farnell,Mouser or Digikey really)Volumes are around 100 units PA by the way, so not huge

author: 8086
author_rank: Super Contributor
timestamp: August 17, 2015, 06:25:19 pm
content: http://uk.farnell.com/maestro-wireless-solutions/a2200a/gps-module-rom-based-mini-outline/dp/2281694I've used the A2235H in a design without issue, so I would recommend the company, even though I have no experience with the A2200A.

author: max_torque
author_rank: Super Contributor
timestamp: August 17, 2015, 06:40:02 pm
content: I've actually got a few A2200A modules knocking around somewhere, but i thought they were 1Hz only??

author: 8086
author_rank: Super Contributor
timestamp: August 17, 2015, 06:45:06 pm
content: According to the marketing brief (click datasheet on farnell) they support 5Hz...I guess you would need to peruse the datasheet to find out for sure.

author: rollatorwieltje
author_rank: Unknown
timestamp: August 17, 2015, 06:46:18 pm
content: I have usedu-bloxmodules several years ago, they performed very well. Up to 10Hz position updates, I think the current models can do even more. Not sure where to get them though, but considering how common these modules are it can't be difficult. It was (is?) pretty much the go-to module for autonomous vehicles.I think we used the LEA-5 module back then (6+ years ago), currently they are at LEA-8 and according to the product page the footprint is pin compatible.

author: Koen
author_rank: Frequent Contributor
timestamp: August 17, 2015, 06:52:40 pm
content: µBlox MAX-M8Q (TCXO version), 5Hz capable, concurrent GNSS, ~25mA.Datasheet :https://www2.u-blox.com/images/downloads/Product_Docs/MAX-M8_DataSheet_(UBX-13004644).pdfUK shop :http://ava.upuaut.net/store/index.php?route=product/product&product_id=107&search=max-m8q

author: lincoln
author_rank: Regular Contributor
timestamp: August 18, 2015, 07:58:11 pm
content: http://www.gtop-tech.com/en/product/Gmm-u2P-GPS-Module/MT3339_GPS_Module_01.html

author: max_torque
author_rank: Super Contributor
timestamp: August 18, 2015, 09:15:28 pm
content: Thanks all. That Ublox module looks like a good option. Small, cheap, and probably not going to become obsolete or unsupported in the near term
5MHz TTL clock oscillator giving 20Hz. What's wrong? - Page 1
Forum section: electronics / projects

author: robertbaruch
author_rank: Regular Contributor
timestamp: June 18, 2016, 10:37:19 pm
content: Hey all,I'm usingthis TTL oscillator, specifically the MXO45-3C-5M0000.It seems simple enough. So, I get out my benchtop power supply, set to 5VDC, and a breadboard.Pin 1 is on the lower left, looking down at the package. That's the enable pin, so hook it to +VCC.Pin 14 on the upper left is power, hook to +VCC.Pin 7 on the lower right is GND, hook to GND.Pin 8 is the output, connect to oscilloscope.Power up with 5VDC, get... 20Hz out. WAT.Replace, try another one. Get... 150Hz. WAT!Okay. Clearly there's something I don't know about this thing. Does anyone have an idea what I'm doing wrong?

author: void_error
author_rank: Frequent Contributor
timestamp: June 18, 2016, 10:44:23 pm
content: Did you use a ~100n ceramic decoupling cap between +VCC and GND? Lots of weird things can happen on a breadboard if you don't use one.

author: robertbaruch
author_rank: Regular Contributor
timestamp: June 18, 2016, 10:45:40 pm
content: *sigh* Never mind. Apparently I turned the time setting on the Rigol that I'm using down to 1 ms/div, and the input capacitance at that point was enough to drop the oscillator into some other mode. When I moved the time up above 20 us/div, I was finally able to see high-frequency oscillation, and at 50ns/div I can clearly see bang-on 5MHz.

author: Andy Watson
author_rank: Super Contributor
timestamp: June 18, 2016, 10:56:43 pm
content: Quote from: robertbaruch on June 18, 2016, 10:45:40 pmI suspect that what you were seeing was aliasing. Try putting the scope in a different capture mode.

author: uncle_bob
author_rank: Unknown
timestamp: June 19, 2016, 12:38:34 am
content: Quote from: robertbaruch on June 18, 2016, 10:45:40 pmHiThat's not an input cap issue. As mentioned in another post, digital scopes are not ideal broadband frequency counters. They only take just so much data and only do so just so fast. When you slow the sweep speed down, the sample rate drops as well. This gets you into trouble if you try to look at a very fast signal. It will down convert it into a perfectly good looking signal ... at the wrong frequency.Bob

author: robertbaruch
author_rank: Regular Contributor
timestamp: June 19, 2016, 01:33:57 am
content: Ah, now that makes sense. Thanks!

author: tggzzz
author_rank: Super Contributor
timestamp: June 19, 2016, 02:02:03 pm
content: Quote from: robertbaruch on June 18, 2016, 10:45:40 pmThe input capacitance is invariant, unless you have averystrange and faulty scope!Always learn to use your instruments by playing around with a known signal. Make sure you can relate what you see to what's inside the instrument. All instruments lie in one way or another, so you need to learn each one's foibles.