hybridfree/eevblog-posts huggingface dataset:
How to implement LEDs in my design? - Page 1
Forum section: electronics / projects

author: dreaquil
author_rank: Regular Contributor
timestamp: March 27, 2015, 02:53:20 pm
content: Hi,So I recently started working on a frequency counter using a pic18f and two 4 Digit 7 Segments and decided it would be a nice project to put into an enclosure so I got onto ebay and ordered the following enclosure like Dave had recommended on the blog.http://www.ebay.com/itm/231422367563?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITNow I'm gonna be cutting a rectangular hole for the seven segment to poke out the top and I need to add a few LEDs (maybe 4 or 5?) and I was wondering what the best way to do that is. I've never used light pipes so don't really know how to match them up. The LEDs will be right below the surface soldered onto the board face where i need them to be, so the way I see it is that my options are to use light pipes or to poke out some through hole LEDs and give the pins some kind of support. Any thoughts or other suggestions? I live in europe and will be probably placing an order with Mouser or Farnell Export.

author: ajb
author_rank: Super Contributor
timestamp: March 27, 2015, 06:57:01 pm
content: You have a couple options:- Use a TH LED, installed at the appropriate height. For best results, use anLED spacerto hold it the appropriate heght. Height is measured from the bottom of the LED to the top of the board.- Use an SMD LED with a suitable board-mount lightpipe.here are some vertical options, Lumex make a bunch of other shapes, as do other manufacturers.- Use a panel-mount lens and lightpipe assembly.Here are some lenses, if you look at the datasheets you'll find there are lightpipes that snap into the rear of some of them to conduct the light into the lens from an LED mounted further back in the enclosure. You can also use these with a through hole LED as above, with the LED stood off from the board to land at the right point inside the lens. The lenses give a very nice, finished look to an enclosure, and can off increased viewing angle over a standard LED that just pokes through the panel.

author: dreaquil
author_rank: Regular Contributor
timestamp: March 27, 2015, 08:32:15 pm
content: Thanks for the reply. Might go for the through hole design as it seems to be the easiest to implement while having room for error. If i were to go for a light pipe, do i need the exact size or can they be bought longer and then shortened?

author: ajb
author_rank: Super Contributor
timestamp: March 27, 2015, 09:50:47 pm
content: Light pipes are typically polycarbonate, so could certainly be cut short, but a cut end won't be as efficient as the factory end, which typically has a bit of a convex shape or a slight texture to improve illumination. You'd probably need to sand if not polish the cut end to restore efficiency.
How to implement long press button on/off for STM32 - Page 1
Forum section: electronics / projects

author: Wilson__
author_rank: Frequent Contributor
timestamp: May 31, 2024, 12:08:21 pm
content: Many devices have mechanical push button. Long press 2 seconds for on/off. How to do on STM32? Which mode to use?Shutdown mode: 31 nAStandby (+ RTC) mode: 360 nAStop2 (+ RTC) mode: 1.07 μAMany thanks

author: pcprogrammer
author_rank: Super Contributor
timestamp: May 31, 2024, 12:31:10 pm
content: What you can do is use P channel mosfet to turn the power on and off and have the MCU completely powered down. The power switch pulls the gate of the P channel mosfet to ground and in the mean time the processor starts up and set a signal to hold the gate down using another transistor.To power things off the processor reads the state of the power switch. As long as it is high it keeps the gate of the p channel mosfet down. When it sees it low it turns off the power by making the gate of the p channel mosfet high.Take a look at how it is done in theFNIRSI 1013D and 1014D scopes.
How to Implement Multiple Burden Resistors for a CT Leakage Current Sensor? - Page 1
Forum section: electronics / projects

author: kagoun
author_rank: Newbie
timestamp: July 22, 2025, 11:23:08 am
content: I have a circuit schematic for measuring leakage current using a current transformer (CT). I'm trying to understand how it works, but there are a few parts that don't quite make sense to me.You can see the schematic in the attached image. In this schematic, T0 and T1 are the CT connection points.I'm particularly trying to figure out the MOSFET structures used here. It seems like they were trying to make the burden resistor configurable (selectable). But since leakage current produces an AC signal, I'm not sure if the MOSFETs will work correctly under such conditions.Do you also think this setup is intended to switch between different burden resistor values?In my own design, I may also need to use 2 or 3 different burden resistor values, depending on the measurement range.What would be a good way to implement that?
How to implement V. 35 in an embedded system - Page 1
Forum section: electronics / projects

author: rakeshm55
author_rank: Regular Contributor
timestamp: November 23, 2023, 05:09:18 pm
content: How can one implement V. 35 Terrestrial interface in an Embedded system?Is there specialized chip for this? Does a uC has standard peripheral for V. 35 similar to Spi annd i2c etcHow to model V. 35 embedded system implementation ? Fpga??

author: fchk
author_rank: Frequent Contributor
timestamp: November 23, 2023, 06:20:59 pm
content: V.35 is a very old standard that is not common today. There are no standard peripherals for that. Nowadays you would use a DSP for this task. But you are largely on your own.

author: rakeshm55
author_rank: Regular Contributor
timestamp: November 24, 2023, 12:39:53 am
content: DSP + bit bang a gpio pin.Is this standard open? And how i can test this interface?Is it too complicated to be implement in FPGA logic?

author: aeg
author_rank: Regular Contributor
timestamp: November 24, 2023, 01:18:46 am
content: It's synchronous serial, you'd use something like a USART. It's a CCITT standard.

author: wasedadoc
author_rank: Super Contributor
timestamp: November 24, 2023, 09:16:51 am
content: Quote from: aeg on November 24, 2023, 01:18:46 amCCITT was renamed to ITU-T decades ago.
How to include the ramp up time of step input in the RC circuit design? - Page 1
Forum section: electronics / projects

author: electrowhiz
author_rank: Contributor
timestamp: April 06, 2019, 03:50:35 am
content: Hi All,I wished to design the RC circuit with a delay of 5ms to reach 5V. In actual case, if the 5V is supplied by the DC-DC converter, it will not be step input i.e DC-DC converter will take some time to reach the 5V. Suppose it takes 0.2ms (assumption) as a ramp up time to reach the 5V, how to include the effect of ramp up voltage in this equation Vc=V(1-e^(-t/RC)Thanks
How to interface AD2285 accelerometer with Pic32 - Page 1
Forum section: electronics / projects

author: smashedProton
author_rank: Frequent Contributor
timestamp: December 03, 2014, 07:47:15 pm
content: Hello all,I'm working on a new project, an electronic sensor and datalogging system for a high power rocket. As part of it I need to interface an accelerometer with an analog 0-5v signal to an adc on my pic mcu that accepts 0-3v3 signals. To complicate things, I only want to the negative g data, so I only need the 0-2.5v signal and want anything above that clamped and want the 0-2.5v signal expanded so that I can use the full resolution on the adc in my microcontroller. This is a lot of precison analog stuff..... I've never done this before. Any solutions would be very helpful to me.Thank!

author: jlmoon
author_rank: Unknown
timestamp: December 03, 2014, 09:59:03 pm
content: Are you sure that is a AD2285 (Analog Devices)? I don't find any data on that particular part

author: dannyf
author_rank: Super Contributor
timestamp: December 03, 2014, 10:33:05 pm
content: QuoteExactly the same way as with other mcus.
how to interface cmos to VGA  - Page 1
Forum section: electronics / projects

author: Dan Moos
author_rank: Frequent Contributor
timestamp: June 04, 2021, 03:09:11 am
content: What is the proper way to interface a 5 volt signal to the red, green and blue channels of a vga monitor? Lets assume I am going for white, full brightness. I know how to create a simple resistor DAC.I know from research the upper voltage level of the signal is .7 volts (sounds suspiciously like the monitor input is diode clamped)I've found that leaving the signals at 5 volts results in a "smeared" looking image. a 1k resistor in series cleans it up considerably. Haven't tried a diode to ground yet to clamp the signal. Resistor divider obviously results in a less bright image. I get pretty passable results with the 1k resistor in series between the logic and the monitor input.This is a home rolled VGA video circuit for a home-brew computer . It works great, but I've kinda procrastinated on properly doing this part.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 04, 2021, 03:14:40 am
content: The VGA signals have a 75 ohm termination, so 470 ohms is the closest standard resistor value to give the ideal signal level. Maybe bump that down to 390 ohms to compensate for the impedance of the output drivers.

author: Dan Moos
author_rank: Frequent Contributor
timestamp: June 04, 2021, 03:30:07 am
content: So just to make sure I'm following, What I am trying to do is create a voltage divider with the 75 ohm termination that results in .7 volts at full input? Thus, the 1k I'm currently using is a slightly attenuated signal compared to what I could send?Also, is any sort of filtering recommended? My pixels are sent at a 25.175 Mhz clock rate. Should I be high or low pass filtering this signal? With the 1k series resistor, i get very faint smearing of the signal. You have to really look to see it.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 04, 2021, 04:21:55 am
content: No need to filter, the whole point is to have the pixel values transition as quickly as possible.

author: james_s
author_rank: Super Contributor
timestamp: June 04, 2021, 06:00:08 am
content: This is commonly done with FPGAs using a simple resistor DAC, for an example see herehttp://searle.x10host.com/Multicomp/index.htmlWith additional resistors you can get 4 or more bits per pixel.Keep in mind the above example is 3.3V rather than 5V.
How to interfere with electret microphones? - Page 1
Forum section: electronics / projects

author: delicado
author_rank: Contributor
timestamp: February 19, 2017, 04:34:09 am
content: HiDoes anyone know how to interfere with electret microphones? AFAIK, they don't have magnets inside, so they shouldn't be vulnerable to magnetic interferences. Basically, I'm trying to create an external source that can jam an electret microphone. Are there other ways beside playing a very loud tone?Any thought appreciated.

author: JimRemington
author_rank: Regular Contributor
timestamp: February 19, 2017, 08:43:04 am
content: There is a FET inside, so a decent electrstatic discharge might fry it.

author: Assafl
author_rank: Frequent Contributor
timestamp: February 19, 2017, 09:25:39 am
content: Odd question. How much interference do you want? Do you want to add noise to a recording - or do you want to make speech undecipherable? Do you know where the microphone is? Does it have an AGC?A few ideas:1. Very high SPL very low frequency waves that max out the diaphragm's motion. I think speech will need a good amount of analysis to make intelligible. but doable. Annoying.2. Very high power RF Signal directed at the module. I am sure at some levels this will upset the FET, albeit it is a Faraday cage so I don't know whether that is feasible. Also - at sufficient high power may overwhelm the next stage. Not healthy...3. Induction coil - Use a high power induction coil and hope something inside the capsule melts. This sort of assumes you know where it is.4. High power noise to muffle speech - I don't know how high that needs to be. Something like MLS squeaks... Annoying. a lot.5. Alternatively - high power noise + electromagnetic bonanza - a Jacobs ladder, a VDG or Tesla coil with a short gap as close as possible to the mic.5. If you know where it is - and it has an AGC - direct sound at it (like a radio station). Use a phased array or a parabolic speaker (like they use in museums). The AGC will mute far away noises.None of these are pet friendly.

author: 2N3055
author_rank: Super Contributor
timestamp: February 19, 2017, 09:40:44 am
content: Most electret mics go very high in frequency... 22kHz or such at decent SPL might overload preamp....

author: Ian.M
author_rank: Super Contributor
timestamp: February 19, 2017, 09:44:19 am
content: Pulse the 22KHz with a random repetition rate between 1Khz and 5KHz to maximize intermodulation effects in the preamp. Not pet or small child friendly.
How to intrepret the FT232HQ timing diagram? - Page 1
Forum section: electronics / projects

author: zapta
author_rank: Super Contributor
timestamp: June 12, 2024, 04:10:26 am
content: I am trying to interface an FTDI FT232HQ in asynchronous FIFO mode to an FPGA, datasheet herehttps://ftdichip.com/wp-content/uploads/2023/09/DS_FT232H.pdf#page=26, and the relevant timing diagram is below.The writing to the FIFO is done on the high-to-low transition of the WR# input. My question is, how long after the high-to-low transition of the WE# input it's safe to sample the TE# output to determine if the next byte can be written? I would think it's max(t6)+max(t7) but max(t7) is not given.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: June 12, 2024, 05:04:38 am
content: Quote from: zapta on June 12, 2024, 04:10:26 amMy reading is you can sample for a low from T6, which is max 14ns, or you could wait for TXE high, which has a min of 49ns, then look for =\_The lack of a MAX T7 might depend on the host reading the part so it could hit ms on a slow PC ?

author: moffy
author_rank: Super Contributor
timestamp: June 12, 2024, 05:30:31 am
content: Their TN_167 FIFO basics note states that for Asynchronous mode the maximum throughput is 8Mbyte/s, page 4 of:https://ftdichip.com/wp-content/uploads/2020/08/TN_167_FIFO_Basics.pdfnot sure if that helps, but it puts a limit on the maximum continuous write speed.

author: zapta
author_rank: Super Contributor
timestamp: June 12, 2024, 05:36:58 am
content: Quote from: PCB.Wiz on June 12, 2024, 05:04:38 amI think this makes sense, after T6 it's high and then I can sample until TE# becomes low.

author: zapta
author_rank: Super Contributor
timestamp: June 12, 2024, 05:41:33 am
content: Quote from: moffy on June 12, 2024, 05:30:31 amThat's a useful app note. I will read it. Thanks.In my case I may need to spend also two cycles on FPGA input metastability protection so may be even slower but 4MB/s should be sufficient for my use case. Currently I do about 1.5MB/s blindly, ignoring the TE# signal and don't seem to loose bytes.
How to keep USB battery power flowing? - Page 1
Forum section: electronics / projects

author: rea5245
author_rank: Frequent Contributor
timestamp: April 30, 2022, 06:46:35 pm
content: I'm plugging a USB device into a USB battery pack. After a minute or so, the battery stops supplying power.I've tried two different battery packs, both bought from Amazon a while back, and neither is still being sold.The device is a USB to 12V "cigarette lighter" converter (https://www.amazon.com/dp/B093KXL19S). After a short while, it loses power, even if I haven't put a load on the 12V side.If I plug the converter into a USB AC adapter, it stays powered on indefinitely.Is this a problem of the converter not doing any power negotiation? It seems inconceivable that the battery packs would require it; I would expect them to happily provide 5V and at least 1.5A forever.Any thoughts?Thank you.

author: ledtester
author_rank: Super Contributor
timestamp: April 30, 2022, 07:05:44 pm
content: You may need a "power bank keep-alive" circuit:https://www.eevblog.com/forum/beginners/defeat-powerbank-auto-shutdown/msg3884138/#msg3884138

author: rea5245
author_rank: Frequent Contributor
timestamp: April 30, 2022, 07:48:31 pm
content: Quote from: ledtester on April 30, 2022, 07:05:44 pmThank you.I can't add a "keep alive" circuit in my application - everything needs to be off-the-shelf. But if that's just the way these battery packs work, I'll need to let the user(s) know they have to "wake up" the battery.Thanks.

author: tooki
author_rank: Super Contributor
timestamp: May 01, 2022, 05:51:26 pm
content: You can get power banks with a low-current mode that won’t shut off. I have one from Anker like that. You hold the button for a few seconds till one of the LEDs changes color. I use that to charge my Bluetooth earphones, which don’t draw enough current to keep most power banks alive

author: tooki
author_rank: Super Contributor
timestamp: May 01, 2022, 05:57:16 pm
content: Quote from: rea5245 on April 30, 2022, 06:46:35 pmNo.Quote from: rea5245 on April 30, 2022, 06:46:35 pmWell, it is necessary for USB-PD charging at higher voltages. Most decent power banks use “smart” ICs that can detect and negotiate with all the major standards, including the older proprietary standards that predate USB-PD, so that every device can charge as fast as possible.Quote from: rea5245 on April 30, 2022, 06:46:35 pmAnd they would if you were drawing 1.5A. But you’renotdrawing 1.5A and that’s precisely the issue: power banks have power-saving auto-shutoff circuits that look at current draw on the port. If it’s below some threshold value for long enough time, it shuts off. Small devices — like your 12V boost converter without a load — are below that threshold so the power bank shuts off.
How to limit current draw of device from PSU? - Page 1
Forum section: electronics / projects

author: monster_of_electronics
author_rank: Contributor
timestamp: November 09, 2015, 02:54:26 am
content: How can I prevent a device (load) from drawing too much current from a power supply without modifying the device/load? Say I have a product (the land) I want to charge from a power supply (PSU). The PSU can only handle 1A max, but the device normally draws 15A. How do I easily limit the current that the PSU will supply down to under 1A so my PSU doesn't blow up but continues to charge, just at a slower rate.

author: EE-digger
author_rank: Frequent Contributor
timestamp: November 09, 2015, 03:41:27 am
content: A current limiter like the one shown is a good solution.A cheap and dirty method, but one that would need some experimenting, is to use a light bulb of the right type.Automobile interior lamps might get you close, depending on the voltage drop you need. The bulb approach also gives some inherent protection as the filament resistance climbs quickly as the filament heats (from excess load).What's the voltage difference between your source and load?Den

author: arvindgr
author_rank: Newbie
timestamp: November 09, 2015, 11:58:52 am
content: You can consider resetable CB's which restrict current flow at max easily, though they're avilable for rated voltage and current and not variable volts...
How to limit inrush current on transformers - Page 1
Forum section: electronics / projects

author: MattC
author_rank: Newbie
timestamp: July 17, 2012, 09:57:21 pm
content: Hi guys,My Product Training Module for Digikey is done:http://mkt.digikey.com/ga/ptm/us/en/tod/Ametherm/NTC-Thermistor-Transformer-Protection/NTC-Thermistor-Transformer-Protection.htmlmatt@ametherm.com
How to make a +, a - voltage and gnd ? - Page 1
Forum section: electronics / projects

author: Hextejas
author_rank: Frequent Contributor
timestamp: March 03, 2018, 07:00:42 pm
content: I don't know how to do this but I think it might be simple.I have a project that requires a +15, a -15, and a gnd. Both DC if that makes sense.I have 2 different voltage source, both have a red and green 15 volt connector.So how to hook them together and where does that silly gnd come from ?ThanksOh yeah, another student while wrestling with this same problem, mentioned a voltage divider but I don't know how that would work so I am going to go read up on it.

author: Nusa
author_rank: Super Contributor
timestamp: March 03, 2018, 07:27:31 pm
content: Depends on what your "voltage sources" are. If they're proper isolated bench supplies, it's easy -- just hook two 15V supplies in series to get a 30V supply. Then you simply change your GND reference...what was 0, 15, and 30 V can also be looked at as -15, 0, and +15 V. 0 (aka GND) is chosen reference point for everything else.If they're NOT isolated supplies (e.g. most wall-warts and computer supplies), I would not recommend that at all.

author: danadak
author_rank: Super Contributor
timestamp: March 03, 2018, 08:37:30 pm
content: Post the manufacture name and model number of the supplys.If no markings some pics might help.The resistor divider approach works OK if the current in the supply railsvery low, otherwise its best to use a buffer to create the virtual ground,that avoids supply droop with load.The above example, examine output current spec, and take care to note worst case power dissipation.If your load exceeds OpAmp capability then asomething like this -Regards, Dana.

author: Hextejas
author_rank: Frequent Contributor
timestamp: March 04, 2018, 03:25:05 am
content: They are both isolated supplies so I will give it a try tomorrow.Thanks
How to make a cheap analog switch pass analog video signals? - Page 1
Forum section: electronics / projects

author: HSPalm
author_rank: Regular Contributor
timestamp: August 16, 2016, 11:15:30 am
content: I want to use this cheap video switch to pass analog video signals:https://www.digikey.com/product-detail/en/texas-instruments/74LVC1G3157DBVRE4/74LVC1G3157DBVRE4-ND/1688785But it can only pass signals from 0v to Vcc. Composite video signals often swing below 0v. Can I cheat by raising the switch gnd potential with a voltage divider?

author: Zero999
author_rank: Super Contributor
timestamp: August 16, 2016, 12:21:51 pm
content: All analogue switches can only switch signal voltage within the power supply rails, unless it includes an in-build voltage doubler.The usual way to do this is to bias the signal at half the supply voltage and AC couple it.

author: HSPalm
author_rank: Regular Contributor
timestamp: August 16, 2016, 01:48:52 pm
content: Thanks for replying. BTW, I also just realized how my proposed solution was completely not an alternative because I would really just even raise the gnd potential and make the video signal run even "lower".

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 16, 2016, 04:32:41 pm
content: mechanical relay works on almost any voltages, but if mechanical is not your taste, you can cheat by supplying the IC with dual rail supply, ie IC's gnd = -ve voltage. not looking at the IC's datasheet, but if the IC doesnt have drain capability then you may need to homebrew, simply like pull down resistor to -ve rail, ymmv.

author: HSPalm
author_rank: Regular Contributor
timestamp: August 16, 2016, 04:47:07 pm
content: Quote from: Mechatrommer on August 16, 2016, 04:32:41 pmRelay no can do, I'm trying to switch graytones in between lines on video frames. Thanks for your input. I was hoping for a very small design so I think I may prefer the biasing voltage way.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 16, 2016, 07:39:43 pm
content: The CMOS switches only work for signals within there supply and maybe some 100 mV beyond.There are some that have an extra negative supply, like the 74HC5053. So you can have 0 ond 5 V for the control signal and -5 to +5 V signal range.

author: PChi
author_rank: Frequent Contributor
timestamp: August 16, 2016, 08:24:07 pm
content: Yes you can cheat by adding bias resistors and AC coupling the video signal with a large enough capacitor. I beleive that most monitors used a 'black level clamp' circuit that set the internal 'DC' level during blanking back to the black level. I used 4066 CMOS switches in a crappy video multiplexer many years ago and that is what I did.
How to make a function generator with variable duty cycle.. - Page 1
Forum section: electronics / projects

author: richcj10
author_rank: Unknown
timestamp: June 19, 2012, 02:48:42 am
content: I was thinking of using the Tone() fcn of Arduino but can't find out how to alter the duty cycle...Any suggestions?Thanks,rick

author: mwhooker
author_rank: Newbie
timestamp: December 02, 2013, 12:42:51 pm
content: You need the arduino duo which can callhttp://arduino.cc/en/Reference/AnalogWriteResolutiontone() by definition has a 50% duty cycle.See this articlehttp://arduino.cc/en/Tutorial/DueSimpleWaveformGenerator

author: Six_Shooter
author_rank: Regular Contributor
timestamp: December 02, 2013, 02:55:38 pm
content: Quote from: mwhooker on December 02, 2013, 12:42:51 pmAm I reading that right, the maximum frequency is 170 Hz? That's not very useful as a function generator. There are tutorials for the Uno that will go to at least 20 kHz, I think I've come across one that will go to 100 kHz.

author: BravoV
author_rank: Super Contributor
timestamp: December 02, 2013, 03:00:03 pm
content: See the date of the first post.

author: dannyf
author_rank: Super Contributor
timestamp: December 02, 2013, 10:37:59 pm
content: Two options:- use analogwrite.- use hardware pwm.
How to make a Lorentz contraction voltage measurement ? - Page 1
Forum section: electronics / projects

author: John Heath
author_rank: Frequent Contributor
timestamp: February 26, 2017, 02:35:47 am
content: This one has been on my bucket list for a while. How to make a Lorentz contraction voltage measurement ? It is my hope by putting some of my failed attempts on the table that others on the list could breath new life into this problem. An out of the box approach from different shoes that would not occur to myself.First of all what is a Lorentz contraction voltage measurement. If one probe is grounded and the other toughing a magnet the voltage should be extremely negative , 100 KV or so. Not just a magnet but a copper wire carrying 10 amps should also have effective electron contraction leading to an extreme negative voltage around the wire. However it can not be measured with a conventional meter as the meter leads are entering the magnetic frame of reference therefore it cancels out. Its a no win.Failed attempts on my part. Use a magnetic probe. Close but no cigar as a magnetic probe , current probe , makes a distinction between north and south poles. Lorentz electron length contraction makes no such distinction as both north and south poles have effective length contraction therefore negative charge. Same is true of current in a wire regardless of current direction.Build a mechanical mono pole south in and another north in with flat magnets then measure the voltage between both opposite mono poles from the inside. Can not remember why I thought that would work. Suffice to say it did not work.Not tried yet. A gold leaf jar. Replace the gold leaf with two pieces of iron then connect the new iron leaf jar with thin bars of iron to make contact with the magnet. An iron leaf jar would not make a distinction between north or south poles of a magnet as in both cases the iron leafs would separate a little. However would this be measuring a Coulomb force caused by Lorentz electron contraction or just a dirty trick to lose the distinction between a north and south poles?One more that came from a member on this list to measure sky charge. Sky charge is about 100 volts per meter or 200 volts from head to toe. Like the Lorentz electron contraction this is a voltage that can not be measured with a conventional meter. The solution is a voltage field meter. It consist of a fan , sheet of copper and a hole on top. If there is a fluctuating voltage at the copper plate that equals the frequency of the fan blades than there is an electric field. Maybe this would work?Any thoughts on this would be welcome.
How to make a smart charger behave like a dumb charger - Page 1
Forum section: electronics / projects

author: e100
author_rank: Frequent Contributor
timestamp: February 18, 2021, 09:03:32 am
content: I have a 12v 40 Ah sealed lead acid battery bank which I use as a continuously connected UPS for my home network. Everything is permanently connected to the 12v. There is no 12v to mains converter involved. The continuous current draw is about 2 amps.To keep the battery charged I bought a CTEK 12v 3.8amp charger as that seems to be popular with people who know about car stuff.https://www.ctek.com/uk/products/car/mxs-3-8-ukInstruction manualhttps://www.ctek.com/storage/9E4D59B2526B4C3C54C61873C881CAACFC4C93F306DE1C8A2788E26EA6E506DA/f9b26d5eaeeb4787a51e5fc933ae1eae/pdf/media/687dd00827b44e44afee8695c5d0efab/MXS_3.8-manual-low-UK-EN.pdfThis is one of those fancy 7 stage chargers with a microcontroller. The 7 stages are shown on page 5.It seems that this was designed to charge a disconnected battery, not one being continuously discharged via a load.The net result is that it never raises the battery voltage above 13.8v. The indicator lights on the front say that it has reached stage 7, but I don't think it has.The voltage waveform I see is pictured below. The time axis along the bottom has 5 minutes per division.Every few minutes it goes into a charging phase then pauses at 13.8 to monitor the voltage. The 2 amp load causes the voltage to drop rapidly until it hits 12.5v and then it triggers a charge cycle again. So the average voltage of the battery is only about 13.1v. From what I have read I should be aiming for something between 13.8 and 14.4v.So how can I trick this smart charger into charging to a higher voltage?

author: Gyro
author_rank: Super Contributor
timestamp: February 18, 2021, 10:02:44 am
content: 13.6 - 13.8V is a typical float charge voltage for a 12V Lead Acid battery. Higher voltages are used for a cyclic charge, where the battery is experiencing heavy discharges (eg. automotive use), but just sitting at low load, you don't want to exceed the float charge voltage.The charger appears to be monitoring the battery properly - 12.5V is about right for a 100% charged battery.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 18, 2021, 01:41:10 pm
content: Get a separate 12V power supply module (something like 4-5A would be ideal) and a Schottky diode. The power supply should be set to about 14V (might be better to use a 15V module and turn it down) and the diode prevents reverse current flow back to the charger/battery. If you like, you could use a relay (powered by a separate wall wart) to bypass the diode to eliminate the losses, which also lets you use a regular diode since that would only operate for the very brief time it takes for the relay to switch.
How to make a tactile switch act as a pushbutton switch + state reset - Page 1
Forum section: electronics / projects

author: Skleb
author_rank: Newbie
timestamp: March 26, 2019, 05:28:41 pm
content: Hi all,I am still a newbie here.I've been experimenting and trying to make a circuit which has four tactile switches which are used to turn on and off leds.I am using J-K flip-flop for saving a tactile button state.Circuit should work as follow: when user clicks button 1 LED1 should light up. When user clicks button 2, LED 2 should light up but LED 1 should immediately go off.To conclude, only one LED should be lit.I am having a problem with this "reset" feature. I can reset output by pressing a same button once again but then it acts like a push-button switch which I would like to avoid.I attached a schematic with my circuit.Any help is kindly appreciated.Regards

author: David Hess
author_rank: Super Contributor
timestamp: March 26, 2019, 07:01:07 pm
content: If you do not want a single push-button toggling its LED, then use the set and clear inputs instead of the clock input.I would probably do it using 7474 type dual D flip-flops and driving the clear inputs through a diode array so 3 diodes per flip-flop. Someone here likely knows a better way other than just programming a microcontroller.

author: bsfeechannel
author_rank: Super Contributor
timestamp: March 26, 2019, 08:16:15 pm
content: Observing how ganged push-button switches work, when you press a button, it resets all the other switches and then latches. So let's try to mimic this behavior electronically.When you press a button, it will send a rising edge pulse to all the FFs. J and K' will be 0 for the buttons that are not pressed forcing their respective FFs to reset, at the same time J and K' will be 1 for the pressed button.As with mechanical switches, if you press the same button again it'll remain "pressed". Nothing will happen. Likewise if you press two or more buttons at the same time they have a chance to get simultaneously latched. Pressing one of them again will release the others.I haven't built nor simulated this circuit so I don't know if things like timing will affect its operation. It's just an idea. Good luck.
How to make a tristate output? - Page 1
Forum section: electronics / projects

author: miceuz
author_rank: Frequent Contributor
timestamp: May 18, 2015, 10:45:12 am
content: Hi all,For my application I need a shift register that could output either LOW or high impedance. All I came up with was a pile of transistors hooked up to a 74hc595 shift register:I will use those outputs to switch in resistors setting levels in opamp amplifier gain and comparator threshold subcircuits:Can anyone suggest me a more elegant solution to create low/high impedance outputs?I know I could use digital potentiometers for the whole thing, but I really can't because of reasons that are out of my control.

author: German_EE
author_rank: Super Contributor
timestamp: May 18, 2015, 11:18:55 am
content: The normal way of doing things in the digital world is to wire a buffer chip between the shift register and the data bus. With Output Enable low any or all of the digital outputs can be high or low and with Output Enable highalloutputs are high impedance.Your requirement is different, you want to pull one or more resistors to ground depending on the shift register outputs. This isn't really 'Tristate' as there are only two conditions (grounded and high impedance). The best way of doing this I can think of is to use some of the CMOS switches that are around, a 74HC4066 contains four single-pole switches so in your case you would ground one end and connect the other to the resistor bank using the control pin to switch it on and off.NOTE: All of these analog switches have a defined 'ON' resistance. For a 5V supply the 74HC4066 has an on resistance of about 50 ohms and this needs to be factored into your resistor values.

author: Psi
author_rank: Super Contributor
timestamp: May 18, 2015, 11:48:20 am
content: Would i be yelled at for suggesting a 50c mcu programmed to act like a shiftreg?

author: H.O
author_rank: Frequent Contributor
timestamp: May 18, 2015, 11:51:20 am
content: Basically you want a shift register with open collector or open drain outputs. The TPIC6C595 etc family of chips springs to mind.

author: daqq
author_rank: Super Contributor
timestamp: May 18, 2015, 12:38:26 pm
content: Can't you use a DAC directly? There are some very nice ones that allow you to do pretty much anything as they have both sides of the resistor network/string available on the pins.

author: miceuz
author_rank: Frequent Contributor
timestamp: May 18, 2015, 02:36:05 pm
content: Quote from: H.O on May 18, 2015, 11:51:20 amYESSS!! Thanks, this is exactly what I want, had it "on the tip of my tongue" whole time... silly me!
How to make a Xbee P to P network "bullet proof"?  - Page 1
Forum section: electronics / projects

author: richcj10
author_rank: Unknown
timestamp: March 09, 2013, 11:47:03 pm
content: I am using the xbee's (S1) to make a P to P connection between a computer and a device. The device will be packaged into a box once done is non-reopen-able. I want to be able to do firmware updates over the serial stream using a boot loader. I have it working but it can be buggy. It likes to stop mid process and time out. I have a feeling it is dropping a packet and the boot loader / computer program doesn't know what to do.I am using the UART boot loader provided by Mikro Elektronika (PIC in Basic) and using there programmer (PC app).Thanks for any help,Rick

author: Bored@Work
author_rank: Super Contributor
timestamp: March 10, 2013, 01:01:50 am
content: Well, people here regularly try to convince us that MikroE stuff is so great. If you believe them then the MikroE bootloader certainly can't be at fault. If you believe, however, the bootloader is no good then your options are to fix it, to replace it with another one, or to write your own.So what is your choice?

author: richcj10
author_rank: Unknown
timestamp: March 10, 2013, 01:06:15 am
content: I like there IDE. There programmer (Hardware) is a POS.It isn't my choice about using Mikroe. My boss selected it.Is there a UART boot loader for the pic that I can use?Thanks,Rick

author: richcj10
author_rank: Unknown
timestamp: March 10, 2013, 01:37:10 am
content: I have tested the boot loader with a hard serial (not using xbee) connection and it worked really well.I need the xbee to be as good. (hopefully)
How to make an acoustic sensors preamplifier? - Page 1
Forum section: electronics / projects

author: Zack2325
author_rank: Newbie
timestamp: April 03, 2025, 02:45:18 pm
content: Hello,This is my first time posting here. Currently, I am working on project that aims to amplify the signal of an acoustic sensor (VS-900m). According my researches, I need to use buffers and preamplifers for impedance matching and amplifiying the signal of the sensor. To do this, I am taking as a reference this preamplifier from vallen [https://www.vallen.de/zdownload/DataSheets/Preamp/Datasheet_AEP5.pdf].Does anyone have already made a similar circuit before to tell me which are the characterestics should I take into consideration to design the circuit? The sensor datasheet is here [https://www.vallen.de/wp-content/uploads/2019/03/VS900-M_1512.pdf]. I am asking if a simple buffer like the BF862 or 2n4416 can handle the problem of impedance matching and if two amplifiers like the AD8099 can make the it easy to amplify the signal of the sensor 40dB?Otherwise, feel free to give me any information that can make the design more easy.Thank you in advance.

author: moffy
author_rank: Super Contributor
timestamp: April 03, 2025, 09:06:07 pm
content: You might find this discussion helpfull:https://www.eevblog.com/forum/projects/low-noise-hydrophone-preamplifier/msg5838669/#msg5838669

author: Zack2325
author_rank: Newbie
timestamp: April 04, 2025, 10:03:03 am
content: Already seen, but appearently we are not having the same configuration...

author: moffy
author_rank: Super Contributor
timestamp: April 04, 2025, 11:27:24 am
content: Quote from: Zack2325 on April 04, 2025, 10:03:03 amWhat is this configuration if not a JFET first stage followed by an opamp?
How to make cheap SMD rework preheater - Page 1
Forum section: electronics / projects

author: flolic
author_rank: Frequent Contributor
timestamp: May 16, 2011, 06:49:32 am
content: Hi, I just want to share few pictures of my homemade preheater.It is essential for BGA rework, and very helpful for any SMD rework on a larger multilayer boards.XBOX360 board ready for rework:GPU chip removed:Solder ball stencil:Reballed chip:Resoldered on PCB:

author: flolic
author_rank: Frequent Contributor
timestamp: May 16, 2011, 07:19:44 am
content: Shafri, I much prefer wood grillYes, that's just a normal heater. I prefer to heat the whole board because bigger boards tend to warp if heated partially.If for some reason I don't want to heat whole board, I mask part that needs to be cool with a aluminium foil.

author: mobbarley
author_rank: Regular Contributor
timestamp: May 16, 2011, 08:17:51 am
content: I really like your board holder! I was going to make something similar out of an adjustable hot air gun with a custom nozzle

author: nukie
author_rank: Frequent Contributor
timestamp: May 25, 2011, 04:42:22 am
content: is it funny when parts on the other side of the board starts falling off?

author: flolic
author_rank: Frequent Contributor
timestamp: May 25, 2011, 06:20:05 am
content: Surface tension is a magical thing

author: shijeesh
author_rank: Newbie
timestamp: July 21, 2011, 12:15:43 am
content: Which type heater is using

author: Unknown
author_rank: Unknown
timestamp: July 21, 2011, 12:55:15 am
content: Nice mounts flolic, they are are important as the heater itself. Thanks for sharing. One idea you can consider is adding a sheet of say steel a few mm on top of the heater to diffuse the radiaton even more, which should further prevent the formation of hotspots under the pcb.

author: mgg
author_rank: Newbie
timestamp: August 28, 2011, 09:54:11 pm
content: Good evening, after seeing the tutorial, I was really excited because a station BGA cost a fortune and the basic principles of this machine is quite appealing, my question is is used a heat source on top of the graphics chip to remove or to re-weld? I await news ..Best RegardsMiguel

author: nzo
author_rank: Regular Contributor
timestamp: August 29, 2011, 11:09:49 am
content: Beautifully craftedflolic. Thanks for sharing.
How to make Keypads - Page 1
Forum section: electronics / projects

author: 5321488
author_rank: Contributor
timestamp: June 29, 2018, 06:11:49 am
content: HiI'm trying to construct a keypad for a calculator style Arduino device I am constructing, so that it can use momentary switches but also fit into a case.I've had a look at Ben Heck's keypads in several projects and they seem to have some kind of 3D printed pieces that sit in a grid and then press down onto PCB mounted momentary switches (see for example), kind of like a membrane keyboard. Ultimately this is roughly what I'm trying to achieve.Does anyone have further info or ideas for making keyboards/keypads that would be useful?
How to measure amps and heat for 18650 cells? - Page 1
Forum section: electronics / projects

author: spinningmagnets
author_rank: Newbie
timestamp: January 23, 2019, 05:57:39 pm
content: Hello, I am a writer for electricbike.com, and I have been waiting for someone to perform a series of tests on 18650 cells, so I could publish the results. I've promised compensation to several candidates who had already posted about testing cells, so they already had most of the required set-ups. And yet, they are very busy, just as I am.I now find myself with some time on my hands, and money in my pocket. There are several often-quoted sources for the continuous and max output results of testing 18650 cells (perhaps ten different popular models). Rather than tell customers to trust that number, I'd rather post the temperature results at a dozen amp-draw levels, and then let the customer decide what the "true" amp-drain limits are.I have a certain familiarity with electrical terms and components, but I am weak on electronics. Plus, when I search Google I get 1,000 results. I believe I need two devices:1. A variable current-load for a single 4.1V cell with digital readout, perhap 1A-40A? Some way to data-log...2. A surface mount temperature probe to be clamped to the side of an 18650 cell, with data-logging3. Some way to capture and overlay the two data lines, so I can make those cool graphs we are all familiar with.Any advice is appreciated. I have a soldering iron, and I'm not afraid to use it...

author: metrologist
author_rank: Super Contributor
timestamp: January 23, 2019, 06:17:16 pm
content: I like datahttps://lygte-info.dk/review/batteries2012/Common18650Summary%20UK.htmlhere is a small sethttp://danyk.cz/test18650_en.htmlIf I were to DIY, I would use current shunt and an NTC or temp sensor plugged into an Arduino to read the sensors, then Arduino writes to SD card or over serial to PC with a serial monitor logging program like PuTTy.

author: spinningmagnets
author_rank: Newbie
timestamp: January 23, 2019, 07:30:14 pm
content: Thank you, I appreciate you taking the time to reply. I will look into this suggestion.

author: metrologist
author_rank: Super Contributor
timestamp: January 23, 2019, 09:04:28 pm
content: I suggest this because I built that solution to monitor my solar panel production. There are hall effect current sensing modules and I used a simple divider to bring the 24V+ down to the 5V range. I planned to apply the solution to the same thing you want here. You may even have enough ADC pins to monitor each cell.
How to measure battery capacity of various chemistry? - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: April 29, 2019, 09:07:37 am
content: I have a few old Li-ion and lead acid batteries that I would like to test for actual capacity however I am not sure at what current draw their rated capacities where deduced. I have the measuring equipment that gives me a mAh/Ah reading.If i am correct, Large lead acid batteries' capacity are based on a 20 hour constant current draw. I have the measuring equipment needed just not sure how to set the load.Also, to what voltage should they be discharged? I am only interested in knowing the actual capacity today to know how they stand up and if they need replacing.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 03, 2019, 09:09:10 pm
content: BUMP!

author: KC0PPH
author_rank: Unknown
timestamp: May 03, 2019, 09:19:45 pm
content: Li-Ion batteries should be discharged at 1C for measuring capacity. I dont remember off of the top of my head what the Low Voltage Cutoff is as I only take mine down to around 3.7V per cell.

author: Hiemal
author_rank: Regular Contributor
timestamp: May 03, 2019, 11:00:25 pm
content: Low voltage cutoff for li-ions is usually around 3.0 volts i think.

author: Rerouter
author_rank: Super Contributor
timestamp: May 03, 2019, 11:14:50 pm
content: If you want to compare to the rated capacity, then you measure at the load they specify for the ratingIf you want to know the capacity for your specific use case, then you measure it at that load.Lead acids you stop discharging at about 10.5V, li-ion you stop at about 3.2V

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 03, 2019, 11:20:48 pm
content: Quote from: Rerouter on May 03, 2019, 11:14:50 pmThanks for that!So if my car battery is dying and I would like to test it's actual capacity vs its rated one (80 Ah, 800 CCA). I should discharge at a constant 80 amps?If I am not mistaken, all lead acid batteries's capacity ratings are derived from a 20H rate.

author: Rerouter
author_rank: Super Contributor
timestamp: May 03, 2019, 11:33:27 pm
content: for its actual capacity, test it at 4A discharge to a 10.5V cut off., (lead acid are rated at about 1/20C)For cold cranking amps, measure the resistance to ground of your starter motor circuit to battery negative (can usually pull the starter relay and measure from there) this gives you your load, now the cranking amps are measured as the current it can draw without falling under 7.2V from a fully charged state, so roughly a battery ESR of 7.5 milli-ohm,At a basic level if you see the battery voltage fall under 7.2V while cranking, its likely an issue, if not and you want to know the value, take note of the voltage at that starter contact to battery negative while starting, from there its easy enough to figure out how many amps it was pulling, then another start measuring just at the battery terminals and this will let you calculate the battery ESR pretty closely.