hybridfree/eevblog-posts huggingface dataset:
simple ECG (heart beat monitor) - Page 1
Forum section: electronics / projects

author: xchip
author_rank: Regular Contributor
timestamp: July 07, 2013, 11:49:58 am
content: Full schematics and write up here:http://codinglab.blogspot.be/2013/07/my-heartbeat.htmlOpinions and feedback are very welcomeCheers!

author: trophosphere
author_rank: Frequent Contributor
timestamp: July 07, 2013, 04:19:42 pm
content: Nice project. One suggestion: Either try shifting your virtual ground closer to your negative rail or reduce your gain so that the QRS complex is not clipped.I've designed something similar a couple years back. Feel free to borrow if you like.

author: lgbeno
author_rank: Frequent Contributor
timestamp: July 07, 2013, 05:04:37 pm
content: Cool project, I'm also doing something similar with pulse oximetry!

author: xchip
author_rank: Regular Contributor
timestamp: July 07, 2013, 09:56:04 pm
content: Quote from: trophosphere on July 07, 2013, 04:19:42 pmHi, great stuff, thanks for sharing!The part about setting the external ref is quite interesting, in fact i was thinking about this today so it was nice to find that section. For setting the virtual ground i was thinking about using a MCU to charge/discharge a capacitor through a resistor, the MCU would monitor the charge of the cap using the ADC..Does it sound like a crazy idea?Cheers!

author: Paul Price
author_rank: Super Contributor
timestamp: July 08, 2013, 02:50:00 am
content: Xchip, Yes!

author: trophosphere
author_rank: Frequent Contributor
timestamp: July 08, 2013, 06:50:20 pm
content: I've seen that method used before for setting a voltage. Go for it and see if it works for you.

author: xchip
author_rank: Regular Contributor
timestamp: July 08, 2013, 11:20:00 pm
content: Quote from: Paul Price on July 08, 2013, 02:50:00 amTell me more

author: camhguh
author_rank: Newbie
timestamp: July 08, 2013, 11:39:34 pm
content: Popular topic it seemshttp://www.elektor.com/magazines/2013/july-047-august/android-elektorcardioscope-(1).2494375.lynkx
Simple electronic circuit of AC current DPDT switch  - Page 1
Forum section: electronics / projects

author: abdulbadii
author_rank: Frequent Contributor
timestamp: April 02, 2023, 11:56:41 am
content: Any experienced one on electronic circuits performing DPDT switch (AC signal/current H bridge DC switch equivalent), what and how is the simplest yet completely reliable circuit and main components preferably at latest semiconductor tech ?need arose to replace the mechanical one commonly found in AC handy tools

author: ajb
author_rank: Super Contributor
timestamp: April 03, 2023, 01:40:58 am
content: It's hard to understand what you're asking for. Sounds like you're talking about a reversing switch like you'd find in a corded drill? Those typically use "universal" motors where swapping the polarity of the stator relative to the rotor reverses the direction of rotation.The simplest solution would be a DPDT relay. If you really want a semiconductor solution, then you basically need an H-bridge just like you'd use for DC, but made of AC switches. The AC switches could be triacs or back-to-back FETs, either way the tricky bit is driving them properly, and protecting them from transients. That's all very dependant on the nature of the load you're driving, starting with the required voltage and current. It's impossible to say what the "simplest" solution or a "completely reliable circuit" might be without any information about what you're doing.
Simple R C time response electronic simulator recommendation - Page 1
Forum section: electronics / projects

author: Wilson__
author_rank: Frequent Contributor
timestamp: May 06, 2024, 06:25:33 am
content: Please advise simple (for now, R C Volt Current, Pulse charge up, discharge) simulator, off line or on line. Web has dozen of these. Wonder which is simple.TIA

author: wasedadoc
author_rank: Super Contributor
timestamp: May 06, 2024, 07:21:42 am
content: Quote from: Wilson__ on May 06, 2024, 06:25:33 amYou do not seem to know the difference between 'stimulator' and 'simulator'.You got it wrong twice so not an isolated typo.

author: matts-uk
author_rank: Contributor
timestamp: May 06, 2024, 08:10:44 am
content: With the emphasis on simple...https://icircuitapp.com/

author: Zero999
author_rank: Super Contributor
timestamp: May 06, 2024, 05:55:44 pm
content: It depends on what you mean by simple?I'm a big fan of LTSpice myself, but many beginners say they find the interface challenging to learn. TINA TI is another option.
simple encoder/decoder I/O multiplexer solution - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: November 29, 2018, 10:10:01 am
content: I am devising a unit. I have one button and 4 LED's at present. So I need 6 wires. Is there a simple chip and/or protocol out there that con be used instead of 6 individual hard wires? The cable may be as long as 10m between control panel and system.LIN bus time?

author: mikerj
author_rank: Super Contributor
timestamp: November 29, 2018, 10:53:44 am
content: Sounds an ideal application for one of the numerous I2C I/O expander ICs.

author: FrankBuss
author_rank: Unknown
timestamp: November 29, 2018, 10:55:43 am
content: Maybe use 1-wire with a DS2408. It is not a cheap chip, but you could implement it with 2 wires. 1-wire has been tested up to 300 meter. Don't use I2C, anything longer than some cm is asking for trouble.

author: Simon
author_rank: Unknown
timestamp: November 29, 2018, 10:56:25 am
content: I thought I2C meant IC to IC comms, ie on the same PCB. I do have the option of the ATmega3208 I am already using that has built in LIN

author: Buriedcode
author_rank: Super Contributor
timestamp: November 29, 2018, 11:04:40 am
content: LINbus seems overkill for a few LEDs... why not just a small MCU running very slow serial? Or even MIDI? 10m would be pushing TTL level serial but you could always try it with the cable you have. There's always the simple PPM/PWM used in cheap RF remotes although given you have an input as well you could jsut use that for the LED's, and a single wire for the button, that way comms is oneway.

author: Simon
author_rank: Unknown
timestamp: November 29, 2018, 11:11:53 am
content: LIN bus works with serial hardware.

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 29, 2018, 02:54:33 pm
content: I would keep it simple and use an UART-based communication and RS-485 transceivers. That will allow you to use much longer cables than 10m and is dead simple.

author: Simon
author_rank: Unknown
timestamp: November 29, 2018, 02:57:36 pm
content: i think I will leave this aspect alone and just use the 6 wires for now. We use CAN as a company and I am planning an optional CAN board attachment for this project so I'll just make it an excuse to start learning CAN.
Simple fiber optic data transfer - Page 1
Forum section: electronics / projects

author: Etesla
author_rank: Regular Contributor
timestamp: March 14, 2017, 03:20:36 pm
content: I need to transmit very low frequency signals (100 - 1000 hz square wave) accurately with very high noise immunity. Fibre optics seem to be the way to go, but off the shelf receivers and transmitters seem to be expensive and confusing. So my question is, is it possible to make my own super simple fibre optic receiver / transmitter using things like LEDs on the transmitter end, and photo resistors, comparators and schmitt triggers on the receiver end?The things I'm worried about are:LED not turning on and off fast enough to give a nice clean fibre optic signal.Photo resistor not recovering fast enough between pulses to accurately represent waveform on other end.PS.I already have about 3/32" fibre optic cable and the travel distance is about 15 feet, not sure if that matters.Thanks!

author: rstofer
author_rank: Super Contributor
timestamp: March 14, 2017, 05:29:34 pm
content: No reason for this to be a problem. Here is a kit for moving voice over fiber and there are a lot of LED and laser tranmitters. At higher speeds and longer distances, lasers are more commonly used.http://www.jameco.com/z/FO-30K-Elenco-Electronics-Kit-Fiber-Optics-Tx-Rx-Boards-Voice-1Khz-Signal-Via-Optical_2124200.htmlI might get a kit similar to this and then modify it to meet my needs.There are some issue re: single-mode versus multi-mode fiber and information is usually send digitally. I'm not sure how well an analog signal can be sent over fiber.

author: Benta
author_rank: Super Contributor
timestamp: March 14, 2017, 06:05:25 pm
content: The simplest would be the TOSLINK TORX111 and TOTX111 connectorless receiver/transmitter. Just stick the POF fiber into each and you have a connection.Bad news: discontinued. But if you only need a few, it should be possible to find them somewhere.

author: max_torque
author_rank: Super Contributor
timestamp: March 14, 2017, 07:10:20 pm
content: There are plenty of industrial fibre connectors and transcievers, used a lot in power electronics like motordrives to send control signals over high isolating barriers:they use cheap plastic multimode fibres and are available in direct to pcb mounting etc

author: Someone
author_rank: Super Contributor
timestamp: March 14, 2017, 09:49:09 pm
content: Quote from: Benta on March 14, 2017, 06:05:25 pmConsumer optic-fiber parts still exist for the audio/video market, and they sure are cheap. Everlight PLT133 and PLT135 for example, fine for 3V3 operation too.

author: Benta
author_rank: Super Contributor
timestamp: March 14, 2017, 09:59:38 pm
content: Quote from: Someone on March 14, 2017, 09:49:09 pmYeah, I know, but you need POF with connectors, the TOSLINK part you could just cut a piece of POF with a scalpel and stick it into the device.From the picture above, though, it seems that Avago/Broadcom has something equivalent (the three parts in the lower left corner).
Simple free digital waveform drawing software? - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: November 08, 2021, 09:46:15 pm
content: Hi,is there any freesimple to learn/use(one off use so don't want to spend time learning "complex" software) timing diagram software?Nothing fancy, I just need to draw various waveforms showing delays (i.e. with the classic vertical alignment lines) and few labels here and there to label what happens at certain points in time.I have come across some which require you to input the waveforms via text/program. I am actually looking for something I can just "draw" the waveforms.If not a software specifically designed for this, then what software do you use?(obviously I could use most graphic design software to design the signals lines but I am looking for something more "dedicated" to avoid wasting time redrawing a lot of it if I need to shift waveforms around (in time or vertically to reorder them)Thank you

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 08, 2021, 10:37:18 pm
content: Not what you asked and probably one of those you mentioned, buthttps://wavedrom.com/is pretty good otherwise.For a GUI-based one, you can try this:https://waveme.weebly.com/It was introduced in this forum a few years ago.https://www.eevblog.com/forum/projects/waveme-free-digital-timing-diagram-drawing-tool/

author: ricko_uk
author_rank: Super Contributor
timestamp: November 08, 2021, 11:27:13 pm
content: Thank you Silicon Wizzard!

author: CaptDon
author_rank: Super Contributor
timestamp: November 09, 2021, 02:22:34 pm
content: If Wizard's solution has got you up and going then problem solved. If you are still looking, there are some programs that can be downloaded from Agilent, Tektronix and others that allow you to draw waveforms which can then be utilized in various AWG Arbitrary Waveform Generators. Ultimately your hand-drawn waveform get processed into a .CSV file although other file types can also be created one of which is .AWG naturally. I even saw one that converted to .DDS Direct Draw!!Check out some of the waveform stuff from Yokogawa. The Yoko stuff wants an authentication code but they give it to you in the readme.txt file.

author: ricko_uk
author_rank: Super Contributor
timestamp: November 09, 2021, 05:18:16 pm
content: Thank you CaptDon
Simple FT231X Circuit - Page 1
Forum section: electronics / projects

author: zbot1
author_rank: Newbie
timestamp: May 12, 2014, 02:55:23 pm
content: I need a sanity check with a simple circuit for using FTDI's FT231X chip.After many, many checks I'm pretty sure the schematic and board layout are correct:https://www.dropbox.com/sh/w7slz8sjkgozwcz/AAChFTKg7JEIkihklc2pn5Yya*Both source files, and .pdf printouts available. Source files are for EAGLE 6.5However, when I hook things up on the prototype PCB, VIN drops to anywhere between 2--3V. I substituted the PTC and diode for 0-Ohm resistors, and still no dice.Do I have some glaring mistake that I am failing to see?Thanks in advance for your help.

author: mariush
author_rank: Super Contributor
timestamp: May 12, 2014, 03:23:35 pm
content: The LD1117 regulator is unstable without a capacitor on the output. The datasheet recommends 10uF, and you added one but what you probably missed is that the esr of that capacitor should be higher than what typical ceramic capacitors have... about 0.1 ohm or higher. That's why they say "electrolytic' in the datasheet. Try adding 0.1-0.3 ohm resistor in series with that 10uF capacitor and see what happens.The regulator also needs at least 2mA (some datasheets say 5mA) of load to work right.Be aware that usb voltage can be as low as 4.75v with usb 2.0, 4.0v with usb 3.0, the ld1117 has about 1-1.1v dropout, so that leaves you with 4.75-1.1 = 3.65v ... the diode will drop a further 0.2-0.3 v so you're right there at 3.3v in the worst case.If you don't need more than 200mA, you could use something like MCP1700:http://www.digikey.com/product-detail/en/MCP1700T-3302E%2FTT/MCP1700T3302ETTCT-ND/652677which only needs 0.2v above 3.3v to work and works with just 1uF ceramic on the output.Other than this, I'm not really sure, check your wiring, see if there's something shorted, check if the regulator is in some current limit or maybe you pull more than 100mA from the usb port..

author: zbot1
author_rank: Newbie
timestamp: May 12, 2014, 03:42:33 pm
content: Thanks for the help. Right now, I'm not even hooking up the VREG. I only have USB power directly to the FT231X chip. I have also removed the PTC and Diode, and am feeding in 5V directly to the FT231X. I can read ~5V before hooking up the FT231X. As soon as I do, the voltage drops down to 2--3V.I'm trying to avoid having to solder tiny wires to a QFN package to troubleshoot the PCB connections, but it seems that might be the only way...

author: David_AVD
author_rank: Super Contributor
timestamp: May 12, 2014, 09:06:52 pm
content: Link content has been deleted?
simple help with LTspice model - Page 1
Forum section: electronics / projects

author: cncjerry
author_rank: Unknown
timestamp: March 21, 2019, 09:03:27 pm
content: If I wanted to lower the slew rate of a transistor, basically limit it frequency response, what parameter would I modify, assuming this is so simple?I'm trying to figure out what is going on where my spice model doesn't match the live circuit. Only thing I can figure is that the MC3346 NPN array is somehow not performing as expected.ThanksJerry

author: Wimberleytech
author_rank: Super Contributor
timestamp: March 22, 2019, 01:30:35 am
content: CJE and CJC, but you are just poking around in the dark fiddling with these. You should try to find the models for that device.

author: cncjerry
author_rank: Unknown
timestamp: March 22, 2019, 03:38:55 am
content: Wimberleytech, thanks. I have the model for the RCA part, CA3046 and as expected the bandwidth is much higher than the live circuit (I don't see the rise time increase through the amp). I wanted to play with as you suggest CJE and CJC to see if by increasing them I can in effect better duplicate the live circuit. Adding 50pf just about anywhere will cause the problem I am seeing in the actual circuit.I find it hard to believe the NPN array failed as well as it having such a high junction capacitance from the start. I mean it is always possible, as I've only ever seen these used in low frequency applications but then again, that would only be about 4 or 5 data points.Thanks again,Jerry

author: Wimberleytech
author_rank: Super Contributor
timestamp: March 22, 2019, 01:22:58 pm
content: Quote from: cncjerry on March 22, 2019, 03:38:55 amYup, that seems a bit large. What is the circuit you are building/simulating?I suggest that you simulate a single transistor and test for ftand see if it matches with the datasheet.
Simple inertia dyno Arduino shield, need more eyes on my pcb/circuit.  - Page 1
Forum section: electronics / projects

author: adegnes
author_rank: Contributor
timestamp: November 28, 2015, 05:18:13 pm
content: Hi, I'm new here! (and fairly new to electronics)Here's a arduino shield for a motorcycle inertia dynamometer I've built.I've got the dyno up and running with just the roller pickup wired into the arduino with a pull up, but I also need engine rpm.I'm using this software: (works great BTW, and is free)https://sites.google.com/site/simpledyno/homeMy rpm pickup circuit is based on/copied from this site:http://www.sportdevices.co.uk/rpm_readings/index.htmThe connector labeled with the lightning is from the spark plug wire pickup, wich is just a coax cable coiled two turns around the plug wire. "-" is connected to the coax shielding. The signal is entering the board on the top layer and is transmitted to the bottom layer by capacitive coupling before it enters the 100p cap.The connector labeled with the "wheel" is the roller pickup, a Honeywell 1gt101dc.It would be great if someone could comment on my pcb layout and the circuit;Anything obviously wrong?What could be done better?Right choice of component values?Thanks!

author: pmbrunelle
author_rank: Regular Contributor
timestamp: November 29, 2015, 05:14:12 am
content: What is the Arduino for?Do the sensor inputs go to the Arduino, and then the data is sent to the computer program by UART?Because the SimpleDyno website shows that the data acquisition is by the computer sound card... but I don't think you want to blast the sound card input with a 5V square wave from the 555.

author: adegnes
author_rank: Contributor
timestamp: November 29, 2015, 07:17:12 am
content: Quote from: pmbrunelle on November 29, 2015, 05:14:12 amYou've just overlooked it...from their front page:"SimpleDyno 6.3 expands your data acquisition options by introducing support for microcontrollers such as the Arduino UNO."Digital pin 2 is rpm1 - dyno roler, pin3 is rpm2 - engine rpm.Analog pin 0-6 is used for logging analog signals from temp sensors etc.

author: rickey1990
author_rank: Regular Contributor
timestamp: December 02, 2015, 02:20:50 am
content: Hope this helpshttps://www.reddit.com/r/arduino/comments/2o4vxp/reading_engine_ignition_pulses/and nice looking board

author: adegnes
author_rank: Contributor
timestamp: December 02, 2015, 08:19:07 am
content: Thanks!

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: December 02, 2015, 11:09:40 am
content: Looks good to meGood job!Velkommen

author: adegnes
author_rank: Contributor
timestamp: December 07, 2015, 08:15:52 am
content: Takk takk!
Simple integrated wireless power receiver chip ? - Page 1
Forum section: electronics / projects

author: Koen
author_rank: Frequent Contributor
timestamp: May 06, 2019, 05:51:00 pm
content: Hello,some DIY wireless power transmitters and receivers use convenient SOP-8 pins chips like so :https://www.aliexpress.com/item/23mm-single-layer-high-frequency-ultra-thin-coil-wireless-charging-power-supply-module-circuit-diagram-XKT/32735172377.htmlhttps://www.aliexpress.com/item/2pcs-lot-Large-Current-Wireless-Power-supply-Module-Transmitter-Receiver-Charging-Coil-5V-2A-for-Mobile/32819374166.htmlThese would be XKT-412 and XKT-333, available from Alibaba and the likes.When I look for devices from big western manufacturers, I can only find 20+ pins chips in painful packages and, worse, with 10+ discretes required like TI BQ51xxx, Semtech LinkCharge.Would anyone have a nice chip to share ? I would like 5V/300mA out of it all.Thank you !Koen
Simple IR Camera From an Old Webcam - Page 1
Forum section: electronics / projects

author: Nothing
author_rank: Newbie
timestamp: May 02, 2020, 03:09:48 am
content: I remembered reading a while back about how all digital cameras can see into the IR but are limited by an IR filter they put en the lens. So tonight, I dug up an old webcam, took it apart and removed the filter. Had some trouble getting it back together, so it's not the prettiest looking thing, but it does the business. Here's a demo of it in action:

author: jackthomson43
author_rank: Contributor
timestamp: May 02, 2020, 07:29:41 am
content: hmmmm wastes 1:57 mins of my life, coz I stopped watching the video after that.Check thishttps://www.theengineeringprojects.com/2018/08/esp8266-pinout-datasheet-features-applications.html

author: Prehistoricman
author_rank: Regular Contributor
timestamp: May 02, 2020, 01:50:09 pm
content: I did this a while back but installed some old photographic film to block visible light. It makes some things look weird in particular, but mostly underwhelming.

author: Nothing
author_rank: Newbie
timestamp: May 04, 2020, 07:22:23 am
content: There are some interesting videos of various things that are opaque in visible light but transparent in infrared. Bromine was one that I found surprising. Or there's the classic experiment where you can see through a garbage bag in IR. That's a good idea about blocking out visible light, though. I'll have to look into that. I'd really love to have a pure IR camera that doesn't cost an arm and a leg. Did you just put the film in front of the aperture or something? Or was there more to it?

author: Rerouter
author_rank: Super Contributor
timestamp: May 04, 2020, 07:31:41 am
content: Some of the more interesting things you can see with an infrared luminance camera is clouds and plants, for a lot of small leafy plants you can see in the camera how healthy they are from much furthur distances than visable light, Equally I think I remember ripe mulberries having a very strong contrast compared to the plant.For clouds, you can see the water that is not normally visible.Slight downside is UV leakage, and you do need to refocus it, as the focal distance changes for different colors.
Simple LED light project - Page 1
Forum section: electronics / projects

author: I_may_be_drunk_right_now
author_rank: Contributor
timestamp: February 23, 2014, 05:24:47 am
content: Hi,I asked about jellybean microcontrollers because of a silly project.I bought a cheap battery powered white LED light that has a simple push on/push off switch. It's just three AAA's, a resistor, 5 LEDs and the switch, and the plastic case.I stuck it under the kitchen sink, but of course I press the light and forget to turn it off, so I wanted to add an auto-off feature.Inside the light, there's a single-side PCB about 1cm by 10cm.There's just enough height clearance to put an 8 pin DIP in there. I'll read the pushbutton and simply start a 2 minute ON cycle for every change of state of the switch.I'll short three output pins together to drive the resistor and LEDs, it's quite enough drive capability, no power transistor needed.I can add PWM drive to keep a constant illumination over battery voltage, or add fancy ramp up and ramp down behaviors, etc.That's what I mean by jellybean microcontroller.Maybe it's just the project I need to make a youtube video, very simple and has an obvious use.

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: February 23, 2014, 07:03:55 am
content: batteries cost a lot your the best thing you could do is get a wall plug i don't mean you could also do the auto off but i would make it an auto DIM just because it would be cooler

author: I_may_be_drunk_right_now
author_rank: Contributor
timestamp: February 23, 2014, 03:18:21 pm
content: Quote from: noah_fakelastnamelike_bob on February 23, 2014, 07:03:55 amBatteries are dirt cheap and there is no power socket under the sink. It's just a light I use occasionally to find something that's way in the back under the sink.If I start whacking around the mains power under the sink the condo board will get upset.

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: February 23, 2014, 06:43:10 pm
content: oh you live in a condo ok. well you could have a little pressure sensor i guess inside the cupboard but that jelly bean stuff is out of my league

author: dannyf
author_rank: Super Contributor
timestamp: February 23, 2014, 06:46:04 pm
content: I have seen a few such projects, with only one button to control a bunch leds.

author: electronics man
author_rank: Frequent Contributor
timestamp: February 23, 2014, 06:47:12 pm
content: Use a microcontroller such as arduino or u could use a 555 timer

author: SeanB
author_rank: Super Contributor
timestamp: February 23, 2014, 06:54:25 pm
content: How about a microswitch attached to the door that powers the light when you open the door? Simple and cheap.

author: I_may_be_drunk_right_now
author_rank: Contributor
timestamp: February 24, 2014, 11:08:46 pm
content: Quote from: SeanB on February 23, 2014, 06:54:25 pmI like you. Direct and to the point. That's engineering. But I was planning on buying more of these cheap lights and putting them elsewhere so I want to keep it simple.Also, I don't want the light on every time I open the door, just when I look for stuff in the back.
Simple LED PSU Fade in mod (Works with any regulated PSU)  - Page 1
Forum section: electronics / projects

author: Berni
author_rank: Super Contributor
timestamp: April 26, 2015, 08:19:54 pm
content: Recently installed a bunch of 12V LED lightning in the living room and along with the LED bulbs picked up a genuine WonHunLow switching PSU. The thing is pretty decently built inside considering how cheep it was(Fused, MOVs, clearances etc) but those chinese caps are probably not going to live long (Eh il replace em when it happens). I soon discovered that it had a almost 1 second startup time upon getting mains input. I fixed that by changing some caps, but then i got another idea. What if i gave the LEDs more style by making them fade in slowly like a halogen. And so this simple afternoon project was born.The mod works by tapping in to the feedback circuit of the PSU in order to make it slowly ramp the output voltage. This is done by adding a large capacitor in series with the top divider resistor of the PSU. This cap slowly charges up and makes the feedback network see less voltage, making the PSU compensate by boosting the output up. That is until the diode across the capacitor starts conducting and stops the process.(I used a blue LED because i couldn't find a 3V zenner in my part bins)That worked great alone, however i found out that the capacitor discharges very slowly. This meant that the PSU needed to be off for more than 30 seconds to make it ramp properly on next switch on. To solve that i added the transistor Q1 that shorts the capacitor when the output falls below about 7V. This is done by Q2 turning off when the divider on its input can't forward bias the base anymore and so lets R2 turn on the base of Q1. R3 is there just so that the base of Q1 does not see too much negative voltage and breakdown.The circuit was built and frankensteined in to our victim PSU and it actually worked!This is a scope trace of the output voltage, showing a nice quick shoot up to the point where the LEDs can turn on and then slowly ramping up to full brightens. On turn off later there is a slow output capacitor discharge that gives the mod circuit time to discharge the timing capacitor.I re soldered the wires in to more permanent locations, put the mod cirucit in some heatshrink and buttoned the puppy up, ready to be installed in the living room. Since this mod just taps in to the feedback circuit i thought id share it since it can be done to any regulated PSU out there, but the resistor values might need to be adjusted for anything else than 12V.
Simple LED pulser - Page 1
Forum section: electronics / projects

author: mawyatt
author_rank: Super Contributor
timestamp: September 26, 2025, 01:17:12 pm
content: While posting on EDN Design Ideas a reader reply mentioned using this inverted transistor to pulse a LED. Adding a LED in the inverted 2N3904 Collector to Ground produces a simple LED pulser.Check here for the circuit concepthttps://www.eevblog.com/forum/testgear/fooln-around-with-dso-awg/msg5939296/#msg5939296And here for EDN article, note reader comments:https://www.edn.com/unusual-2n3904-transistor-circuit/Best

author: Dan N
author_rank: Contributor
timestamp: September 26, 2025, 01:53:43 pm
content: Interesting idea.When I needed an LED flasher for a piece of equipment where the supply could vary from 6-14V I found that almost all of the common flasher circuits frequency varies with voltage. Does yours?I found this circuit where the frequency doesn't vary much and used with R=1.5M, C=1uF, and added 1k base resistors because simulation showed peak base currents higher than I liked:https://web.archive.org/web/20190415225416/http://www.josepino.com/light/transistor_led_flasher

author: mawyatt
author_rank: Super Contributor
timestamp: September 26, 2025, 02:22:28 pm
content: Quote from: Dan N on September 26, 2025, 01:53:43 pmYes the pulse rate varies with bias voltage as this determines the charging current for the shunt capacitance. This circuit is about as simple as possible, requiring just 1 resistor, 1 cap, 1 transistor and the LED.Best

author: jwet
author_rank: Frequent Contributor
timestamp: September 26, 2025, 03:01:08 pm
content: Interesting thread. The negative voltage stuff is just weird.Note 555 type circuits don't vary with voltage, the charging current is an RC but the thresholds are 1/3, 2/3 of Vcc so track. Modern CMOS 555's draw flea power.

author: themadhippy
author_rank: Super Contributor
timestamp: September 26, 2025, 03:46:29 pm
content: bring back the lm3909

author: jwet
author_rank: Frequent Contributor
timestamp: September 26, 2025, 04:06:01 pm
content: One the 3909 vector- I ran into this recently- Ken Sheriff reverse engineered one- fascinating hacking.https://www.righto.com/2021/01/reverse-engineering-low-power-led.html
Simple MOD for a LED light for bike - Page 1
Forum section: electronics / projects

author: Yamin
author_rank: Frequent Contributor
timestamp: August 12, 2021, 06:06:43 pm
content: Hi guys,Wanted your opinion about a simple circuit I'm thinking of MODing. Basically its one of those LED lights on a bicycle. When you turn it on and off and on again it changes the brightness. Its controlled by a unidentifiable IC RL001.Anyway I want to change the button to a latching type button and when its on the LEDs are at full brightness. Take out the control IC altogether.I've attached the original circuit and the two options I was thinking ofOption A:When I place the switch at the position and when its in the off position the LEDs are completely off (obviously). But whats interesting to me is that if I touch the open end near the 1M resistor the LEDS come on. If I touch it with the DMM probe it lights as well. I'm wondering why that is? Its not a huge issue but my reservation is that if the light is assembled and if there is any sort of static it would turn the LEDs slightly on which would drain the battery.Option B:This is the simplest design I can think of. But wanted to ask if there would be any issues by placing the switch there. Do I need capacitors across the switch?Also I'm thinking of changing the 5.6K resistor to a 10K resistor by doing so low current is drawn from the supply and I'm pretty happy with the illumination level.Lastly I wanted to ask with this circuit how does the transistor used. Is it used for the purpose of a constant current source? Or is the only reason because the light was designed to illuminate at different brightness.While experimenting I noticed that I can take down the input voltage(supposed to be 6V) all the way down to 3ish volts without seeing any difference in the illumination level.Thanks in advance.P.S: The transistor is 8550

author: thm_w
author_rank: Super Contributor
timestamp: August 14, 2021, 01:13:59 am
content: QuoteThink of your body or DMM as a 10M resistor, if you touch it you are connecting the circuit somewhere.S8550 transistor is:Continuous Collector current (IC) 500mACurrent Gain (hFE), 85 to 300So if Vcc is 6V current should be something around 80 to 280mA.Then you won't see a drop in current or brightness until you reach the voltage of the LEDs + the voltage across the transistor.You should play with it in a simulator and get a feeling for the circuit.

author: timenutgoblin
author_rank: Regular Contributor
timestamp: August 14, 2021, 01:52:44 am
content: Quote from: Yamin on August 12, 2021, 06:06:43 pmHave you considered a soft start switch?
Simple MOSFET load switch design - Page 1
Forum section: electronics / projects

author: FBMinis
author_rank: Regular Contributor
timestamp: April 21, 2021, 09:17:15 pm
content: I would like your help designing a circuit that would use a PIR sensor to turn ON an ESP32 CAM.The PIRoutputs 3.3V when it detects motion and remains HIGH for up to 5min ( 1sec min, user defined). This signal would pull the P-Channel Mosfet LOW, powering the ESP32 CAM, which would send me a notification to Telegram with the option to take a photo. I would then either turn the camera off by pulling the N-Mosfet gate LOW again (assuming no motion detected by the PIR), or I could just set the output of the PIR to remain high for only couple of minutes to give the camera time to send a notification and expect for my instruction to take a photo or not.I read this document:https://www.onsemi.com/pub/Collateral/AND9093-D.PDFNot sure if I got it right and which resistor values to use. The camera momentarily pulls up to 300mA when doing WIFI operations.Please take a look at the circuit diagram in attachment.

author: ledtester
author_rank: Super Contributor
timestamp: April 21, 2021, 11:53:42 pm
content: QuoteJust connect the PIR to a GPIO pin and put the ESP32CAM in sleep mode waking up when the GPIO pin changes.Have a look at this project:https://randomnerdtutorials.com/esp32-cam-pir-motion-detector-photo-capture/

author: FBMinis
author_rank: Regular Contributor
timestamp: April 22, 2021, 10:01:07 am
content: Quote from: ledtester on April 21, 2021, 11:53:42 pmThe ESP32 CAM consumes 6mAh during deep sleep, which isn't adequate to a battery powered project.

author: ledtester
author_rank: Super Contributor
timestamp: April 22, 2021, 03:23:17 pm
content: Quote from: FBMinis on April 22, 2021, 10:01:07 amOk, I see.Here is some more info I found related to the "deep-sleep strategy":This article investigates the source(s) of this current consumption:https://time4ee.com/articles.php?article_id=126It suggests performing some surgery on the board which allows the existing P-MOSFET to control power to the SD card and camera.And this github discussion shows how someone did this for the camera power:https://github.com/espressif/esp32-camera/issues/247#issuecomment-801109299

author: FBMinis
author_rank: Regular Contributor
timestamp: April 22, 2021, 10:02:58 pm
content: I am aware of that, thank you. However, my project does not rely on deep sleep.I'd still appreciate some criticism regarding the circuit in my first post.
Simple Nimh pcb/bms for Raspberry Pi zero - Page 1
Forum section: electronics / projects

author: milika
author_rank: Newbie
timestamp: April 01, 2017, 02:37:00 am
content: Hello everyone, been reading the forums and watching YT for a while now, but now I will start bothering for advicesI have a simple rpi0 project and would love to make a 4 cell nimh charger/discharged (non English speaker sorry), so i could power rpi0 from it, and just plug in to 9v-12v when batteries are empty, cell phone style...Been roaming the net for nice MAX713 circuits with low voltage cutoffs, but could not figure it out completely. Some example of 2 cell, but they are not making sense, for me. Also no low voltage cutoff integrated at all...I would cal myself begging in electronics so be merciful...Could not believe i can not find simple already made pcb for this... (there is 100s for li-ion)Any help with simple circuit would be great...Thanks!!!
Simple out-of-the-box software protocol - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: July 05, 2024, 12:03:37 am
content: Hi,I have a custom master PCB connected to a few slave custom PCBs via serial. In some systems they are connected via I2C and in other systems they are connected via RS232. And they all run STM32 micros.I am looking for out-of-the-box protocols with source code available, one for the I2C and one for the RS232. They need to be very simple because only very little and simple data is exchanged (enable motor, change state machine state, turn LED on/off, etc) and none of it is time critical. But possibly they must be reliable (i.e. including some level of self recovery such as timeout).Which protocol would you suggest and where can I find the source code?Thank you as always

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 05, 2024, 12:15:27 am
content: If you have a mix of i2c and UART, I think STM32 supports 9-bit UART mode, where 9th bit selects address/data ?Your messages can then be similar, to any i2c EEPROM - [Device address] [RW.Internal Address][Data Tx or Rx][optional checksum]The protocol is very simple, it is just a means to write/read to a small memory array, and you decide in upper SW what the memory contents mean.

author: tggzzz
author_rank: Super Contributor
timestamp: July 05, 2024, 04:26:29 am
content: Quote from: ricko_uk on July 05, 2024, 12:03:37 amDefine "reliable", or specify what can and cannot be tolerated.People have been reinventing TCPpoorlysince the 80s.TCP can run over just about anything, e.g. RFC2549.

author: brucehoult
author_rank: Super Contributor
timestamp: July 05, 2024, 04:52:06 am
content: One SLIP to rule them all...

author: r6502
author_rank: Regular Contributor
timestamp: July 05, 2024, 02:53:32 pm
content: Hi ricko_uk,have you heard aboutMQTT?This is something, we are using in our company.BR Guido
Simple PC GUI programmable DSP analog i/o audio filter board? - Page 1
Forum section: electronics / projects

author: Circlotron
author_rank: Super Contributor
timestamp: April 01, 2018, 12:05:15 pm
content: With all these cheap small boards you can get nowadays, has anyone seen one that you can connect via USB to your pc and with some sort of GUI set audio filter parameters e.g low pass, band pass, frequency, slope etc? Analog line level input and output.

author: KhronX
author_rank: Frequent Contributor
timestamp: April 01, 2018, 12:11:36 pm
content: At least over on the DIYaudio forums, the MiniDSP stuff seems to be quite popular. I'm sure there must be others, as well. Although the ones i'm thinking of, are "only" the line-level stuff.I wouldn't be surprised if they had some that included amps as well, but you can google that, i'm sure.Or if you're feeling adventurous, you can cook up your own with Analog Devices' ADAU1401/1701 chipsThey're analog 2in/4out DSP's, around 3-4$ a piece, i think?I've still got a couple samples from years ago, still waiting to be put to use
Simple PCB Design Review - Page 1
Forum section: electronics / projects

author: 691175002
author_rank: Regular Contributor
timestamp: February 28, 2015, 03:18:14 am
content: I'm trying to fit a fairly simple circuit into a DB9 Backshell. I don't really know what I'm doing but I've tested the parts on a breadboard and it works.The circuit sits in the middle of a servo encoder cable and converts sinusoidal encoder signals to quadrature signals. There are a bunch of hall sensors, temperature sensors and miscellaneous other wires that are passed through unaltered. All the work is done by the IC-NV chip. Both the input and output signals are differential.Relevant datasheets:http://www.ichaus.de/upload/pdf/Nv_c1es.pdfhttp://www.ti.com/lit/ds/symlink/ua9638.pdfNothing particularly notable able the circuit other than its size. Maximum frequency of the sine input is 200KHz, and the square wave is 2MHz.I will have it made on 0.8mm FR4 so it can slide between the connector pins. The circuit is 20x18mm. The display grid is 1mm. It passes the Seeed Fusion DRU file using 0.3mm vias.Could you please let me know if I've done anything stupid.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 28, 2015, 04:13:03 am
content: Seems reasonable...I would make these changes:- Traces between SOIC pads are undesirable, because they screw up AOI (automated optical inspection) -- looks like shorts. Even though they're supposed to be shorted, that's the point, but yeah. Not that that matters any for hand assembly, just good practice.- There are only three vias/through pads connecting the top and bottom ground fills. While that's probably fine for something so small, I like to put vias in all ends/peninsulas and corners to better marry the two together. Again probably doesn't matter here, given the small size, but it's a good practice.Tim
Simple Power Supply Design - Page 1
Forum section: electronics / projects

author: snailFury
author_rank: Contributor
timestamp: January 17, 2015, 08:55:22 pm
content: Hi All, I've been messing around in the KiCad schematic editor. I've come up with this schematic for a power supply.I've got a 40VA transformer going to a bridge, the output of which is about 37V. Then I've got a capacitor, a voltage divider (to get the voltage into the range of the 78XX which is 35V max), then capacitors on the outputs.I've breadboarded this and it works, but the resistors I used are the wrong rating, it works but they get hot. Is this all I need for a simple regulated supply?Anyone have a recommendation on capacitor sizes?I attached the schematic as a pdf.thanks

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 17, 2015, 09:49:58 pm
content: That's a resistor divider backwards...Resistor dividers are fine if you don't need to draw any current from them, but as soon as you do... yep.. you have that problem.There's not really any desirable benefit at all from using resistors in a power supply, even if you have excess voltage and current to spare.Better to get higher input voltage regulators or lower voltage transformers, ideally matched to each other, so you don't have this problem. The regulators themselves will also get very hot when dropping more than a few volts, so that you won't be able to use their full load capacity (over an ampere) unless you use massive heatsinks. A 7812 in this circuit (with >30V input) will probably give up around 300mA, even with.Tim

author: snailFury
author_rank: Contributor
timestamp: January 17, 2015, 10:03:52 pm
content: Ok, so basically, though I might get some voltages right, I will have problems with current limitation. Is that right?

author: void_error
author_rank: Frequent Contributor
timestamp: January 18, 2015, 07:37:21 am
content: I'm guessing you're using a 24V transformer? 15V would be enough for the 7812 under full load. That would give you roughly 20V at the input of the regulators at no load. For the capacitors check the datasheet, or use 100nF caps at both the input and output of the regulators.Quote from: T3sl4co1l on January 17, 2015, 09:49:58 pmYou can useLM317pre-regulators (Figure 5) to drop the input voltage and spread the power dissipation.Even with massive heatsinks the junction-case thermal resistance is probably high enough that it doesn't prevent them going into thermal limiting mode. Had that happen with a LM317 under similar conditions.Some load resistor across the regulator output is required, check the datasheet for minimum load current. It's something like 5mA.
Simple power supply hack - Page 1
Forum section: electronics / projects

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: January 09, 2012, 05:31:29 pm
content: Sometime ago i got these two power supplies (they were so cheap i could not resist) Voltcraft RNG 1501 and 1502. The 1501 is 15 V -1 A and the 1502 is 15V- 2 A with adjustable current limiting.Uploaded withImageShack.usI did not have time to check them out until now and compare them with a similiar Chinese power supply. The power supplies were originally built for German market so they should be better!Check the heatsinking of Chinese unit compared to this one :Uploaded withImageShack.usAlso the units are properly grounded while the Chinese one is not. The Chinese one used a ultra thin power cable with a knot as strain relief. The German units even have heat resistant insulation on the wires. They also put heat shrink tubing on the mains switch and used a proper one (while Chinese one used a crappy switch, certainly life threatening). Altrough if the wire somehow got discconected it could easily contact the low voltage side and give you a shock.Uploaded withImageShack.usUploaded withImageShack.usThe transformer in Chinese unit was burned so im powering it trough a wallwart. Im using single voltage and the display and electronics are powered trough a dropper resistor (original transformer has multiple windings for powering them). Compare the transformer removed from Chinese unitUploaded withImageShack.usI noticed the electronics are completly the same, there is even place for the current pot, so i just had to mod it :Uploaded withImageShack.usHere is step by step to hack the power supply without current limiting to one that will have it...Solder 2 missing jumpers:J4 and J 5Uploaded withImageShack.usSolder this bridge togetherUploaded withImageShack.usRemove R3Uploaded withImageShack.usRemove this sticker carefullyUploaded withImageShack.usInsert a potentiometer in a prepared hole and solder its wires to PCB where is as X1 - A (above the voltage pot):Uploaded withImageShack.usAssemble and enjoy your free current limitingUploaded withImageShack.usUploaded withImageShack.us

author: saturation
author_rank: Super Contributor
timestamp: January 09, 2012, 06:35:02 pm
content: Great job and photos, thank you. How do they regulate and ripple under load?

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: January 09, 2012, 06:50:20 pm
content: Quote from: saturation on January 09, 2012, 06:35:02 pmUh um to be true i even did not bother to do any measurements except calibrating the display accuracy. I have much better power supplies for serious stuff, but i can do it if there is interest
Simple precision frequency comparator - Page 1
Forum section: electronics / projects

author: S57UUU
author_rank: Regular Contributor
timestamp: August 11, 2021, 05:40:00 pm
content: Hello!Since I see many people here playing with OCXOs, GPSDOs, and stuff, I thought this littleproject of mine might be of interest:http://lea.hamradio.si/~s57uuu/scdsp/frcomp/index.htmlMarko Cebokli

author: fourfathom
author_rank: Super Contributor
timestamp: August 11, 2021, 06:28:23 pm
content: Thank you for posting this. Very well done!

author: schmitt trigger
author_rank: Super Contributor
timestamp: August 11, 2021, 06:30:45 pm
content: Very interesting read. Thanks for sharing.

author: mikerj
author_rank: Super Contributor
timestamp: August 11, 2021, 08:14:54 pm
content: Really nice job, you've clearly put a lot of work in this.