hybridfree/eevblog-posts huggingface dataset:
Chorus Pedal help (not working) - Page 1
Forum section: electronics / beginners

author: Scornn
author_rank: Contributor
timestamp: May 29, 2024, 05:07:10 am
content: I tried to make one of these a few weeks ago and I decided it would be best if I started again. Everything was much cleaner and I had an overall smoother process putting this one together. However this one also doesnt work. Bypass and power works but when I click my footswitch I only get signal if I flip the switch from VIB to CHORUS and even then, its dry signal, the same as the bypass. Any help would be appreciated. Thanks!https://www.diyguitarpedals.com.au/shop/boms/Lich%20King%20Chorus.pdf- Build, schematics, components.

author: selcuk
author_rank: Frequent Contributor
timestamp: May 29, 2024, 06:52:30 am
content: I don't know about the circuit but isn't there a short on right side of SW2?

author: Scornn
author_rank: Contributor
timestamp: May 29, 2024, 06:56:58 am
content: i see what you mean but unfortunately not, as much as the picture makes it look like there is

author: pcprogrammer
author_rank: Super Contributor
timestamp: May 29, 2024, 08:48:54 am
content: Looks like a very well documented piece of kit.You mention that with the switch in VIB position it gives an output signal, so that means the input amplifier (U1A) is working. This means there is either a problem with the output filter, the bucket brigade, LFO or the PLL.You can test the output filter by removing the bucket brigade IC and connect pin 3 to pin 7 on the now empty ic socket. If there is sound on the output with SW1 in the open position, it narrows it down to the bucket brigade, LFO or the PLL.These are harder to test without some test equipment. The LFO could be tested with a LED in series with a resistor, and maybe a FET to drive it and lower the load on the LFO. On low frequency you should see it turn on and off. The PLL most likely needs an oscilloscope to check if it is working. When both these generate the needed signals it leaves the bucket brigade, and there is nothing to check on that. If it does not work it will be dead.
Chossing the proper fuse - Page 1
Forum section: electronics / beginners

author: tutzeroone
author_rank: Newbie
timestamp: March 08, 2016, 10:16:34 am
content: Hi everyone,I've got a desktop lamp that looks roughly like this.The base contains a power switch, a fuse and a cheap 220V > 12V transformer and the arms of this thing are acutally used to carry the current from the transformer to the lamp.The fuse is rated 250V 6.3A while the bulb is supposed to be a 12V 35W unit, so I was wondering is 6.3A for the fuse wasn't too much and possibly unsafe.I actually went a bit rough on the lamp and shorted the arms, the fuse blew but it took approx. 3s which seems "long" for a safety feature.What do you think about it ? Should I use a 6.3A fuse or one with a lower value ?Thanks in advance for your help.

author: MK14
author_rank: Super Contributor
timestamp: March 08, 2016, 10:28:27 am
content: Quote from: tutzeroone on March 08, 2016, 10:16:34 amCan I check my understanding.Is the fuse on the mains side (115V/230V) or on the 12V side ?12V x 6.3A = 75.6WOn startup from cold, as a rule of thumb bulbs (filament ones), use something like x10 the usual current (briefly because the bulbs resistance is considerably lower, when cold).So it could be about right ?Also the fuse's 250V (as I assume you realize), is only a rating (its maximum safe voltage). NOT anything to do with the wattage.Because Wattage = Actual Voltage x Actual current

author: Brumby
author_rank: Unknown
timestamp: March 08, 2016, 11:42:53 am
content: This is the question thatmustbe resolved for any clear answer...Quote from: MK14 on March 08, 2016, 10:28:27 am

author: tutzeroone
author_rank: Newbie
timestamp: March 08, 2016, 12:36:01 pm
content: Thanks for your answers MK14 and Brumby, I just checked and the fuse is on the 12V side, I thought it was on the mains side (220/230V here) which seemed odd.But after what you explained MK14 it seems to be fine ! I didn't knew thoses bulbs had that kind of behaviour, thanks for explaining it ! The 6.3A fuse should be right so. Thanks for your help !

author: MK14
author_rank: Super Contributor
timestamp: March 08, 2016, 12:44:29 pm
content: Quote from: tutzeroone on March 08, 2016, 12:36:01 pmYou're Welcome!yes, filament bulbs resistance is rather odd.It's an easy mistake to make.
Christmas Lights (LED) interfere with a Garage door opener... hmm - Page 1
Forum section: electronics / beginners

author: BTBlueSkies
author_rank: Newbie
timestamp: January 06, 2016, 11:19:59 pm
content: My co-worker just explained an issue to me that his christmas lights (leds) were causing his garage door opener to not work.What would be the reason? I have some electronics understanding, so I can work with led's and such with no issues. However, the driver circuit for these lights must have some circuitry that can produce interference in the 300MHz range.The only reason I can think of is a switching type of behavior in the driver circuit that may be making noise in that range.If I were to buy LED lights, how can I know up front if they are noisy like this? Why would this be allowed to happen in the market? How could I shield the light if I do end up in this situation?Thoughts?and Thanks!

author: ice595
author_rank: Regular Contributor
timestamp: January 06, 2016, 11:47:57 pm
content: Are both the LEDs and garage door opener on the same electrical outlet?If so then it might be conducted interference instead of radiated EMI.

author: Azhar
author_rank: Regular Contributor
timestamp: January 12, 2016, 09:36:54 am
content: connect the lights with a different power outlet. maybe try to isolate the LED driver with a aluminium foil or put it in a tin
CIRC code generation (CDROM) - Page 1
Forum section: electronics / beginners

author: Allegas
author_rank: Newbie
timestamp: November 15, 2017, 11:57:19 pm
content: Hey everyone!I am currently thinking over a low-level cdrom optical pickup emulator (fpga+arm). I took a look at ECMA-130 doc, there is a diagram of byte interleaving. The main problem - I do not understand what "delay of two symbols" means, as well as "D-4 delay lines" and "delay of 1 symbol", mainly because of my poor english skills. Do these delay lines mean, that I must take "delayed" bytes from following F1 frames? And what about last 98th frame, which has no following frames?A simple explanaition would be just great.

author: helius
author_rank: Super Contributor
timestamp: November 16, 2017, 01:01:46 am
content: As best as I can understand it, each box containing "tD" means that it represents a t-stage shift register, in which each signal that enters, comes out t cycles later. You do need to know how the registers are initialized by a reset, which should be specified somewhere in the document. I don't know what the small "D-4" under the unequal delay section means: maybe "D" is itself variable, so the length of delay changes based on the frame's position in the sector?Quote from: Allegas on November 15, 2017, 11:57:19 pmContrariwise, the symbols which pass through the delay line are usedbylater frames, which mean they must comefromearlierframes than the one being encoded. This is made clear by the penultimate column of the chart, which shows the word of the audio data from which each byte of the sector derives. For example, byte 18 says "W12n+6-12(18D+1),A", which tells you that it comes from "W12n+6,A", which derives from the input word "L6n+3", after being delayed by "18D+1" frames.Note that there is an obvious typo in the chart: the last four rows should say "/P12n-12", etc.QuoteThis should also be explained in the document. Either the registers are reset, throwing away the symbols in the pipeline, or they continue to flow into the next sector.

author: Allegas
author_rank: Newbie
timestamp: November 16, 2017, 09:41:05 am
content: Quote from: helius on November 16, 2017, 01:01:46 amOh, never thought about these numbers in this way. Now I understand the meaning of numbers at C2 encoder, thank you!So far, I do not understand : how W12n-24A corresponds with W12n-12(3), exactly what is D and what is the meaning of numbers between brackets.

author: helius
author_rank: Super Contributor
timestamp: November 16, 2017, 05:47:50 pm
content: there are 12 words of PCM in each frame (24 bytes), so "W12n" means that the same part of the generator is used for W0, W12, W24, etc in the audio stream (all natural numbers of n). "W12n-12(3)" means that the value comes from a word that is in the third previous frame (12 words per frame, times 3 frames previous).
Circuit analysis estimation techniques - Page 1
Forum section: electronics / beginners

author: ItsMike
author_rank: Contributor
timestamp: June 03, 2015, 07:38:39 pm
content: Hi everyone,I'm currently taking a "Analog Linear Circuit" course and during the course we have used the open/short-circuit time constants technique to estimate bandwidth of amplifiers.This technique seems pretty useful on real circuits where you just want to estimate the dominant pole.Are there any more of these techniques ? Or any tricks/mental shortcuts or whatever for quick estimates of circuit analysis ?

author: w2aew
author_rank: Super Contributor
timestamp: June 03, 2015, 07:49:06 pm
content: Quick and dirty estimation of gain of a common emitter amplifier without emitter degeneration is simply equal to the voltage drop across the collector resistor divided by vt (26mV).

author: rbola35618
author_rank: Frequent Contributor
timestamp: June 08, 2015, 02:54:24 am
content: Here are two examples in how to use the open time constant to calculate the bandwidth.Robert

author: LvW
author_rank: Frequent Contributor
timestamp: June 08, 2015, 06:29:45 am
content: Quote from: ItsMike on June 03, 2015, 07:38:39 pmThe gain of a common emitter stage with Re feedback (emitter degeneration) can be estimated as G=-Rc/Re.
Circuit Analysis Help - Page 1
Forum section: electronics / beginners

author: Cujo
author_rank: Regular Contributor
timestamp: January 04, 2021, 06:25:33 am
content: How do I solve for the resistance for R1?

author: retiredfeline
author_rank: Frequent Contributor
timestamp: January 04, 2021, 06:43:03 am
content: You need to know the forward voltage of the LED and the current you wish to put through it.

author: Keith956
author_rank: Regular Contributor
timestamp: January 04, 2021, 06:47:34 am
content: You use Kirchoff's laws which state that the current flowing into a node equals the current flowing out, and voltages round a closed loop must sum to zero. Put more simply, V1 + V(R1) + V(D1) = 0. And I(V1) = I(R1) = I(D1).You can then determine the voltage and current through the resistor. The data sheet for the LTL-307EE states a forward current of 20mA at 2V forward bias, its recommended operating point.So using the 1st law, V(R1) + 2 - 5 = 0 (Note the signs: current traditionally flows from + to -, and in a diode in the direction of the arrow). So V(R1) = 3V.Using the second law, the current flowing through the resistor equals the current through the diode, 20mA.So by Ohms law, V(R1) =I * R1 i.e. R1=3/0.02 = 150ohms.

author: retiredfeline
author_rank: Frequent Contributor
timestamp: January 04, 2021, 06:52:54 am
content: Are you repairing old equipment or you happen to have that model LED, from 2005 according to datasheet? Modern LEDs are more efficient and are quite bright at a few mA.

author: Cujo
author_rank: Regular Contributor
timestamp: January 04, 2021, 07:00:44 am
content: Quote from: Keith956 on January 04, 2021, 06:47:34 amThank you
Circuit assistance - Page 1
Forum section: electronics / beginners

author: OutbackBob
author_rank: Contributor
timestamp: March 13, 2017, 10:18:13 am
content: Hello,Can someone please confirm if I am reading the attached schematic properly or not.My questions:1) U101 can not be powered from battery ONLY as Q101 will be OFF unless USB is plugged in?2) What is the purpose of D100?3) Q101 is required in order to allow VIN to have +5V and prevent overcharge of battery?4) What is the purpose of R100? Does this not bypass the switch Q100 and allow current to flow permanently via 0R?Thanks!

author: OutbackBob
author_rank: Contributor
timestamp: March 13, 2017, 10:27:28 am
content: One more question:Ignoring Q101, if the circuit was powered directly by single cell lipo, using an LDO is not ideal is it as it only regulates down to 3.3v, but lipo is usable down to 2.7-3v, so a DC/DC controller (buck/boost) would be better option right?

author: pix3l
author_rank: Regular Contributor
timestamp: March 13, 2017, 03:26:16 pm
content: 1.) Other way around: Q101 will conduct when it's gate is low (it is a P-channel mosfet)2.) D100 makes sure that the gate of Q101 is controlled by the 5V of the USB and not by the output of Q1013.) Q101 has nothing to do with overcharging protection. It serves as a way to make sure that you can power your circuit AND charge the battery at the same time4.) R100 will probably be an optional footprint: just in case you don't want to use Q100 to be able to switch on/off the load

author: pix3l
author_rank: Regular Contributor
timestamp: March 13, 2017, 03:33:59 pm
content: Regarding your last question: yes that's true but usually buck/boost converters need quite some external components (coils / fets / caps). You might want to have a look at battery charger chips that have an integrated boost converter

author: Nusa
author_rank: Super Contributor
timestamp: March 13, 2017, 04:11:23 pm
content: Quote from: OutbackBob on March 13, 2017, 10:27:28 amSingle cell is probably just so cell balancing issues don't exist.Usable doesn't mean advisable. Full charge on an 18650 is 4.2V. Probably 90% of its capacity lies above the 3.3V mark, so this may be a smaller issue than you think it is. If the output votage starts to drop, you know you either need to plug it in or stop using it.

author: OutbackBob
author_rank: Contributor
timestamp: March 13, 2017, 09:46:40 pm
content: Quote from: pix3l on March 13, 2017, 03:26:16 pmCould you not just remove D100 altogether? Or is it required to allow current to flow via it to the load instead of via the gate? What field in a data sheet specifies the max gate current?Thanks!

author: MatthewEveritt
author_rank: Unknown
timestamp: March 13, 2017, 09:50:05 pm
content: The gate of a FET is insulating, it looks like a small capacitor rather than a diode (like the base of a BJT).
circuit board damage assessment - Page 1
Forum section: electronics / beginners

author: Abe
author_rank: Newbie
timestamp: July 01, 2019, 02:27:17 am
content: I'm a newby, sort of, so pls ignore my possible ignorance. I didn't study engineering, but I studied physics and was a hobbyist. Then, electronics recently became a source of income. I'm still uncertain when it comes to being absolutely sure that a board has been fully restored. l work on fairly high-power circuits like 3-phase VSDs, so the client can't always give me the whole device to troubleshoot, just faulty sections of it, usually with water damage. How do I make absolutely sure that I've found all the damaged components BEFORE connecting the board back into the system and powering it up? I can't always simulate ideal test conditions. Is there a clever method, or is this just the nature of the beast? Also, I can't always confidently identify SMDs by the packaging markings.

author: cur8xgo
author_rank: Regular Contributor
timestamp: July 01, 2019, 09:31:42 pm
content: Quote from: Abe on July 01, 2019, 02:27:17 amYou need to design tests that can evaluate the board function out of the unit. For things you can't evaluate directly because they need to be in-system or you have no way of simulating real world conditions, you need to come up with some rationale as to why that particular sub circuit or component is good to go..for instance if the board normally operates at 300 billion amps inside a nuclear reactor you cant really simulate that..but you can sign off that you replaced all the components that are involved in switching that high current and you also ran some tests proving that they have some functionality. Thats the best you can do and compromises like that are done every day in every industry.If the clients you are doing this for have any kind of formal quality management system they are either checking your work anyway or they would require you to adhere to strict, risk managed procedures for rework and verification. If they dont have a quality system then whatever you come up with here is probably going to be better than what they use to make sure they don't install broken stuff anyways.
circuit board manufacturer - Page 1
Forum section: electronics / beginners

author: nmmbeginer
author_rank: Contributor
timestamp: October 07, 2013, 12:58:50 am
content: hey every one i am looking for a circuit board manufacturer in the usa who is cheep reliable. all i want to do is ten small boards. so if any one know of a company please let me know

author: DarkStar
author_rank: Contributor
timestamp: October 07, 2013, 01:52:53 am
content: Definitely check outOSH Park. They're based in Portland, Oregon and specialize in small runs.

author: azi
author_rank: Contributor
timestamp: October 07, 2013, 02:06:43 am
content: I just stated using OSH Park recently and I'm very happy with them. I've already done about 7 orders.You do need to order in groups of 3, so if you need exactly 10, have to buy 12. Also, they use a dark purple solder mask that's not going to suit everyone's tastes.Aside from those things, it's a great prototyping or small run service. The turnaround is about 10 days for me here in Arizona.If you use Eagle, you can upload your .brd files directly and it's very easy to use! The charge is simply $5 per square inch for 3 boards, and there are no additional costs. You get the boards shipped loose in a purple plastic bubble envelope.

author: Sar
author_rank: Contributor
timestamp: October 07, 2013, 04:52:49 am
content: Third for OSHPark. Previous to a project I did this year, the last board I had manufactured commercially a few years cost close to $80 dollars for 2 fairly small boards. They came with no solder mask or anything else, just bare copper on some FR4.This year I needed some custom boards done, was led to OSHPark through a friend and wow! the whole process and final product was more than I could have expected.

author: NoNRG
author_rank: Newbie
timestamp: October 07, 2013, 04:59:26 am
content: Advanced Circuits is a good online board manufacturer. They get more expensive for multilayer boards, but are pretty cheap for a 2 layer.http://www.4pcb.com/

author: chibiace
author_rank: Regular Contributor
timestamp: October 07, 2013, 06:04:33 am
content: done my last 3 runs with seeed. boards turned out alright.
Circuit board repair on a Miller Welder Model Max Star 16 1 stl - Page 1
Forum section: electronics / beginners

author: dingalberry13
author_rank: Newbie
timestamp: May 22, 2025, 09:18:20 am
content: Yes my circuit board arc out on the power supply side of it it arked out and blew out the ceramic disk capacitor and it blew the solder in fuse what caused it I don't know I'm thinking of power surge but I'm trying to replace these components to see if it works and I have a question on the ceramic disk capacitor I have a partial number on the old one and I have a whole bunch of new ones in a plastic tote that I acquired or trying to find the right one the correct one to replace it and go from there I'm a beginner I've taken more stuff apart than I've put back together I'm trying to find someone that can lead me in the right direction or guide me or help me thank you The partial numbers I have on the original ceramic disk capacitor are 75L20 and the number below that is 2042 I can't find no literature on this circuit board from the manufacturer all they want to do is sell me a new circuit board and I don't have that kind of money

author: dingalberry13
author_rank: Newbie
timestamp: May 22, 2025, 01:46:20 pm
content: I figured it out I solved it I fixed it i'm proud of myself I just got to go to skycraft and get a solder infused because I piggybacked bus views it was way too small I soldered it to the solder then fuse and just to see if it will work and it did but I'm so happy this welder has been broke for quite some time now and now it's fixed just thought I'd let you all know

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: May 27, 2025, 07:41:55 am
content: Good to know that you got it working. Congrats.

author: Analog Kid
author_rank: Super Contributor
timestamp: May 27, 2025, 07:44:01 am
content: Now you just need to learn how to use punctuation.
circuit breaker finder doesn't work with isolated AC? - Page 1
Forum section: electronics / beginners

author: ledtester
author_rank: Super Contributor
timestamp: June 06, 2024, 08:21:52 pm
content: I was playing around with a Sperry CS550A circuit breaker finder:https://www.sperryinstruments.com/en/p/CS550A/Sperry-Instruments-CS550A-Circuitand I found that if I plugged the transmitter into my Heathkit IP 5220 Variable Isolated Power Supply the receiver didn't pick up the transmitter's signal.The emitted tone from the transmitter was a slightly lower frequency than you would hear from a regular wall outlet, but even going through the "calibration" procedure for the receiver didn't work.The transmitter only has two prongs - I'm wondering what's going on...Operating instructions for the CS550A:https://www.sperryinstruments.com/-/media/inriver/CS550A_USE.pdf?modified=20200714143629

author: Manul
author_rank: Super Contributor
timestamp: June 06, 2024, 11:19:43 pm
content: I imagine, this device injects a frequency which is quite high, like in kHz or 10s of kHz range. In that case, it is expected that signal does not pass very well through a mains transformer, especially when the rest of circuit (mains power line) is quite low impedance, it simply gets attenuated too much.
Circuit breaker question - Page 1
Forum section: electronics / beginners

author: Crambone
author_rank: Frequent Contributor
timestamp: June 24, 2023, 12:43:58 am
content: If I have a 240 vac 40 amp load can I protect it with a single pole 40 amp breaker on one leg of the 240 vac?

author: Monkeh
author_rank: Super Contributor
timestamp: June 24, 2023, 12:49:50 am
content: Ponder the outcome of a ground fault on the unfused leg. And then hire an electrician..

author: helius
author_rank: Super Contributor
timestamp: June 24, 2023, 01:54:45 am
content: If using the common 120-0-120 North American split-phase power, you must use ganged two-pole circuit breakers on 240V circuits.

author: WattsThat
author_rank: Frequent Contributor
timestamp: June 24, 2023, 04:56:55 am
content: No. You need a two pole ganged breaker as mentioned and #8 awg wire. If you use 8/2 with ground, mark the white lead with black tape on both ends.Ovens/Ranges/Dryers now require a GFCI breaker.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: June 24, 2023, 05:25:28 am
content: You have to have two adjacent slots free to get 240 out of an American panel.
circuit breaker/fuse for relay switched fail safe temperature sensors  - Page 1
Forum section: electronics / beginners

author: vjekobalas
author_rank: Regular Contributor
timestamp: September 22, 2022, 09:22:02 am
content: I would like to use a uC + relay with 230V output to control a 230V input/400V three phase output contactor.The contactor is connected to a 3kW water heater/3 elements).At the moment, the setup is not controlled by a uC+relay but rather a 230V timer, so I'm using two230V bi-metal temperature sensors and an automatic circuit breaker/fuse in series in the 230V circuit for safety.When I replace the timer with a uC+relay, what is the best fail-safe mechanism and "automatic fuse" to useand how can I keep the uC alive in case of worst case failure (e.g. both bi-metal sensors are shorted)and sense the failure ?

author: rooppoorali
author_rank: Regular Contributor
timestamp: September 23, 2022, 03:48:23 pm
content: I think opto isolated relay is an option. Let's see what others have to say.

author: vjekobalas
author_rank: Regular Contributor
timestamp: September 27, 2022, 08:45:54 am
content: At the moment, the bi-metal temperature sensors are in the 230V circuitwhich drives the contactor. I also thought of using a uC driven opto-isolatedrelay with NO contacts to again switch the same 230V circuit.My aim is to have the uC to communicate with a more powerful uC/pc etc.for central processing.The thing I was not sure about was the "usual" setup/circuitry used for the followingassuming the more powerful uC/pc needs to be informed:- fuse/safety in 230V circuit for the case both bi-metal temp sensors short circuit andhow to sense the failures- check that the 230V circuit power is on/off, check each phase of 400V circuit is on/off- check that the uC power is on/off
circuit design and analysis  - Page 1
Forum section: electronics / beginners

author: majorkuso
author_rank: Contributor
timestamp: July 24, 2015, 08:43:38 pm
content: I am wanting to get better at design and analysis. what resources could I use to achieve this? I understand components by themselves,but when I try to understand them together I usually go blank when I see a complete schematic.

author: Simon
author_rank: Unknown
timestamp: July 24, 2015, 08:47:16 pm
content: you can build it and investigate it. Usually a circuit can be broken into blocks who's response is known

author: Electro Fan
author_rank: Super Contributor
timestamp: July 24, 2015, 11:58:46 pm
content: +1 for building and measuring whatever combination interests you in blocks or pieces at a time - try different test points and different value components until it becomes clear what is causing what.When you run into something that needs explanation, if the Internet in general doesn't help, try searching YouTube - it's a pretty amazing resource; a picture is worth a thousand words and video is worth about 24-30 pictures (frames) per secondIf that doesn't clear things up and you can post a very specific question (and maybe include some images or schematics of the circuit in question) there are probably lots of people here who can help sort it out.Sometimes it just takes time.

author: tggzzz
author_rank: Super Contributor
timestamp: July 25, 2015, 03:34:49 pm
content: Quote from: majorkuso on July 24, 2015, 08:43:38 pmThere are certain "design patterns" which you learn to recognise, e.g. a common-emitter amplifier, a low pass filter, a logarithmic amplifier, etc etc etc. Learning to recognise those can only be done the hard way, and it is easily thwarted by ignorant b*******ds that don't draw the circuit in a way that highlights the pattern. There are too many of those nowadays, and there is a special circle of hell reserved for those that have inputs on the right and outputs on the left.Often the best help is a circuit description which mentions the design pattern by name.

author: edavid
author_rank: Super Contributor
timestamp: July 25, 2015, 03:54:00 pm
content: 1. Read "The Art of Electronics" (2nd edition is good enough if you need to save money)2. Install LTSPICE and run the examples
circuit  diagram on line library  - Page 1
Forum section: electronics / beginners

author: JohnWW
author_rank: Contributor
timestamp: October 03, 2017, 03:27:49 am
content: Hello AllLooking for a online (hoping for free) circuit diagram and schematics library. Mainly looking for something that includes power supplies.Thanks

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: October 03, 2017, 04:04:02 am
content: Depends upon what you mean power supplies. In old days we used to use High Country Service Data for TVs, VCRs Microwaves etc.http://www.hcsd.com.au/These included full circuit diagrams and was a paid service. Since the internet...these services are used less and less an some free places have shown up.But for power supplies...if you mean computer PSUs....then probably not. mfgrs change design so much they hit the market. Or try this link in the repair forum:https://www.eevblog.com/forum/repair/repair-documents-and-links-sticky-me-please-mods/

author: JohnWW
author_rank: Contributor
timestamp: October 03, 2017, 04:24:55 am
content: spend a lot of time fixing power supply's for flat panel displays. It there a good online library for that?Thanks

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: October 03, 2017, 05:04:06 am
content: Meh....after repairing the first 5~6.... their SMPSs are all the same.I have found these type of PSUs part number online. On the PCB will be lots of numbers. One Sequence or part there of will probably pop up. Usually drop the revision number when searching.edit:usually PCB number searches brings up other part number references for other models the PSU may fit. Sometimes a fleabay search for the panelmay give some assistance.

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: October 04, 2017, 12:38:59 am
content: Forgot Bad Caps Forum...just saw a post on EEVBlog......jogged my memory. The reason many many SMPSs fail from failing electrolytic capacitors ESR going high. This has been happening since the advent of SMPSs back in 80's and unfortunately is still in plague proportions. SMPSs put huge higher frequency ripple load current draw on voltage rails (hot side) and this heats caps which start to wander out of tolerances.Cold side caps are also prone to fail which folds the SMPS (hot side, via opto couplers) to shut-down. You can sometimes hear a "tick" which is the PSU trying to restart then shutting down because cold/hot side feedback is shutting it down....and it continues.https://www.badcaps.net/forum/index.php
circuit diagram - Page 1
Forum section: electronics / beginners

author: sarose
author_rank: Newbie
timestamp: December 03, 2020, 10:58:38 am
content: Why is it recommended to use diodes and resistors for serial communication as shown in the circuit given? It is given in datasheet of SIM800C. Why we cannot directly connect TX and RX?

author: Manul
author_rank: Super Contributor
timestamp: December 03, 2020, 11:37:22 am
content: It is primitive level shifting. UART devices need to use same logic levels, like for example 0-5V. If two devices use different logic levels, then you need level conversion to not drive 3.3V input with 5V output for example.
Circuit digram from PCBA photos  - Page 1
Forum section: electronics / beginners

author: Muhammad
author_rank: Newbie
timestamp: April 24, 2025, 08:53:23 am
content: Hello members,I'm redirected here after long time efforts in drawing the circuit diagram of a PCB from its photographs.The circuit is of a 30-second voice recorder and playback circuit which contains UC25HQ16 IC.I'm attaching all the three images I got. Can somebody help me to draw the connection digram, please?Thanks in advance.

author: tigrou
author_rank: Regular Contributor
timestamp: April 24, 2025, 09:00:36 am
content: I feel like nobody is going to do the hard work for you.You can easily trace where each PCB trace is going (even without seeing them) using a multimeter in continuity mode (aka beep mode)Other than that, if you look at theUC25HQ16datasheet and search for the "typical application circuit" (or example circuits on the web that use such an IC), it might give you a clue about how it works (and make the task easier).

author: Muhammad
author_rank: Newbie
timestamp: April 24, 2025, 12:58:10 pm
content: Thanks tigrou for your valuable advice. Unfortunately, I don't have the circuit in real except the photographs I shared! Id I'm able to list out the components, can somebody help me to draw the connections, what do you think?
Circuit don't work in Microcap (555-based class-D) - Page 1
Forum section: electronics / beginners

author: nast
author_rank: Newbie
timestamp: May 25, 2020, 07:35:24 pm
content: Hello. I try to make first circuit from this articlehttps://www.radiolocman.com/shem/schematics.html?di=152208,but it doesn't work and I can't find what I miss, when make it in Microcap. Input frequence is 10000 Hz and ampletude is 5 V.
circuit explanation - Page 1
Forum section: electronics / beginners

author: pete g
author_rank: Regular Contributor
timestamp: June 02, 2017, 10:22:11 pm
content: hi all, can someone explain how the charge pump works as in the pickit 2 clone programmer.

author: Zero999
author_rank: Super Contributor
timestamp: June 02, 2017, 10:58:04 pm
content: https://www.google.co.uk/search?q=charge+pump&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&ei=Ze0xWfCHMrDS8Ae2urNA

author: rfeecs
author_rank: Frequent Contributor
timestamp: June 03, 2017, 12:23:37 am
content: Pickit 2 uses a boost converter.Schematic is on page 78:http://ww1.microchip.com/downloads/en/DeviceDoc/51553E.pdf
Circuit explanation please, Possible use for constant current load? - Page 1
Forum section: electronics / beginners

author: CustomIngenuity
author_rank: Newbie
timestamp: January 24, 2015, 04:47:47 am
content: HelloI am hoping someone will take the time to explain the circuits highlighted in the attachment wrt driving the inverter fets. I hope to use one or the other, what I think are the inverter fet drive circuits, to drive the fets for a quick and dirty constant current load. Not sure if there will be a further use for the load tester. For now though I would like to load test a 48v x ~50A DC supply. The components are all sourced from what is laying around here.If there are other options for load testing at this power level I am open to suggestions.The schematic is from a UPS.What I know (or think I know) about circuits.The inverter fets are irf3710 200w dissipation 100vOne set of inverter fet controls I will call "fet controlled" and "direct control"fet controlled:A 2n7000 N-channel is used to drive the pnp and npnQ31, Q34 are controlled from an inverted schmitt trigger outputQ30, Q29, Q33, Q32 connect to +12v and xfmr "rail"Q31, Q34connects to +12v and gndR37, R41 2.2 Ohm resistor is between the emittersIrf3710 gates are connected between the emittersThese circuits control the +Battery railDirect control:No mosfet connected to the Q28, Q27, Q36, Q35Driven from 2 inverted schmitt trigger outputs, non-inverting then?BJTs connect to +12v and groundThese circuits control the - Battery railIrf 3710 gates are connect to the BJTs emittersIf either of these circuits can be used to drive the fets I will eliminate the one that is not needed. Then move to another planning phase to drive the control circuits that will drive the load fets. My plan is to literally cut traces on the PCB, solder/bolt jumpers where needed and put a fan on the heat sinks.I seek the knowledge of the circuit operation to empower me to decide whether or not to proceed with these components. However, please advise if this is lunacy, the thought of scraping the whole idea is fine. I am not looking to be spoon feed a load design. I am interested in learning how to use readily available (to me) devices to suit my needs. In the process learning about the devices themselves.Also attached is a schematic of DC supply to give an idea of the values I am working with. All of the protection fuses are original to the devices which I have used to estimate current values. The voltages are measured.
Circuit for Hall Effect Position Sensor - Page 1
Forum section: electronics / beginners

author: Adam60
author_rank: Regular Contributor
timestamp: December 12, 2016, 07:44:51 pm
content: Hey all. Looking for a couple of things regarding a hall effect sensor as a position sensor. First of all, does anybody have a clear description, tutorial, video on how a hall effect switch acts as a position sensor? Secondly, I want to demonstrate how an automotive throttle position sensor is used to provide the ECM position information using a circuit that can be built relatively easy. Any ideas?Please do not confuse this with a camshaft/crankshaft position sensor. I am looking for a way to demonstrate how it replaces a potentiometer as a position sensor.

author: voltsandjolts
author_rank: Unknown
timestamp: December 12, 2016, 08:37:50 pm
content: Formula student?Penny and Giles are the bees knees for that kind of thing, eg. their TPS280 throttle position sensor:http://www.cw-industrialgroup.com/Products/Sensors/Rotary-Hall-Effect-Position-Sensors/Contactless-Throttle-Position-Sensor-Dual-TPS280DP.aspxhttp://www.cw-industrialgroup.com/Products/Sensors/Rotary-Hall-Effect-Position-Sensors.aspxHave a browse on their site you might find what you seek.

author: Adam60
author_rank: Regular Contributor
timestamp: December 12, 2016, 09:28:45 pm
content: That was bang on the money. We use a WM830 in our highway trucks and that is what I am looking for.Now I just need a laymans way of explaining how Hall Effect works as a position sensor and build a small demonstration of it actually working. Any thoughts?
Circuit for low current pulse measurement with 315 V DC ? what solution ? - Page 1
Forum section: electronics / beginners

author: Maxoverdrive
author_rank: Contributor
timestamp: September 06, 2021, 11:49:14 am
content: HelloI search a circuit ( I suppose base on a current sense IC or OPAMP) able to measure low current ( in the 100mA range ) with a 315V DC voltageMy problem is all the HV circuit I have located are base on power supply taken from the bus as :But : As my signal is a pulse of 0,2s I will not be able to power the OPAMPSo: Does there is another electronic solution ? I need 50 KHz of BW minimum 200 KHz will be niceMost current sense IC are limited to 80 VThanks in advanceMOD

author: PartialDischarge
author_rank: Super Contributor
timestamp: September 06, 2021, 02:57:58 pm
content: If high-side is the only option, then you are going to have to use a dc-dc converter to supply that op-amp

author: Maxoverdrive
author_rank: Contributor
timestamp: September 06, 2021, 03:11:29 pm
content: Hello@mastertechOk so :Question 1 : Shall I use an isolated one ? as the ground of the 315 V DC is not the same as the ground of the instrumentationQuestion 2 : Normaly on a OPAMP there is maximum imput voltage , in the case the voltage taken at the current resistor is low but in all TI/AD application bus voltage is under the OPAMP maximum imput voltage .I ask these two questions as after sevral days of circuits earch on google ( TI. AD and other maxim ) I have located any exemple of something which sound quite usefull as circuitThanksMOD

author: voltsandjolts
author_rank: Unknown
timestamp: September 06, 2021, 04:33:56 pm
content: Quote from: MasterTech on September 06, 2021, 02:57:58 pmWhat's wrong with the power supply as shown?

author: PartialDischarge
author_rank: Super Contributor
timestamp: September 06, 2021, 04:36:46 pm
content: Quote from: voltsandjolts on September 06, 2021, 04:33:56 pmHe mentions the voltage is pulsed

author: PartialDischarge
author_rank: Super Contributor
timestamp: September 06, 2021, 04:41:12 pm
content: I was assuming you don’t need isolation, in case you do then the measure also has to be isolated.All in all you may want to use an isolated current sensor , something like this or similarhttps://www.farnell.com/datasheets/2149975.pdf

author: voltsandjolts
author_rank: Unknown
timestamp: September 06, 2021, 05:35:51 pm
content: It's a pulse, but with the circuit as shown in the OP, I would say 200ms is a reasonable time for the op-amp to stabilise and provide a useful measurement.Depends how clean the HV pulse is, and what the current measurement requirements are.Of course, with fast HV rise times there is plenty opportunity for things not to go according to plan

author: David Hess
author_rank: Super Contributor
timestamp: September 06, 2021, 05:37:55 pm
content: I might use a pulse transformer to make an inverter to provide a floating supply for the operational amplifier.
Circuit for MCU IO or VCC switch (help!) - Page 1
Forum section: electronics / beginners

author: Sarcarean
author_rank: Contributor
timestamp: February 20, 2019, 06:25:59 am
content: I have a MCU I/O that connects directly to the input pin of another IC. I want to insert a circuit/IC that will use anotherto an input pin of another IC. I want to use a second MCU IO to control a circuit / IC that will switch between either the first I/O or a +12V power source.So my question is, what is the best way to do this? Off the top of my head, I am thinking of putting a standard diode on the MCU pin and use a couple of transistors or is there a single IC that will accomplish this for me?(Note: the MCU pin is not 12V tolerant).Thanks in advance for any help and/or schematics from working projects that do this

author: tszaboo
author_rank: Super Contributor
timestamp: February 20, 2019, 09:20:38 am
content: Sorry, but what?

author: Moriambar
author_rank: Unknown
timestamp: February 20, 2019, 09:50:36 am
content: Quote from: Sarcarean on February 20, 2019, 06:25:59 amyou mean something like a SPDT circuit?I found this:https://datasheets.maximintegrated.com/en/ds/MAX381-MAX385.pdfwhich perhaps can meet your standards. Otherwise check for multiplexers or that kind of circuits on digikey, etc... and you will have parametrics to narrow down your search. Please do mind that in general the V of the commuted input is different from V+

author: Sarcarean
author_rank: Contributor
timestamp: February 20, 2019, 11:01:55 pm
content: That won't work because the output has to be either a signal or load current.What I am thinking is a general purpose diode on the MCU pin and a MOSFET between diode and input pin. The transistor when on will flow current into the line and when off, the signal will pass directly through the diode to the input.

author: Sarcarean
author_rank: Contributor
timestamp: August 08, 2019, 07:42:31 am
content: I thought I would update this post and share the verified solution that I came up with.The 74LS595D output pin (5V CMOS) connects to a schottky diode (30V Vrrm 0.37 Vf) and then to a 22K ohm resistor and also the main output pin A9. The other end of the resistor goes to ground. Between the diode and resistor, a connection is made to the output (L1) of a solid state relay (CPC1017N). The input (L2) of the relay is connected to the 12V rail, the CTR_N connects to ground and CTR_P connects to a MCU GPIO (configured as output, default logic low).When the MCU is in the default state, the GPIO pin is low and the relay is OFF and the output from 74LS595D can drive the A9 pin. When the GPIO pin is HIGH, the relay is active and will allow the 12V to flow to the A9 pin while the diode will protect the 74LS595D from reverse current.
Circuit for powering a "dumb" USB device? - Page 1
Forum section: electronics / beginners

author: ryanmills
author_rank: Unknown
timestamp: October 30, 2019, 07:05:18 pm
content: I only have a basic understand of USB. Redesigning a PCB so I can power an LCD screen (https://www.adafruit.com/product/2232) directly off the board. I assume the LCD is a "dumb" device in that there is no need for data pins to negotiate current like you might have with a phone. The board already has a stable +5 volt rail with plenty of amps to spare courtesy of a 5v LDO regulator (LM1084ISX-5.0/NOPB:http://www.ti.com/lit/ds/symlink/lm1084.pdf).I assume I can just run that +5v rail and maybe a bypass cap into a standard Type A header and call it a day? Or are there some standard protections I should be adding?

author: magic
author_rank: Super Contributor
timestamp: October 30, 2019, 07:55:47 pm
content: Most USB ports use a polyfuse to prevent 5V rail collapse and/or regulator overload in the event of external short circuit.Whether you anticipate external shorts to happen and if/how your device is expected to survive them is another thing.If you want to be pedantically compliant with USB spec, you should be able to withstand indefinite short between any pair of USB pins.

author: ryanmills
author_rank: Unknown
timestamp: October 30, 2019, 09:20:57 pm
content: Quote from: magic on October 30, 2019, 07:55:47 pmThank you, is there a reason you might pick a Poly over a Ceramic in this application?

author: Brumby
author_rank: Unknown
timestamp: October 31, 2019, 04:21:14 am
content: A polyfuse resets itself after it has cooled down sufficiently.
Circuit for replacing Potentiometer  - Page 1
Forum section: electronics / beginners

author: yashrk
author_rank: Frequent Contributor
timestamp: May 12, 2014, 06:05:45 pm
content: There are like tons of places where we need variable voltage but using 10 turn pot is not economical every time so I was looking for a circuit to replace 10 turn pot. Any suggestions ?

author: mdszy
author_rank: Unknown
timestamp: May 12, 2014, 07:30:10 pm
content: Digital pot?

author: rexxar
author_rank: Frequent Contributor
timestamp: May 12, 2014, 07:37:47 pm
content: Replace it with what?Ask yourself this: If there were a better or cheaper way to get precise variable resistance than a 10-turn pot, then why are 10-turn pots still used? If there were a cheaper solution, then everyone would be using it.To answer your question, you can get digital potentiometer ICs, but then you also need a microcontroller and a rotary encoder to control the thing. If you're just doing something like a LM317, then the added complexity is not worth the $10 a good pot would cost.

author: yashrk
author_rank: Frequent Contributor
timestamp: May 13, 2014, 05:52:25 pm
content: Quote from: rexxar on May 12, 2014, 07:37:47 pmTrue silly question sry

author: electr_peter
author_rank: Unknown
timestamp: May 14, 2014, 06:43:36 pm
content: Well, solution for adjustment problem or user input depends on specification/requirements. What kind of setup does the pot drive? Does that setup have enough resolution and does it care about 10 turn pot granularity, etc.?Anyway, if you can use 10 turn pot in your application, but it is a bit too expensive for you, then you still have multiple options to choose from:single turn pot (sufficient for most general applications)two single turn pots with "coarse" and "fine". You can see it on cheaper power supplies - it works technically, but is super annoying in comparison to 10 turn potdigital pot with rotary encoders or "up" and "down" buttonsfixed ratio, selectable with rotary switchfixed ratio, selectable with multiple binary switchesbuttons to control MCU which controls some mosfets...
Circuit Fun Video: Using a variable DC voltage to control an RC style servo - Page 1
Forum section: electronics / beginners

author: w2aew
author_rank: Super Contributor
timestamp: December 11, 2014, 07:40:26 pm
content: This circuit was by request, and is a nice basic tutorial of how RC servos are controlled, and how assembling a few basic op amp building block circuits (integrator, hysteresis comparator, summing amplifier, etc.) can allow you to control one of these servos from a simple DC voltage. Of course, there are many, many ways to do this. This video shows an op amp based solution - just for fun...

author: AlfBaz
author_rank: Super Contributor
timestamp: December 11, 2014, 11:15:59 pm
content: Sorry not to talk about the technical content of this video, but for some reason I can't get past the waving "Circuit Fun" flag. I break out giggling and just cant stop!

author: w2aew
author_rank: Super Contributor
timestamp: December 12, 2014, 01:01:25 am
content: Quote from: AlfBaz on December 11, 2014, 11:15:59 pmGlad you liked it! I was trying to figure out a way to make the movement of the servo obvious and still keep the theme relevant. I especially liked the use of the glass diode as the flag support.