hybridfree/eevblog-posts huggingface dataset:
Farad capacitor anatomy - Page 1
Forum section: electronics / beginners

author: daming
author_rank: Newbie
timestamp: December 06, 2021, 10:30:19 am
content: Farad capacitor anatomy.https://www.bilibili.com/video/BV1Cr4y1S7Zn?share_source=copy_web

author: daming
author_rank: Newbie
timestamp: December 13, 2021, 02:07:02 pm
content: Farad capacitor anatomy 2https://www.bilibili.com/video/BV1Ti4y1d7ww?share_source=copy_web

author: mc172
author_rank: Frequent Contributor
timestamp: December 13, 2021, 03:03:52 pm
content: Visiting the first link got me stuck in a quite annoying loop. The website opened the Google Play Store app on my phone, so I closed it. My phone automatically went back to Chrome which opened the Play Store again. This kept on going for at least a minute as I tried to figure out what to do. Closing Chrome didn't help because as soon as I opened Chrome again (to come here and write this message) the tab was still there and it carried on going.

author: jmelson
author_rank: Super Contributor
timestamp: December 13, 2021, 03:53:57 pm
content: Yes, quite annoying, it wants me to place a puzzle piece into the empty position, then there is no video. That is a desktop running Firefox.Jon

author: Zero999
author_rank: Super Contributor
timestamp: December 13, 2021, 08:45:47 pm
content: https://en.wikipedia.org/wiki/Double-layer_capacitance

author: daming
author_rank: Newbie
timestamp: December 15, 2021, 01:19:28 am
content: ok ,change the connection.

author: daming
author_rank: Newbie
timestamp: December 15, 2021, 01:28:49 am
content: The plates are coated with graphite material
Farnell D30 2 project finished - Page 1
Forum section: electronics / beginners

author: M0BSW
author_rank: Frequent Contributor
timestamp: April 27, 2013, 07:00:13 am
content: I bought this of ebay, a Farnell D30 2, 30volt 2 amp variable power supply,which was a bit of an old wreck,shall we say some sellers must be photographers showing things in their best light.Any way got it eventually,and it wasn't in good shape, so I change some part ,no alot of parts, cleaned it up, gave the outer case a paint.Taking my New pride and joy down to a small calibration centre ,where I know the owner, he let me calibrate it, that was a good experience, and a really good lesson, now I have a fully calibrated really useful 0-30 by 2amp variable bench power supply,plus I've found something I really enjoy doing, getting old equipment and bringing it back from the edge of the junkbox, just got to find a manual for it now and learn how to use it.. I think these must be 20/30 years old ? and I wonder what it would have cost.PaulPS Dave is right , you do have to get the tongue in the right position and squint , makes all the difference

author: seb1982
author_rank: Regular Contributor
timestamp: April 27, 2013, 03:04:46 pm
content: Oh, that's a lovely thing!Nice work!You simply can't beat old equipment. Much sexier!

author: M0BSW
author_rank: Frequent Contributor
timestamp: April 27, 2013, 05:29:41 pm
content: Quote from: seb1982 on April 27, 2013, 03:04:46 pmThank You ,it looked a bit sorry for it's self when I got it, the chips on the inside date it as 1980, I'm really pleased with it.
Farnell DT12-5 manual - What does this mean? - Page 1
Forum section: electronics / beginners

author: GordonB
author_rank: Newbie
timestamp: September 12, 2023, 06:52:58 am
content: I recently picked up a reasonable condition Farnell DT12-5 oscilloscope for next to nothing and found that apart from the focus tending to drift it works fine. However, it's clear that it isn't calibrated. I've got a pdf copy of the manual and in the section on setting the calibration waveform it states; "Adjust P2 on trigger boards to obtain 1V as accurately as possible. Check that the frequency is 1kHz + or - 200Hz. If necessary S.O.T. R31." There is no explanation of what "S.O.T." means, can anyone interpret for me?Many thanksGordon

author: wasedadoc
author_rank: Super Contributor
timestamp: September 12, 2023, 07:38:58 am
content: Select On Test.Means you try some fixed resistors until you find one that results in the measurement being in spec.If both horizontal and vertical axes are out of calibration that could be caused by voltages on the CRT being too far off nominal.

author: GordonB
author_rank: Newbie
timestamp: September 12, 2023, 08:07:29 am
content: Quote from: wasedadoc on September 12, 2023, 07:38:58 amMany thanks for the quick reply, that now makes perfect sense. It's only the Y axis that seems to be out of calibration and I'm not too keen on messing around with the high voltages on the CRT. I'm borrowing another oscilloscope later today so I can check the calibration signal.

author: tggzzz
author_rank: Super Contributor
timestamp: September 12, 2023, 09:53:20 am
content: Quote from: GordonB on September 12, 2023, 08:07:29 amI wouldn't bother with changing R31 to get 1kHz. The cal out signal's principal purpose is to enable twiddling of the compensation capacitor in 10Mohm "high" impedance *10 probes. The frequency doesn't need to be exact for that; even 10kHz or 100Hz would be OK.Be aware that analogue scopes are only likely to have a 2% accuracy rating. That doesn't matter, since their purpose is to see the waveform shape; the transient response is the important metric.

author: liaifat85
author_rank: Regular Contributor
timestamp: September 12, 2023, 10:10:38 am
content: Here are also some info about this oscilloscope model. You can check these out.

author: GordonB
author_rank: Newbie
timestamp: September 12, 2023, 11:11:09 am
content: Quote from: liaifat85 on September 12, 2023, 10:10:38 amCan't see any links.
Fast AC-DC Converter - Page 1
Forum section: electronics / beginners

author: ramonest
author_rank: Contributor
timestamp: August 25, 2016, 10:25:35 pm
content: Hi all, I was wandering through some datasheets when I saw an example schamatic of a "Fast AC-DC converter" on a OPAmp datasheet, and "fast half wave rectifier". I can't understand how they work.Maybe I should understand it but I don't because I've been slacking too much during summer or maybe I'm just an idiot...I'd really apreciate some help undertanding these.

author: ebclr
author_rank: Super Contributor
timestamp: August 25, 2016, 10:54:23 pm
content: It's a active full wave rectifier.Negative cicles goes to ground positive cicles pass with a gain near 1, the second stage is nothing more than a adder and "pseudo active capacitor" or low pass filterThe adder will add the ac plus one half cicle inverted with double amplitude ( note r3 = 1/2 r6 ) and this will make a full wave rectifier

author: ramonest
author_rank: Contributor
timestamp: August 26, 2016, 09:36:21 am
content: Got it thanks! What aplications might it have?

author: CJay
author_rank: Super Contributor
timestamp: August 26, 2016, 09:42:24 am
content: Measurement circuits, it eliminates the diode drop. also known, I think, as a precision rectifier or super diode.https://en.wikipedia.org/wiki/Precision_rectifier

author: ramonest
author_rank: Contributor
timestamp: August 26, 2016, 09:54:30 am
content: Ok thank you very much! You guys take less time to answer that the time my professor would need to decide to answer smoething nonrelated...Hope you don't mind an idiot asking some more dumb questions in the future.

author: David Hess
author_rank: Super Contributor
timestamp: August 27, 2016, 07:23:34 pm
content: The thing which makes these "fast", and they are not that fast, is that A1 does not have to recover from saturation. Slower precision rectifier designs allow the operational amplifier to saturate on alternate cycles and operational amplifiers, even fast ones, recover from saturation slowly.
Fast Pulse Generator - Page 1
Forum section: electronics / beginners

author: kumar
author_rank: Contributor
timestamp: July 05, 2014, 11:18:27 am
content: Given below is the link to a video which demonstates a high voltage fast pulse generator.http://www.eevblog.com/2012/07/06/eevblog-306-jim-williams-pulse-generator/I would like to buy this generator (either the one shown in the video or simillar).I wrote to siliconvalleygarage but did not receive any reply.Can anyone please post contact details of manufacturer of these generators?
Fast PWM IC - Page 1
Forum section: electronics / beginners

author: elki
author_rank: Regular Contributor
timestamp: April 28, 2024, 05:26:34 pm
content: Is there any IC that could provide a PWM at 100 MHz or so? I would love to use atmega ICs but these go up to 20 MHz, if I am not mistaken. The idea is to use it for a voltage control in sample-and-hold circuit for short input pulses. Thanks!

author: strawberry
author_rank: Super Contributor
timestamp: April 28, 2024, 06:53:40 pm
content: custom circuit with digital logic gates or FPGA

author: langwadt
author_rank: Super Contributor
timestamp: April 28, 2024, 07:16:08 pm
content: Quote from: elki on April 28, 2024, 05:26:34 pm100MHz pwm frequency or 100MHz time resolution?

author: elki
author_rank: Regular Contributor
timestamp: April 28, 2024, 07:25:22 pm
content: Frequency.Quote from: langwadt on April 28, 2024, 07:16:08 pm

author: langwadt
author_rank: Super Contributor
timestamp: April 28, 2024, 07:36:26 pm
content: Quote from: elki on April 28, 2024, 07:25:22 pmand how many bits of resolution?

author: selcuk
author_rank: Frequent Contributor
timestamp: April 28, 2024, 08:47:07 pm
content: It seems that you will need fast/expensive ICs for that. How about implementing analog control by using comparators etc.? I'm not an expert in this but you can check datasheets of such controllers for block diagrams to have an idea.

author: Zero999
author_rank: Super Contributor
timestamp: April 28, 2024, 09:07:09 pm
content: I still don't understand why you need 100MHz PWM.The problem is, it needs to be able to generate much higher frequency harmonics. 10% duty cycle has a 1ns on time, so you need much sharper rise and fall times, say 100ps, so you need a slew-rate of 33GV/s for a 3.3V signal.

author: coppice
author_rank: Super Contributor
timestamp: April 28, 2024, 09:19:44 pm
content: If you really want a PWM channel running at 100MHz with any kind of reasonable resolution for the pulse width trying looking at things like the TI C2000 MCUs. They have a pulse width resolution far beyond their clock rate, using calibrated delays.
Fast recovery diodes, How do i choose a replacement? - Page 1
Forum section: electronics / beginners

author: pitpat
author_rank: Contributor
timestamp: February 25, 2021, 09:26:17 am
content: Hi guys thanks for cheking in!, i need to replace this old diode (byd730g) which it seems not to be sold in all europe a a resonable price.Since I'm really new to fast recovery diode and psu design in general what should I be looking for a good replacement?Which values has to stay the same and which can be upgraded? Es. I think that the velocity of the recovery can be ugraded with something faster (50ns to 30ns) and the reverse voltage and current can be ugraded too, what about the farward voltage?

author: pitpat
author_rank: Contributor
timestamp: February 25, 2021, 09:27:52 am
content: Also this is the culprit to be changed.photo_2021-02-25_10-12-53.jpg(24.61 kB. 1280x961 - viewed 127 times.)

author: Docara
author_rank: Regular Contributor
timestamp: February 25, 2021, 04:38:06 pm
content: HiI had 5minutes - tried to find some info on your diode - I couldn't find anything anywhere not even a mention or a pdf!Found this site whichmightbe able to helphttps://www.vintage-radio.net/] https://www.vintage-radio.net/(not affiliated know nothing about them)Hope it helpsAh! well back to the grind

author: Terry Bites
author_rank: Super Contributor
timestamp: February 25, 2021, 07:20:34 pm
content: Did you mean BYD73 fast recovery diode (original gangster) 400V rated part?https://html.alldatasheet.com/html-pdf/17466/PHILIPS/BYD73G/495/2/BYD73G.htmlIf sohttps://www.ebay.co.uk/p/1473862219or a HER155G diode which is similar.

author: pitpat
author_rank: Contributor
timestamp: February 26, 2021, 08:30:15 pm
content: Oh my bad it is indeed a BY73G thanks a lot for the time. I still need to find a good alternative though, for now I'm using an anonymous one that the local electrical supply guy gived to me.
Fault finding AC heater - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: June 22, 2013, 05:51:03 am
content: HiAny advice would be much appreciated.The mains AC powered heater in our house stopped working after 2 years, it was expensive, I would like to safely figure out if its the 10V AC transformer that appears to power the control board inside that's failed?I was looking at a variac as a way to supply the 10V AC to the control board to see if that brings it to life.I have a DMM and oscilloscope, obviously I am totally aware that beginners shouldn't be playing about with AC, that why I am asking for advice before doing anything other than taking a peek with it all unplugged.Thanks for looking.CheersRichard

author: Unknown
author_rank: Unknown
timestamp: June 22, 2013, 05:53:08 am
content: pictures?

author: IanB
author_rank: Super Contributor
timestamp: June 22, 2013, 05:53:34 am
content: What kind of heater is it?The most common fault with an electric heater is that the heating element has failed. Usually replacement elements are available as spare parts. You would check for this fault by disconnecting the heater from the mains and then measuring continuity through the heating element with a DMM.

author: G7PSK
author_rank: Super Contributor
timestamp: June 22, 2013, 08:49:06 am
content: Check the fuses first, then power to the appliance and power out of appliance, I have seen many cases of people using a power detector (volt stick or neon) and finding that power was going to the equipment and then blaming said equipment for being faulty and all the time it was the neutral wire that was at fault. Then if all that is good check the thermostat before pulling anything apart.

author: 807
author_rank: Frequent Contributor
timestamp: June 22, 2013, 09:22:04 am
content: I would advise against using a variac.Why not power up the heater & check out the secondary side of the transformer?

author: SeanB
author_rank: Super Contributor
timestamp: June 22, 2013, 09:38:13 am
content: Just use another 9VAC transformer to check, it will tell you. Simpler is to disconnect the transformer from the board and measure primary and secondary resistance. Primary will be anything from 1k to 20k resistance, secondary anything from 0.1R to 50R. If it is open circuit on the primary ( most likely) then there is a thermal fuse under the first layer of insulation that needs replacing with another 110C thermal cutout.

author: rthorntn
author_rank: Frequent Contributor
timestamp: June 22, 2013, 09:44:35 am
content: Thanks everyone, we have heat!As an FYI it's a Delonghi SDH2000 heater.I opened up the belly of the beast and was just about to take a photo when I thought let me just try and bypass the tip over switch so I just went directly from the power switch to the power board PCB, I will replace the switch as it's clearly faulty.CheersRichard
Faulty analogue scope - suggestions on where to look next - Page 1
Forum section: electronics / beginners

author: timbos
author_rank: Contributor
timestamp: April 20, 2014, 01:26:24 pm
content: Hi,Not sure whether this should be here or in the test-gear forum...I've got an old Crotech 3132 20MHz scope that stopped working yesterday. After having it switched on for a couple of hours, it's released an acrid burning smell and isn't producing a trace on screen. I've taken the covers off and think that I've diagnosed that there's a fault on the EHT board (see page 4 of the attached diagram):http://www.tjstephens.com/images/Crotech3132 _circuits(wm).pdfObservations:I've got the circuit diagram for the board after trawling the web, and I think that the board consists of an oscillator (a Wien oscillator?) and a two-stage (Cockroft-Walton ?) voltage multiplier. That's where my understanding kind-of ends.The NPN transistor Q601 is on a heatsink and was very hot when I first checked it after unplugging the scope (and making sure that the various caps on this board were discharged).The two resistors (R613, R614) on the output stage of the transformer have clearly been very hot. Their paint is peeling and the surfaces are charred, although they measure 5.8K and 6.1K, so they're still performing at about specification.Can you suggest where I might look next? I'm not sure how to confirm whether these observations are a symptom or the actual fault (my guess is that something else may have failed upstream)? Is there anything else that I should be looking for?

author: RiverTown
author_rank: Regular Contributor
timestamp: April 20, 2014, 02:05:34 pm
content: I would first check all the capacitors on that board. That acrid burning smell could be electrolytic or tantalum capacitor failing. Even some block capacitors (mostly X2 rated) will produce bad smell when failing.

author: valentinc
author_rank: Regular Contributor
timestamp: April 20, 2014, 09:06:14 pm
content: First, check for any obvious blown components... If it was a burning smell, certainly there is something obvious that needs to be adressed first... It could be a faulty capacitor, as RiverTown said, but check first... It could also be something else or, if it's a tantalum that shorted out, it could be blown out some active devices too...

author: tautech
author_rank: Super Contributor
timestamp: April 20, 2014, 09:44:19 pm
content: Shift this thread to Test Equipment, where it will be seen by more members that can help.The schematic has various test points for fault finding(circled).Check all PSU voltages are in spec.I could spot only 1 tant on the schematic, but if they are used at all, there are likely more.Think about the components that are stressed(current, voltage, heat) and check them next.
Faulty Gigabyte keyboard  - Page 1
Forum section: electronics / beginners

author: jipaionutcatalin
author_rank: Newbie
timestamp: January 09, 2017, 09:46:22 am
content: I recently bought a second hand Gigabyte Stealth gaming keyboard, model number GK-FORCE K7 and from time to time some of the keys, like 't', 'backspace' and other keys do not work. The odd thing is when I plug in the keyboard the '4' key is stroking without me doing anything.I am using Windows 10 but tried the keyboard on different OS's with the same results. Opened the keyboard tested the control board for voltages, faulty parts, traces and connectors with no bad one's found. The main IC is HT82A525R and EEPROM chip is T24C02A.I am trying to reprogram the EEPROM as soon as I will get the code and see what will happen.Any suggestions will be much appreciated.Thanks in advance.

author: tautech
author_rank: Super Contributor
timestamp: January 09, 2017, 10:14:23 am
content: Sell it to another sucker.It's fooked, probably had something spilt or dropped on it.I wouldn't dare use it especially if you do any online buying or banking.

author: jipaionutcatalin
author_rank: Newbie
timestamp: January 09, 2017, 11:05:19 am
content: I rather bin it then sell it,but thanks for your replay.

author: Inflex
author_rank: Regular Contributor
timestamp: January 09, 2017, 11:15:11 am
content: 99.9% like someone's spilled something on it. The membrane / switches are contaminated and causing the odd behaviours.

author: jipaionutcatalin
author_rank: Newbie
timestamp: January 09, 2017, 11:41:35 am
content: HiI was thinking it might be faulty IC or EEPROM chip.

author: SeanB
author_rank: Super Contributor
timestamp: January 09, 2017, 07:54:33 pm
content: No, classic wet membrane problem. You might be able to dismantle the keyboard and remove the membrane, clean and dry it and put it back together and have it work again. You probably will have to fix a broken trace or two for those non working keys, but that will be somewhat easy, if fiddly.
Faulty power supply - Page 1
Forum section: electronics / beginners

author: franciscoPT
author_rank: Contributor
timestamp: February 05, 2020, 03:18:49 pm
content: I have a uni-t utp3315 that is showing 0.50ma in current display however i dont have any load on it??? does someone already has this problem with same product??? calibration problem??? i buy it 5 months ago and she was showing the current measures of voltage and current.

author: Vovk_Z
author_rank: Super Contributor
timestamp: February 05, 2020, 04:01:16 pm
content: If is it a real problem it depends on this device manufacturer characteristics.
Faulty schematic. - Page 1
Forum section: electronics / beginners

author: bastouw
author_rank: Newbie
timestamp: February 28, 2014, 04:30:16 pm
content: Hello, I am reading the The Art Of Electronics 2e Edition.The topic VOLTAGE REGULATORS AND POWER CIRCUITS have examples of bad cirquits.And 2 of them i have troubble reasoning whet the fault is.Can someone help me? Here are the attached schematics:

author: grumpydoc
author_rank: Super Contributor
timestamp: February 28, 2014, 04:40:21 pm
content: I'm wondering how the first one starts given that the op amp power supply is taken after the pass element.Not sure about the second for a moment....Ah, yes - once the current limit transistor has turned on it will feedlotsof base current to the pass transistor, probably not what was intended.Ithinkthose are the faults - anyone agree (or disagree for that matter).

author: Andy Watson
author_rank: Super Contributor
timestamp: February 28, 2014, 05:14:53 pm
content: Agreed. The first pass transistor in the first circuit will require driving with a base voltage 0.6-0.7abovethe supply rail to the op-amp. It's not going to happen, even with a rail-to-rail op-amp!
Fax machine teardown, what is missing ? How does it work ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 26, 2018, 02:38:33 pm
content: I took apart a 1990s FAX machine, some nice parts I can re-use/add to the collection. I'm having a hard time finding any schematics or repair threads on them, just google ads basically. Found 1 similar Panasonic manual tho.At the front end of the machine there's about a 30cm/11" row of 29 SMD LED's, I thought they would be for lighting a page through, to read it. But I don't see anything 30cm/11" that would read it.I don't see anything optical at all that size that could read what's on a page. Doesn't all fax machine have the ability to insert a page and copy/send it ?I guess I only remember seeing fax machines in Die Hard 1/2And how does the thermAL PRINTER WORK ? I found a 24cm/10" bar with what I guess is the heater element, it has a 15pin serial connector.How does that work so that it can burn how ever many pixels wide 10" is ?

author: james_s
author_rank: Super Contributor
timestamp: March 27, 2018, 12:31:30 am
content: These machines use a linear CCD sensor, normally about an inch long. The bar of LEDs is usually green and illuminates a strip of the page, then a lens focuses the result into a line across the sensor consisting of a single row of pixels.The printer is thermal, the bar you found is the print head, it's a row of single pixel wide heating elements that are activated in the proper sequence as the page passes over them. I've never looked at how they are controlled but I suspect they use a shift register.
Feasibility of Using Xinya XY2500 4-Pin Pluggable Terminal for Three-Phase PCB - Page 1
Forum section: electronics / beginners

author: Shubham
author_rank: Contributor
timestamp: June 16, 2024, 09:55:27 pm
content: Hello everyone, I am designing a PCB for a three-phase system and considering using thehttp://www.xinyaelectronic.com/product/xy2500fa-50-xy2500fb-508Xinya XY2500 4-pin pluggable terminal connector (pitch 5.08 mm, rated 15A @ 300V) to connect R (Phase 1), Y (Phase 2), B (Phase 3), and N (Neutral). My concerns are whether this connector can safely handle the voltage requirements:1) Is the 300V rating sufficient for typical three-phase voltages, especially considering peak values?2) Are the creepage and clearance distances provided by the 5.08mm pitch sufficient for safety and compliance with standards such as IEC and UL?Additionally, if there are other factors I should consider or alternative connectors you recommend, I would greatly appreciate your insights. Thank you!

author: aliarifat794
author_rank: Regular Contributor
timestamp: June 19, 2024, 02:21:28 pm
content: The Xinya XY2500 connector can be used for your three-phase system provided that the line-to-line voltage does not exceed 300V and the creepage and clearance distances are verified against the specific environmental conditions and standards.

author: floobydust
author_rank: Super Contributor
timestamp: June 19, 2024, 04:08:38 pm
content: It depends on the overvoltage category and system voltage, the humidity, the altitude. Will there be Cat. II or Cat. III overvoltage transients?A connector can be rated to "300V" but no good once mounted on a PC board. You don't really achieve the spacings. The PCB connector can have 5.08mm pin spacing, but then you need to add the pad size and not forget the pin hole.Example 5.08mm pin spacing, 2.5mm dia. pads w/1.5mm hole gives you 2.58mm spacing and only 0.5mm annular ring which is not much.If the wires going in to the connector are poorly done - over-stripped, loose strand, it can arc there. Ferrules can help but are not always used.For this reason, I go upsize to 7.5mmNote there is no mention if the Xinya connector have UL/CSA approvals.
Feather M4 Express + PropMaker Wings + WS2812b LED - Page 1
Forum section: electronics / beginners

author: Daniel_Fdrvc
author_rank: Newbie
timestamp: March 24, 2024, 04:29:19 pm
content: Guys, i need help. Im new to electronics and do everything how i find on youtube/google. What im doing wrong that my simple 4 led strip (non neopixel) dont whant to light up. I asked ChatGPT to write simple python code to light up all led when controler is turned on:Code:Code:import boardimport neopixel# Define the pin for the data lineled_data_pin = board.D5# Number of LEDs in the stripnum_leds = 4# Create NeoPixel objectpixels = neopixel.NeoPixel(led_data_pin, num_leds)# Function to turn on all LEDs with a specific colordef turn_on_all_leds(color):pixels.fill(color)# Example usage:# Turn on all LEDs with white color when the microcontroller startsturn_on_all_leds((255, 255, 255))But nothing happened. I checked the connection of the red (5 V) and black (gnd) wires to a simple LED lamp and it works. I think something is wrong with the yellow (din) connector, but I don't know what and how to check. Or maybe everything is wrong. I loaded the neopixel library into the controller and tried many different solutions. Nothing has helped me, but I don't want to give up. I hope for your help. I have attached pictures of my newbie wiring.
Federal Signal PA300 electronic siren - circuit producing sound - Page 1
Forum section: electronics / beginners

author: Tallie
author_rank: Regular Contributor
timestamp: April 11, 2015, 08:26:49 pm
content: I recently purchased a Federal Signal PA300 electronic siren "AS IS"(schematic here:http://www.simonthenerd.com/files/policesiren/PA300.pdf). After locating the pin-out, I wired it up to my power supply... and something in the circuit is producing the siren sounds... what is it? Is this normal? No speaker hooked up.

author: amyk
author_rank: Super Contributor
timestamp: April 11, 2015, 08:56:15 pm
content: I see at least one transformer in the circuit... and they can produce sound like a speaker, although with far less efficiency.

author: Tallie
author_rank: Regular Contributor
timestamp: April 12, 2015, 01:55:18 am
content: Quote from: amyk on April 11, 2015, 08:56:15 pmThanks. Yes. It appears to be the driver transformer. I put a probe on it and it's putting out 1.2Khz. I guess this is normal...
Feed-Through BNC Terminators - Page 1
Forum section: electronics / beginners

author: selkathguy
author_rank: Unknown
timestamp: June 13, 2014, 06:55:02 pm
content: I was thinking of adding a BNC kit to my DS1000Z order, and I noticed it comes with a "Feed-Through" 50-ohm terminator.http://www.tequipment.net/Cal-Test/CT4042/?OrderItemId=569664Is this the same thing as just a regular 50-ohm terminator? Does the feed-through just pass through what would be reflected? Not sure what the difference is, and there doesn't appear to be any such verbage on the Wikipedia for BNC.

author: johansen
author_rank: Super Contributor
timestamp: June 13, 2014, 07:01:17 pm
content: its the same electrically, as using a "T" to attach a non feed through terminator to the circuit.some oscopes have a switch to engage an internal 50 ohm terminator.

author: selkathguy
author_rank: Unknown
timestamp: June 13, 2014, 07:19:44 pm
content: Ok thanks.

author: w2aew
author_rank: Super Contributor
timestamp: June 13, 2014, 08:01:29 pm
content: Quote from: johansen on June 13, 2014, 07:01:17 pmElectrically the same, but will have better performance at higher frequencies. Useful when you need to properly terminate a coaxial line to 50ohms, and still want to inject the signal into the high impedance input of a scope, frequency counter, etc.
Feed through capacitors, do I need them and how to choose them? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 22, 2015, 10:29:23 pm
content: I have used feed through caps in various projects to stop RF entering or leaving alloy enclosures, or to isolate walled sections of chassis's. But they have always been specced by the circuits designer. I now need to decide if I need to use them, and what values to use for a "combination" project. I have a phase sensing circuit to measure phase into an antenna system.This circuit then feeds a circuit that reads a + / - voltage and drives a DC motor to move a variometer coil to bring the antenna to resonance remotely. My gut feeling is that I should build the RF phase sensing stuff in one enclosure, and the motor drive stuff in a different or divided enclosure, and use feed through caps to ground any RF from entering the motor drive circuit. The motor drive circuit will drive the motor and gearbox set up via a twin cable about 20 mters in length, at 12V DC. This cable itself may pick up RF from the antenna and bring it back to the motor drive circuit.Do I need feed through caps on the motor DC cable entry points, and on the two wires between the RF sensing stuff and the motor drive circuit components, and if so, how do I choose suitable values?The RF is at 136 kHz, and the amp that feeds the antenna is 1kW.The circuits in question are shown below, the phase meter is deleted and instead the wires to the meter are run from the phase circuit enclosure to the motor drive circuit enclosure, or enclosure section. All advice welcome, and thanks for looking.
Feedback for my coin box project  - Page 1
Forum section: electronics / beginners

author: Noobigirl#01
author_rank: Newbie
timestamp: October 18, 2024, 11:05:21 pm
content: Hello everyone. I am a complete noob in electronics and I started off my first project. I want to make a "coin box" that would simulate a key press ( when a coin is entered obviously) for an arcade retro consonle (next step of the project). It's gonna be like a peripheral. I scketched the circuit and I wanted some feedback about potential mistakes/improvements

author: thm_w
author_rank: Super Contributor
timestamp: October 18, 2024, 11:15:20 pm
content: I would recommend when starting out using a 12V supply (like a laptop or LCD monitor supply), so you don't have to deal with the dangers of 230V.You haven't shown the pinout on the RP2040, but it looks like you are using the pullup to 5V. I think it can go to the 3.3V pin just below it.Otherwise it looks good to me.https://mischianti.org/waveshare-rp2040-zero-high-resolution-pinout-and-specs/
Feedback on current limiter circuit +  - Page 1
Forum section: electronics / beginners

author: liviu.gelea
author_rank: Contributor
timestamp: March 03, 2025, 01:27:26 pm
content: Hello. I'm working on a current supply/limiter circuit for some fungicidal UV ledsCircuit here->V2 after your feedback hereMy main problem is I don't trust potentiometers to always keep contact with the lead, and disconnecting the pots would result in the FET gate going high and maxing the current.Is that an issue I should be worried about?Can I somehow protect against this? Perhaps inverting the voltage somehow, so that disconnecting pot makes current go to 0?

author: pqass
author_rank: Super Contributor
timestamp: March 03, 2025, 01:51:20 pm
content: You could put a 1uF cap between pot wiper and GND.It won't help if the wiper is completely disconnected but should smooth-out a scratchy pot.FYI: you're using the default parameters for the FET; small signal vs power.Usethis falstad.com pageto calculate the correct parameters for your chosen FET.eg. IRF540 has a Vgsth=3V and Rdson=0.055R.Entering 0.055, 12, 3 in the above page generates a 2 for beta.Then double-click on the FET symbol and enter 3V and 2 for beta.It won't change much in your case but is more realistic.

author: liviu.gelea
author_rank: Contributor
timestamp: March 03, 2025, 02:05:02 pm
content: That's a great idea and it might prove sufficient. Is the value of 1uF from experience?Thank you

author: pqass
author_rank: Super Contributor
timestamp: March 03, 2025, 02:12:46 pm
content: Quote from: liviu.gelea on March 03, 2025, 02:05:02 pmA higher value will slowdown the change in current but offers better protection from wiper bouncing.I don't have a preference. It's your call. Experiment.

author: ledtester
author_rank: Super Contributor
timestamp: March 03, 2025, 03:31:59 pm
content: Quote from: liviu.gelea on March 03, 2025, 01:27:26 pmJust wanted to say that generally you want to put the N-MOSFET below the load like shown in the attached schematic. The reason is that your op-amp is limited in the voltage it can output and if its above the load it has to output Vgs + the voltage drop of the load vs. just outputting Vgs.

author: liviu.gelea
author_rank: Contributor
timestamp: March 03, 2025, 06:10:08 pm
content: Thank you for the tip. Very good observation. I've done high side op-amps in the past, but then I had a fet driver with bootstrapping. It's not the first time i do this mistake.It seems I don't do electronics often enough to remember these things. Updated the post withthe new link to the V2of the schematic.
Feedback on transistors - Page 1
Forum section: electronics / beginners

author: chagli
author_rank: Contributor
timestamp: November 23, 2019, 12:54:19 pm
content: Hi,I am building a low-power FM transmitter based on a pre-existing design.The first stage is a simple discrete audio amplifier consisting of one NPN transistor (see attached picture).I would like to understand and adapt it.I think I have the minimum education concerning bipolar transistors (Ebers and Hybrid-Pi models).But I am not very familiar with feedback on transistor level. I often see some qualitative statements concerning the effects but no rigorous development.Could you recommend me a book which addresses feedback at transistor level ?Thank you.

author: ferdieCX
author_rank: Regular Contributor
timestamp: November 23, 2019, 01:35:05 pm
content: This circuit has only DC feedback.You will find the basic circuit discussed in chapter 10 of "Electronic Devices and Circuits" by Millman and Halkiashttps://archive.org/details/ElectronicDevicesCircuits/page/n142Feedback is discussed in chapter 17

author: chagli
author_rank: Contributor
timestamp: November 23, 2019, 01:45:42 pm
content: Hi,Thanks for your answer I will look at the reference.I think the capacitor C2 is a way to apply pre-emphasis to the audio signal by lowering the feedback at higher frequencies (thus increasing the gain).

author: ferdieCX
author_rank: Regular Contributor
timestamp: November 23, 2019, 02:24:42 pm
content: You are probably right. The feedback is high at 20 Hz and very low at 15 KHz

author: newbrain
author_rank: Super Contributor
timestamp: November 23, 2019, 02:36:08 pm
content: Note that the symbol for the transistor is wrong!It should have the arrow pointing out (NPN) not in (PNP).The 2N3565 is, in fact, an NPN transistor.

author: chagli
author_rank: Contributor
timestamp: November 23, 2019, 03:51:40 pm
content: That's right !

author: chagli
author_rank: Contributor
timestamp: December 19, 2019, 07:33:26 pm
content: I finally found a book which is quite exhaustive about feedback and has examples on transistor level :'Feedback Circuits and Op. Amps' from D. H. Horrocks.
Feedback regarding circuits design  - Page 1
Forum section: electronics / beginners

author: ggeorgiev
author_rank: Contributor
timestamp: January 10, 2022, 11:34:30 am
content: Hello everyoneI am designing a circuit to measure the laser power pulse curve. I don't need the actual power or the laser's average power, but the power pulse curve. Therefore, the power of the laser is reduced so that the diode is not damaged.The circuit consists of a photodiode, a transimpedance amplifier(TIA), and an ADC. The output from the ADC is read and stored with a Raspberry Pi.The laser has a maximum frequency of 100kHz, and the minimum pulse duration is 10 μs. The rise time of the laser pulse is < 12 μs, and the fall time is < 10 μs.The photodiode is fast enough to capture the pulse and has a shunt resistance of 1 M and a capacitance of 950 pF. The Dark Current is 20nA.According to the LTspice simulation, the circuit must function correctly. By functioning, I mean that it is fast enough to capture the 100kHz signals and that it does not oscillate. On the picture, you can see that at 1 mA, I get about 1V at the output.Since it is about a single circuit, the price of the components is not critical; it simply must work. According to the datasheet, the OPAM is intended for exactly this purpose(fast TIA). The ADC will be the ADS8691, but unfortunately, I couldn't find an LTspice model. I hope that the selection of elements is correct.I hope that I can reduce the power of the laser to the extent that I can get a photocurrent of about 1mA at 10% of the laser's power. But since I can't estimate it, I plan to replace the R3 with a potentiometer if I need more gain.I've done some circuits already, but I'm not a professional, and that's why I would be very happy for your feedback!Here are some specific questions:1. Will the circuit work as I imagined at 100kHz? Photodiode + OPAM + ADC + Raspberry, assumed components, circuit and PCB layout are correct.2. Should I improve anything to ensure I don't have any problems at 100kHz?3. Are there any circuit protection I should consider?4. I know the 50-ohm termination in an oscilloscope for high frequencies. Do I have to consider something equivalent to that in my circuit?I really appreciate any help you can provide!

author: Terry Bites
author_rank: Super Contributor
timestamp: January 10, 2022, 02:43:36 pm
content: If your lazy, like most of us, you just use an online tool. eghttps://tools.analog.com/en/photodiode/Or knife and fork it.https://www.mdpi.com/1424-8220/21/10/3455/pdfhttps://www.ti.com/lit/an/sboa220a/sboa220a.pdf?ts=1593413675172&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fdocs%252Funiversalsearch.tsp%253FsearchTerm%253DAnalog%2BEngineer%2527s%2BCircuit%2BCookbookOr buy a ready made tranisimpedance amp and relax.
Feedback requested for enclosed clock-generator schematics - Page 1
Forum section: electronics / beginners

author: bitman
author_rank: Unknown
timestamp: January 16, 2019, 04:22:13 am
content: Hello,I've been working on creating a CPU using 7400 series TTL chips only (except for the 555 timers). It's a fun project which has taught me a lot - to begin with, that drawing lines on a piece of paper isn't even close to what reality looks like when we actually bring components together. This is my first real schematics - and I would like some input on how to format/display schematics and on the circuit itself.The build I have has a TON of leds to illustrate how everything from clocks, registers, busses etc. work. The design I have uses 3 shifted clock pulses to complete a full operation. For a while I used simple schottkey diodes to create a delay but that did not give me the ability to manually step through each pulse. So hence this design. The 4th pulse (status) is the idle position - just needed to show/explain what's going on. I use very simple BJTs to create enough current for fanout to all modules.A few things that I still am not sure how to implement:* When manually stepping right now I only have a rising edge since the clock stays active (high) while waiting for the next pulse. I am not sure how to implement this so I can get a falling edge too as part of a manual clock - ie. I need no signal. Some kind of delay when in manual mode on the enable signal is what I think is needed. Not sure how to implement the delay - and worse, that would remove the visual aspect of showing the clock signal, so I'm thinking that's not possible.* Entering manual pulse may need to reset the clock to phase1. I most likely will just add a swich to set the Rset pin high on the counter, but I do wonder if it's possible to trigger this reset on when the "step" feature is activated? In other words, I just need a short pulse when the signal goes high, and then it needs to stay low.Note - this is not made for speedWhile I try to keep noise down, this is never going to even get close to the 500Hz I've set the max on the frequency for. The whole idea is having a teaching instrument - for me to learn the physical electronics side, and for others to learn how a CPU actually works. As I get more used to creating schematics I'll eventually get everything else made into a diagram.

author: Kasper
author_rank: Frequent Contributor
timestamp: January 16, 2019, 05:41:57 am
content: Your schematic is nice and clean looking with the different parts separated into blocks. Net labels help with that and they are nice for reading schematic and for drawing the PCB but it is good to include wire connections also when it is feasible without making a big mess. Wire connections make it easier to see how everything connects without having to read all the net labels.For example, auto and step in the top middle and top left should be connected.Also it is good for current to flow from top left to bottom right. For example, auto and step in the top middle should be mirrored across y axis.
Feedback resistor smokes up - Page 1
Forum section: electronics / beginners

author: lsabourin
author_rank: Newbie
timestamp: March 02, 2016, 01:03:34 am
content: Hi all, I've setup the BA283_AM portion of a Neve-style 1073 preamp on breadboard just to test voltages (schematic attached). Problem is that I smoked the 47 ohm R tied to the 2N3055 emitter and to 5k trim on startup. I've got the 5k trimpot all the way down (it clicks). Any clues?L

author: Audioguru
author_rank: Super Contributor
timestamp: March 02, 2016, 01:19:12 am
content: The schematic does not say and does not show what the lettered terminals are for or their voltages. The 47 ohm resistor cannot smoke because it is connected to nothing.Why would a preamp use a 2N3055 power transistor and a transformer? Transformers have not been used for audio since about 1960.

author: lsabourin
author_rank: Newbie
timestamp: March 02, 2016, 01:30:11 am
content: It is connected to the emitter of the 2N3055 and the trimpot and ground. Transformers are being used regularly in vintage audio applications.

author: Audioguru
author_rank: Super Contributor
timestamp: March 02, 2016, 01:58:17 am
content: "Vintage" means old antique stuff. Hey, I am vintage. I am old but I am not an antique yet.Maybe you have the transistor pins mixed up.

author: Seekonk
author_rank: Super Contributor
timestamp: March 02, 2016, 08:57:33 am
content: First off, NEVER start with the pot all the way down. This is a bad design just because you can do that. That sends the output transistor into maximum current.
feeding 72watt to the ts100 - Page 1
Forum section: electronics / beginners

author: DutchNewbie
author_rank: Newbie
timestamp: February 04, 2019, 06:25:53 pm
content: Hi everyone,So I am just getting into electronics got myself an Arduino to just mess around to learn the basics of programming as well as soldering.So I also ordered an ts100 (idk why just fell in love with it) but if I use a 24v 3A power supply it will generate 72watt but the iron is rated for 65watt, would this burn the iron or will it just work fine and only use 65watt? I can't find a cheap power supply for it that is 24v and 60 watt, I come across 24v 48w, and 24v 72w.Thanks in advance!

author: mariush
author_rank: Super Contributor
timestamp: February 04, 2019, 06:43:08 pm
content: The power supply doesn't generate 72 watts. It has the capability to produce UP TO 72w and maintain the voltage at 24v. It only produces as much as a device demands from it.So as an example, if your soldering iron is warming up it may pull 30-50w, when it's already hot and just works to maintain temperature then it may only use 10w or less pulsing the iron on and off periodically.
FeelTech FY3200s - why bother mains earthing it? - Page 1
Forum section: electronics / beginners

author: claytonedgeuk
author_rank: Contributor
timestamp: December 30, 2016, 11:18:40 pm
content: I've got a bit of a question on this. There a bunch of posts around on the FeelTech FY3200s units - that only come with a two pin plug, have no ground - and therefore are free and floating. The modifications I've seen take a three pin socket, take mains earth from this socket, and connect up the low voltage side of the power supply to the grounds on these properly grounding the probe grounds and USB socket in the process.If I check out my oscilloscope - all the probes are grounded back to mains earth - so I would expect just in the process of connecting the function generator to the oscilloscope, you're getting a route back to mains earth for the function generator anyhow.I'm not trying to be clever here - just trying to understand - what extra benefit do we get from connecting mains earth directly on the function generator itself? Or is this more of a best practice thing - in the event we want to run the function generator away from something like the oscilloscope?Thanks!Clayton.

author: cdev
author_rank: Super Contributor
timestamp: December 31, 2016, 03:42:14 am
content: Because the voltage on some of them is high enough to damage projects people are working on, if they don't ground the thing. Very low current, but it is definitely high enough to damage semiconductors.

author: claytonedgeuk
author_rank: Contributor
timestamp: December 31, 2016, 08:57:48 am
content: Ah true...I suppose all well and good if you're just hooking it up to an oscilloscope...but generally you're trying to pass the signal you've generated through a circuit first.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 31, 2016, 09:10:38 am
content: To reduce EMI the switched mode supply essentially need a capacitive ground connection. With only a 2 pin cable this are two small class Y caps, usually something like 2- 4.7 nF to both sides. So effectively you have something like 5 - 10 nF to half your mains voltage. If the supply circuit is bad, this could be more (e.g. larger caps, or only 1). One can measure this voltage with essentially all equipment using 2 wires and a SMPS.Using a grounded 3 wire cable gives you the option to avoid this. Regulations than can require that the metal parts like the BNCs need to be directly connected to PE and not just via small caps to filter RF emissions.

author: jkf1000
author_rank: Regular Contributor
timestamp: January 01, 2017, 12:46:01 am
content: If I remember correctly, there was a youtube video about this device. As part of the review he measured the floating voltages at the BNC output socket against a mains earth reference and concluded that it was substantial enough that some may receive a small shock from there if they were grounded by touching other equipment at the time. I think it was SDG Electronics, but he also chirps in on here occasionally. Check his video for more info and the mods he made. Karl