hybridfree/eevblog-posts huggingface dataset:
Help to identify part AL516 - Page 1
Forum section: electronics / projects

author: dnotq
author_rank: Contributor
timestamp: July 22, 2021, 03:07:21 am
content: I'm trying to repair a small board that received 12VDC when I'm pretty sure it was only designed for 5VDC. I was pretty confident I could fix things until I started trying to find out exactly what the failed component, an AL516 (SOT-25-6 package), actually is.I suspect it is something like a current-mode DC-DC converter, since I can find similar part numbers (AL815) in the SOT-23-6 package on places like Alibaba.Really what I need would be the specs for the AL516 so I can just find a suitable replacement. The circuit controls a 7.4VDC motor and also charges a 7.4V 1200mAh battery (this one, actually:http://wlyoung.com/index.php?m=Product&a=show&id=207).Any info on this part would be greatly appreciated!

author: Buriedcode
author_rank: Super Contributor
timestamp: July 22, 2021, 06:50:52 pm
content: I've seen quite a few ebay boards using SOT23-6 boost converters. Seems to use these:FP6291marking code is ALxxx with xxx being year/date code.http://www.feeling-tech.com.tw/km-master/front/bin/ptdetail.phtml?Part=PA-28

author: dnotq
author_rank: Contributor
timestamp: July 22, 2021, 11:02:53 pm
content: Thanks, that looks like you nailed it! The resistors that control the output voltage (30K and 390K) also make sense according to the datasheet, and would limit the output to 8.4V. It cannot take more than 5.5V input max, which also explains it blowing up with 12VDC is received. The circuit layout also matches the typical-use circuit from the datasheet.Now I just need to find a few in stock somewhere, or find an equivalent. I might see if I can find a better part, since a max input of 5.5V means it is always at the high-end of the allowable range, and it would be nice to have a little more safety margin. Maybe not, IDK. Depends on how hard they are to source.

author: DEHiCKA
author_rank: Contributor
timestamp: July 31, 2022, 10:25:43 am
content: Dirtcheap boost module from aliexpress. Similar layout, but different markings. Can not find the datasheet.

author: Buriedcode
author_rank: Super Contributor
timestamp: July 31, 2022, 07:48:05 pm
content: I have a couple of similar modules, the output cap is far too low value, but its reasonable for low output currents.Mine has the marking B628, which I beleive is this chip:http://www.uugear.com/doc/datasheet/SDB628.pdfas your board seems identical I'm guessing it has the same pinout as the one linkedEdit: just googled the top mark "S25B", and got the PT6221 as the top result:http://www.puolop.com/uploads/pdf/20200513/8fdaa4e14cfbf836da594024e3a4f2ed.pdf(not the best datasheet, askes to install a language pack)

author: DEHiCKA
author_rank: Contributor
timestamp: August 01, 2022, 12:26:10 pm
content: Looks like the one I have is S35B:https://datasheet.lcsc.com/szlcsc/2007241905_TMI-STI3508_C708881.pdfAll three of them are similar with 3-4A switch and 80mOhm MOSFET.
Help to identify part SS1070 - Page 1
Forum section: electronics / projects

author: dnotq
author_rank: Contributor
timestamp: August 12, 2021, 02:41:45 am
content: I am trying to repair a circuit board that received 12VDC instead of 5VDC. After removing the first failed part (Feeling FP6291 boost converter) that was physically blown (and getting help from the forum identifying that part, so thanks!), I found another failed part. The unmarked SOIC-14 on the board was shorting V+ to ground, and upon removal I found some numbers on the bottom:04506 2046SS1070There is also a capital "J" that looks like a manufacturer mark? I suspect the top row is date-code stuff. Searching around the Internet has turn up nothing useful.This part seems to control the on/off function, as well as controlling the 6 motor speeds and driving the 6 LED indicators.Any help identifying this part would be greatly appreciated!
Help to identify this device. - Page 1
Forum section: electronics / projects

author: fc3000
author_rank: Regular Contributor
timestamp: October 17, 2023, 01:25:22 pm
content: Hi all.I have a number of these devices (see picture) that i have not been able to identify.I did some search without any luck.The device is from ON semi.It is a diode. It measures 0.2V (SCHOTTKY).I need some data to check is it is suitable for project.Regards.

author: Ian.M
author_rank: Super Contributor
timestamp: October 17, 2023, 02:01:40 pm
content: MBR745Search terms: BR745 TO220-2Next time, please try to provide enough oblique lighting to make the laser etched part number clearly visible.

author: fc3000
author_rank: Regular Contributor
timestamp: October 17, 2023, 02:30:10 pm
content: Thank you for the help.Thank you very much for the advice on searching.Regards
Help to identify unusual transistor. - Page 1
Forum section: electronics / projects

author: W1ngs
author_rank: Contributor
timestamp: May 21, 2021, 04:55:50 am
content: I tried very hard but came up with nothing! I have this old NPN Si transistor and done rough measures of a few of its parameters but would love to find out what it is. I don't even know what package type this is. I tried looking through JEDEC and didn't come up with a match.The quick measures I performed give the following data:NPN-SiVceo~174VVcbo~235VVces~212VVeb~23VhFE~71 @ Vc=5V, Ic=100mAhFE~71 @ Vc=5V, Ic=500mAhFE~59 @ Vc=1V, Ic=100mAhFE~57 @ Vc=1V, Ic=500mAVceSat~72mV @ Ic=500mA, Ib=140mA (hFE~3.6)hfe~92 @ 100Hz, Vc=5V, Ic=100mAhfe~46 @ 26kHz, Vc=5V, Ic=100mA (inferred fT of ~1.2MHz)Confirmed fT~1.2MHz as Ib=Ic at that frequencyBased on these measurements, I've made an error as hFE shouldn't exceed hfe, but I can re-do that.The package looks as if you took a TO-66, removed the mounting flange and gave a triad of pins rather than a pair.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 21, 2021, 04:59:17 am
content: seems like an to-39 casing ??Was it in a drawer on installed a test equipment ?? maybe with some usb camera or a photo camera who can do macros or zoom big time some markings could be read ?

author: W1ngs
author_rank: Contributor
timestamp: May 21, 2021, 05:20:51 am
content: I was able to read them with the naked eye; no amount of zoom seems to help as there is just so little contrast left.The top row of characters looks like "CGS"Second row looks like J2N148somethingThird looks like a date code and is 76xx or 78xx far as I can tell.I ended up finding the RCA 2N148x series just after posting my message. They are in the TO-8 package and their characteristics match up well with mine. My voltages are considerably higher, but if you are specifying transistors conservatively then it really makes a great deal of sense.So my guess is I have a 2N148xA as the A variants have fT 1.2MHz and the base versions are all 1MHz. Perhaps 2N1486A which is Vcbo=100Vmax in the specs.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 21, 2021, 06:26:52 am
content: some datasheets say this one can heat a lot25w ??

author: W1ngs
author_rank: Contributor
timestamp: May 21, 2021, 04:24:56 pm
content: Yes indeed, the TO-8 is about the same size as a TO-66 (looks like a half-size TO-3) and is designed to be attached to a heatsink. 25W would be out of the question of course in free air; maybe a couple watts in that case.
Help to recognize reference of Connector - Page 1
Forum section: electronics / projects

author: wilmer
author_rank: Contributor
timestamp: October 06, 2021, 05:49:22 am
content: Hi,I have this A AND D scale that use a max2332 to transform TTL to RS232. I need to turn 90 degrees the connector. However, The use a 15-pin connector that I can not find.15 Pin , Pitch 0.1Does someone recognize the connector in the attached picture?
Help to simulate capacitor charge from oscilloscope square wave plus math - Page 1
Forum section: electronics / projects

author: RonFred2
author_rank: Contributor
timestamp: May 19, 2022, 10:56:49 pm
content: [ Specified attachment is not available ]I can display a square wave on ch4 of my scope using built in arb generator: 1kHz from 0 to 5 voltsThen using the scope's advanced math option I would like to show a capacitor charging while the square wave is high.I try to use the typical capacitor charge equation of an RC circuit, but time does not seem to be in my scope's math as an input.Any suggestions on how to plot a capacitor charge plot starting from the scope's square wave display along with scope's math feature? Seems like a time a "time" variable.In photo I feature the capacitor charge equation (simplified) in red and a non-linear curve I would like to see.Any ideas on how to simulate a "time" variable with scope math?

author: ledtester
author_rank: Super Contributor
timestamp: May 19, 2022, 11:13:23 pm
content: There appears to be a key for an integral function (to the left of "Max" and above "d/dx").If that integrates a signal over time you can integrate your square wave to get a value which is proportional to time (while the square wave is high) and then you can use apply exp(-t/RC), i.e. something like:V * (1 - exp( - (integral of square wave signal) / A / (R*C) ) )Here A is the amplitude of the square wave -- i.e. it's voltage when on.

author: eugene
author_rank: Frequent Contributor
timestamp: May 20, 2022, 12:30:28 am
content: Let's see. Your scope will output a square wave. Do you have a capacitor and a resistor?Seriously, a scope is the right tool toobservea capacitor charging. Excel is the right tool to calculate the voltage on a charging capacitor. If you don't have MS Office then download LibreOffice.

author: RonFred2
author_rank: Contributor
timestamp: May 20, 2022, 12:42:51 am
content: Nice LedTester! Your math suggestion worked out very well.

author: RonFred2
author_rank: Contributor
timestamp: May 20, 2022, 12:55:49 am
content: Eugene, My question and task at hand was to learn how to use "time" as a variable in my scope's MATH service. RC charge on a scope was just an example of a function that needs time.See photo below of the other ways I am displaying RC charge on my scope: breadboard, RiGOL arb wave, TEK scope arb wave. Using MATH was the final way I can think of to display the RC charge on a scope.

author: rstofer
author_rank: Super Contributor
timestamp: May 20, 2022, 02:08:51 pm
content: I think it is easier to do with an Analog Discovery 2 - see attached. Nevertheless, it should be pretty simple with a scope, just be sure to trigger on the square wave. FWIW, that example uses a 10k resistor and a 0.1 ufd capacitor so the time constant is 1 ms and I charge/discharge for about 6.25 time periods.
Help to source a high resolution micro display - Page 1
Forum section: electronics / projects

author: Boscoe
author_rank: Frequent Contributor
timestamp: May 11, 2016, 05:16:36 pm
content: I'm currently building a digital camera and I would like to use an EVF for the viewfinder (i'm a photographer and like viewfinders rather than looking at a screen on the back.I'm having trouble finding one that comes from vendors that will actually reply to my emails or that don't cost the earth. I would like something around 0.5" diagonal and VGA resolution with a parallel interface and under £50 each (could go to £100 but don't want to if I don't have to). Those are my preferred options however because the search is proving difficult i'm more than happy to change them.I've tried contacting Kopin - nothing. I've contacted Kopin's distributors however they don't reply to emails and ask you to email them when you ring them (the receptionist won't put you through to anyone). eMagin replied after about the fifth attempt but the basic model is £350exVAT without shipping.Anyone know where I could get something like this?PS I want to use parts that I can buy over and over again with proper documentation eg I'm not salvaging parts out of broken cameras.
Help troubleshooting a DC power supply - Page 1
Forum section: electronics / projects

author: Fluxed Matter
author_rank: Regular Contributor
timestamp: August 18, 2012, 04:14:32 am
content: I picked up this power supply recently at a yard sale hoping I was getting a deal. It works and I started to do some preliminary testing. It was during that time that I found the problem. I was checking the voltages for overshoot when turning on the supply with my fluke using the min/max feature because I did not have a scope at the time. Well I was feeling kind of happy because fluke did not detect any overshoot but that is when I noticed that when the power supply is switched off there is a huge overshoot, I mean a large spike before it goes to 0V. I was testing the supply at 5V and when switched off the fluke recorded a maximum of 21V. Well last night, after finally getting a scope, I got the supply hooked it up to it and here is what I captured.I tested the supply at various power settings such as 3.3, 5, 15, 20, 25 and the maximum of 30V. Here are just a few of the screenshots.This leads me to my next questions. Has anyone seen this before? What was the problem? What should I start checking first?All suggestions are welcome. Thank you.

author: Rerouter
author_rank: Super Contributor
timestamp: August 18, 2012, 04:21:31 am
content: based on the response i would imagine its the control loop powering down before the output falls, as its too well formed for an inductor,
[SOLVED] Help trying to understand voltage requirements from old data sheet  - Page 1
Forum section: electronics / projects

author: gmc
author_rank: Regular Contributor
timestamp: June 12, 2024, 08:19:38 pm
content: I've got some Intel 1103A RAM chips from the early 70's and trying to understand the data sheet.Took a lot of googling but eventually found the Intel data book and after reading through the data sheet a few times I'm not not sure exactly what the voltage requirements are to power these chips.I've read through many datasheets but this one has me stumped.Max Ratings:All I/O voltages with respect to the most positive supply voltage, Vbb is -25V to 0.3VSupply Voltages Vdd and Vss with respect to Vbb is -25V to 0.3VAm I missing some in the datasheet, or is it just poorly documented. What should Vss, Vbb, Vdd be?I've tried to find a schematic that uses these chips and from there I can see what voltages it's hooked up to but coming up empty handed.

author: TimFox
author_rank: Super Contributor
timestamp: June 12, 2024, 08:24:28 pm
content: Those max ratings are "smoke" ratings that will damage the device if exceeded.Not recommended operating conditions.

author: MarkT
author_rank: Frequent Contributor
timestamp: June 12, 2024, 08:29:58 pm
content: The DC and AC characteristics both give the standard operating conditions for supply voltages at the top.

author: gmc
author_rank: Regular Contributor
timestamp: June 12, 2024, 08:31:31 pm
content: lol. How did I miss that!!
help understanding diagram (class D amplifier) - Page 1
Forum section: electronics / projects

author: moretti12
author_rank: Newbie
timestamp: November 17, 2018, 08:00:26 pm
content: Hello guys.I have this diagram of a class D amplifier that im trying to understand and i stumbled across this "DC stabilizer".Obviously the first op-amp creates a triangular curve. But what's the purpose of "DC stabilizer" and how does it work? To me it looks like another integrator with feedback to the first one.

author: Zero999
author_rank: Super Contributor
timestamp: November 17, 2018, 08:49:44 pm
content: Quote from: moretti12 on November 17, 2018, 08:00:26 pmThe embedded link to the schematic is broken. Please upload it here as an attachment. Another issue is I often check this forum using my work's computer when on my coffee/lunch break or after hours and the firewall blocks many other sites.

author: moretti12
author_rank: Newbie
timestamp: November 17, 2018, 08:54:26 pm
content: corrected

author: jmelson
author_rank: Super Contributor
timestamp: November 17, 2018, 10:11:08 pm
content: Quote from: moretti12 on November 17, 2018, 08:00:26 pmIt is to keep the triangle wave perfectly centered around zero. This keeps DC out of the load, which would be a problem if feeding a loudspeaker, for instance. I used a very similar circuit in a class-D servo amplifier I built.Jon

author: schmitt trigger
author_rank: Super Contributor
timestamp: November 17, 2018, 10:22:33 pm
content: Many times, opamps with excellent AC performance, may not have the best DC performance. In a DC-coupled amplifier, a DC performance parameter of particular interest is DC offset, for the reasons outlined above.Therefore, you incorporate an opamp with outstanding DC performance in the feedback loop, and you get the best of both worlds.Nowadays, there may be modern amplifiers with both outstanding DC and AC performance, but I suspect that they are either too expensive or single sourced. Or both.

author: moretti12
author_rank: Newbie
timestamp: November 17, 2018, 11:01:01 pm
content: Thanks for the answerIm starting to grasp this circuit, but i have one more question.What is the purpose of the resistors in the output stage? (680 ohm)

author: schmitt trigger
author_rank: Super Contributor
timestamp: November 19, 2018, 02:46:08 pm
content: Hmmmmm...........My guess is that it is a Zobel network.http://www.wavecor.com/html/zobel_networks.html

author: MiDi
author_rank: Frequent Contributor
timestamp: November 19, 2018, 03:59:24 pm
content: Would guess it is to dampen the LC resonance (LPF) to avoid peaking of frequency response for different loads (impedances).
Help understanding MCP3201 Datasheet. - Page 1
Forum section: electronics / projects

author: fc3000
author_rank: Regular Contributor
timestamp: December 01, 2023, 05:27:08 pm
content: Hi all.Referring to MCP3201 Datasheet:https://ww1.microchip.com/downloads/en/devicedoc/21290f.pdfOn page 19 'SERIAL COMMUNICATION' it describes the method for getting data from the device.If i understand correctly the clocking method is to generate two clocks, to initialize the device.And then another 12 clock to get the data.And the sequence of data is Bo first up to B11.Is this correct?thank you.Regards

author: globoy
author_rank: Frequent Contributor
timestamp: December 01, 2023, 05:42:28 pm
content: Count the positive edges. I think you have to give it 3 clocks and then latch B11 on the rising edge of the 4th clock. So this means a total of 15 clock edges to get a word of data. The first clock triggers the sample.And then if you keep clocking the data order switches to LSB and on the 16th clock you get B1 again followed by B2, etc. I guess they figured for the potential cost of a bunch of clocks at the beginning you could get the data in either endianness and not have to deal with it in software.

author: fc3000
author_rank: Regular Contributor
timestamp: December 02, 2023, 03:50:34 pm
content: Hi globpy.Thank you for the help.I got it working now. I can read data.However the readings seems to be incorrect when the voltage is low.Foe example, at 2.1V I get 0.7V out of the Adc.The readings get much more precise when the input voltage gets close to 2.8V.I looked t the datasheet, but I got confused by all the charts.Can someone tells me which chart describes this error?Regards.

author: iMo
author_rank: Super Contributor
timestamp: December 02, 2023, 05:33:55 pm
content: What is your Vref?How are your IN+ and IN- wired?

author: fc3000
author_rank: Regular Contributor
timestamp: December 03, 2023, 11:41:36 am
content: Hi thank you for the reply.I have a Vref of 4.096.VRegards

author: fc3000
author_rank: Regular Contributor
timestamp: December 04, 2023, 07:53:24 pm
content: Just a not to let you know.I have found the final issue.The problem was in the software.Regards.
Help understanding power consumption in circuit with and without bulk capacitor - Page 1
Forum section: electronics / projects

author: pcaddict
author_rank: Newbie
timestamp: October 08, 2020, 11:03:51 pm
content: I have recently assembled a PCB of my own design that uses a Nordic NRF52840 and will be powered by a coin cell. Before I get too deep into my question, I should mention that I am not at all qualified to be designing PCBs but with the help of forums like this and a significant amount of other reading, I did anyway.The project at the heart of this question is a relatively simple temperature sensor that communicates wirelessly using zigbee. As I have higher ambitions for this project than just using it for my own enjoyment, I started doing quite a bit of research into what it takes to create a wireless sensor node using a CR2450. I have read a number of threads here and on the Nordic forum discussing the use of coin cells and the effects of high pulse currents on these batteries, and allowed room to mount a few different bypass capacitors. After readingthisTI whitepaper and taking some advice from Nordic, I decided to add three bypass caps to the input of my uC, a 47uF (0805), 100nf (0402), and 10pf (0402). For initial power testing, using a power profiler kit from Nordic, I left all three capacitors un-populated.Below, I am attaching a few different measurements taken with my PPK, first without any capacitors mounted, and finally with only the 47uF cap mounted. My understanding, however limited, is that the 47uF cap should lessen the effects of high current pulses. What my graphs seem to show me however is that I am seeing higher peak currents, particularly at the beginning of the window, with plateaus that have rounded characteristics as opposed to flat.The circuit is powered from an onboard regulator on the PPK set to 3.003v. The length of data transmission varies a little but I tried to get an equal sample of short and slightly longer transmissions. The window of the images below is 5.8ms.First, no caps:Now with 47uF cap mounted:I am not really sure what to make of this information. Based on my calculations, the 47uF cap should have plenty of stored energy for these transmissions but it looks like it may be charging in the middle? Any feedback as to what is going on here is greatly appreciated. I'd really like to understand this.
Help Understanding This Voltage Regulator Circuit - Page 1
Forum section: electronics / projects

author: t1d
author_rank: Super Contributor
timestamp: February 20, 2017, 06:34:56 am
content: I found an interesting circuit at Linear Technology and I don't understand what is going on with the voltage regulator section. The circuit is powered by a 9 volt battery and the VR drops it down to 5 volts. What I don't understand is the LED in series in the power rail and the resistor in parallel to the LED. Maybe they are using the LED to drop the voltage, before the regulator? It is a diode... "Dunno," as they say... Obviously, I am not an EE...Thanks for your help...1 - Voltage Input2 - Ground3 - Shut Down4 - Bypass5 - Voltage Output

author: edpalmer42
author_rank: Super Contributor
timestamp: February 20, 2017, 07:12:31 am
content: it's not part of the regulator itself, it's just a sneaky way to get a 'power on' light without wasting any current. You have to drop the voltage anyway so might as well include the LED instead of just dropping it in the regulator. To get 2.0V dropped across the resistor, you'd have a load current in the range of 25 -30 ma.Where is this circuit from?Ed

author: t1d
author_rank: Super Contributor
timestamp: February 20, 2017, 07:19:07 am
content: Thank, Ed...Well, it is a clever approach and I like those...The circuit is a Differential Probe:http://www.linear.com/solutions/6058Thanks for your help!

author: Zero999
author_rank: Super Contributor
timestamp: February 20, 2017, 08:59:20 am
content: The main downside is it reduces the minimum operating voltage by a couple of volts, which could be an issue with a small 9V battery. The traditional approach but with a high efficiency LED with a forward current of 1mA might give better battery life.Nice circuit. It's a shame it's AC coupled only though.
Help understanding W5500 Ethernet hardware design details - Page 1
Forum section: electronics / projects

author: conducteur
author_rank: Regular Contributor
timestamp: October 10, 2025, 10:36:07 pm
content: Hi all,I am working on a project and initially plan to use an Arduino for quick prototyping.For networking, I want to add a wired Ethernet connection using a Wiznet W5500. This chip handles the full TCP/IP stack and is also used on the Arduino Ethernet Shield.While I could just use the shield, I would like to implement the W5500 directly on my own PCB to better understand how it works. Using reference schematics from Wiznet and Arduino, I have already made good progress.What I am still unsure about is how to properly connect the differential pairs to the RJ45 connector. I understand that I will need either an RJ45 jack with integrated magnetics or separate magnetics between the W5500 and the connector.I have noticed that the reference designs include several passive components (resistors, capacitors) between the W5500, the magnetics, and the RJ45. I have looked at various examples and application notes, but I am still not completely sure what each of these parts does.Since I would prefer not to just blindly copy the Arduino schematic, I am trying to understand what each of these components does.If anyone can point me to good resources or explain the purpose of the key parts, I would really appreciate it.Thanks in advance!

author: Selectech
author_rank: Regular Contributor
timestamp: October 11, 2025, 03:23:31 am
content: https://docs.wiznet.io/img/design_guide/Wiznet%20Ethernet%20Design%20Guide_ENG.pdf
Help understanding welder current control circuit - Page 1
Forum section: electronics / projects

author: avitsur
author_rank: Contributor
timestamp: July 03, 2021, 11:05:55 am
content: HiI would like to ask for your help and opinion regarding a scr based current control circuit that I've found on the web. first, let me explain that I'm aware of the fact that there are compact IGBT welders at a reasonable price. the purpose of my attempt is sort of educational and hobby. so, to the point. I have a old "buzz box" welder (230vac single phase input) it has up to 150amp output welding current, selected by taps on the transformer. what I would like to do, is to add this scr based current control circuit that I've found. it is of Russian origin and I've managed to achieve the high current diodes and scr's. I would like to ask for your opinion about it. there is at least one question that I would like to make clear. as you can see in the circuit attached, the cathodes of VS1 and VS2 that produce the "+" output of the welding current are connected to the "earth clamp" of the welder while the "-" the anodes of VD1 and VD2, are connected to the welding rod (elektrod). that is not uncommon, there are situations that reverse polarity welding is needed. now comes my question, as you can see, the negative output of the control circuit rectifying bridge is connected to the positive output of the welding current. is it wired so in order to enable to turn off the scrs? (the control circuit voltage is 24v).thanks for your help.

author: Ian.M
author_rank: Super Contributor
timestamp: July 03, 2021, 12:44:51 pm
content: No. There is no provision in the circuit for forced commutation so it cant turn the SCRs off. They have to turn off naturally, when the current through them drops to near zero.Its wired to delay the turn-on of the SCRs like a simple (leading edge) TRIAC light dimmer. R1 + R2 & C1 provide the variable delay time constant. VD6 (a 5.6V Zener) and SCR VS3 replace the DIAC in the light dimmer circuit, providing the threshold the voltage on C1 must reach before firing. R3 limits the firing pulse current. Diodes VD3 and VD4 feed the firing pulse to whichever SCR VS1, VS2 is forward biased to fire it, and presumably also act to prevent the gate voltage of a SCR already on from the previous half cycle trigging the other one prematurely.
Help Wanted! Pinout/Manual Of VAKO DISPALYS CL501/CS CRT Modual - Page 1
Forum section: electronics / projects

author: TheEPROM9
author_rank: Frequent Contributor
timestamp: October 05, 2019, 07:24:35 pm
content: I have a VAKO DISPALYS CL501/CS CRT Display Modual. It is a really neat greenscreen display that I want to use for a retro computer project. However I have had 0% luck with this, I have however found the 12V power input & when I power it up the HV works as you can hear the 15KHz. However there is no raster on the display or any other sign of life.I have tryed to find documentation on line but I have currently found nothing. I don't know if anyone has tips & tricks or has worked with these at some point as it is from 1988, or can help me reverce engineer it as I am not to familour with the nitty grity detailes CRT circitry.Only IC Is UPC1031H2 Vertical Deflection Driver. The rest of the active comonets are transistors.I have attached sevrail images to provide at least some context.
Help wanted - building a prototype - Page 1
Forum section: electronics / projects

author: thefloridian
author_rank: Newbie
timestamp: June 11, 2020, 06:06:45 pm
content: Hello all. I did a little searching on the forum to make sure i post this in the right place, so I hope that is here.I have a small project that requires some electronics skill. I am personally at a deficit of the required skill set so I’m reaching out to the EEV community.I am building a prototype that involves a device that reports a position to a two digit numerical display. As the position changes the numerical display has to instantly change to update the new position. It is battery operated.So it has a read head or sensor head that moves along a strip of pre-defined positions, and the second component with the LCD readout that also houses a battery compartment.I need someone who can create schematics that can be submitted to manufacture for the required PCB’s.If anyone is interested in a side job please message me and we can arrange to go over more details. I have drawn up some rough schematics that will shed more light. Also, I don’t have much of a budget to work with, so this will probably not be the job that pushes the retirement plan over the top.Thanks!

author: rhodges
author_rank: Frequent Contributor
timestamp: June 12, 2020, 09:22:37 pm
content: Can you give more details here, or do you want to limit the public information?Two digits seem fairly coarse, but I don't know if the position is over a few inches or much more. Maybe the strip could have two sets of stripes, and two optical sensors could report the light and dark pulses to the microcontroller.I have a nice set of libraries for the STM8S on github, including some cheap LED and LCD displays:https://github.com/unfrozen/stm8_libs/wiki/lib_max7219:-LED-controller-for-7-segment-or-matrix-displays.https://github.com/unfrozen/stm8_libs/wiki/lib_tm1637:-4-digit-LED-controllerhttps://github.com/unfrozen/stm8_libs/wiki/lib_tm1638:-8-digit-LED-and-keypad-controllerFeel free to email me if you would like to discuss more.richard@hodges.orgBest of luck with your project!

author: Dmeads
author_rank: Regular Contributor
timestamp: June 13, 2020, 04:29:46 am
content: You can also try freelancer sites like Fiverr and Upwork if you dont find anyone. I have had some success there.

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 14, 2020, 07:45:35 pm
content: Quote from: jonathanelrod@gmail.com on June 11, 2020, 06:06:45 pmThis forum is more about DIY and about sharing an own experience but not about doing somebody's work. So I'm not sure it is the right place.But good luck, I hope somebody can help. There are definitely a lot of professionals (which I am not).
Help wanted suppressing conducted mode EMI - Page 1
Forum section: electronics / projects

author: rhb
author_rank: Super Contributor
timestamp: December 10, 2018, 11:23:01 pm
content: I've discovered that I still have an EMI problem from my 4 ft LED T-8 lamps. I installed a $3 Chinese EMI filter and that made a huge improvement. But I've discovered I still have a lot of noise in the 45-120 KHz region.I reinstalled my 1/8" galvanized metal screen and that had no effect, so it seems pretty clear it is conducted mode EMI being radiated by the house wiring. I'm beginning to think very seriously about getting up in the attic and rewiring my test bench area with BX cable.The attached screen shots show the spectrum with the lights on and then off using 256 sweep averaging. The scope probe is just laid out on a wooden shelf in a straight line from the Instek (which is also quite noisy and in need of shielding the SMPS) to a point about the middle of the room along the wall.I need to design a filter to suppress this, but I'm a bit unsure how to go about that. I tried designing a stop band filter with Elsie, but that convinced me I didn't know what I was doing. So I thought I'd ask for some advice. Designing a filter for the AC line is enough different from past filters to feel the need to do more research.IIRC the total current draw of the two lamps is about 1/2 A, though I'll measure it before actually building and installing an additional filter. I'm also going to test just adding a 2nd of the $3 filters if sweeping one on the Instek suggests it will be effective.FWIW The spectrum displays were made with an Instek MSO2240EA. I discovered I could start the MDO SA demo on my MSO, turn off the AWG and use the SA. It's quite good and with the MSO on 1 mV/div much more sensitive than my 8560A. It also goes to DC while the 8560A only goes to 9 KHz. With a bare 1X probe tip without a ground it's a very sensitive E field detector, and equally good H field detector with a small loop. And by adjusting the input vertical you can desensitize it to make exactly pinpointing a noise source on a PCB very easy.Sadly, GW marketing insists this is for the MDO line only and don't understand how important it is as a tool for embedded system designers which is the target market for the MSO line. So I keep using 1.32. Once I mentioned how much I liked it, they locked the MSO out of the demo in subsequent releases.
Help, what does the g value in the picture mean? - Page 1
Forum section: electronics / projects

author: daisizhou
author_rank: Super Contributor
timestamp: February 18, 2022, 10:27:35 am
content: This is an instrument for testing the power of high frequency energy.I see a "g=20" indication in this calibration screen.I don't know what g=20 means,For example, sometimes when a=10, it means that the instrument performs -10DB attenuation,g will be displayed as g=40.It looks like the g value will follow a (the decay value), but I don't know what mathematical relationship or other rules exist between themPlease let me know if you know, thanks

author: mycroft
author_rank: Regular Contributor
timestamp: February 18, 2022, 12:04:16 pm
content: g=gain?

author: daisizhou
author_rank: Super Contributor
timestamp: February 18, 2022, 01:57:01 pm
content: If it is a gain value, what parameter does it correspond to?
help whit tone circuits - Page 1
Forum section: electronics / projects

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: October 15, 2019, 08:55:09 pm
content: So I am trying to design a tone control for a guitar, and it will probably sound crazy but I want it so when you start turning down the tone it bleeds out the treble and then boosts the mids/lower the other frequencies. I think this can be accomplished whit variable capacitors but that isn't an option for me. I was thinking if it can be done whit 1 potentiometer. the resistance also shouldn't be too low like 1M-500K would be great for the potentiometer.so am I asking for magic or can it be done if so can you please send me a schematic or something so I can implement it in my circuit?
Help with McMurdo Connector - Page 1
Forum section: electronics / projects

author: ludzinc
author_rank: Unknown
timestamp: September 18, 2019, 04:33:20 am
content: Hi AllTrying to find replacement plugs and sockets for the connector in the pics.Data I have at work is that it is a "Plug 4 Way McMurdo OO4/PC 1169-12-02" but googling turns up nothingAny ideas?ThanksSimon

author: Wendy_Preston
author_rank: Contributor
timestamp: September 20, 2019, 07:24:46 am
content: Hi Ludzinc,Here at Harwin we do a few products that line up with the ITW McMurdo ranges - but not this one, I'm afraid. It's not familiar to me at all. Probably the best people to assist are FC Lane Electronics. They took over a lot of the McMurdo range when McMurdo were bought out by ITW - you can see some details on that on this web page:http://www.mcmurdoconnectors.com/Their main site on current McMurdo products is here:https://www.fclane.com/filter/products/manufacturer/itw-mcmurdoThey've been doing McMurdo stuff for a long time, so they are probably the best people to contact. Hope this helps!Wendy

author: ludzinc
author_rank: Unknown
timestamp: September 24, 2019, 03:25:32 am
content: Thanks very much - will reach out them!Cheers,Simon
Help with 1.8 voltage regulator making 2.2V - Page 1
Forum section: electronics / projects

author: cmumford
author_rank: Contributor
timestamp: June 28, 2021, 12:59:46 am
content: I'm making a board (schematic) which uses aMIC5504voltage regulator and aLSF0204logic level shifter to allow my ESP32 S2 to communicate with 1.8 V IC (LM8330) via I2C. I can't get the LM8330 to ACK the I2C read request, and I think the problem is that the 1.8V VCC line is too high. The LM8330 datasheet specifies a max voltage of 1.98 V, and the MIC5504 is putting out up to 2.2V. In the attached screen capture VCC goes down to 1.8V when I try to do a bunch of I2C communications, but when I stop (for 4 sec.) the voltage goes back up to 2.2V.The MIC5504's datasheet says that it will "remain stable and in regulation with no load". Do any of you have any idea what I'm doing wrong in my design?

author: Whales
author_rank: Super Contributor
timestamp: June 28, 2021, 02:38:21 am
content: Possibly some part supplying current to the 1.8V rail rather than sinking it.I'm trying to follow your schematic to work out what it could be, but I'm struggling to find out what is wired to what. Drawn wires would be much easier than a set of parts with net names, I'm basically printing it out now to cross things out and draw wires to understand it.EDIT: A bit of pencil later: schematic looks fine, can't see anything that would bridge 1.8V to anything higher other than the LSF level shifter itself.

author: Whales
author_rank: Super Contributor
timestamp: June 28, 2021, 02:47:20 am
content: Huh? From the afore-mentioned level shifter's datasheet:My brain is too addled today to make proper sense of this, but it looks like VrefB (3.3V) gets joined to VrefA (1.8V) through a 200Kohm resistor and a mosfet. This mean the level shifter leaks current between VrefA and VrefB. Ie you need some sort of permanent load on the 1.8V rail to compensate (1Kohm should be more than enough).EDIT: yep, lookup "leakage" in the shifter's datasheet. If your keyboard IC is low power then it may not draw enough on its own to compensate (except when communicating, as you mention).

author: cmumford
author_rank: Contributor
timestamp: June 28, 2021, 03:11:24 am
content: Oh thanks I didn't occur to me to consider the level shifter. I'll study that datasheet and see what I need to do. Thanks for your response.
Help with a  Buck Transistor - Page 1
Forum section: electronics / projects

author: AtomAmp
author_rank: Newbie
timestamp: November 19, 2013, 04:42:08 am
content: Somewhere I saw a schematic of a Buck transistor. I can't for the life of me find it again or remember where I saw it.It would go in this order: 18v 1a ac to a 1a bridge rectifier to a capacitor to the transistor,(not a dip. Simple 3 pin trans.) to another capacitor andend up with 12v to feed a fan running at 12v 0.07aI can't remember which transistor they used or the size of the caps.Can anyone help?Thanks...

author: Jon86
author_rank: Frequent Contributor
timestamp: November 19, 2013, 06:49:43 am
content: Do you mean a voltage regulator?

author: kxenos
author_rank: Frequent Contributor
timestamp: November 19, 2013, 06:59:39 am
content: I think this is the buck transistor (!)you wanthttp://www.farnell.com/datasheets/1696820.pdf

author: Dragonfly
author_rank: Contributor
timestamp: November 19, 2013, 07:03:08 am
content: I agree. I sounds like you are looking for the LM7812. Here's a reference schematic similar to the one you described.http://schematiccircuit.com/12-volt-power-supply-lm7812/

author: AtomAmp
author_rank: Newbie
timestamp: November 19, 2013, 07:11:16 am
content: My apologize. Yes, I am speaking of a voltage regulator.The transistor that I saw was a 3/4 round, flat top, 3 pin, E,B,C I believe is a TO-92 I think it was a PNP.

author: Dragonfly
author_rank: Contributor
timestamp: November 19, 2013, 07:27:37 am
content: Like this?http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/LM78L12ACZ/?qs=sGAEpiMZZMug9GoBKXZ757KFYdywgvBVGeJTtZXlf7A%3d

author: AtomAmp
author_rank: Newbie
timestamp: November 19, 2013, 06:33:39 pm
content: Yes Dragonfly, just like that!you're the best.Thank you, thank you all for your help!Now I can get back to work...
Help with a ICSP programmer project - Page 1
Forum section: electronics / projects

author: Alaezae
author_rank: Contributor
timestamp: July 25, 2020, 06:40:57 pm
content: Hello,I am trying to design my own ICSP programmer for use with AVR microcontrollers. I am very new to this but figured it would be challenging enough to keep me occupied for a while. Let me preface what I'd like to do:My plan (after researching a few programmers which are out there) is to use a USB to SPI converter chip (datasheet below) and then send that out to the ISCP pins, the problem is that there is extra information in each field. I wanted to know if all that extra stuff (packet identifier, address, etc.) will be a problem since I only want to send the data from the .hex file to the microcontroller. I'm using an FT221 chip, FTDI's USB-SPI converter, all their documentation seems to point to me not using this since they say "No detailed knowledge of USB protocol needed to use our chips."The way the off-the-shelf programmers do it is with a separate microcontroller which converts to SPI from a USB interface on the board. None of them do it the way I was planning to, which is why I was curious if I was completely wrong. I thought that it might have been the cost of the FTDI chip, at $1.50/chip in bulk, it might get kind of expensive when mass producing. I don't know, I figure it's more likely that they don't do it because I'm wrong.Anyways, any help I could get would be very much appreciated. You all are smart people, I don't think this project is that complicated.... I'm still new to this so if I said something dumb please forgive me. Thanks!CamFT221X Datasheet -https://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT221X.pdfICSP Pocket Programmer -https://www.sparkfun.com/datasheets/Programmers/AVR-Pocket-Programmer-v15.pdf

author: oPossum
author_rank: Super Contributor
timestamp: July 25, 2020, 08:01:33 pm
content: FT221X won't work because it is a SPI slave. You need a SPI master to program an AVR.The CH341 does SPI master and can be used for programming AVR.https://ericdraken.com/avr-amtel-attiny-ch341a-isp-programmer/
help with Agilent 82357a GPIB on linux - Page 1
Forum section: electronics / projects

author: cncjerry
author_rank: Unknown
timestamp: January 16, 2022, 11:00:22 pm
content: I switched to linux to see if I could control an HP instrument using python 2.7 and an Agilent 82357a USB/GPIB adapter. I loaded the firmware into it and strangely enough, Keysight connection expert sees it and puts up the ID string. So something must be right, or close to right. I tried tracing it but for some reason when I start connection expert, those commands don't show up in the trace.So I sent a bunch of commands to the device, an HP8904, and I can see the green light blink like it received it but it's not taking any action or replying. I tried multiply termination characters and combinations. You would think that if Keysight Connection Expert can get the the ID, then I should be able to use the Interactive IO facility to do the same, no?I've tried loading the firmware a couple times, etc.Anyone have experience with this? I amj running ubuntu latest and keysight 2021.Thanks

author: m k
author_rank: Super Contributor
timestamp: January 18, 2022, 04:17:47 pm
content: What exactly is blinking green?
Help with an On - Off - On circuit to turn night night lights on? - Page 1
Forum section: electronics / projects

author: DougSpindler
author_rank: Super Contributor
timestamp: November 02, 2023, 09:46:26 pm
content: Purchased an LED lights with an LED night light glow ring. To turn the LED light on the power switch is just flicked to on. But for the LED night light the power switch must switched on for 1 sec, off for 1 sec and on again. Instead of one switch to control the LED light and the LED night light I’d like to use 2 physical switches. One switch to turn the main LED lights on. Easy enough. But then I would like a second on/off switch for the night light LED. When switched on it pulses on 1 sec, off 1 sec and on.Any ideas?I’m thinking of using 2 - 12 Volt time delay relays. When the power switch on the wall is flipped (SPST) on the two time delay relays are powered delays of 1 and 2 seconds. The first would be NC and set to open at 1 second for the first pulse. TDR 2 would be NC too set at two seconds. I’m thinking I would need a 3rd latching relay to keep power flowing to the night lights.Am I on the right track? Or someone have a better idea?

author: coromonadalix
author_rank: Super Contributor
timestamp: November 03, 2023, 06:36:07 am
content: you have programmable timer relays on fleabay with nice capabilities / events for mere dollars

author: DougSpindler
author_rank: Super Contributor
timestamp: November 03, 2023, 05:26:15 pm
content: Could you provide a link to one? Thank you.