hybridfree/eevblog-posts huggingface dataset:
Positive, Negative and Ground via single pin - Page 1
Forum section: electronics / projects

author: kiran_shrestha
author_rank: Regular Contributor
timestamp: April 01, 2020, 05:47:04 am
content: Hey everyone. I have been designing circuits for years but I never thought this could be a problem for me.This time I came up with a problem. I need to design a small circuit based on mosfet or OPAMP which can switch between 0 , +V and -V from single output pin with control signal.I can't use relays or multiplexers, I need a OPAMP or MOSFET design idea. If someone have idea please let me know.

author: KaneTW
author_rank: Frequent Contributor
timestamp: April 01, 2020, 07:04:35 am
content: Any R2R opamp could do it with binary inputs on inverting and noninverting. Kinda overkill though.For MOSFETs, just do a halfbridge but with a third MOSFET for V- IMO.

author: kiran_shrestha
author_rank: Regular Contributor
timestamp: April 01, 2020, 07:10:15 am
content: Yes, thank you for it. The op amp solution i not good for me but i think the mosfet circuit would work for me. I will give it a try.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 01, 2020, 07:34:38 pm
content: Quote from: kiran_shrestha on April 01, 2020, 05:47:04 amwhat exactly is the specification? what power rails available? whats magnitude +V and -V we are talking about? what control signal level and speed? what is the single output? and what its driving? if you ask for people's time, you should give more details. better with diagram or existing circuit/schematics.

author: kiran_shrestha
author_rank: Regular Contributor
timestamp: April 02, 2020, 04:45:24 am
content: Thanks for reply Mr Mechatrommer but I just required a logic not a final schematic.

author: ajb
author_rank: Super Contributor
timestamp: April 02, 2020, 05:59:54 am
content: Start with a digital output that can be tristated (set to high impedance). Use a resistor divider to pull the output to the middle of the rails when tristated. You now have a node that can be set to 0V, your logic voltage (call it VD), or halfway between 0V and VD.Now you just need an op amp circuit to offset and amplify that range to V+, V-, and 0V.If VD = V+, then this is very simple: use a non-inverting amplifier with a gain of 2 (both resistors are equal), use the above tri-level output as the input, and connect the reference node of the amplifier (usually ground) to V+. So an input of 0V gives V-, V+/2 gives 0V, and V+ gives V+. The whole thing can be done with one op amp and four identical resistors.If VD != V+ you'll need to adjust the gain and reference voltage to get the right behavior.

author: kiran_shrestha
author_rank: Regular Contributor
timestamp: April 06, 2020, 09:00:58 am
content: Thank you very much. This is what I am looking for.

author: Zero999
author_rank: Super Contributor
timestamp: April 06, 2020, 11:45:52 am
content: An analogue multiplexer?http://www.ti.com/lit/ds/symlink/ts5a3357.pdfhttps://assets.nexperia.com/documents/data-sheet/74HC_HCT4052.pdf
Positive vs Negative photo resist and the positives and negatives to both - Page 1
Forum section: electronics / projects

author: Anks
author_rank: Frequent Contributor
timestamp: December 02, 2014, 03:26:09 pm
content: Hi I've been making a lot of PCB's lately as not really had the time it takes for the cheaper china based PCB fab's so I've been using the toner transfer method. Now this works but I would like to reduce the failure rate (that isn't too bad now once used to it) and also be able to do finer track spacing.Now that being said I'm very confused about the positive and negative procedure and the different chemicals used for such a method.Are the chemicals that are used in the positive method the same as the ones used in the negative?Is one method much cheaper than the other?And dose either method produce much better results?I have noticed that you can buy negative photo resist film that seems pretty cheap and also you can buy the positive resist in a spray can that seems very expensive. Now I understand that the can may do x amount of board but without trying its hard to know the answer and also read a lot of people have trouble with this method and tend to use pre-coated boards.Any help and advice much appreciated

author: oldway
author_rank: Super Contributor
timestamp: December 02, 2014, 05:54:34 pm
content: A great tip: start with pre-coated boards.You must print your layout on transparencies for laser printer.To get a good toner adhesion, it is necessary roughen the surface by rubbing with emery paper 120.It is essential to have the best possible contrast.To do this, set the printer to the maximum contrast.I glue two impressions one upon the other to remove the defects of impression and to have high contrast.Use commercial developper, not NaOH.Insolation for 2 minutes at 50cm with a 400W UV lamp. (Philips HP 3133)http://www.extralight.info/sun-gallery/ultraviolet-armatures/Philips_HP3133_UVO_st.html

author: void_error
author_rank: Frequent Contributor
timestamp: December 02, 2014, 09:59:13 pm
content: There's another method which replaces transparencies (some printers don't print well on them) with regular printer paper and TRANSPARENT 21 spray to make the paper transparent to UV light. I use a piece of 2 mm thick glass to keep the paper flat, printed side down onto the coated board. I've done PCBs that had SOT-23-5 packages and 0.4mm wide traces and 0.3mm (or less, can't remember) spacing with this method.

author: Anks
author_rank: Frequent Contributor
timestamp: December 02, 2014, 10:23:37 pm
content: Quote from: void_error on December 02, 2014, 09:59:13 pmHave you used this method with negative resist. also mike from mikes electric stuff uses tracing paper and says its better than using transparencies
positives attract? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: March 02, 2024, 08:49:44 pm
content: https://science.slashdot.org/story/24/03/02/1851208/new-study-shows-like-charged-particles-attract-or-repel-in-solutionI wonder if you can use that for electronics some how
Possible bad batch of RTL8201's in circulation - Page 1
Forum section: electronics / projects

author: 5U4GB
author_rank: Super Contributor
timestamp: March 15, 2024, 08:11:19 am
content: For anyone working with RTL8201 PHY's, arecent post on the Konnected.io blogindicates that there may be a bad batch of these in circulation:Quote

author: CaptDon
author_rank: Super Contributor
timestamp: March 15, 2024, 01:18:01 pm
content: One of the 'Big' manufacturers of instrument grade opamps had an internal quality control issue. They informed us that they would replace 1 for 1 any chips we sent back within the failed code date range but they WOULD NOT be responsible for our labor costs. We had a few hundred circuit boards out in the field using those date codes with around 6 'suspect' chips per board. What a freaking night mare!!!!

author: 5U4GB
author_rank: Super Contributor
timestamp: May 25, 2024, 04:51:33 am
content: An update on this, turns out the problem was a missing pullup resistor which didn't matter for previous revs of the RTL8201 up to date code 'M' but suddenly became an issue with the latest revs, date code 'N' and onwards. Apparently this also affected other devices using the RTL8201. Full detailshere, in the entry for 10 May.
Possible Checksum Calculation - Page 1
Forum section: electronics / projects

author: Chet T16
author_rank: Frequent Contributor
timestamp: October 25, 2017, 11:27:38 am
content: Hi guys,I'm going nuts here trying to figure out how the last byte in a packet is being calculated, the final column in the below hex value table.I have the rest of the values figured out.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 two is a sequential number and when all the others stay the same the "checksum" generally decreases by 1, which may tell me something! I've been trying all sorts of things like addition and bit flipping but not getting anywhere.Pointers very much appreciated.

author: HKJ
author_rank: Super Contributor
timestamp: October 25, 2017, 12:02:06 pm
content: Have you tried XOR

author: stmdude
author_rank: Frequent Contributor
timestamp: October 25, 2017, 12:07:26 pm
content: Appears to be 8-bit XOR.Try this tool:https://www.scadacore.com/tools/programming-calculators/online-checksum-calculator/

author: WillHuang
author_rank: Contributor
timestamp: October 25, 2017, 02:07:57 pm
content: The checksum is calculated as follows:Checksum = 0xFFFor each byte in packet excluding the last byte:Checksum ^= byteFinally, checksum ^= 0xFF.This should yield the last byte in the column

author: Peabody
author_rank: Super Contributor
timestamp: October 25, 2017, 02:11:57 pm
content: It's two's complement. Add the bytes, XOR the least significant byte of the sum with 0xFF, then add 1.

author: hlavac
author_rank: Frequent Contributor
timestamp: October 25, 2017, 03:33:36 pm
content: it seems to be simple xor of the bytes. if you xor them all you get 00.to calculate, xor all the bytes except the checksum and put the result in checksum

author: Chet T16
author_rank: Frequent Contributor
timestamp: October 25, 2017, 05:43:45 pm
content: You guys are good, I knew someone would know..just not what seems to be everyone except meIt is indeed an XOR, I ran some code to check incoming packets and they all matched.Thanks!
Possible competition for the LTC2057? - Page 1
Forum section: electronics / projects

author: DiligentMinds.com
author_rank: Newbie
timestamp: August 23, 2015, 12:38:11 am
content: .

author: Andreas
author_rank: Super Contributor
timestamp: August 23, 2015, 06:50:53 am
content: Hello Ken,depends on what parameters you are after.Yes the specs look good.But like the LTC2057 the input bias current is relatively high.And current noise is relatively high on the ADA.So you are limited to input impedances lower than about 10-100k.With best regardsAndreas

author: Kleinstein
author_rank: Super Contributor
timestamp: August 24, 2015, 09:07:54 am
content: It depends on the application which AZ OP fits. One parameter is the size of the input stage. This is a balance between bias current and noise. Low noise types generally have higher bias currents. So the ADA4522 is more on the side of very low noise, but high bias. The LTC2057 still has significant bias - about half of the ADA4522. There are also types with much lower Bias but than more noise.So there is not 1 good AZ OP to fit all needs.The rather unique feature of the LTC2057 is the high working voltage, especially as LTC2057HV. There are not many alternatives at the high voltage. The AD4822 is one, especially at low source impedance.The high voltage low noise types have an additional problem: they get relatively warm und thus thermal design gets more important.

author: tszaboo
author_rank: Super Contributor
timestamp: August 24, 2015, 12:39:45 pm
content: I think it is similar to the ADA4638. That one also has bullshit overshoot with very minimal capacitive load. 20% with 100pF while the LTC has less than 5%.

author: dom0
author_rank: Super Contributor
timestamp: August 24, 2015, 04:22:30 pm
content: Well it only has a typical 69° phase margin at unity gain and that will go down even further when loading it stronger (especially considering the somewhat high closed-loop output impedance of 340 ? in the unity loop gain region!), so, not really surprising.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: August 24, 2015, 04:42:07 pm
content: Quote from: NANDBlog on August 24, 2015, 12:39:45 pmADA4638 is a totally different beast. LTC2057 have bullshit EMIRR.

author: tszaboo
author_rank: Super Contributor
timestamp: August 24, 2015, 04:58:33 pm
content: Quote from: dom0 on August 24, 2015, 04:22:30 pmI was able to make the ADA4638 oscillate by loading it with some PCB trace, some components, cable and a DMM. Wasnt very happy about it. Especially that we were replacing them by hand on so many units due to a deadline.
Possible error in API command description? - Page 1
Forum section: electronics / projects

author: Karel
author_rank: Super Contributor
timestamp: April 26, 2025, 11:02:17 am
content: This is a question about the U-blox NINA-W152 radio module's AT command set description.The pdf document can be found here:https://content.u-blox.com/sites/default/files/u-connectXpress-ATCommands-Manual_UBX-14044127.pdfI don't understand how to use command AT+UBTDIR? What values do I need to use for the parameters when I wantto read the actual values?The command is described on page 86, paragraph 6.30.3.Any ideas?

author: tooki
author_rank: Super Contributor
timestamp: April 26, 2025, 12:12:48 pm
content: Quote from: Karel on April 26, 2025, 11:02:17 amI suspect that’s just a copy-and-paste error in the document, and that the command is one of two things (or both):1. Individual parameter:AT+UBTDIR?<param_tag>, e.g.AT+UBTDIR?vendor_ID, returning+UBTDIR=<vendor_id>.2. All parameters:AT+UBTDIR?, returning+UBTDIR=<vendor_id>,<vendor_id_source>,<product_id>,<vendor_id_version>.

author: Karel
author_rank: Super Contributor
timestamp: April 28, 2025, 01:14:53 pm
content: Thanks for trying to help. I tried your suggestions and also some others but no luck.I always get the response 'ERROR'

author: mikerj
author_rank: Super Contributor
timestamp: April 28, 2025, 01:32:45 pm
content: Supplying a param_tag and a param_val for a query makes little sense. Have you tried without the question mark as per most other commands? e.g. "AT+UBTDIR" or "AT+UBTDIR=0"

author: Karel
author_rank: Super Contributor
timestamp: April 28, 2025, 01:39:30 pm
content: I tried that as well, no luck.What works is using the command to write new settings, it responds 'OK'.But reading the actual settings always gives an error.

author: Andy Watson
author_rank: Super Contributor
timestamp: April 28, 2025, 02:34:34 pm
content: Quote from: Karel on April 28, 2025, 01:39:30 pmCould it be trying to tell you that the settings have not been set, or are set to invalid values? Note 6.30.4 says that you have to use extra commands to fix the settings into the database.

author: Karel
author_rank: Super Contributor
timestamp: April 28, 2025, 03:37:21 pm
content: Quote from: Andy Watson on April 28, 2025, 02:34:34 pmThe firmware in the radio module comes preloaded with a vendor id and a product id from u-blox. The command should be able to show that.And yes, I know that there are also other (external) tools for discovering these id's but that's not the point.
Possible grounding problems on 3d-printer - Page 1
Forum section: electronics / projects

author: LarsT
author_rank: Contributor
timestamp: October 24, 2016, 07:59:54 am
content: Okay, so I've build a 3d-printer made from aluminum which is powered by a 12V swiching adapter and connected to a laptop with USB. I very often experience the connection between the printer and the computer is lost (disconnects and the controller on the printer restarts), when I touch the printer with metal tools (spanner to tighten bolts or tweezers for removing filament etc). What could be causing these problems or what should I check for?

author: singapol
author_rank: Frequent Contributor
timestamp: October 24, 2016, 08:32:31 am
content: It can be a few things. Usually the data cable from PC to motor driver x,y,Z axis. Also the type of interface ic you have used. eg. 74HCxxx type which may be incompatible to TTL level signal if you are using parallel port .What cnc software are you usin, Mach3 windows ? Maybe also cnc software configuration settings that is not compatible with motor driver or hardware. Grounding problem not likely.

author: LarsT
author_rank: Contributor
timestamp: October 24, 2016, 06:17:43 pm
content: Quote from: singapol on October 24, 2016, 08:32:31 amThe cable is USB and to be honest I'm not 100% sure about the communication, but I think it's serial@250k. The printer has a control board with an Atmega 2650 programmed with a 3d-printer firmware called Marlin, and the computer software I'm using is called Repetier Host.The power cable from the switching adapter is connected to the controlboard, which is mounted on nylon, isolated directly from the printer frame (aluminum). So the only contact the control board has with the printer is through the stepper motors (4pin connectors) which are mounted on steel brackets bolted to the frame. I've tried to measure voltage between ground (the casing on the USB port) to the printer frame, but the voltage potential is zero.

author: singapol
author_rank: Frequent Contributor
timestamp: October 24, 2016, 07:01:01 pm
content: Try reloading the firmware (marlin). Also check the connectors.
Possible new definition for Ampere - Page 1
Forum section: electronics / projects

author: gdewitte
author_rank: Unknown
timestamp: April 11, 2014, 03:03:31 pm
content: http://www.eetimes.com/document.asp?doc_id=1321870

author: calexanian
author_rank: Super Contributor
timestamp: April 11, 2014, 04:33:44 pm
content: Interesting. Not much value from an electronic engineering perspective but on a QED scale it would be valuable to know. They are not speaking so much about the absolute value of the ampere in a macro way (Where we live so to speak) but getting a handle of the value of a single electron jump. This will need a whole new set of definitions. Cool stuff.

author: ejeffrey
author_rank: Super Contributor
timestamp: April 11, 2014, 04:53:47 pm
content: No, it is definitely also about getting an absolute reference that can be scaled up to uA, mA, and amps -- much like a JJA for voltage references. A single josephson junction has a typical voltage of 10s of microvolts, but you build an array of them and you get get a larger voltage to use as a reference, which you can then scale with resistors and bridge circuits to compare to whatever voltage you need.

author: calexanian
author_rank: Super Contributor
timestamp: April 11, 2014, 06:23:48 pm
content: You are looking at it a different way than I am. They are not changing the "value" of an amp. They want to express that same value in another more precise way, in other words how many jumping electrons constitutes an ampere. Naturally it would have to be 42... O0

author: notsob
author_rank: Frequent Contributor
timestamp: April 11, 2014, 10:19:59 pm
content: Wouldn't an Amphour Compere be called an Ampere
Possible Static Issues - Page 1
Forum section: electronics / projects

author: mribble
author_rank: Regular Contributor
timestamp: April 03, 2021, 11:53:16 am
content: I've made a electric spinning wheel (the kind that turns wool into yarn). You can see a few images of it below.A few people using it have issues with it randomly turning on/off. After rebooting everything continues working. I'm starting to wonder if it has to do with static electricity building up and then shorting to the circuit board or switch. I don't have any experience with this sort of thing. Are there some best practices for designing circuit boards to resist static or things I could do to the enclosure to help with this? Even if you have idea on crazy hacks to protect it (tin foil) or maybe some kind of spray you could put on the plastic case? The plastic case is mostly glass reinforced nylon if that matters.I've attached the pcb schematic which is pretty simple. The brushless motor controller is inside the metal motor case and I suspect that is fine against these sorts of issues. The pcb itself is just a 2 layer design with a ground plane on the top layer.The issue that makes this hard to debug is I still haven't been able to reproduce the problem locally and only a few people have seen it. I would like to have a little more knowledge about this before I start to have users who can reproduce this test things. Internet searches didn't point me to very useful things, but I'm happy to read existing documents if people know of good sources that might be useful.If you folks have any suggestions I'd much apricate it!
Possible to use half bridge gate driver for boost converter? - Page 1
Forum section: electronics / projects

author: mark86
author_rank: Newbie
timestamp: June 07, 2017, 01:53:31 pm
content: It seems like there's plenty of half bridge gate drivers specified for use in motor control or buck converters but no mention of of boost converters.Can these be used for a synchronous boost converter like this?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 07, 2017, 03:33:44 pm
content: Take a close look at the circuit you've drawn. Synchronous boost == synchronous buck.So, yes, this is fine.Tim

author: mark86
author_rank: Newbie
timestamp: June 08, 2017, 01:06:19 am
content: When you put it that way it's obvious...

author: jbb
author_rank: Super Contributor
timestamp: June 08, 2017, 05:32:11 am
content: Reasonable question.One minor issue: 0% duty cycle (i.e. connect output to input) isn't possible. This is because you need to turn on the lower side MOSFET sometimes to charge up the bootstrap capacitor.Also remember to check that the gate driver is rated for the peak output voltage of the switcher :-)
Possible to use pin-compatible displays from other models/makes with my phone? - Page 1
Forum section: electronics / projects

author: MadMir
author_rank: Newbie
timestamp: June 15, 2020, 06:25:04 am
content: Hi all,First post please let me know if this belongs somewhere else or I if need to jump through a hoopProblem:I recently broke the screen on my Sony Xperia L1 G3313, and due to the prevailing worldwide situation I can't find a replacement screen in the local market.The LCD has slightly leaked in the corner, and only the bottom ~1 inch of the touch is working.I am unable to use ADB (https://developer.android.com/studio/command-line/adb) or scrpy (https://github.com/Genymobile/scrcpy) to get into the phone because the phone is powered off, and has a power-on password. i.e. I cant get it to boot and run the adb service etc...Embarrassingly, I have broken the screen twice before, and replaced it myself - which means I have three broken known compatible screens on hand.Question:1) Can I use a 'pin-compatible' display from a different phone? (One available in the market, aesthetics are not a primary concern.)2) If so, how would I find a display that is pin-compatible? The G3313 user manual is of no help and I don't know where else to start looking3) I have seen off-brand displays everywhere - how do the OneHungLow chaps get their schematics?4) Can I interface with the mb directly? I have a Raspberry Pi, and a Xilinx ZYNQ FPGA handy, wondering if there is a way to hack the display output directly. I also have a lot of time on my hands.5) Any other ways around my predicament? Root the phone, hack the other broken screens into one frankenstein working screen, idk.Any help is much appreciated, cheers.PS: The images below are of my current setup and replacement screens I have used in the past, I can't find pictures or part numbers of the original screen.
Component ID - Page 1
Forum section: electronics / projects

author: BillyO
author_rank: Super Contributor
timestamp: June 09, 2023, 02:17:24 am
content: I'd appreciate it if anyone could get me on the right track with this thing.It's obviously an optical device of some sort. The internal device is TO-5 sized and it has a thick aluminum enclosure. None of the 4 leads are grounded to the case.There are no markings of any kind on it.

author: BillyO
author_rank: Super Contributor
timestamp: June 09, 2023, 07:17:10 pm
content: Ahhh,I think I may have found it. It might be a Melexis MLX90614 infrared sensor.Some day I'll have to hook it up to an Arduino and try it out.

author: Benta
author_rank: Super Contributor
timestamp: June 09, 2023, 07:53:54 pm
content: Looks more like a laser diode to me.

author: barshatriplee
author_rank: Regular Contributor
timestamp: June 11, 2023, 02:27:15 pm
content: Yeah. Can be an MLX90614. Personally, I used only silver coloured ones like this:https://www.theengineeringprojects.com/2019/05/introduction-of-mlx90614.htmlBut I can see this one has a black version too:https://www.aliexpress.us/item/3256801230944509.html?gatewayAdapt=glo2usa4itemAdapt

author: Kean
author_rank: Unknown
timestamp: June 11, 2023, 02:51:06 pm
content: I have some of the black MLX90614ESF-BCC parts, and they look just like that - but they also have a part/batch? number printed on the side in white "BCC4578D01". Same with the longer BCI variant.
a question about PCR Amplification  - Page 1
Forum section: electronics / projects

author: Crystal-JU-206
author_rank: Newbie
timestamp: October 31, 2016, 02:53:25 am
content: Whether crystals or oscillators can be used in a PCR Amplification?Ps: I am not familiar with electronics.Thanks in advance!

author: Crystal-JU-206
author_rank: Newbie
timestamp: October 31, 2016, 03:40:32 am
content: So you know something about that ?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 31, 2016, 01:57:23 pm
content: It's my understanding, PCR is done entirely in liquid phase, no crystals required.Tim

author: LukeW
author_rank: Frequent Contributor
timestamp: November 03, 2016, 05:33:13 am
content: It's basically just a programmed cycle of temperature steps up and down.Some thermocyclers do use Peltier arrays, and technically I suppose they are crystals of semiconductor.(Bismuth telluride, usually.)And most thermocyclers would indeed contain an ordinary crystal for the MCU clock.
post your pretty electrical distribution box - Page 1
Forum section: electronics / projects

author: sarepairman2
author_rank: Frequent Contributor
timestamp: February 21, 2016, 07:26:17 am
content: my electrical distribution box is pretty scary because when you open it you get attacked by live conductors etc. It's kind of like opening a jar of pissed off electric eels. I am surprised I did not find a empty bottle of liquor or a xenomorph inside of it to be honest.I am looking to redo it but i was wondering if people here have some inspiration for this job.
Potential pitfalls in adapting an old PSU? - Page 1
Forum section: electronics / projects

author: jcreigh
author_rank: Newbie
timestamp: June 18, 2013, 01:23:35 am
content: I recently came into possession of an old power supply unit lacking a front panel. (Really, four power supply units in a single housing. See attached pictures.)It powers up fine, and poking around (carefully!) with a volt meter reveals that there are +5 V, +12 , and -12  output rails.I'm thinking about taking one of these units, building a housing around it, exposing the existing power rails on banana plug receptacles, and adding a variable power rail. (probably provided by a adjustable linear regulator)Is this a reasonable thing to do? If I were to do it, what pitfalls should I be aware of? (especially those related to safety!)The claimed specs of the supply (printed on the PCB):INPUT:AC115V 1.4AAC230V 0.8A50/60 HZOUTPUT:5V 5.6A+12VP 2.7A+12V 0.5A-12V 0.6BTW, any ideas on what the difference between the two +12 V rails is, and why they have a different current rating?

author: c4757p
author_rank: Super Contributor
timestamp: June 18, 2013, 01:36:26 am
content: Quote from: jcreigh on June 18, 2013, 01:23:35 amMy guess is that "+12VP" is 12 Vpower. It would sacrifice a bit of regulation and low-ripple performance in exchange for a higher current output. Throw a big load on it and look at it with a scope - I bet it's not too closely regulated.

author: Smokey
author_rank: Super Contributor
timestamp: June 18, 2013, 05:02:08 am
content: It was impossible to check out the huge pictures on my phone.but.......That supply kind of sucks based on the specs. Its really not worth the effort to mod in my opinion. Any dead computer will have a supply with more juice than that by a lot. Unless there is something special, scavenge it for parts and start with a PC supply or a laptop supply if you just want some juice on +12V.As for the dual 12Vs, one is probably for system power or something mechanical and the other just for biasing something like opamps.

author: smashedProton
author_rank: Frequent Contributor
timestamp: June 18, 2013, 05:09:04 am
content: I would separate them and embed them in future projects

author: babysitter
author_rank: Frequent Contributor
timestamp: June 19, 2013, 04:54:19 am
content: Keep them for embedding them into your projects they are suitable for. Get your circuits running on the lab bench, then box them up together with one of the power supplies. Have a look, they might be very similar, maybe just varying with the feedback voltage divider that you can use to set your own voltages needed. If your project is a lab supply - I recommend a post-regulator with current limit, these would dump a lot of energy into failing circuits under test, guaranteeing to kill them.

author: smashedProton
author_rank: Frequent Contributor
timestamp: June 26, 2013, 06:37:12 am
content: You should probably need to worry about the minimum load for these because they are switching supplys. My haxed computer psu floats over 5 volts and ripples under no load. I suspect these would do similar. But anyway, nice find ; )
potentiometer more control - Page 1
Forum section: electronics / projects

author: Liteace
author_rank: Regular Contributor
timestamp: July 20, 2019, 11:56:30 pm
content: Ive got here a modification pc power supply that Im using as a bench power supply, I am having a problem with the adjustable output,I have tried a 10k pot and its only the last few degrees that adjust the voltage, because its using a small area its difficult to get it to the precise volts I need, I thought I would try a 50k pot, thinking more range more control but that does the same, whats the best solution for this please?Thanks

author: Airmann90
author_rank: Newbie
timestamp: July 21, 2019, 03:40:22 am
content: A multiturn pot is nice. I use a ten turn for my psu.Sent from my SM-G930W8 using Tapatalk

author: Whales
author_rank: Super Contributor
timestamp: July 21, 2019, 04:19:26 am
content: If only the last few degrees affect the output:(1) Add a resistor in series with the pot. If done correctly you will make all of your pot's turning range usable.(2) Check if you are using a log pot (in a circuit that expects a normal linear pot) or visa versa.

author: coppercone2
author_rank: Super Contributor
timestamp: July 21, 2019, 05:37:06 am
content: you can put two pots many power supplies do this instead of a ten turn trimmer. no reason not to put 2 ten turn trimmers other then the fact that it gets stupid to adjust

author: sleemanj
author_rank: Super Contributor
timestamp: July 21, 2019, 06:14:45 am
content: Well, last few degrees could mean close to max, or close to min depending on how it's wired, in either case the difference over that last few degrees is less than the pot value. If you are using a 10k pot, I would try a 2k pot and an 8k resistor in series, which end it is in series with will depend on if you need to adjust the bottom end or top end.

author: Liteace
author_rank: Regular Contributor
timestamp: July 21, 2019, 02:01:27 pm
content: Ive got 12 volts with the 2 wires open and 16 volts with the wires shorted, whats the best combo of resistor in series with the pot to get smoother control rangeThanks

author: Liteace
author_rank: Regular Contributor
timestamp: July 28, 2019, 08:24:52 pm
content: I made this in the end as the combinations of pot and resistor I just couldn't get it correct
Potentiometer replacement  - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 25, 2019, 09:53:24 pm
content: I have attached a picture of the 50kpot that needs to be replaced.Problem is I can't find any pots with an integrated switch which is what the two side pins are for so I'm looking at possible alternatives on Aliexpress but still couldn't find a similar shaped one but what about this one:https://bit.ly/2K3OeTT.Will it get the job done? If not is there a certain name this type of potentiometer carries?

author: bob91343
author_rank: Super Contributor
timestamp: May 25, 2019, 10:20:06 pm
content: The pot you have found will work as long as:1. The switch rating is sufficient (voltage and current)2. The taper of the pot (linear or logarithmic) is the same.Judging from the link you show, there is no way to tell these things. If the switch rating isn't sufficient, the new switch will fail sooner than it should. If you replace a linear with a logarithmic or vice versa, you will get a strange action, with most of the control at one end or the other of rotation. It will work, though. Volume controls are usually logarithmic and tone controls usually linear.From your picture it appears that what is wrong is that the old switch is broken or worn out. At least what it looks like to me is that the switch point is missing and it won't make contact. That is a very common configuration that was used for many years and perhaps you can find a junk radio to cannibalize or, even, just move the switch section over.
potentiometers that have leads up swept toward the knob  - Page 1
Forum section: electronics / projects

author: slim
author_rank: Contributor
timestamp: February 01, 2014, 01:56:22 pm
content: Hello all,I am looking for a potentiometer that has leads up swept towards the knob so I can mount it from under the pcb.I have looked everywhere and no luck.anybody know a source for these? 250KThanks in advance

author: Rerouter
author_rank: Super Contributor
timestamp: February 01, 2014, 01:58:13 pm
content: why not just take a pair of pliers to a standard pot? more specifically a vertical mounting one (longer leads)

author: slim
author_rank: Contributor
timestamp: February 01, 2014, 02:02:08 pm
content: Thanks for the reply, Thats a good idea. and I would do that for a few one offs. but the amount I need would be a burden..Thanks again for the idea, I will keep it in mind.

author: dannyf
author_rank: Super Contributor
timestamp: February 01, 2014, 03:19:44 pm
content: QuoteCall ALPS or panasonic or any other decent manufacturers and they can do anything you want, as long as you pay.

author: Macbeth
author_rank: Super Contributor
timestamp: February 01, 2014, 06:24:37 pm
content: Just use a roll of tinned copper wire? poke through pot tab and hand solder to PCB, then tab, then use side cutters in-situ from the reel. Rinse and repeat.

author: calexanian
author_rank: Super Contributor
timestamp: February 01, 2014, 06:34:05 pm
content: They used to use those in ampeg amplifiers. They are around. Do you just need a few for a repair?

author: rollatorwieltje
author_rank: Unknown
timestamp: February 01, 2014, 08:49:06 pm
content: With these Piher potentiometers you can stick the shaft into the back. Just mount them on the bottom of your board and make a hole for the shaft.Be aware that those are not really suited for regular use, they are cheap trimmer pots.

author: Rory
author_rank: Frequent Contributor
timestamp: February 01, 2014, 09:39:31 pm
content: Maybe Bourns PDB18 series.Single gang PDB181DDual gang PDB182DAlso Bourns PDB24 seriesSingle gang PDB241DDual gang PDB242D
Pots in series? - Page 1
Forum section: electronics / projects

author: digik
author_rank: Regular Contributor
timestamp: October 02, 2016, 07:09:57 pm
content: I have a step-up converter that has voltage and current adj. It can deliver a maximum of 3A current, but i only need 1A maximum. I want to connect another pot in series with the one that adjust current so that i can turn one pot to maximum and still deliver 1A max. Can it be done by simplu put in series another pot? Sorry for the convoluted question.

author: Ian.M
author_rank: Super Contributor
timestamp: October 02, 2016, 07:24:57 pm
content: Possibly, but its impossible to be certain without knowing what chip it uses and knowing whether they've stuck to one of the standard corcuits for that chip,or done something 'clever'.

author: retrolefty
author_rank: Super Contributor
timestamp: October 02, 2016, 09:05:42 pm
content: Yes, but you have to determine the correct leg of the original pot to add your additional pot. Plus wire your new pot as a rheostat (two terminals) not a potentiometer.

author: Fungus
author_rank: Super Contributor
timestamp: October 02, 2016, 10:04:28 pm
content: You mean add a resistance to the pot so that the output range is [0..1A] instead of [0..3A].Yes, it should be possible but you need the extra pot to be twice the resistance of the existing one.Or you could just add a fixed resistance in series instead of using another pot....all this assumes the existing pot is linear and that increasing resistance is more amps. If it's non-linear or uses an inverse relationship then it won't work (you'd need to remove resistance, not add it)
Potting for Automotive electronics - Page 1
Forum section: electronics / projects

author: DeanA
author_rank: Regular Contributor
timestamp: September 12, 2021, 01:12:04 am
content: Can anyone advise me what type of potting is used for this type of Automotive electronics.It has a sort of rubbery feel to it.Even better if it has good thermal conductivity.Thanks in advance.

author: james_s
author_rank: Super Contributor
timestamp: September 12, 2021, 03:23:15 am
content: The rubbery stuff is typically a silicone based compound. I don't have a specific product for you but I'm sure there are a whole range of them.

author: bdunham7
author_rank: Super Contributor
timestamp: September 12, 2021, 04:58:13 am
content: Look for Sylgard from Dow. Don't expect great thermal conductivity, although there are epoxies that are better at that.

author: Miyuki
author_rank: Frequent Contributor
timestamp: September 12, 2021, 10:43:42 am
content: I think it was in a Big Clive's video when he opens some of this potted stuff and found potting is relatively thin and inside is filled with sand-like materialBut it was probably a cost measure as those pittings are on an expensive side

author: james_s
author_rank: Super Contributor
timestamp: September 12, 2021, 07:25:58 pm
content: Yeah that's definitely not the correct way to do it, potting should be used on its own, but yeah it's relatively expensive so that would be the reason a sketchy company might use sand as a filler.
Potting influence on RF inductors and capacitors - Page 1
Forum section: electronics / projects

author: Koen
author_rank: Frequent Contributor
timestamp: December 06, 2015, 04:29:52 am
content: Hello, do potting compounds (in this case of relative permittivity 4.6, similar to FR4) completely surrounding inductors and capacitors influence their characteristics ? If so, would shielding the 0402 components beneath a small bubble of air or beneath a cube of low density foam help ? I have been trying to match an antenna for weeks now and, sadly, it finally dawned on me this morning that the matching network might not behave equally potted or potting-free.Thank you very much, Koen.

author: Rerouter
author_rank: Super Contributor
timestamp: December 06, 2015, 04:45:53 am
content: Look closely at the potting compound datasheet, if its intended for circuit board work, then it should have all the relevant information, if you have control of your potting process you can analyse how it will effect your signals like it is traces and components on an inside layer with different layers made of different materials, its something that is already done, but generally at a pcb fab,

author: DanielS
author_rank: Frequent Contributor
timestamp: December 06, 2015, 05:33:59 pm
content: Quote from: Koen on December 06, 2015, 04:29:52 amIs 4.6 for your compound different from 1.0 for air that would normally surround your components? Yes? Then it creates additional parasitic capacitance around all the components it touches and may be sufficient to detune RF circuits beyond its expected working range.
Potting inside of the Wall plug Power Supplies - Page 1
Forum section: electronics / projects

author: elefurtronik
author_rank: Regular Contributor
timestamp: April 18, 2023, 01:24:36 pm
content: Hello,Is it logic to add potting inside of the wall plug power supply if it is working in a humid area? Do I see any issue if I add potting material on the circuit?

author: jpanhalt
author_rank: Super Contributor
timestamp: April 18, 2023, 02:33:48 pm
content: Potting can decrease thermal conductivity between the circuit elements and room air. Your circuit would run hotter. Since wall warts are designed to be as cheap as possible, there may not be much thermal margin. There are non-electrically conductive and highly heat conductive materials (e.g., epoxy-BN mixtures), but I would probably just insure everything was well protected with conformal coating. For BN-epoxy, see example here:https://www.mdpi.com/2073-4360/11/4/597/pdf
potting low leakage? (electrometer probes) - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: September 04, 2013, 06:30:40 am
content: I would like to make a triaxial cable probe. I was going to solder teflon wire to the triaxial cable end (cutting and unraveling it) but I am unsure if it is possible to ruggadize this connection.I was thinking about putting epoxy or GOOP strain relief on the solder joint, but I don't really know if it will effect the reading on a electrometer.I guess the other method would be to cut some grooves into teflon plates and press the wires in there, so they are press fit and the pressure provides strain relief without a glue type compound.

author: qno
author_rank: Frequent Contributor
timestamp: September 04, 2013, 10:13:34 am
content: Carefull a lot of nylons are hygroscopic.His will increase leakage.Teflon is until now the best. Free air is better.

author: Unknown
author_rank: Unknown
timestamp: September 04, 2013, 10:36:54 am
content: Did you read the Keithley low level measurement handbook (available from their website)? It contains several hints how to reduce leakage, which insulation materials perform the best, guarding, etc.
Potting of PCB and mechincal stress on componenets (thermal cycling) - Page 1
Forum section: electronics / projects

author: walkeryyj
author_rank: Newbie
timestamp: May 24, 2018, 09:38:48 pm
content: Hi all,I have a project where we have a small fairly complex PCB with lots of SMD components (as small as 0402). The device will be subject to strong vibration and needs to be potted for other structural/mechanical reasons (it’s part of a motor and load transfer is something we need to take into account.)I have selected an epoxy that seems to be a good fit with respects to thermal conductivity and hardness (D90, Tensile Strength ~10,000 PSI) etc however what I am concerned about is having components tear off our boards while being thermal cycled.The material I’m looking at is marketed as having low shrinkage (.002 In/In) and lists its thermal expansion at 1.5x10^-5 in/in F. The PCB measures maybe 1.2”x6” and will live in an epoxy block that is ~ 2”x2”x 7”. Normal operation will be 25C to 80C but COULD be used in an environment as low as -30 CCan anyone give any insight into if we need to be concerned about PCB failure due to the epoxy destroying components?What’s best practice here?Thanks!
Potting RJ45 with epoxy - Page 1
Forum section: electronics / projects

author: batteksystem
author_rank: Regular Contributor
timestamp: November 26, 2021, 11:49:39 am
content: I am designing some RJ45 connection and to protect them against water ingression, I would like to pot the whole PCB, but I am worry how to protect the epoxy from going into RJ45, which is vertically oriented, there are some perforation at the bottom of the connection, should I use conformal coating or RTV silicone to seal the compound first?Thanks.

author: sicco
author_rank: Regular Contributor
timestamp: November 26, 2021, 12:43:51 pm
content: Most connectors, and RJ-xx in particular, rely on the idea that a spring corrects for any displacement. The spring is the metal wire / pin. It needs the freedom to move.Displacement will come from thermal expansion / shrinkage. Shock. Vibration.If you disable the spring, then you no longer have a guaranteed connection over time…Potting in epoxy is a perfect way to disable a spring.

author: Terry Bites
author_rank: Super Contributor
timestamp: November 26, 2021, 06:09:02 pm
content: I wouldnt, gunk will find a way in. Get a sealed RJ45https://www.aliexpress.com/w/wholesale-ethernet-rj45-waterproof-panel-mount-connector.html

author: ajb
author_rank: Super Contributor
timestamp: November 26, 2021, 08:14:34 pm
content: You can use a more viscous material to seal around the connector before potting the PCB, but you'll need to make sure the two are chemically compatible. It may also be possible to seal the connector with tape or something before potting, depending on the geometry.

author: jonpaul
author_rank: Super Contributor
timestamp: November 27, 2021, 05:48:39 pm
content: Bonjour, Neutrik makes liquid sealed RJ-45X. Made in Germany not China.Potting generally decreases reliability due to chemiques and mechanical stress.It can be done but required a lot of technique and experience.Bon ChanceJon

author: batteksystem
author_rank: Regular Contributor
timestamp: December 01, 2021, 11:09:01 am
content: Thanks for all the information!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 01, 2021, 12:05:16 pm
content: Also if you're considering potting, you're probably much better served by a circular M8 or M12 connector and cables. Cables are available as standard products, between various ends including to 8p8c.Your first option should be a sealed (IP65+) enclosure with bulkhead connectors. Circular or sealed 8p8c ("RJ45") connectors can be used. If condensation or leakage can occur inside the box, then conformal coating should be considered. If that is insufficient, finally, potting should be used.Note that potting serves two primary purposes: physically occupying space so that liquid water cannot condense, and supporting the contents mechanically. A flexible material is generally preferred, to avoid stressing the components. Hard epoxy is likely to shear components completely off the board. There are soft epoxies, or silicone or urethane compounds. The choice depends on desired durometer (rubber firmness), thermal conductivity, chemical compatibility, etc.Tim