hybridfree/eevblog-posts huggingface dataset:
Lab power suply - Page 1
Forum section: electronics / projects

author: DrMikeCZ
author_rank: Newbie
timestamp: February 05, 2015, 05:13:05 pm
content: Hello everyone!I want to build my own lab power suply, I already have toroid transformator (100VA, 24V). I want to somehow control voltage from 0,something to 20-24V and there is the problem.I dont know what technique use. I want to use maximum power of that transformer so about 4-5A so i can´t use linear regulators. I´ve done some research on di-gi key, but I haven´t found anything to do that job... can somebody help me?

author: diyaudio
author_rank: Frequent Contributor
timestamp: February 05, 2015, 05:19:13 pm
content: Build a HP E3620A based on the schematics. simplicity == beauty.http://user.engineering.uiowa.edu/~expeng/equipment/HP_E3620A_manual.pdf

author: angelioto007
author_rank: Contributor
timestamp: February 05, 2015, 05:21:21 pm
content: Well, you can add several linear regs in paralel to achieve high currents...btw Welcome to the EEVBlog comunity

author: void_error
author_rank: Frequent Contributor
timestamp: February 05, 2015, 09:46:13 pm
content: You can starthere- it's a long read but it might give you a few ideas. Some things were tested, most of them were not.

author: richard.cs
author_rank: Super Contributor
timestamp: February 05, 2015, 10:26:21 pm
content: Quote from: diyaudio on February 05, 2015, 05:19:13 pmI find it interesting that the two outputs have a different preregulator setup. Maybe they stole the extra winding to power the display or maybe it was just decreed a little extra dissipation was ok on one channel. If I were building a clone I think I'd make them both the same.
Lab power supplies glitch protection idea - Page 1
Forum section: electronics / projects

author: unitedatoms
author_rank: Frequent Contributor
timestamp: July 11, 2020, 02:10:52 am
content: Lab power supplies need glitch protection, and I think I found a solution, though may be an overcomplicated one.Is it correct solution ? And is there a simpler solution ?Problem:There is a problem for any digitally controlled supply or motor driver to prevent sending uncontrolled energyto load. In two cases. When the circuit is powered on and when it is powered off. Just for few milliseconds while CPU is beingbooted or staying in reset.Solution is a circuit with use of TCA9534A:Start: For start there is a relay with normally closed contacts to shunt load to a 10 Ohm resistor.Phase 1: When AC power is applied, the +24V and +3V rails gradually reach their nominal voltages.During phase 1, relay driver input is held low by 10k pull-down resistor, gate capacitance of relay driver and fact that TCA9534A is high-Z input.Phase 2: The power-on reset IC sends a LO pulse. The relay driver is still keeping relay de-energized.Phase 3: The voltages are all settled. The CPU has control over all circuits and can drive relay any time. User or firmware drives DC.Phase 4: AC power is removed. Rails start gradually to go lower. CPU is running until power-on reset IC begins a reset pulse.Gate capacitance of relay driver is discharged using diode and 10k resistor. Relay is deenergized. Load with it's own capacitors quickly reaches zero through 10 Ohm bleeding resistor.Phase 5: Everything is de-energized. There is no remaining uncontrolled energy on rails. Load is disconnected.I think the chip with I2C protocol is good solution, because no matter how long it takes for CPU to boot, it can keep some guaranteed state from first microsecond.Edit: The IO extender chip output needs a 150 ohm resistor to prevent shoot-through.

author: David Hess
author_rank: Super Contributor
timestamp: July 11, 2020, 08:20:27 pm
content: I am not sure why it needs to be so complicated. Old analog only designs did things like clamping the reference and drive to the pass element until the control circuits were operational.

author: Andreas
author_rank: Super Contributor
timestamp: July 12, 2020, 09:05:30 am
content: Hello,the 10 Ohms resistor will be happy when you are charging batteries during black out.In my self built power supply (also with processor) I am doing the following:I set the setpoint for the output to zero volts and disable the constant current source (pull up) for the pass elements if there are 3 mains cycles missing.with best regardsAndreas
Lab Power Supply 0-30V 0-3A /CV/CC/  - Page 1
Forum section: electronics / projects

author: ZeTeX
author_rank: Frequent Contributor
timestamp: June 23, 2016, 09:32:52 pm
content: (Previous thread that went off-topic:https://www.eevblog.com/forum/projects/pass-transistor-driver-problems/msg903960/#msg903960)So it's summer break and I'm working the my PSU again, the schematics are pretty much ready! I ordered some parts and I'm waiting for them now.Anyways at the end I decided to not use switching pre regulator and just have 2 voltages from my duel secondary transformer (0-12V-24V 160VA, pretty overkill really but that's what I have), so I tried to design tap switching circuit without using relay or any mechanical components as they wear out, pretty hard to get in my local electronic store and most important - slow.So, can I improve the tap switching circuity but using less compoents \ something easier? I'm pretty sure there is a way around U5 without inverting the output from the zener.*The components that I use in LTspice simulation are not the components that I'm going end up using.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 24, 2016, 07:55:54 am
content: For using the 2. nd transformer tap, there are two more simple solutions:1. Use a robust transistor (e.g. like 3N3055) that can stand a high base current. At low output voltages this transistor works as an emitter follower with the low rail at the collector. At higher output voltages the transistor can not work as an emitter follower, but just the base emitter diode is active, so the normal driving stage does all the work. For protection a diode is needed in series with the collector.2. Use a circuit like a class H audio amplifier: Similar to you circuit, but using a N_MOSFET as source follower or an NPN as a emitter follower, with a constant voltage at the base of gate. So no need for U5. Often just something like 5 V used for the supply of the OPs is about right.The downside of both methods is that the power dissipation will shift between the two output stages, as there is not hard switching, but linear operation.

author: ZeTeX
author_rank: Frequent Contributor
timestamp: June 24, 2016, 10:14:55 am
content: Quote from: Kleinstein on June 24, 2016, 07:55:54 amIs there a way to make it so there will be almost no power dissipation at all?

author: StillTrying
author_rank: Super Contributor
timestamp: June 24, 2016, 01:27:14 pm
content: Quote from: ZeTeX on June 24, 2016, 10:14:55 amThis method done by timsu inhttps://www.eevblog.com/forum/projects/linear-power-supply-based-on-hpagilent-e3610a/msg942813/#msg942813seems to work. Because you don't need the mosfet to switch massively fast you can get the currents down to a few mA.I simulated it at the time...

author: ZeTeX
author_rank: Frequent Contributor
timestamp: June 24, 2016, 07:10:26 pm
content: Quote from: StillTrying on June 24, 2016, 01:27:14 pmGreat! Took it to my design:Seems to be working fine.
"Lab power supply in chip" - Digitally Controllable Off-Line CV/CC QR Flyback - Page 1
Forum section: electronics / projects

author: Miyuki
author_rank: Frequent Contributor
timestamp: May 05, 2020, 11:40:42 am
content: Hi,I just browsing new chips and found this interesting beastInnoSwitch3-Pro FamilyDigitally Controllable Off-Line CV/CC QR Flyback Switcher ICwith Integrated High-Voltage Switch, Synchronous RectificationIt have digitally controlled CV/CC/CP over I2C and cost very littleIt have output 3 V to 24 V up to 100WSo nice base for small lab supply, I dont need one, but awesome what you can get today in one package

author: Miyuki
author_rank: Frequent Contributor
timestamp: May 06, 2020, 07:35:21 am
content: Thanks for great inside infoJust wonder if it is silicon based integrated switcher do they use separate logic and power device chips or do they build it on same die ?I can agree with you about way to two transistors at higher power levels, just need that high side driverI dont see issue with digital feedback if whole controller is digital. When they have it good implemented. Or they use some way of DAC and analog control loop ? That make no sense with today computing speeds. Complete digital controllers are much more convenient in this way.

author: unitedatoms
author_rank: Frequent Contributor
timestamp: May 07, 2020, 11:43:56 pm
content: Nice chip. Just for now I looked at their design tool and managed to get an optimized 10W DC-DC supply with input voltage of 36-42V. Not risking to build a real mains AC-DC.
Lab Power Supply - Page 1
Forum section: electronics / projects

author: Bluespark
author_rank: Newbie
timestamp: October 13, 2012, 07:50:44 pm
content: hi alljust watched all blogs 1-12 about dave building a lab power supplywhat a good project.also read all topics on shipping/postage/ebay sounds like a right (one hung low) system.to send out the power supply.DAVE how about selling your design (ie gerber files/cad files and schematic drawingsthat way you could make more cash and dont have to send anything in the post,iam sure a lot of members would be intrestedin this also.you could possibly send out a few to members who want a pre assembled one.regards Alan

author: FenderBender
author_rank: Super Contributor
timestamp: October 13, 2012, 08:06:14 pm
content: Well he says its OSHW so I thought those files would just be available free...I think people would be more interested in a pre-manufactured system, or atleast ready to build.But who knows..

author: Rerouter
author_rank: Super Contributor
timestamp: October 13, 2012, 09:35:36 pm
content: it is OSHW, but he put the full sized one on hold while he works on the USB model, but it was at such a point nearly anyone could send of the gerbers and get it made, or easily add there own tweaks (currently doing that myself)
LAB PSU (Analog circuit for µC driving) - Page 1
Forum section: electronics / projects

author: JS
author_rank: Frequent Contributor
timestamp: May 16, 2018, 01:06:44 am
content: Thinking about something like this, started playing around in spice and this starts to look like it does what's supposed to do. I'm thinking on LM338 (LM350 or LM317 for lower current options) two LM358 for now, a µC on a PCB (blue pill STM32C108 ready to test) and LCD display. I've already wrote a firmware to test it, waiting for a protobard to eat the components or something...First step at least. µC sends a PWM signal for voltage, another one for current. Two signals go back to the ADCs. Also added a current range select pin that should be open drain (as the STM32 has or switched between output low and analog input if open drain not available) I'm not aiming for the precision of the µSupply but a rather simple approach with off the bin components.If I want to keep this almost as simple as it looks now and avoid an extra output switch (relay or something) I might need to fix the output to get to zero (right now gets to about 0.8V in simulations) but that might be an easy fix swapping D1 and D2 with BJTs (and reversing the two left opamps)Other thing I'm considering to add as an option is a input voltage selector, to select between two different DC PSU, to swap ranges and not burn all that much heat. I do have a suitable transformer so I might be thinking about it. In any case that would be some transistor working as a switch when the output voltage reaches certain limit and a diode, I think I can get that to work. Other options could be added once I get the concept going, 16bit ADC with the ADS1115, DAC for faster response, some options with the regulators (maybe LT308X could work with some circuit and compensation mods)Listening for thoughts, opinions, whatever you want to add.JS
Lab psu with trip mode - Page 1
Forum section: electronics / projects

author: fossmarkluni
author_rank: Newbie
timestamp: April 29, 2019, 10:10:52 am
content: Hi!Anyone knows if there are any commercially available Lab PSU's that has this nifty trip mode. I really like this feature. Please check Mauricios PSU design athttps://youtu.be/14EwqIB1pSkfossmarkluni

author: xavier60
author_rank: Super Contributor
timestamp: April 29, 2019, 10:47:51 am
content: Yes, Agilent U8001A/U8002A.https://www.tme.eu/Document/4ba558920760580da5bc3ea2322a681b/U8001-90001.pdf"Over Current Enables and disables the over current protection function, sets tripcurrent and clears the over current condition."BTW, Its fan noise was so unbearable, I made a temperature control mod to mine.

author: fossmarkluni
author_rank: Newbie
timestamp: April 29, 2019, 10:58:38 am
content: Great, thanks! I'll check it out

author: JackJones
author_rank: Regular Contributor
timestamp: April 29, 2019, 11:04:23 am
content: Isn't it a fairly standard feature? My Korad KA3005P has OCP, and it's on the cheap end of power supplies.
LAB techniuque to avoid higher current then possible  - Page 1
Forum section: electronics / projects

author: john23
author_rank: Frequent Contributor
timestamp: September 21, 2024, 01:48:59 pm
content: Hello,I have build a circuit which intend to use as a driver for PMA5-83-2W+.My main concern is the driver putting more current then the port can handle.For example in my circuit shown in the attached photo I have TL431 which can output much more then 4mA.So In the worst scenario my circuit will see 100Ohm instead of 555Ohm and I will get much higher current flowing into the Vg1 port and damaging it.Is there a way to handle it in the lab?Thanks.LTSPICE file are attached.https://www.minicircuits.com/pdfs/PMA5-83-2W+.pdf

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 22, 2024, 01:45:07 am
content: I'm not understanding the problem, the TL431 cannot supply any current, it can only sink it. The current supply is from the opamp which is limited by the resistor.
Labelling A Rotary Switch - Page 1
Forum section: electronics / projects

author: German_EE
author_rank: Super Contributor
timestamp: November 12, 2016, 07:58:45 pm
content: When laying out a front panel most tasks are easy but I'm having trouble with a common component, rotary switches with 30 degrees between contacts. Does anybody have any tips for laying out a symmetrical label with all the sections correctly spaced from the center? At the moment I'm experimenting with using the graphic of a clock face but things still don't look right.Any ideas?

author: jbb
author_rank: Super Contributor
timestamp: November 12, 2016, 08:23:40 pm
content: GrueziThe classic move is to just carefully place the labels around the dial (seehttp://www.aimtti.com/product-category/pulse-generators/aim-tgp110)If space is a bit tight (e.g. many-pole switch) then doing callout lines can be very effective (see image).(No, I don't work for TTI, I just have one in the cupboard at work and knew it could be a reference)
Laboratory power supply - Page 1
Forum section: electronics / projects

author: frantal
author_rank: Contributor
timestamp: May 07, 2020, 08:41:56 am
content: I would like to build a protected power supply unit for repairs using an isolation transformer and a variac.I have modified a scheme found on the internet and would like to ask if you consider it suitable for the purpose or if you have suggestions for perfecting it.The main and secondary switches are 2 thermal magnetic switches, one 16A, the other still to be taken.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 07, 2020, 12:20:28 pm
content: Hi What kind of equipment do you want to test or connect to it ?Tests and debugging ?

author: eblc1388
author_rank: Frequent Contributor
timestamp: May 08, 2020, 01:16:31 am
content: Quote from: frantal on May 07, 2020, 08:41:56 amBased on your original design, I have come up with a slightly different design which I think will be easier to build and more fun to use.I have replaced the input surge suppression by a simple timer relay(220V 0~5 second delay ON timer) which should greatly simplify the design and improve reliability. I always want an indication on whether the output socket is LIVE or DEAD so I added a voltage indicator. It works down to 12V AC.I stress that will be my personal preference and yours will be different. Please let us know of your final design.
labview with adp or picoscope - Page 1
Forum section: electronics / projects

author: metebalci
author_rank: Frequent Contributor
timestamp: January 15, 2024, 07:43:53 pm
content: I started using labview for something, and I use an NI usb daq, 16 bit, 1MS/s (not simultaneous, I have 3-4 channels). Actually 12-14 bits and higher sampling rate (10+MS/s) fits my use better. Adp3450 and picoscope 4000 or 5000 might be OK (I think similar NI hw is expensive as well as a second hand PXI setup with the 14 bit digitizer). Anyone has experience using these with labview ? Do they work like NI daqs under labview, anything problematic I should know about ?

author: 2N3055
author_rank: Super Contributor
timestamp: January 15, 2024, 09:23:50 pm
content: Quote from: metebalci on January 15, 2024, 07:43:53 pmTake a look here:https://github.com/picotechPicos work with Labwiev quite well.. Picotech has good support and you can ask them about details..
LaCie Power Supplies - Page 1
Forum section: electronics / projects

author: electrode
author_rank: Regular Contributor
timestamp: September 28, 2018, 12:53:42 am
content: Hi all,Thought I'd post this in case it helps someone else, as I couldn't find anything when googling. I have a few old LaCie power supplies from external HDDs.I've used them in the odd project when I need 12V, but it was only now when trying to run some relays, that I realised the "12V" rail only puts out 9-10V, even with small loads (300 mA or so). Turns out that loading the 5V rail with a 100R resistor, bumps the "12V" rail to 11.5V.So it would seem they expect a minimum load on the 5V rail to get the full output on the 12V rail. Does anyone have experience with these (or similar), and know a bit more about how they work?Thanks.Edit: spoke too soon. Seems to be no rhyme or reason to the 12V output, though the 5V output is 5.0V. I've tried 2 different supplies.

author: ConKbot
author_rank: Super Contributor
timestamp: September 28, 2018, 04:51:05 am
content: Older style (TL494 or similar based multi-tap flyback converter) ATX power supplies have only a single feedback point, and the regulation between the monitored rail and the other rails can be a bit off at low loads on the monitored rail. Modern higher end power supplies have a single, or multiple 12V rails, and separate DC-DC converters for 5V, 3.3V and others, these obviously don't suffer from the same problems.Keep on loading the 5V rail more, 50mA seems a bit light, can you get the current draw up to about half an amp on the 5V rail and see if it's better behaved?

author: electrode
author_rank: Regular Contributor
timestamp: September 28, 2018, 05:04:18 am
content: Thanks for your reply.Yeah, I had wondered if the feedback relied on the 5V rail. I tried loading it up to 1A, and nothing really changed much. Nevertheless, got one of them working well-enough, even though it's only 10.5V or so. In the end, it didn't matter whether I loaded the 5V rail or not.I think the lesson here is to be careful when reusing components. Several hours of wasted time is not worth saving $20.
Lady Heather + Raspi Zero + Trueposition - A "For dummies" approach - Page 1
Forum section: electronics / projects

author: tabajaralabs
author_rank: Regular Contributor
timestamp: April 14, 2021, 11:27:02 am
content: Greetings all!Got my trueposition board, a Raspi Zero (not W) board, a LCD, etc.I saw a very interesting build on the net (http://www.keteu.org/posts/gpsdo.html), but zero details of integrating this parts. I believe it yould be a very cute benchtop GPSDO with a nice 7" display running Lady HeatherUnfortunately I have ZERO knowledge of Raspi Zero, Raspibian, Linux, whatever. This cannot be a hard build. You connect 3 wires (RX, TX and GND) to the raspi zero, hdmi out to hdmi in of the LCD, power to the peop...ops, to all the boards, load raspibian (or another raspi linux distribuiton), install LH and configure everything. But I just don't know even how do I start.May I have some help? Maybe a "for dummies" to help everyone? I know this is n00b to the bone, but besides geting etcher and creating a raspibian card, I don't know exactly how to make it workThanks! =D

author: bingo600
author_rank: Super Contributor
timestamp: April 14, 2021, 04:49:59 pm
content: Start by downloading the linux source for Lady Heatherhttps://www.eevblog.com/forum/metrology/lady-heather-v6-beta-for-windows-exe/msg3257200/#msg3257200The source ought to be downloaded from this posthttps://www.eevblog.com/forum/metrology/lady-heather-v6-beta-for-windows-exe/msg1434005/#msg1434005The tinyurl stuff , but it seems not to be working/Bingo
Lafayette fg39b function generator - Page 1
Forum section: electronics / projects

author: Nanospark
author_rank: Newbie
timestamp: December 10, 2014, 08:35:59 am
content: Has anyone had any experience with the Lafayette brand? I'm looking for low cost function generator and wondered whether anyone could give a good recommendation on this particular brand and model. Im pushing towards Instek but thought I'd get your opinions on this first.
Lan Transformer as gate drive transformer - Page 1
Forum section: electronics / projects

author: nickm
author_rank: Regular Contributor
timestamp: August 13, 2014, 01:48:34 pm
content: What is wrong with using a lan transformer as a gate drive transformer? They are nice and small and usually have a 1500Vrms rating.

author: nickm
author_rank: Regular Contributor
timestamp: August 13, 2014, 03:36:55 pm
content: Makes sense. Thanks for the explanation.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2014, 02:18:33 am
content: The insulation is provided by wire enamel only, so is only suitable for Functional insulation. So if you have a gate driver that's power line referenced, driving an inverter that's power line referenced, you're fine; but if the driver is SELV referenced, you must use Basic (if grounded) or Reinforced (if isolated).As mentioned, flux (ET) is small, so you're most likely to succeed with a low voltage, low impedance driver; which is the intended use, after all. You'd then need a differential receiver and gate driver on the isolated side.Power transfer capability isn't much, and you'll need to do it at a pretty high frequency. Which may prove lossy. I would be surprised if you could push 1W over a single transformer without it being unacceptably poor in performance (low efficiency or excessive temperature).Some common mode chokes are reasonable for such purposes, having excellent isolation voltage capacity. (I once hi-potted a ~13mm split-bobbin part up to 12kV!) But they have a high coupling impedance (due to the relatively large leakage inductance), which limits bandwidth and power transfer capability. A watt or two is reasonable. Because the core is ungapped, and each winding is not tapped or split, you must use a full bridge forward converter topology.Tim

author: David Hess
author_rank: Super Contributor
timestamp: August 14, 2014, 04:11:41 am
content: What *will* work well are the transformers used to provide isolated power to communications interfaces which would include 10base-2 Ethernet.http://www.coilcraft.com/prod_isolation.cfm

author: sorin
author_rank: Frequent Contributor
timestamp: August 14, 2014, 09:44:44 am
content: Quote from: AcHmed99 on August 13, 2014, 02:27:39 pmThanks for the explanation.
LAN8720 ETH PHY  Activity LED indicating only inbound traffic? - Page 1
Forum section: electronics / projects

author: Yansi
author_rank: Super Contributor
timestamp: August 18, 2019, 11:19:46 am
content: Hello,just started tinkering with ETHernet, now completed my first hello world using aLAN8720 ETH PHY (Datasheet).What I found interesting (and to be honest, very annoying) is that the activity LED blinks only on inbound (receive) traffic. When I for example send a packet every second, the LED does not blink, stays lit.I think this is beyond stupid, as if I wanted to use the PHY in a device, for example a UDP streaming device, that produces 99% traffic only outbound (transmit), the LED would not indicate absolutely anything.Datasheet of the PHY seems to confirm this stupid behavior of the LED: Section 3.8, quoute:"The LED1 output is driven active whenever the device detects a valid link, and blinks when CRS is active (high) indicat-ing activity"Why is that? Is it normal the link/activity LED blinks only on received data (CRS, carrier sense)?
LAN8720 module power need?? - Page 1
Forum section: electronics / projects

author: Pr0cess0r
author_rank: Newbie
timestamp: February 16, 2021, 05:00:20 pm
content: I want to use LAN8720 module with mh-et live esp32 board. I have a hard time to find documentation for those two devices.Will i be able to power one microSD card and the LAN8720 module from the esp32 dev board regulator?Thank you for you help.

author: nardev
author_rank: Unknown
timestamp: June 29, 2021, 11:40:12 am
content: What ESP32 "regulator" you are talking about?

author: bson
author_rank: Unknown
timestamp: June 29, 2021, 07:52:49 pm
content: If the module vendor hasn't measured and documented it, then you will probably need to measure it yourself.
Land pattern on RP2040, flash, and crystal on the raspberry pi pico - Page 1
Forum section: electronics / projects

author: drakejest
author_rank: Regular Contributor
timestamp: September 23, 2021, 06:23:20 pm
content: Hello I would like to make my own board with a pico on it , but the pico board is too long to fit in the dimension i need. So i decided i have to transfer the components,I only need the land pattern for 3 componentsThe rp2040The crystal oscilatorAnd the flash chipI do not need the buck converter since my circuit already has its own power rail, and also of course i will need to replace most of the passive components as they are to small for me to hand solder.

author: drakejest
author_rank: Regular Contributor
timestamp: September 23, 2021, 06:27:29 pm
content: I have so far found theRP2040and what i think theflash chipbut the hardest one is the crystalhttps://ibb.co/8dPN6Vzhttps://ibb.co/sjx6wH5

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 23, 2021, 08:57:29 pm
content: I supposed you have looked at the schematics:https://datasheets.raspberrypi.org/pico/pico-datasheet.pdfThe exact reference of the crystal is not given, but it's a 12 MHz crystal.You can probably select another 12 MHz crystal of your choosing.You can refer to this doc:https://datasheets.raspberrypi.org/rp2040/hardware-design-with-rp2040.pdf- which will give you all info you need to design your own board. In particular, refer to the "2.3. Crystal oscillator" section. But the part about power is probably also something you should read.

author: drakejest
author_rank: Regular Contributor
timestamp: September 23, 2021, 10:55:16 pm
content: Quote from: SiliconWizard on September 23, 2021, 08:57:29 pmAs much as possible i would like not to buy anymore components as i would have to pay for shipping for a very small part, I pretty much have everything at hand exempt for those 3 important parts. I guess what i have to do is search for a crystal that has a very close dimension to it and pray that their land pattern mach

author: thm_w
author_rank: Super Contributor
timestamp: September 23, 2021, 11:30:37 pm
content: It look like your measurement is 3.2 x 2.5mm? (you can post the actual numbers here, in the photo the caliper is not quite touching the edge).Its probably the same as this:https://www.digikey.ca/en/products/detail/ecs-inc/ECS-120-20-33-CKM-TR/2781815
Landline to cellphone USB interface - Page 1
Forum section: electronics / projects

author: grmsyd
author_rank: Newbie
timestamp: February 16, 2019, 04:09:36 am
content: Looking for a USB interface circuit to make and receive calls with the old landline telephone using the cellular telephone network.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 16, 2019, 04:24:30 am
content: You're looking for a "FXS box" or "Analog Telephone Adapter (ATA)".

author: viperidae
author_rank: Frequent Contributor
timestamp: February 17, 2019, 05:48:32 am
content: Reminds me of the old sparkfun producthttps://www.sparkfun.com/products/retired/286All you really need is a cellular module, maybe an Arduino.
Laplace transformation --> Time varying capacitance - Page 1
Forum section: electronics / projects

author: happylex
author_rank: Contributor
timestamp: May 17, 2018, 12:33:07 pm
content: Hi,I have a network with about 3 milion resistors and 1 milion load sensitive capacitors. The capacitance is directly proportional to strain, and I would like to see what happens in my system when the capacity is varying with C = C_0 + C_A*sin(omgea*t).How do I now use Laplace transformations to analyse my circuit? Does anyone know?Edit: I don't think it makes any difference, but all capacitors are connected to the same constant V_ref.Thanks in advance!

author: Benta
author_rank: Super Contributor
timestamp: May 17, 2018, 12:55:27 pm
content: LaPlace is normally only for time-invariant systems. You could do the analysis with different fixed capacitances and plot the result to connect the dots.

author: happylex
author_rank: Contributor
timestamp: May 17, 2018, 01:06:14 pm
content: Thank you Benta. What you say is not correct, since varying the capacitance induces a change in voltage and current. Think about a microphone, where the voltage goes up as charge stays the same while the capacitor 'plates' come closer together.Usually we have C*dV/dt = I,but in this case we have C(t)*dV/dt = I - V(t)*dC/dt

author: Gibson486
author_rank: Frequent Contributor
timestamp: May 17, 2018, 01:43:27 pm
content: Quote from: happylex on May 17, 2018, 01:06:14 pmI am a little confused.Are you actually pumping a a sine wave signal through?Laplace will let you solve this equation in a linear fashion (ie with just algebra), but you may be misguided as to what you are trying to do. That being said, you do not need laplace to do it, so doing the whole transform would be a lot of work for nothing. Everything is first order.But if you want to figure out, google first order equations and Laplace. As Benta pointed (and he is not incorrect), you will need an assumption of the initial condition.

author: happylex
author_rank: Contributor
timestamp: May 17, 2018, 02:36:02 pm
content: Yes the only source of the sine wave is coming from the compression of the system. It is like a huge number of condensor microphones in one circuit:http://www.learningaboutelectronics.com/Articles/Condenser-microphones

author: RoGeorge
author_rank: Super Contributor
timestamp: May 17, 2018, 02:48:32 pm
content: Quote from: happylex on May 17, 2018, 02:36:02 pmIf you want to use an array of microphones like the one pictured in the link, please be aware that the drawing in the link might bewrong. Usually those are active microphones, not passive as drawn in the schematic, they have an internal FET transistor, and the moving plate of the sensing electret capacitor is connected to the FET's grille. That is why an external resistor connected to V+ is needed (the resistor powers the DS of the internal FET). If your microphones are active (with electret and the usual FET inside), then it outputs a voltage proportional with the pressure's variation, so no need to take into account the capacitors at all.www.es.co.th/Schemetic/PDF/KUC.PDFhttps://en.wikipedia.org/wiki/Electret_microphone
Laptop bios serial flash in circuit programming - Page 1
Forum section: electronics / projects

author: Stonent
author_rank: Super Contributor
timestamp: July 24, 2013, 04:16:23 pm
content: I'm considering buying a laptop that has a BIOS lock on it for a good price. I'm reasonably certain it isn't stolen because the seller is a refurbishing company that buys computers by the pallet from companies and has sold about 20 of this same model laptop without bios password locks.According to HP the bios password can be reset by removing the main battery and clock battery and powering up off of the wall charger IF the extra security mode hasn't been enabled. If that's the case, the password is flashed into the bios chip and HP says you have to replace the motherboard.There are some people on ebay selling replacement bios chips for this laptop to remove the password lock for $25 and it appears to be just a small so8 serial flash chip.Those chips from what I've seen, seem to use MOSI MISO SCK to access the chip which is good for me since that's something I'm somewhat familiar with programming AVRs.Back when PC motherboards had removable DIP flash chips, you used to be able to hot flash a chip by booting another computer, pulling the BIOS chip, dropping in the blank or donor chip and flashing the BIOS for the target motherboard with a flag to force the flash even if the model didn't match.So I had a couple of ideas on this. One would be to buy the replacement bios chip and perhaps lift one of the legs of the onboard bios while it is still on the board so that it won't function and use some micro grabbers and wire to link the replacement chip in to get the laptop to boot, then set the leg back down and try to reflash it.If that works, sell the bios chip I bought on ebay.Another option would be to somehow get a copy of the flash file and try to program the chip without removing from the board.How would you go about this little hack? It somewhat reminds me of when Mike was hacking the Xray machine to remove the password.What do you think? Are most so8 flash chips just SPI or are there other kinds?

author: Stonent
author_rank: Super Contributor
timestamp: July 25, 2013, 08:10:27 pm
content: Nevermind I guess, someone snapped it up.

author: amyk
author_rank: Super Contributor
timestamp: July 26, 2013, 10:38:27 am
content: It might not be the BIOS chip itself; a quick look at the schematic reveals 2 SPI flash chips, and this model also has a TPM. More likely the password is in the latter, in which case resetting will be difficult, to say the least...
Laptop DC Power Adaptor Barrel Connector Jack? - Page 1
Forum section: electronics / projects

author: nbritton
author_rank: Frequent Contributor
timestamp: October 10, 2015, 07:11:55 am
content: What kind of barrel connector jack is used on HP laptops? I'm looking for a PCB and/or panel mounted connector so that I can reuse laptop AC power adaptors for projects. I believe HP and Dell use the same connector, I think it's 7.4 mm wide. I have attached some pictures of it.

author: amyk
author_rank: Super Contributor
timestamp: October 10, 2015, 03:08:13 pm
content: What model of laptop in particular? You might be able to find a schematic and then determine the part# of the connector from it.Foxconn make 7.4mm jacks:http://www.fit-foxconn.com/Search/Product_Series_Details.asp?P_Industry=&P_Type=Power+Connector&P_Family=Power+Jack+Connector&P_Series=Power+Jack+Connector&FeatureArray=&ValueArray=&searchTypeID=1

author: Stonent
author_rank: Super Contributor
timestamp: October 10, 2015, 07:51:06 pm
content: Yeah dell and hp are the same. HP laptops will charge off of a Dell cord.

author: nbritton
author_rank: Frequent Contributor
timestamp: October 10, 2015, 09:51:39 pm
content: Quote from: amyk on October 10, 2015, 03:08:13 pmGreat, thanks, but the minimum order quantity direct from Foxconn is 8000+ pieces. Do you know of a reseller I can buy them at? I see six part numbers on that page that might work:JPDD71-CA0BA0B-4HJPD113D-LBA21-7HJPD113D-DB570-7HJPDD7C-CA0WA0B-4HJPDD71-C80AC0B-4HJPD113D-NBA50-7H

author: amyk
author_rank: Super Contributor
timestamp: October 11, 2015, 03:27:01 am
content: http://www.ebay.com/itm/AC-DC-Power-Jack-Plug-Input-Dell-Inspiron-E1405-E1505-E1705-JPD113D-NBA50-7H-OEM-/160459296536(Despite the name, I don't think this seller is actually related to Foxconn in any way.)
Laptop PSU Failure - Page 1
Forum section: electronics / projects

author: ion
author_rank: Regular Contributor
timestamp: July 04, 2014, 04:40:44 pm
content: A few days ago my mum's laptop PSU failed. Approx. 3V output instead of 19V.Cracking open the case released the unmistakable smell of burnt electronics, and it didn't take long to find the source:There was a blackened smd component with a hole blown out of it, but when I tried to clean it it disintegrated. I recovered a small fragment so at least I can say it was a ceramic capacitor. I've marked where it was with a red line.After seeing the extent of the damage to the PCB, I'm not looking to repair it. Actually I'm not even sure if a repair is possible.I am however curious as to what could have caused this failure. I'm no expert in SMPS, but maybe it's obvious to someone more familiar with them.The cap was connected between the poitive leg of the large electrolytic and the cathode of the large diode near the transformer. The diode is reading short, but I suspect that's because of the charred PCB.I also suspect that the capacitor caught fire when it failed - the worst bit of the charred area is approx. 1mm below the surface of the board.

author: mij59
author_rank: Frequent Contributor
timestamp: July 04, 2014, 05:00:35 pm
content: The diode is reading short, but I suspect that's because of the charred PCB.Carbon is not that conductive, the diode is just shorted.Time to get a new supply, this is not repairable.

author: rob77
author_rank: Super Contributor
timestamp: July 04, 2014, 06:17:26 pm
content: +1salvage some useful parts (e.g. the inductors) and trash itbut regarding the fire... ceramic capacitors are usually not catching fire. probably it was a tantalum capacitor - those like to catch fire.

author: Tinkerer
author_rank: Frequent Contributor
timestamp: July 04, 2014, 06:20:11 pm
content: Quote from: mij59 on July 04, 2014, 05:00:35 pmCarbon is not that conductive, the diode is just shorted.Time to get a new supply, this is not repairable.Yea, when you have everything scorched like that, it doesnt lend itself much in the way of repairability, definitely time for a new one.

author: ion
author_rank: Regular Contributor
timestamp: July 04, 2014, 08:52:39 pm
content: Oh, I already got a new one. As I said, I'm more interested in what might have caused the capacitor to blow (power surge / high temperatures / some other component failing / etc). That is, assuming it is possible to tell from where the capacitor was on the board.Quote from: mij59 on July 04, 2014, 05:00:35 pmI guess I must have hit something else with my probes when I got 10 ohms across the charred bit. Measured again and you're right.Quote from: rob77 on July 04, 2014, 06:17:26 pmWell, I identified it as a ceramic capacitor from a tiny bit of light brown material that was still attached to the metal end, looks like the same stuff every SMD ceramic cap I've seen is made out of. So I could be wrong - I didn't even know you could get tantalums in 0805.
Laptop second display - Page 1
Forum section: electronics / projects

author: Mustakari
author_rank: Newbie
timestamp: February 02, 2018, 06:36:10 pm
content: Just when trying to work on my T440S tiny display it occurred to me why not add another display behind the main one, with a hinge so that I can fold it open when needed.Laptop panels are cheap and easy to find but how to connect it to the computer?The T440s has a miniDisplayPort and vga out of which former must be the better option. I see many hdmi/dvi/vga to lvds adapters in eBay but don't really know how well they work and is the common laptop panel pinout so generic those actually have a chance at working. The adapters are rather bulky but are quite easily slimmed down removing unneeded connectors and replacing upright caps and inductors with slimmer components.I must not be the only one with the idea of having a second display permanently attached. Any suggestions how to proceed?

author: meeko
author_rank: Contributor
timestamp: February 06, 2018, 03:39:57 pm
content: I'll just leave this here...https://www.yourslide.com/I don't have any connection to these guys, just found them with a quick Google.

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 06, 2018, 04:42:56 pm
content: Most recent panels targeted at laptops have eDP connections. eDP happens to be close to DisplayPort. All you need is a DP to eDP interface board.You'll find some on eBay, AliExpress and so on.Just look for "DisplayPort to eDP", and make sure your panel has eDP as well. You may also find kits including the panel and the interface, thus with better chance of compatibility.

author: Mustakari
author_rank: Newbie
timestamp: February 08, 2018, 08:12:35 pm
content: Thanks guys, eDP simplifies things some. Now if I only could find a very short miniDP connector with a flat flex in the end. I don't want a long connector sticking out of the computer side.Someone in China will surely make me one..or a thousand.
Large Capacitive Wheel - Page 1
Forum section: electronics / projects

author: Aodhan145
author_rank: Frequent Contributor
timestamp: November 04, 2015, 08:43:37 pm
content: Hi,I'm currently working on a project which is an LED visualiser. It is in the shape of a cube and has a 4x4 rgb led matrix on each side accept for the bottom where Im putting a loudspeaker. It will be made out of acrylic but to get the code working I soldered it inside a cardboard frame.I am using the arduino bootloader on the atmega328p just because I don't have a lot of experence with C++ and programing microcontrollers so I find it easier to use C as it is more high level and simpler. So I need to get a set up which will work with the arduino.I want to be able to change the volume of the speaker with a capacitive wheel on the top but the problem is I would need to make a wheel that has an outer diameter of 110 - 120mm and an inside diameter of 70 - 80mm. I have not yet found a capacitive wheel this big. I have found a way to create one this big in eagle using atmels application note for designing capacitive sensors with Qtouch.Full SizeThe only problem is Im using arduino and the Qtouch library is not arduino friendly. I was looking into the Arduino CapSense library and It mentions the Quantom Scroll Wheel sensor kit for the scroll wheel design.Full SizeThe two designs look fairly similar. Could I use an atmel scroll wheel design with the arduino capacitive touch library? and also I was going to mill out a slot for the scroll wheel to go to so the acrylic is thin between it and your hand. Does anybody have any experence with covering them with plastic that could recommend a thickness for the plastic? I was going to mill 2mm down into the 3mm plastic so there would be 1mm of plastic between someones finger and the scroll wheel its self. I am open to other alternatives as well.Thanks in advance for any helpFor those confused to what I am making:Youtube videoSolidworks RenderUploading Later

author: Fungus
author_rank: Super Contributor
timestamp: November 04, 2015, 11:56:53 pm
content: Quote from: Aodhan145 on November 04, 2015, 08:43:37 pmI don't see why not.Quote from: Aodhan145 on November 04, 2015, 08:43:37 pm3mm should be OK without milling.

author: Aodhan145
author_rank: Frequent Contributor
timestamp: November 05, 2015, 12:08:25 am
content: Quote from: Fungus on November 04, 2015, 11:56:53 pmThanks very much I will post up my results when I make it.
Large Colour Electronics book, about 1000 pages in pdf? - Page 1
Forum section: electronics / projects

author: Chris56000
author_rank: Frequent Contributor
timestamp: August 04, 2018, 12:32:13 pm
content: Hi!I had somewhere in my collection, a large PDF of a beautifully produced Electronics Teaching book in full colour - it had pictures of breadboards and seven-segment displays on the front cover and was over 1000 pages, starting with an LED and a PP3 battery in the first chapter going right through components, circuits and software programming of increasing complexity until you get to projects involving advanced coding at the end!Can anyone tell me the title and author so I can buy another copy please?Chris Williams

author: Cliff Matthews
author_rank: Unknown
timestamp: August 04, 2018, 03:24:08 pm
content: Perhaps it was one by Charles Platt?https://www.amazon.com/Charles-Platt/e/B000APYAR4/ref=dp_byline_cont_book_1

author: Chris56000
author_rank: Frequent Contributor
timestamp: October 12, 2018, 11:55:43 pm
content: Hi!Update on this post - I found my copy and now you don't have to buy it!It's called:-"An Introduction to Practical Electronics, Microcontrollers and Software Design"by Bill Collis from New Zealand and a copy may be freely downloaded here:-https://github.com/billcollis/textbook/blob/master/IntroToPracticalElectronicsMicrocontrollersAndSoftwareDesign.pdfChris Williams
Large digit LED voltmeter & ammeter - Page 1
Forum section: electronics / projects

author: wagon
author_rank: Frequent Contributor
timestamp: April 10, 2015, 07:30:35 am
content: Greetings!I have a customer needing a large digit (upto 100mm high) LED voltmeter & ammeter for educational purposes.Accuracy is not important, but one decimal place is needed. 12V operation.The budget is fairly tight.I had thought of modifying those little LED panel meters to drive larger digits via a transistor or something.Has anyone else done or seen it done? Is there an 'off the shelf' product to do this?Thanks!

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 10, 2015, 07:37:25 am
content: Transistor approach with cheap Chinese DMM module sounds sensible. Past that its probably either some IC like ICL7106/7 and a shunt for ammeter and the same transistor driver array but those are quite hard to get hold of. You could also go analogue and use an old fashioned integrator/counter. That would be fun.If you're being paid, the latter probably wouldn't be cost effective though.You can get 4" high 7 seg modules on eBay though. Think they have 4 LEDs per segment.
Large mosfets leaking - Page 1
Forum section: electronics / projects

author: epitaxial
author_rank: Contributor
timestamp: April 13, 2023, 11:44:04 pm
content: I'm trying to determine if these large mosfets are good or bad. The part is a TE53N50Ehttps://datasheetspdf.com/pdf-file/621788/Motorola/TE53N50E/1The component tester identifies them correctly but using a 12 volt battery and a light bulb they still pass current with the gate tied to ground? The light is not full brightness and the mosfets are eating 4-5 volts. Is it possible for them to test good at low currents but fail under a real load?

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: April 13, 2023, 11:56:39 pm
content: I can't tell from the photo if you've got it wired right. If you do, I'd expect it to work like any other N-channel MOSFET and not conduct with the gate at source potential. Can you try some other MOSFET just to confirm the wiring? The datasheet gives you the expected current, and it's not enough to light a bulb!

author: boB
author_rank: Frequent Contributor
timestamp: April 14, 2023, 12:07:31 am
content: Looks to me like the top picture with the light on has the gate floating.If that is the gate and it is floating, then all bets are off.The bottom photo with the tester looks like tester pin 2 (gate) is connected to the FET terminal that is floating in the picture with the light on.But then again, the top photo is kind of blocking connections from being seen.boB

author: thm_w
author_rank: Super Contributor
timestamp: April 14, 2023, 01:04:51 am
content: Gate is connected to Drain in the top photo, which is wrong.Other side of the resistor should go to the green lead instead of the yellow.

author: epitaxial
author_rank: Contributor
timestamp: April 14, 2023, 01:18:45 am
content: Doh, yes it was connected wrongly. Mosfets behave as they should and the suspected bad one is shorted on. Thanks all