hybridfree/eevblog-posts huggingface dataset:
Digital DECT Phone Audio Tap - Page 1
Forum section: electronics / projects

author: kolbep
author_rank: Frequent Contributor
timestamp: August 10, 2020, 06:51:46 am
content: Hi All.One of my customers has an 8 Channel Audio Recording PCI card. It accepts Line Level Inputs or Direct connection to an Analogue Telephone Line (Selectable per port).We have it connected to several Analogue Extensions on the PABX (Paralleled with the Phones), and that works fine.They also want to record their conversations on their main switchboard phone. But that is a Digital Dect phone. With it being a digital line, we cant just tap into the PABX Extension, because you get the digital hash noise.Before they upgraded their PABX and Switchboard Phone, all I did was tapped the recording interface onto the Speaker signal that goes from the phone base to the handset. That worked fine. However with their new PABX/Switchboard combination, it is not working too well.They say it is drops the volume down too much, and it is hard to hear.The Recording Interface has a high input impedance (>10kohm) and the Telephone Speaker is 8 Ohm, so I did not expect that to be a cause of the problem. I then thought it could be a problem between different ground potentials, so I took a small choke out of a CCTV Balun, put one winding in Parallel with the phone speaker (also used a 10k resistor in series, just to make sure it did not load down too much). The 2nd Winding I ran to the Interface. Even then they say that it drops the volume.I now have 2 thoughts about how to do this (Not to load down the existing phone, and to provide isolation), and could use some advice :1, Get a small coil with Multiple turns, run the handset speaker wire through it. Then feed an opamp or small preamp. That way it is electrically isolated from the phones wiring itself. The Problem is, where to find a suitable coil, with lots of turns on it that would be suitable. or2. Get a Mic with Preamp (eg Max9814 preamp with AGC). I then install the mic in the handset in a position where it can pick up the sound from the speaker.I prefer no 1, as I can possibly put the coil and opamp/preamp in the phone base itself. That will mean neater wiring as I can bring separate power, and audio out direct to the phone base. Minimizing wiring all over. Without the acousitc pickup of a microphone the signal should be clearer.With no 2, by putting a mic in the handset itself, it means that I will need to run another wire to the handset itself (in addition to the curly cord for the phones mic and speaker). This will be messy, and get in the way.I did discuss with them that their New Panasonic PABX has a facility for Automatic 2 Way Recording, as they already have a DSP Card, and the Voicemail SD card, but they were quoted over R40000.00 just for a Supervisor licence to enable the recording, which caused the manager to nearly fall off his chair.Any Suggestions.Thanks

author: texaspyro
author_rank: Super Contributor
timestamp: August 11, 2020, 07:06:18 am
content: Get the coil from a relay... some relay coils can have thousands of turns.
Digital electronics troubleshooting guide/book - Page 1
Forum section: electronics / projects

author: WakeUpWolfgang
author_rank: Contributor
timestamp: October 31, 2013, 12:59:41 pm
content: I do some digital electronics troubleshooting but some times I have to have someone else finish it. Anyone know any good book or guides for troubleshooting digital electronics? I test voltages but I really don't know what to do past the power supplies.

author: WakeUpWolfgang
author_rank: Contributor
timestamp: October 31, 2013, 04:19:14 pm
content: I know how they work I took some classes at college but we did not design or troubleshoot. I have designed some projects and still making some. What is hard for me is trying to figure out other peoples work. What I am doing at work when fixing electronics is similar to a motherboard in a computer. (DVRs for CCTV systems and AMPS for sound systems) Most of the companies will give out the schematics so I can fix them but its the DVRs that I have problems.
Digital humidity sensor - Page 1
Forum section: electronics / projects

author: Torrentula
author_rank: Regular Contributor
timestamp: October 23, 2012, 05:06:05 pm
content: At the moment I'm working on a data logger project which monitors temperature, air pressure and humidity and then logs these to an SD card.I've already found suitable pressure and temperature sensors but I can't find a reasonably priced digital humidity sensor. I've seen the SHT11/15 but they're very expensive at 20+ bucks per chip.Do you know of any sub 5$ IC's for measuring the relative humidity with an I2C interface?

author: ciccio
author_rank: Frequent Contributor
timestamp: October 23, 2012, 05:15:47 pm
content: Most decent humidity sensors are expensive.The cost comes from the calibration process that, if done correctly, is really time consuming.The lowest priced one that seems suitable for your needs is this one, at 9.95 USD:https://www.sparkfun.com/products/10239What will be the operating temperature range? Any corrosive environment? This can lead to a very pricey sensor.Best regards

author: DavidDLC
author_rank: Frequent Contributor
timestamp: October 23, 2012, 06:01:44 pm
content: http://hackaday.com/2012/01/11/dht11-humidity-and-temperature-sensor-package/http://www.ebay.com/sch/i.html?_trksid=p5197.m570.l1313&_nkw=dht11&_sacat=0&_from=R40Check those out.David.

author: jabramo
author_rank: Regular Contributor
timestamp: October 27, 2012, 10:56:11 pm
content: ^ If your considering the DHT11 check out the DHT21 and DHT22 both ~5$ and it seems like the DHT22 is the most accurate out of the 3. I'm pretty sure they all send data on the Dallas 1 wire protocol.
Digital Isolator component equivalent to ±30V Output Photocoupler - Page 1
Forum section: electronics / projects

author: willPowell
author_rank: Contributor
timestamp: January 31, 2022, 09:31:15 am
content: Hi guys,I am looking at digital isolators for faster isolated switching of high voltage (±30V) - i.e. the output voltage will be switching polarity.I am currently using a photocoupler solid state relay with the following datasheethttps://docs.rs-online.com/02d2/0900766b81699edf.pdf?bcs-agent-scanner=a26f2f40-8acf-dc4d-be3e-89c9a6b868ae.Do you guys know of any that may be an appropriate substitute just with faster switching speeds (maximum of Ton = 0.1ms)?Thanks,Will

author: razvan784
author_rank: Regular Contributor
timestamp: February 01, 2022, 09:55:17 am
content: You do not specify what load this is driving.For low output current (under a few mA) you might use a dual optocoupler with bipolar transistor outputs (or two single ones). These should switch a faster than a MOS optocoupler.This would only work if the ouptut is being switched to fixed-polarity supplies (one transistor to +30V, the other to -30V), this is also not clear from your post.For general signal switching there are analog switch ICs rated up to 100V, see the ti TMUX8 series for instance; these need isolated supplies but can be driven with a low-voltage digital isolator IC and can switch very fast.
Digital / Linear IC Tester -  Any DIY Project Online  - Page 1
Forum section: electronics / projects

author: Amarbir[Lynx-India]
author_rank: Frequent Contributor
timestamp: March 14, 2013, 06:29:14 pm
content: Hi Folks,I am looking for a diy mcu based ic tester project online that i could make for my lab use .I plan to test digital ttl and cmos ic and also other linear ic if it does support them .I am sure we have something like this but i could not find any worthwhile contenders .Please help and pour in your findings etc to this thread .

author: Smokey
author_rank: Super Contributor
timestamp: March 14, 2013, 06:39:55 pm
content: I'm not exactly sure what you are looking to do, but it sounds like the Bus Pirate will get some of that done out of the box.http://dangerousprototypes.com/docs/Bus_Pirate

author: Amarbir[Lynx-India]
author_rank: Frequent Contributor
timestamp: March 14, 2013, 06:49:42 pm
content: Quote from: Smokey on March 14, 2013, 06:39:55 pmSmokey sir,Not this one ,something more easier

author: Amarbir[Lynx-India]
author_rank: Frequent Contributor
timestamp: March 14, 2013, 06:57:03 pm
content: Well,I Found Some Interesting Stuff Online ->http://www.ebay.com/itm/190811160842" This one is complete in finish condition " .I also found two more project type products anyone has a idea where they have grabbed the circuit from ? .Project 1 ->http://www.ebay.com/itm/321078818488Project 2 ->http://www.ebay.com/itm/181051001235

author: olsenn
author_rank: Frequent Contributor
timestamp: March 14, 2013, 07:03:45 pm
content: The MiniPro Universal Programmer has logic IC tests build in for most common TTL/CMOS IC's

author: Amarbir[Lynx-India]
author_rank: Frequent Contributor
timestamp: March 14, 2013, 07:05:43 pm
content: Quote from: olsenn on March 14, 2013, 07:03:45 pmHello ,I am not looking for that stuff.Have you seen my siggie i am national distributor for autoelectric in india sir .I am looking for a dedicated ic tester project

author: olsenn
author_rank: Frequent Contributor
timestamp: March 14, 2013, 07:13:16 pm
content: QuoteFirst, off, even had I have noticed your username, how am I supposed to know Lynx-India is distributor of autoelectric products? Secondly, is what you sell not good enough for you? You obviously have access to them. If you need additional features, you can very easily program tests into any micro yourself... it's straight forward digital logic

author: Amarbir[Lynx-India]
author_rank: Frequent Contributor
timestamp: March 14, 2013, 07:20:17 pm
content: Quote from: olsenn on March 14, 2013, 07:13:16 pmSir ,I Sell Many programmers in india " Autoelectric , Wellon Also Now As Distributor " + EE Tools USA " .I am looking for a dedicated product and hopefully open source ,Please check some of the links i posted above ..Might be some magazine project also ?
digital logic modeling with clock - looking for free PC program to use - Page 1
Forum section: electronics / projects

author: grips03
author_rank: Contributor
timestamp: March 30, 2014, 12:46:22 am
content: I'm working on a project that uses a clock and d-latches, and some other digital logic. I would like to model on the PC before implementing in a CPLD.What is good free software program for this?

author: vvanders
author_rank: Regular Contributor
timestamp: March 30, 2014, 03:46:28 am
content: if you're going to implement on CPLD then I'd just use the sim software that comes with the vendor you choose to use. Unless there's a different type of model you're trying to do?

author: grips03
author_rank: Contributor
timestamp: March 30, 2014, 04:08:04 am
content: I'll most likely do this if I check it at all. Turns out I only need to add 4 d-latch and 2 decoders to existing CPLD design so might even skip this step.
Digital mini 0,56 inch AC voltage panel replacement meter for variac - Page 1
Forum section: electronics / projects

author: robsims
author_rank: Frequent Contributor
timestamp: September 30, 2020, 07:51:50 pm
content: Hi,I want to replace the analog meter on my variac. The variac is 120 volt. I searched on the web for 0,56 inch AC voltage panel meters, but i can not find one which goes from zero up to a specific voltage, let's say 300 volts. I have looked on ebay and amazon, but all the meters start with a high voltage let's say 30 or 80 volts up to a specific voltage. I live in south america and mains is 120 volt just like the USA. Can you tell me where i can find an 0,56 inch ac voltage panel meter which starts at zero.

author: floobydust
author_rank: Super Contributor
timestamp: September 30, 2020, 08:05:56 pm
content: You have to take apart and modify a digital panel meter. Pick off the voltage-monitor connection. Cutting a pcb trace to the sense resistor and add a wire to it, then to the variac output.It was done in this thread for an energy meter:https://www.eevblog.com/forum/beginners/power-meter-for-variac/Big Clive did a good review and teardown of the 22mm low cost AC voltmeters, same circuit in the 0.56" ones:uh ignore the hydrogen condom pop at the end of his video lol.

author: robsims
author_rank: Frequent Contributor
timestamp: September 30, 2020, 08:42:19 pm
content: The meter in the link you posted is too big. I want to replace the analog 0,56 inch meter with a digital meter on my variac. Meter must be powered by ac mains and must read ac output of the variac

author: floobydust
author_rank: Super Contributor
timestamp: September 30, 2020, 09:08:50 pm
content: You can modify the 0.56" version. Just post pictures of the board you have.

author: robsims
author_rank: Frequent Contributor
timestamp: September 30, 2020, 09:36:47 pm
content: How do you modify the 0.56" version??. I want to know before i order one.

author: Zero999
author_rank: Super Contributor
timestamp: October 01, 2020, 01:46:38 pm
content: It's not possible to have a digital meter which works from 0V up to 120V, because digital electronics don't work under a volt and LEDs need around 2V to work. Add another volt or so for the regulator and rectifier and you get a few volts minimum.You need to power the meter from the primary side of the transformer, that way it'll work, irrespective of the secondary voltage. 200mV panel meters are fairly common. Power it off an isolated 5V or whatever power supply is required. The secondary voltage will need to be rectified and scaled, to give 0 to 120mVDC, from 0 to 120VAC, which can be done with a precision rectifier and low pass filter circuit.
Digital Oscilloscope addon. - Page 1
Forum section: electronics / projects

author: sahko123
author_rank: Frequent Contributor
timestamp: November 12, 2016, 12:21:27 am
content: Hello and thank you for taking your time to view this topic,I wanted to ask if anyone out there has any literature on the functional parts of digital or analog oscilloscopes. I want some reading material for a project I am working on. Its a digital addon for an oscilloscope. It will provide a readout of anything id like with multiple slots for other analog to digital data acquisition, but thats beside the point. Im looking for anything that will help in displaying the information i need or data acquisition methods used in digital oscilloscopes.Thanks for any help.If anyone asks i already have a theoretical way of displaying digital information on a crt screen and want to know of any better ways.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 12, 2016, 02:13:01 am
content: Well,http://w140.com/tekwiki/wiki/Concepts_Series

author: David Hess
author_rank: Super Contributor
timestamp: November 12, 2016, 10:22:28 am
content: Also check out the service manuals for Tektronix analog and digital storage oscilloscopes up until about 1990. They have full schematics and even theory sections describing operation.The evolution of the 7000 series readout character generators are particularly interesting but it sounds like you already have that part covered.
Digital PLL Design for Grid Phase Measurement - Page 1
Forum section: electronics / projects

author: diegoperez
author_rank: Contributor
timestamp: July 11, 2016, 03:32:46 pm
content: Hi,I was looking for a good book or aplication note that explains how to design a discrete time (it would be implemented digitally in a microcontroller) PLL to obtain the phase of the grid voltage.The key aspect that I think is important in this particular application is a good rejection of voltage harmonics, on order to obtain a steady phase.More general documentation on PLL would also be fine. I found a book from Dean Banerjee  (which I just glance over) but I found it too focused in the hardware implementation. And I'm planing to implement it digitally.Thank you for your attention.http://www.ti.com/tool/pll_book

author: johansen
author_rank: Super Contributor
timestamp: July 11, 2016, 03:40:51 pm
content: phase relative to what?you may find it good enough to check the time with nist, or whoever else you can get it from, then correcting for the latancy of the internet connection.or you could build a gps corrected time referance.If you want to accurately measure the grid phase to 1%, then you need a time base that is accurate to 1/6000th of a second. the question is also; do you want absolute accuracy or do you want to just measure the grid frequency shift relative to itself. (and on what time line)

author: diegoperez
author_rank: Contributor
timestamp: July 11, 2016, 04:44:44 pm
content: Quote from: johansen on July 11, 2016, 03:40:51 pmYes, I want to measure the grid phase relative to itself, i.e. to recover from the grid voltage the phase of the fundamental component (50Hz here in Europe, 60Hz in the US).

author: Circlotron
author_rank: Super Contributor
timestamp: July 12, 2016, 03:04:20 am
content: The AC power could have gone through numerous transformers that are WYE on one side and delta on the other and each of these will shift all phases by 30 deg IIRC, so the wire that is A phase at the power station will not be in step with the A phase at your house.

author: coppice
author_rank: Super Contributor
timestamp: July 12, 2016, 03:56:48 am
content: Some utility energy meters measure fundamentals and the angles between them. Look athttp://www.ti.com/tool/msp430-energy-library.The source code is all there. It evaluates the phase and amplitude of the fundamental of the voltage waveform to high accuracy, suppressing the 3rd harmonic by about 60dB. Its actually doing 2 locks to the fundamental component of the voltage waveform - one in phase, using a quadrature correlation approach for the error cost function, and one in amplitude, using an in phase correlation approach.The algorithms take a few seconds to settle, because of the heavy damping needed to achieve that 60dB 3rd harmonic rejection, but they work well. For some versions of IAR, you might need the mod you can find athttps://e2e.ti.com/support/microcontrollers/msp430/f/166/t/447982, which works around a mis-optimisation issue.
Digital Pot Troubles - Page 1
Forum section: electronics / projects

author: Etesla
author_rank: Regular Contributor
timestamp: July 10, 2018, 04:47:41 pm
content: I am working on a buck converter circuit using the AP5100 (Datasheet:https://www.diodes.com/assets/Datasheets/AP5100.pdf). I am using the same circuit as the one in the fixed 3.3v 1A output example, except my inductor is 6.8uH, r1 is fixed at 20k, and r2 is variable via a digital pot from 0 - 100k. When the digital pot is replaced by an analog pot of the same value, the circuit behaves as expected giving me a variable output voltage from about 1 - 13 volts, which is what I need, however, once the digital pot is put in to replace the analog pot, everything goes wrong. Some examples of issues I am seeing are as follows: The switching waveform on pin 6 CUTS ITS FREQUENCY down to about 400 khz (its supposed to be constant at 1.4 mhz, which it is with the analog pot), the output voltage does not correspond with the equation from the datasheet anymore (it does with the analog pot), and overall things get more noisy (analog pot leads are about 2" long, leads from digital pot are on the board and are about .25" long max???). I have verified that the digital pot I am using (MCP4561) is operating correctly, and I can easily set its output resistance when it is separated from the rest of the buck converter system. Any ideas on why the digital pot, which seems to be causing all these issues, is acting as it is? Sorry for the long post and thanks in advance!

author: elecman14
author_rank: Unknown
timestamp: July 10, 2018, 06:55:06 pm
content: How much current are you pushing through the digital pot? You may want to verify that against the MCP4561 data sheet absolute maximum ratings.

author: MasterT
author_rank: Frequent Contributor
timestamp: July 10, 2018, 10:23:30 pm
content: Look p.8 MCP4561 datasheet,http://ww1.microchip.com/downloads/en/DeviceDoc/22107B.pdfparameter - bandwidth. 100k pot is only good up to 100 kHz. You can try 5k pot, but I would try to isolate high capacitance (listed on p.10 Caw, Cw, Cbw) by putting inductance in series with dig pot. Having C6 to keep negative feedback locked, and unaffected by Caw.

author: b_force
author_rank: Super Contributor
timestamp: July 11, 2018, 09:09:59 am
content: Bandwidth was also the first thing that came to mind.
Digital potentiometer - Page 1
Forum section: electronics / projects

author: Lotus
author_rank: Contributor
timestamp: February 27, 2016, 12:18:20 am
content: I am building a heating element to be placed in a closed environment, controlled by PID run on an arduino board.The idea is to use a SMPS with a capacity on 12V 10A. But I would like to have the possibility to control the power output in a certain range - like 50 - 100% transferring to 5A - 10A on the SMPS.The arduino will turn the SMPS on/off using a SSR, but how am I to control the power output digitally with this amount of current?

author: uncle_bob
author_rank: Unknown
timestamp: February 27, 2016, 12:28:40 am
content: HiUse a relay. (either solid state or mechanical).Heating elements do *not* change quickly. Of course, power supplies aren't really speedy either.Consider also that most switchers are happy over about a +/- 15% range unless they are specifically designed to be highly variable. They will typically put out rated power at center voltage and something less at both extremes if you get the "affordable" ones.Bob

author: Lotus
author_rank: Contributor
timestamp: February 27, 2016, 12:58:09 am
content: Do you mean use a relay and activate it with a PWM signal according to what the required power output(50-100% dutycycle)?

author: uncle_bob
author_rank: Unknown
timestamp: February 27, 2016, 01:11:59 am
content: Quote from: Lotus on February 27, 2016, 12:58:09 amHiMore or less:100% for 2 seconds 50% for 18 seconds is fast for most heating stuff. If it's not, you aren't going to do much good with the 50% setting anyway.Bob

author: Lotus
author_rank: Contributor
timestamp: February 27, 2016, 01:18:03 am
content: great idea, thanks

author: Kleinstein
author_rank: Super Contributor
timestamp: February 27, 2016, 10:39:17 am
content: Alternatively to turning of the whole SMPS with a relays one could also switch the output to the heater with a MOSFET. 12 V at 10 A is not that much, if not switched very often.

author: mikerj
author_rank: Super Contributor
timestamp: February 27, 2016, 12:20:06 pm
content: Quote from: Kleinstein on February 27, 2016, 10:39:17 amThat sounds like a good way to kill the switcher pretty quickly.

author: uncle_bob
author_rank: Unknown
timestamp: February 27, 2016, 01:28:04 pm
content: Quote from: mikerj on February 27, 2016, 12:20:06 pmHiAll of this sounds like a great way to find out if the switcher lasts 2 days or 2 weeks in this sort of service.Cycle every 20 seconds = 4,320 cycles a day.Switcher designed to cycle once a dayOne day doing this would be close to 12 years of normal service (in that respect)Indeed this may be a 15 minute heat run every few months. In that case - not a problem.Bob
Digital potentiometer to set the gain of an op amp? - Page 1
Forum section: electronics / projects

author: helloThere
author_rank: Contributor
timestamp: December 04, 2024, 03:37:32 pm
content: Just curious because I'm working on a piezo driver/receiver and was thinking about for another revision having the receive operational amplifier use a digital potentiometer to have more flexible gain control depending on the piezo element. Is this done very often for gain control?

author: nfmax
author_rank: Super Contributor
timestamp: December 04, 2024, 06:01:27 pm
content: Not quite a digital potentiometer, but I used the equivalent in, as it happens, a piezoelectric ultrasound transducer receiver:https://www.eevblog.com/forum/projects/programmable-gain-amplifier-flat-to-10-mhz/msg5617787/#msg5617787It works well

author: mikerj
author_rank: Super Contributor
timestamp: December 04, 2024, 07:08:47 pm
content: You can use a digipot to adjust gain, but pay close attention to their very limited bandwidth.

author: Benta
author_rank: Super Contributor
timestamp: December 04, 2024, 07:23:41 pm
content: Not to mention taking care of DC levels. A digi pot doesn't float like a passive pot.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 04, 2024, 09:23:56 pm
content: The digital pots have a somewhat limited BW. The frequency range for ulrasound is quite large and it would only be the low end to work well with digital pots. Usually one does no need very fine adjustments and porpose build PGA type amplifiers with more corse gain steps may be the better solution.For fine adjust some multiplying DACs are a good alternative too.Many of the digital pots can float (no direct link to ground), but need to be used within the supply limites.

author: coppercone2
author_rank: Super Contributor
timestamp: December 05, 2024, 03:21:59 am
content: how about jfets

author: Terry Bites
author_rank: Super Contributor
timestamp: December 05, 2024, 10:34:06 am
content: As Kleinstein says, the terminal capacitance of these things will severely limit the hf response.But see thiswww.analog.com/en/resources/technical-articles/how-to-increase-the-bandwidth-of-digital-potentiometers-10x-to-100x.htmlThis may interest youwww.edn.com/dpot-pseudolog-log-lookup-table-actual-logarithmic-gainA wideband VGA or PGA is probably the simplest solution. 10-100's Hz bandwidth.Many of them are cheaper than an a digipot wideband amp combination! eg a MAX3523 PGA or or if you still want to use the digipot as the gain control something like a LMH6503 VGA would work well.Also consider analog multipliers as wideband VGAs.www.analog.com/en/parametricsearch/11327#/sort=s3,asc]https://www.analog.com/en/parametricsearch/11327#/sort=s3,ascwww.ti.com/amplifier-circuit/pga-vga/products.html]https://www.ti.com/amplifier-circuit/pga-vga/products.html
Digital power meter mod for voltages down to zero - Page 1
Forum section: electronics / projects

author: ccktek
author_rank: Regular Contributor
timestamp: June 14, 2023, 07:26:35 pm
content: No hardcore engineering here, just a tip that may be useful to others.The widely available D85-2058 panel power meter seemed ideal for a recent variable isolation transformer project. There are several cosmetic variants of the meter that may have very similar or identical circuits. The D85-2058 operates down to 40V, below which the display is extinguished. I wanted to display voltage down to 0V. That necessitated separating the 60Hz fixed and variable feeds to the D85-2058, accomplished by cutting a trace on the PCB that runs from the hot side of the mains input to a string of 510K resistors. The variable voltage from the Variac wiper is then fed to the resistor side of the cut trace while the fixed 120V supply to the display is left intact.
Digital PSU built.. general questions, about what it should have - Page 1
Forum section: electronics / projects

author: B4Me
author_rank: Newbie
timestamp: July 10, 2013, 01:50:29 pm
content: HiIm thinking about building myself a new bench supply as my old one burned out last month.Some basic information about me: I'm electronic technician, and ATM finishing my master degree in mechatronic systems, I have an interest in electronics, but mainly on digital electronics, not analog that much. And then I have programmed to atmega's for some years and also android, windows and linux.. my last interest are in 3d printing..The reason for this thread, is that I need some help to decide how much I should put into my design of a new bench supply.upper limits are 24V 5A (as that's my 230V AC supply...)The system will be controlled by a graphical interface on one of those cheap cortex M3 boards with tft screens on ebay..http://www.ebay.co.uk/itm/STM32F103VET6-ARM-Cortex-M3-Board-2-4-Touch-TFT-LCD-/200609291886?pt=LH_DefaultDomain_0&hash=item2eb53ede6eAnd then V/I control through a combination of LMxxxxx from TI and a linear voltage supply to lower the output ripple.. (hopefully)My thoughts on outputs are:2x 0-24V 5A (shared current)1x 5V xA (shared current)1x 3V3 xA (shared current)BUT..what do you guys this is needed of outputs and so on on a good bench supply ?

author: Thor-Arne
author_rank: Unknown
timestamp: July 10, 2013, 03:01:35 pm
content: There's a few discussions about this in other threads.Check outAmspire's General Purpose Power Supply designandivan747's design based on this.

author: free_electron
author_rank: Super Contributor
timestamp: July 10, 2013, 11:14:29 pm
content: oh goody.. we'll start with a fancy user interface and then build the crappiest possible linear stage. let's see if we can maybe have this digital thingie control a power resistor and simply burn it off in heat.this is the fifteen billionth attempt to make a super fancy control but total crap supply out there.begin by making a bullet proof regulator that can be controlled in voltage and current , doesn't overshoot , doesn't pop at power on or power down , can withstand reverse polarity and reverse current.once you got that nailed down you can look at slapping on a fancy user interface. the user interface can be made by a 6 year old. it's just some code controlling two dacs to give the setpoints and displaying two adc to show the actual voltage and current. any monkey can code that.the hard bit is making a bulletproof and stable regulator.

author: Jebnor
author_rank: Regular Contributor
timestamp: July 11, 2013, 12:15:26 am
content: Thor-Arne beat me to it. Read Amspire's General Purpose Power Supply design. It's long but well worth it. It goes into some detail about the design of a supply.

author: nctnico
author_rank: Super Contributor
timestamp: July 11, 2013, 12:18:04 am
content: I'd go for a switching regulator. Most microcontrollers have PWM...
Digital signal overshoot 1.8V  - Page 1
Forum section: electronics / projects

author: rakeshm55
author_rank: Regular Contributor
timestamp: February 10, 2016, 04:36:26 am
content: Hi,I am working on LVCMOS 1.8V digital logic.... My clock signal has a rise time of 2.5ns..... I observe a 11% overshoot while probing....clock frequency is 1MHz....I have already place a 33ohms series resistor.... Please let me know whether this amount of overshoot is ok....What is the tolerable limit for overshoot??.... How to know this??....Please advice...

author: John_ITIC
author_rank: Frequent Contributor
timestamp: February 10, 2016, 04:48:28 am
content: Yes, it is ok. Inputs normally have protection diodes, which limits overshoot to 0.7V over the power rail. The datasheet for your receiver should state the maximum input voltage. 11% is actually very low overshoot. Many designs, which are completely unterminated, can have overshoot of several volts!

author: ve7xen
author_rank: Super Contributor
timestamp: February 10, 2016, 04:59:27 am
content: Also a very good chance the overshoot is an artifact of your probing...
digital switch cleanup?  - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 09, 2014, 12:03:18 pm
content: How should a digital switch be driven, for instance one that is switching ranges on a precise meter?I guess I am trying to figure out what the attenuation of an HF AC signal is through the buffer that drives the digital switch, internally. Is it comparable to the crosstalk between channels?I am driving a digital switch effecting a low noise system through a MCU.Should I adopt some clean up methods? At first I thought I was going to use optical isolation but maybe its overkill since the switch has a buffer/comparator inside of it, but I don't want the MCU noise being injected into my signal.would you use digital(rf, silicon labs style)/optical isolation for a range switch?
Digital Theremin (AVR) - Page 1
Forum section: electronics / projects

author: Curby
author_rank: Contributor
timestamp: July 03, 2017, 12:27:21 pm
content: Hi there,i just want to show off the project I'm working on. It's a digital theremin, based on an ATxmega128A4U. Why no STM32 or dsPIC16? Because the power of this 8bit µC is still enough. The key things are:12bit DAC Sound, Volume integrated160 kSps (DMA based)Midi In/Out/ThroughControl Voltage for Pitch and Volume antennaUSB support: Midi, software update and PC controlNo trimmer or anything on the PCBLCD Display to configure all the ParametersRotary knob for 8 presetsexcept the microcontroller, everything is DIPThe main parameters are :selectable upper and lower scale rangesoftware calibration of the play field of the antennastone correction about various scales and a rootadjustable mix of tone correction an originalflipable antennas in softwarethe sound can be constructed consisting of up to 10 seperate waveformsIntegrated effects like chorus, tremolo, vibratoIcon based menuany many other things..I'm that far that i will get my third version of my pcb. I expect that this one will be 100% correct, there are only a few things left to do in software (one big thing is the USB suppport) and I will release it somewhere soon. Here are some pictures (most of them are previous versions still with trim pots etc.):If you have some hints or cool ideas, let me know! I think, I will be ready in like two months.Curby
Digital waveform input help needed for electronic steering unit. - Page 1
Forum section: electronics / projects

author: irrational
author_rank: Newbie
timestamp: March 25, 2016, 07:39:17 pm
content: Hello this is my first time on this board and im looking for a little help, or atleast guidance. Ive been going back and forth with this guy in portugal who doesnt speak any english for a control box for my steering unit (EPAS). Here is the link to this mysterious control boxhttp://www.ebay.com/itm/Saturn-Vue-Ion-Chevrolet-Equinox-Electric-power-steering-controller-box-EPAS-/182008071875?hash=item2a6086c6c3:g:5usAAMXQHDlRcSCy&vxp=mtrWhat im looking for is help attempting to re-create my own control box since i bought two of his controllers and they both either started smoking or stopped working for whatever reason. And his "help" on this situation is downright terrible.So apparently this controller replicates the signal from the cars ecm for two channels. One for when the engine is running and another for what speed the vehicle is traveling. Ive read that one channel requires a straight 500hz and the other channel requires a starting 500hz and then adjusted up or down to 10khz for the optional steering input assistance level AKA how easy it is to turn the steering wheel.Anybody have any suggestions on how to makea circuit that can adjust the output linearly up and down from a simple potentiometer? Or perhaps even a DDS like this one?http://www.ebay.com/itm/DDS-Function-Signal-Generator-Module-DIY-Kit-Frequency-Range-1-10000MHz-US-/171812317597?hash=item2800cfe99d:g:FwIAAOSw6EhUN7m-I appreciate the help, and the help you give me will help many others from the automotive community when i figure this out.
Digitalizing the Whites IDX Pro Metal Detector – Hardware Help Needed - Page 1
Forum section: electronics / projects

author: luci295
author_rank: Newbie
timestamp: October 01, 2025, 05:25:52 pm
content: Hi everyone,I’m working on a project to digitize the Whites IDX Pro metal detector. The idea is not to design something entirely from scratch, but to take the proven IDX Pro analog front-end and make it “smarter” with a microcontroller.🔧 Current approachI want to keep the analog coil driver/receiver front-end (TX/RX, NE5534, LM393, CD4066, etc.) running on ±8 V, just like in the original design.The plan is to take the X and Y signals from the CD4066 and feed them into a microcontroller ADC.For testing I’m using an Arduino Nano (easy to develop with), but if the hardware proves stable, I’ll move to an STM32F411 (more powerful and robust).📐 The schematic so farI’ve drawn a schematic in EasyEDA (see attachment).Instead of the original LF347, I tried using MCP6022 op-amps (rail-to-rail, 5 V supply).The Arduino runs on +5 V from a 7805 regulator.The analog section (NE5534, LM393, CD4066, etc.) stays on ±8 V.My goal is to ensure that the MCP6022 stages properly bias, buffer, and condition the X/Y signals for clean ADC input (0–5 V range, centered at ~2.5 V).❓ The main questionWhat modifications are needed around the MCP6022 circuits to get a clean and stable input into the microcontroller?Should I buffer the 2.5 V reference separately?Are extra RC filters needed before the ADC inputs?Would it make more sense to just keep the original LF347 stage, or is replacing it with MCP6022 the better approach?🚀 Next stepsIf the X/Y → MCU interface is solved, I’d like to add:OLED display (I²C 128×64)Rotary encoder for settings (sensitivity, threshold, discrimination)Audio output (tone controlled directly by the MCU, possibly replacing U6A)Maybe other features (logging, battery monitoring, etc.)The IDX Pro is already a solid detector in analog form. If we can successfully digitize it, I think it could become a real beast of a detector 😄.Any advice on the hardware side is greatly appreciated!
digitally adjustable LT3081-based current source - Page 1
Forum section: electronics / projects

author: RustyShackleford
author_rank: Regular Contributor
timestamp: November 01, 2017, 11:09:03 pm
content: I've built a simple adjustable current source based on the LT3081 regulator (see picture, Vadj is used to do a DC sweep on the variable resistor value from 0 to 10K, and the 330-ohm resistor sets the minimum current at 10ma or so).I'd like it to work with supply voltages 12 - 30vdc, and current up to 350ma. The load will be series-connected strings of 1-10 LEDs. (I realize there are off-the-shelf LED drivers, but I find them unsatisfactory, both in dropout voltage and in dimmability).I would like to make the current source be digitally-adjustable (with non-volatile setting). It looks like a good way to do this would be to replace the variable resistor with an MCP4162 digital potentiometer (http://www.mouser.com/ds/2/268/22059a-51937.pdf).A simple way to power the MCP4162 would be a shunt regulator built with a 5v zener diode, a 1K resistor, and a filter cap (max power dissipation less than 1/4 watt with Vdd=35v, can supply 5ma with Vdd=10v, and chip supply current is only 1ma max).The main issue I see is that the MCP4162 does not want to see voltages higher than its supply voltage on its other pins. If the internal resistor network were disconnected from the pin which is connected to the LT3081's SET pin (which can occur, via the SPI programming interface), the 50ua current source could drag that pin well above 5v. I'd address this by putting a 1v zener from the SET pin to GND. Clamping the SET pin to 1v should also prevent the circuit from trying to drive more than 700ma or so.

author: RES
author_rank: Regular Contributor
timestamp: November 02, 2017, 11:47:17 am
content: AD5293Single-channel, 1024-position resolution20 kOhm, 50 kOhm, and 100 kOhm nominal resistanceCalibrated 1% nominal resistor tolerance (resistor performance mode)Rheostat mode temperature coefficient: 35 ppm/°CVoltage divider temperature coefficient: 5 ppm/°CSingle-supply operation: 9 V to 33 VDual-supply operation: ±9 V to ±16.5 VSPI-compatible serial interfaceWiper setting readbackhttp://www.analog.com/en/products/digital-to-analog-converters/digital-potentiometers/ad5293.html#product-overview

author: RustyShackleford
author_rank: Regular Contributor
timestamp: November 02, 2017, 05:30:28 pm
content: Quote from: RES on November 02, 2017, 11:47:17 amThanks for the reply and the pointer. Looks like that device comes only in surface-mount package; that is happening with so many parts these days, it's really a bummer for the hobbyist. I don't need the 10-bit resolution (or the higher price). The higher voltage operation is surely nice, avoids my shunt regulator for the MCP chip's supply and the zener for protecting the pot's pin from being pulled too high by the LT3081's SET pin. But that's only two zeners, a resistor, and a cap, less than a buck worth of parts. A lot cheaper than the AD5293 and dont' have to hassle with the SMD part. Thanks for bringing it to my attention though !
TITLE CHANGED, Multi LM317 current syncs.. - Page 1
Forum section: electronics / projects

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: April 19, 2013, 06:51:01 pm
content: EDIT: I kind of steered this topic away from the original question in this post, did not want to start a new thread.So I know you can use PWM to drive the voltage setting of an LM317, but I would like to control it digitally as a constant current source. No digital pots are capable of dissipating two or three watts across the 1.2v on the ADJ and OUT pin. Is there maybe another way to accomplish this?

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: April 20, 2013, 02:52:57 am
content: Ok well this is a bit off the main topic but I did not want to start a new thread. Basically I have been working on a solder station, for 24v Hakko Irons. I've been basically just using scrapped parts to keep the cost to almost free. The iron handles are 24v 50W so I found two transformers one labeled 60W 24v and the other is about the same size and also 24W.Now I wanted to test the load on these transformers and find out how well, and cool they handle at 50watts of output. This is why I started using the lm317s I had laying around as a dummy load.I took two lm317s, and threw wired them both up with 5watt 1.2ohm resistors as current syncs. This way each one would draw one amp. I kind of want to build daves dummy current load for a fine 0 to 1 amp load, and then use a bunch of lm317s to add one amp at a time to the fine adjustment. Well here is the problem with 1 lm317 connected I would draw the expected 1 amp of current, then I hooked up an identical LM317 to the output of the transformer in parallel, but I did not get two amps!! I ended up drawing 3 to 4 amps of current. What is going on here?? Two one amp loads in parallel should draw 2 amps from the voltage supply not 4??!! Wondering if it was a heat issue I stuck the whole device in the freezer for 30 mins then turned it on, still drew 3 to 4 amps! Even more strange when I swapped transformers the circuit drew 4 to 4.5 amps!!!!

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: April 20, 2013, 03:17:19 am
content: Nevermind this was a wiring error, I missed. Cant delete topics
Digitally controlling resistance between GPIO pins - Page 1
Forum section: electronics / projects

author: imagiko
author_rank: Newbie
timestamp: October 21, 2018, 08:10:52 pm
content: I am looking to electrically control the resistance between two points that will each be connected to a GPIO pin. I also want to have the option of keeping the points "open".My idea to achieve this is to use a digital rheostat such as this one from AD:https://www.analog.com/media/en/technical-documentation/data-sheets/ad5241_5242.pdfTo keep the points open, I think I should use a MOSFET as a switch (one on each GPIO line) to bring the resistance in and out between the GPIOs. Although I am not entirely sure if I should use a p or n channel MOSFET here.Is this a decent way to achieve an open circuit and a finite, digitally controlled resistance between two GPIOs? Thanks!

author: ejeffrey
author_rank: Super Contributor
timestamp: October 21, 2018, 10:29:40 pm
content: Yes, a digital pot is a perfectly good way to do this.To open circuit use an analog switch instead of a single mosfet.

author: imagiko
author_rank: Newbie
timestamp: October 22, 2018, 03:33:26 am
content: I want to use two MOSFETs, one on each terminal as I want to electronically bring the resistance in and out

author: mvs
author_rank: Frequent Contributor
timestamp: October 22, 2018, 05:15:07 pm
content: Quote from: imagiko on October 21, 2018, 08:10:52 pmIt sounds a bit odd. May i ask, why do you need programmable resistance between two digital pins?QuoteSource of the MOSFETs will be floating between rails of GPIOs. How do you plan to controll this MOSFETs (apply gate-source voltage)? Isolated control circuit with own power supply?Analog switch (74HC4066) is IMHO a better solution here.QuoteThere are always some leakage and capacitance in semiconductors... You need to define "open circuit".

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 22, 2018, 05:26:42 pm
content: Yeah. Tell us what exactly you want to achieve, so we can tell you how you can do without it.

author: coppercone2
author_rank: Super Contributor
timestamp: October 22, 2018, 05:53:53 pm
content: you can PWM to bias a JFET to act as a resistance

author: David Hess
author_rank: Super Contributor
timestamp: October 24, 2018, 10:00:40 am
content: Also check out figure 28 in the LM13700 operational transconductance amplifier datasheet for how to make a floating voltage controlled resistor.
Digitizing audio on a laptop  - Page 1
Forum section: electronics / projects

author: iXod
author_rank: Frequent Contributor
timestamp: August 14, 2023, 09:32:28 pm
content: A friend has an old Lenovo laptop running Windows 11. The laptop has no dedicated sound card with input connector.I am telling him that the microphone connector on the 4-wire headphone/mic connector can be used as an analog audio-input port.I know there some hardware has the ability to switch out the preamp if it detects a line-level at the input.Is such an input configuration common on PC laptops?Other suggestions for digitizing audio on a laptop?Thanks,iX

author: Benta
author_rank: Super Contributor
timestamp: August 14, 2023, 09:43:32 pm
content: Well, mic input would normally just be mono. Is that OK?

author: themadhippy
author_rank: Super Contributor
timestamp: August 14, 2023, 09:53:51 pm
content: Quoteusb soundcard?

author: boB
author_rank: Frequent Contributor
timestamp: August 15, 2023, 01:17:09 am
content: There are several different USB audio I/O devices on say, Amazon that are pretty good.I have used a few and they seem to work fine for digitizing.Use the stereo line input.Here is one such interface that worked fine...https://www.amazon.com/StarTech-com-7-1-USB-Sound-Card/dp/B002LM0U2S/ref=sxbs_sbv_search_btf?content-id=amzn1.sym.f15d2f09-357d-4995-986d-e924fbe183e3%3Aamzn1.sym.f15d2f09-357d-4995-986d-e924fbe183e3&crid=L6NHVZ26D8V4&cv_ct_cx=USB%2Baudio&keywords=USB%2Baudio&pd_rd_i=B002LM0U2S&pd_rd_r=df8828fa-caaa-4b73-9121-39370a33f017&pd_rd_w=1lBrr&pd_rd_wg=dxB5j&pf_rd_p=f15d2f09-357d-4995-986d-e924fbe183e3&pf_rd_r=8DRMNFP48XA8VH6VJTMN&qid=1692062157&sbo=RZvfv%2F%2FHxDF%2BO5021pAnSA%3D%3D&sprefix=usb%2Baudio%2B%2Caps%2C205&sr=1-1-a61ee601-6e56-4862-a8a2-1d3da5a5406f&th=1boB

author: magic
author_rank: Super Contributor
timestamp: August 15, 2023, 10:34:46 am
content: Depends on the audio chip and software.Back in the 2000s it was a big deal that many "HD Audio" chips supported "re-tasking" - oftentimes jacks could be switched even from output to input and vice-versa.
Digole brand color OLED displays - Anyone used them? - Page 1
Forum section: electronics / projects

author: Mr.B
author_rank: Unknown
timestamp: July 31, 2014, 09:55:48 pm
content: I am considering buying a couple of these displays for a home project.1.8" Color OLED 160x128 Module:http://www.digole.com/index.php?productID=883Programming Manual:http://www.digole.com/images/file/Tech_Data/Digole_Serial_Display_Adapter-Manual.pdfKey things going for them:1. Reasonably priced. USD 262. 3.3v and 5v3. Supports 3 communications methods: UART, SPI, I2C.4. Onboard font and drawing management.Has anyone here used these displays?Any pros and cons you can offer up?Thanks in advance.

author: andyturk
author_rank: Frequent Contributor
timestamp: August 01, 2014, 12:52:41 am
content: Haven't used that one, but I've worked with displays of the same resolution. The OLED itself looks interesting, but the PIC and all the other stuff on the board seems less than wonderful. The drawing speed is awfully slow, but might be OK for arduino/hobby projects.Here's another source for cheap(er) OLEDs:http://www.buydisplay.com/

author: Mr.B
author_rank: Unknown
timestamp: August 01, 2014, 01:31:29 am
content: Yes, they appear to be quite slow.Fortunately my application will only have one data update or screen refresh every 10 minutes, so it shouldn't be an issue.