hybridfree/eevblog-posts huggingface dataset:
Visualisation of Plasma tubes (?is the RF duct) by research group - Page 1
Forum section: electronics / projects

author: VK5RC
author_rank: Unknown
timestamp: June 02, 2015, 09:00:30 am
content: An interesting news article. On a few occasions I have had trans-equatorial propagation down to my latitude (37 Sth) it sounds like talking down a pipe as well.http://www.news.com.au/technology/science/aussie-student-proves-existence-of-plasma-tubes-floating-above-earth/story-fnjwlcze-1227379756018

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 02, 2015, 05:51:49 pm
content: Cool
Vitreous Enamel Resistor - have I done the right thing? - Page 1
Forum section: electronics / projects

author: mabyrne
author_rank: Newbie
timestamp: February 10, 2019, 09:58:39 pm
content: I have repaired a circuit with an unregulated 48v supply and a 680ohm resistor strapped across the supply to provide stabilisation (I assume).I have installed a 10W vitreous enamel resistor ( TE C10680RJL) as they generally regarded as more heat tolerant than the sand block resistors. The resistor has been mounted on ceramic stand-offs to keep it away from the PCB.I have noticed however that this resistor gets pretty darn hot (about 100 deg as best as I can measure it) and even smells hot!I suspect this resistor is getting hotter than the sand filled resistor I replaced. Is this because of the smaller surface area? The emissivity of the enamel?Will the smell of a hot resistor go away or reduce over time?Am I better off going back to using a sand filled resistor?As I am performing this repair for paying customers, I am concerned about the perception of a poor component choice (ie... it smells like its burning up) vs the technicalities of VE longevity.

author: floobydust
author_rank: Super Contributor
timestamp: February 10, 2019, 10:14:34 pm
content: You have to be careful with power resistors, the trend is making them smaller and smaller while keeping up power ratings.Getting rid of heat- surface area is important, so size matters the most.All manufacturers are doing in shrinking down the size is finding a way for them to run hotter or greater specmanship.Um, the C10 at 10W is rated 300°C surface temperature! I get 48V/680R 3.4W still pretty hot.Compare toYageo SQP-10a bit longer and thicker.I'm saying the physically bigger resistor will run cooler. Basic physics that cannot be avoided, unless you improve convection or use forced airflow.The resistor's leads are also a means for cooling with conduction heat transfer, so a ceramic bead on them will (insulate) make things a bit hotter.

author: dzseki
author_rank: Frequent Contributor
timestamp: February 10, 2019, 10:16:49 pm
content: Did the original resistor broke?If the circuit is unknown to you perhaps it would worth some more investigation whether the resistor in question runs within its specs (Pd <10W?), maybe there is a latent problem in the deeper circuit that cause higher power consumption.
VLF Metal Detector based on STM32F303 - Page 1
Forum section: electronics / projects

author: ppTRN
author_rank: Regular Contributor
timestamp: March 31, 2025, 04:49:23 pm
content: Hi everyone,in the last few weeks many of you helped me in the microcontroller section in order to properly program some STM32F303 peripherals.Well, here's the result, finally I have a working prototipe of a VLF metal detector.There is a lot of optimization to be done, and as a first thing, after testing it on ground, I will try to switch as fast as possible to a PCB version. Then I will optimize the software and then I will embedd everything into a single board.The project is available on GitHub (https://github.com/GiuseppeTrainiti/MetalDetector) but it is being updated day by day.So, thank you very much for all of your help! Updates will follow.Here's a video that shows how it works:https://youtu.be/1Gpw9aEqTXw?si=35bSd2vwrDu9ioWq

author: moffy
author_rank: Super Contributor
timestamp: April 01, 2025, 02:18:15 am
content: For those of us who don't use KiCad could you include a PDF version of your schematic? Excuse the request if it's already there and I missed it.

author: ch_scr
author_rank: Frequent Contributor
timestamp: April 01, 2025, 06:22:41 am
content: Regarding the receive amplifier circuit, maybe have a look atTI's THP210fully differential amplifier.
VN5016AJTR-E with esp32 - Page 1
Forum section: electronics / projects

author: tblunt
author_rank: Newbie
timestamp: July 30, 2025, 12:23:28 am
content: Hey,First time posting after lerking a bit. Please move/remove if not in the right place and let me know.Can I please get some advice/a sanity check for using a VN5016AJTR-E with an ESP32.I have some radio equipment that can draw up to 20/25A while in transmit and I want to be able to control and monitor the power to it. I have an esp32 custom board that does a lot of other things and I want to incorporate this switching of the power line into another add on module.I am thinking to use an MCP23008 to control the VN5016AJTR-E rather than the ESP32 directly as this will be a physically separate (in the same box) pcb that will have i2c going to it for the ads1115.Attached is the schematic connected directly to the ESP32 and larger versions of it.I'm not sure if I have the right layout/components for the VN5016AJTR-E but I think its close.Thanks in advanced.
VNA for LNA Testing - Page 1
Forum section: electronics / projects

author: David
author_rank: Frequent Contributor
timestamp: July 10, 2025, 07:17:15 pm
content: Hi all,I have an SVA1032X and I am currently trying to test a discrete LNA. The SVA only goes down to -20dBm and this is too powerful for my amplifier. I have tried calibrating in an attenuator but the S11 response is then very noisy, I suspect due to the dynamic range of the TG port in reflection?Does anyone have a workaround or recommendation? I was wondering if the SDR kits VNA may be a viable option?Cheers,Dave

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 13, 2025, 11:43:11 am
content: Amplifiers usually are tested with attenuators. An attenuator is placed either before of after the amplifier.It is conveniant to have same attenuation as amplifier gain. You may need several different attenuators in series for it.LNA work with relatively small signals so you put attenuator before LNA.Power amplifiers usually have relatively high output power so you put a large powerfull enough attenuator after an amp.
VNQ5027 HIGH SIDE DRIVER CURRENT SENSING - Page 1
Forum section: electronics / projects

author: ALAN13
author_rank: Newbie
timestamp: November 30, 2023, 02:39:21 pm
content: I'm trying to work out how to calculate the value of the current sense resistor on this high side driver . It has something to do with the K3 value but the datasheet doesn't explain how to calculate the resistor value say for 8A

author: PSR B1257
author_rank: Frequent Contributor
timestamp: November 30, 2023, 03:03:06 pm
content: It's up to you (your application) to calculate the resistor.At 8A load current you get about 3,7mA sense current. So a 1k resistor will give you 3,7V.
Voice Alert System + Convert .Wav Audio File to .Hex - Page 1
Forum section: electronics / projects

author: gevv
author_rank: Contributor
timestamp: September 26, 2022, 08:58:04 am
content: Audible warning circuit for the door that remains open. With Google translate, you can create alerts in your own language and upload them to Eeprom integration. You can use this circuit in different projects or for prank.https://youtu.be/oWovYCjjiXk00:07 General description01:45 Circuit diagram PCB drawing01:53 Test 102:15 Test 202:31 Test 302:41 Test 403:02 Test 503:12 Test 603:22 Download google translate translation voice04:05 Recording Audiocity MP3 file as WAV04:56 Reducing WAV file size with BTC Soun encoder program05:45 Reducing the noise of the WAV file with the Frhed hex editor program06:17 Converting WAV file to HEX file with PonyProg program (or .bin, .e2p, .mot, .csm, .rom, .epp)07:04 Creating a reduced size WAV file with Goldwave program09:09 Volume down for PWM working limit with Goldwave program
voice controled output with a pc  - Page 1
Forum section: electronics / projects

author: bills
author_rank: Frequent Contributor
timestamp: November 29, 2014, 12:40:58 pm
content: I have a system that uses a old verbex isa card to send voice commands via a Allen Bradley Basic Module to a Allen Bradley PLC. This system was last updated in 1995 No replacement parts are available, would like some input on an a idea I have.There is a i/o card that would fit the bill that could be used with modern pc's and I could interface it with the PLCAny ideas on software that would allow voice control? I need it to respond to numbers 1-16 with a .5-2 sec. pulse. or any ideas on a plan b.links.http://www.blackbox.com/Store/Detail.aspx/Relay-Output-Card-PCI-16-Outputs/IC905Chttp://www.blackbox.com/resource/files/productdetails/23001.PDFhttp://books.google.com/books?id=jMKfH6i9OcYC&pg=PA49&lpg=PA49&dq=verbex+isa+card&source=bl&ots=ndVOZ3yGvH&sig=NnWm4qAJwtVq5Z73ft17J1Y25Zg&hl=en&sa=X&ei=ML15VMT6NI6togTfqIKoDw&ved=0CDwQ6AEwBQ#v=onepage&q=verbex%20isa%20card&f=falsethanksbill
Voice inversion circuit - Page 1
Forum section: electronics / projects

author: mpicker21
author_rank: Contributor
timestamp: April 26, 2016, 02:42:42 am
content: I am looking at integrating a simple voice inversion circuit into a project. The schematic I am looking at using ishttp://mail.blockyourid.com/~gbpprorg/mil/scram/index.html. My question is this, I want to output the inverted audio into a microphone level input. If I am correct I won't use the LM386 since I won't be driving a speaker. I assume I just use the output from the transformer. What I'm not sure of is if this is the correct type of transformer then. I will already be running the audio through an isolation transformer before it goes into the mic input.Thanks in advance guys.

author: Paul Price
author_rank: Super Contributor
timestamp: April 26, 2016, 03:37:51 pm
content: Yes, it is.
Voice Recorder - Parrot Repeater Controller - Page 1
Forum section: electronics / projects

author: rvalente
author_rank: Frequent Contributor
timestamp: February 05, 2021, 04:54:29 pm
content: Hello Mates,I'd like to make a small parrot repeater controller for ham radio, this device listens to the RX and playback the message.Usually the controllers apply the classisc ISD2560 but I'd like to make something a little better in audio quality.I'd like to have a 30s record time, maybe 9.6KSa/s (I DUNNO) quality or so...Ill probalby apply a STM32 bluepill, maybe with arduino (just to go easy).Is there any audio compression library? Or maybe use a serial ram?
Void pattern on inner layers under inductors - Page 1
Forum section: electronics / projects

author: Trittonac
author_rank: Newbie
timestamp: November 27, 2023, 09:46:36 am
content: Tesla opened some documents about their 2008 roadster onhttps://service.tesla.com/roadster, one of which is the HVAC PCB schematic and Gerber files. Upon checking them out I noticed that on the inner layers under the inductors, there is a specific pattern. Can anyone shed some light on why the specific pattern is used here? Does the radius of the circles on the edge of the cutout matter, or is this related to better manufacturing, since they also use the wavey cutout edge for other void zones?
Volgen ERK30-1515 change to 1212? - Page 1
Forum section: electronics / projects

author: staze
author_rank: Frequent Contributor
timestamp: April 04, 2016, 06:14:07 pm
content: All,I recently picked up a Volgen ERK30-1515 (triple output, ±15V and +5V), and am wanting to change it on ±12V. I'm guessing it should just be a matter of swapping out some set resistors, but I haven't ever worked on SMPS's other than re-capping. Any thoughts on where I should start? I'll post a picture of the unit later today once I can open it up.I have contacted the company, and they said these units were discontinued about 15 years ago, so they don't have any schematics available. =/
Vollgo VG6328A - tiny Bluetooth (BLE) to UART module from LCSC, working! - Page 1
Forum section: electronics / projects

author: dusan
author_rank: Regular Contributor
timestamp: August 22, 2025, 10:12:35 am
content: I bought tiny (13.6mm x 16mm, sold without header) bluetooth-to-uart module from LCSC (0.84 euro, stock 7000+,https://www.lcsc.com/product-detail/C20539408.html) and I originally had some troubles making it work, I searched here too and found nothing so once I made it work I decided to put it here so that other can find it.The SOIC-8 chip is JieLi AC6328A (32bit mcu with BT and USB support), chip marking is BP2P064-28A2 (classic bullshit JL numbering that means nothing). The oscillator is 4pin 24MHz. I searched for "I6328A schematic" and found something very similar, pinount matches: 1=vcc, 3=gnd, 4=antenna, 5,6=osc, 2 is used for led. It is programmed, I found chip itself on aliexpress, they sell it programed and unprogrammed as well, but it's not much cheaper (0.7 eur) so I wouldn't bother using ali.When I inspected pcb before first use I found small blob of solder under the part connecting the antenna, I measured it and there was short, I desoldered it and the short was still there (approx 2 ohms), RF is weird. I soldered it back on, still 2 ohms. I installed android app "nRF Connect" by Nordic semi, it found the device as XLBLE and when I connected it and sent string via service 0xFFE0 and characteristic 0xFFE1 I was able to read it on uart at 115200. Then I implemented bluetooth in my own android app and it also found it and sending strings also works.I'm powering it from 3v3 that supplies CH340N and connect GND pin a TXD from the module goes to RX pin of CH340N. For app I just use serial monitor from arduino ide at 115200. Green led is on when device is connected. I didn't test receiving, don't need it.It consumes 5mA when idle and 10-17mA when sending data. Range is at least 5m (width of my apartment, can go further than that).
Volt Standard for LAb Grade PS - Page 1
Forum section: electronics / projects

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: August 24, 2024, 09:47:34 pm
content: I rebuilt an old Lambda Lab PS and my ruthless appropriation of other peoples schematics has paid off. The thing works pretty well and volt and amp adjusts work. It does drift and at least one cause of this is my volt standard, a 7.2 V Zener. If I even blow on it the volts change. I would like to replace this part with something a bit more stable. Drift really is not a terrible problem since it is in milli volts but it bothers me.I think that I can easily put in a LM399. I think that would work. There are some on ebay from China. Any advice on using one of these?

author: Benta
author_rank: Super Contributor
timestamp: August 24, 2024, 09:55:21 pm
content: Total overkill. It's a PSU, not a lab reference.Use a TL431 with a couple of resistors to set the voltage.

author: tggzzz
author_rank: Super Contributor
timestamp: August 24, 2024, 10:06:25 pm
content: I rather like my Power Designs 2020, both aesthetically and because it is based around an LM399 .

author: TimNJ
author_rank: Super Contributor
timestamp: August 24, 2024, 11:28:18 pm
content: For your purposes, TL431?

author: TimNJ
author_rank: Super Contributor
timestamp: August 24, 2024, 11:43:01 pm
content: https://www.eevblog.com/forum/metrology/is-tl431-good-for-reference-in-19-999-counts-voltmeter-any-variants/Oh, I didn’t even read the second line of Benta’s post apparently.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: August 25, 2024, 12:53:56 pm
content: Although I like the sound of "total overkill", I think I have a TL431 around here somewhere..Think I will give it a go soon. This is just a Lab PS and is used every week or so. I used Multi turn Bourns pots for the adjustments because I have some and I use the PS to provide some finicky voltages sometimes.

author: guenthert
author_rank: Frequent Contributor
timestamp: August 25, 2024, 02:11:20 pm
content: Quote from: tggzzz on August 24, 2024, 10:06:25 pmYes, they sure are pretty. I was tempted to buy one, but gathered that they were hard-wired for 110V operation. Is it not so?

author: tggzzz
author_rank: Super Contributor
timestamp: August 25, 2024, 09:21:15 pm
content: Quote from: guenthert on August 25, 2024, 02:11:20 pmMany Power Designs PSUs have 110V only transformers.The 2020 transformer has two primary windings. Hence you can use the usual technique of resoldering the primary wires so the primaries are in series (rather than parallel) turns them into 220V inputs.For any PD device, I would check the schematic carefully before purchase.
Voltage AFE with fast rising edge problem - Page 1
Forum section: electronics / projects

author: Mark
author_rank: Frequent Contributor
timestamp: March 20, 2019, 12:03:56 pm
content: Hello,I am having a problem with an AFE (attached) that uses an INA826 instrumentation amplifier to drive an ADS1271 ADC.This is a single 5V supply circuit with a 2.5V reference. The entire AFE channel is powered by an isolating DC-DC and the digital signals also go across the isolation barrier.There is a voltage divider formed from two legs, each 100k and a divider resistor of 806 ohms to give a full scale output of +/-1.7V (referenced to the 2.5V mid point) for a 300VRMS input. The ADC uses a 1.7V reference. The measured voltage input can be 300VRMS (60Hz + harmonics) and can come from anything really.With sine waves, everything looks fine at the output, but with fast rising edges it falls apart, e.g. a differential square wave starts to show an anomaly at the zero crossing.I added some unbalanced stray capacitance between the inputs to the circuit ground and now the simulation shows the same waveforms as I'm seeing on the PCB (so I think I'm in the right area).The two x 475k resistors are intended to keep the common mode of the inputs at mid-supply. These should also provide a return path for the input bias currents for the INA826?Any ideas or suggestions welcome, thank you.
Voltage based automatic switching - Page 1
Forum section: electronics / projects

author: Pygmalion
author_rank: Regular Contributor
timestamp: May 12, 2025, 01:23:21 pm
content: I want to build my ownTransistor Tester. However, I would like it to be able to be operated with a standard USB charger.The problem is that 5.0 USB chargers typically use a switching regulator and the output has several issues, most notably voltage ripple, which makes the measurements inaccurate (according to people related to the Transistor Tester project).One imperfect solution that was suggested was to at least use a good LC filter; the voltage is then a few 100mV lower, but at least with less ripple.Another possible solution is to use higher voltages and send them through the linear regulator to get an almost perfect 5V voltage supply. And yes, the new smart fast USB chargers have various protocols that allow a higher voltage output.So my idea is to design a circuit that negotiates an input voltage of 9V and passes it on to the linear regulator. However, if only 5V is available, the input voltage is passed to the LC filter.After reading some information on the internet, especiallythis website, I came up with this circuit. The left side negotiates the voltage through the QC protocol, the right side passes the current through Q2 if the VCC is 5V, otherwise the current must flow through the linear regulator. The capacitor C1 should prevent Q2 from opening too quickly and letting 9 V through.Could you please tell me if this circuit is OK and which common PMOS would you recommend?

author: Per Hansson
author_rank: Unknown
timestamp: May 12, 2025, 06:35:31 pm
content: Just an idea: some of those testers come with the option of using a DC barrel jack.There exists premade USB-C "trigger" cables with fixed output voltages.So you can get such a cable and pair it with a decent charger and that might work ok.No affiliation with this seller and he does not have the 9v version in stock but at least you get the idea:https://www.ebay.com/itm/154199751911You could also do away with the 9v battery connection if there is no DC barrel input available and use something like this:https://www.ebay.com/itm/394430811053In both cases a better linear regulator and additional capacitance on the input and output will probably be required.Especially for the version that was designed without a DC barrel jack to begin with and thus expects a clean DC input...
voltage boost in buck converter - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: June 30, 2019, 04:30:53 pm
content: Hi guys,I designed a buck converte using PMOS . when I simulated it in ltspice I got a weired result , at 10% PWM the voltage is around 8V with the imput of 12V and I got the same result in hardware and can't go below 6V when it was loaded with 47ohm resistor. can somebody tell what is the problem. I have attached the ltspice file and the waveform at 10% pwm.regardsN.Baskaran

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 30, 2019, 06:32:56 pm
content: Two things at first sight:This doesn't look like a proper way of driving the PMOS's gate. This transistor has a relatively high input capacitance. Even with a 1k pull-up, it will still be ON a lot longer than the ON state of your PWM signal, which IMO explains your problem. Take a look at the gate's voltage in LTSPice (or for real on an oscilloscope on the real hardware.) You will need a different way of driving the gate if you want to get a lower output voltage.Just a quick side note, I know this is just a simulation here, but you said you built it for real. You should put a series resistor between your PWM signal and the base of the NPN transistor.
Voltage booster - Page 1
Forum section: electronics / projects

author: Matster Chief
author_rank: Contributor
timestamp: December 05, 2013, 05:41:29 pm
content: Hey i have a question... I had the idea of trying to find a way to run guitar effects pedals off an iphone battery and also charging it throught the standard iphone charger. well the first obstical i've run into is the fact that the batteries don't run at a high enough voltage. most guitar pedals run on 9v's of power. The highest voltage i've found on an iphone battery is about 3.8v. is there a way to boost the voltage with out having to run a second battery or adding large amounts of circuitry?

author: Marco
author_rank: Super Contributor
timestamp: December 05, 2013, 07:37:13 pm
content: You can buy ready made boost converters off ebay/dx/whatever, I don't see why you would want to use iphone batteries though ... just use a standard cell and some USB charger for standard cells.PS. do those pedals really use batteries up fast enough for this to be interesting?

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 05, 2013, 07:40:57 pm
content: Define "large" amount of circuitry. A boost regulator could get you up to your required voltage fairly efficiently, but that does take some know-how.A better solution might be to put several batteries in series, which adds voltage linearly. Three batteries in series gets you 11.8V; then you can use an LM317 to regulate that to 9V or whatever you need.EDIT: I agree with Marco. Use standard 18650 cells. Three of those will get you 10.8V, and chargers for them are cheap.
Voltage Controlled Adjustable Buck Regulator - Page 1
Forum section: electronics / projects

author: dugherd
author_rank: Contributor
timestamp: April 28, 2016, 11:05:28 pm
content: I would like to design a 3.7 - 12 V, 3 A adjustable supply with 12V input. The output voltage is to be controlled by 0-5V signal.My thought was to use a buck regulator like the LM2678-ADJ or similar. And control the feedback with the 0-5V signal. Are there any ideas on how to approach this? Or, is there a better or common solution for this?My first shot at this used an OPA548 but when operating at outputs of 4V or so it is just too hot and I would like to avoid paralleling an additional op-amp. So, would like to find another solution.Thanks for your help!

author: jeroen79
author_rank: Frequent Contributor
timestamp: April 29, 2016, 05:08:19 am
content: As far as I can tell from the datasheet is that the LM2678-ADJ will try to maintain 1.2V on the feedback pin.You could use an opamp to compare the control voltage to the output and then bias it's output to 1,2V when there is 0 error.How did you use the OPA in your trial?

author: dugherd
author_rank: Contributor
timestamp: April 29, 2016, 06:01:44 pm
content: My original design used the OPA548 as a non-inverting amplifier with gain of 2.4. But, for the particular application the normal operating point is at about 4.4Vout and 1.3A. Operating here the OPA dissipates ~10W. So, I would like a more efficient solution which led me to looking at replacing the op-amp with the adjustable buck regulator.
Voltage-Controlled Amplifier IC Reccomendations - Page 1
Forum section: electronics / projects

author: AntiProtonBoy
author_rank: Frequent Contributor
timestamp: September 07, 2013, 03:34:34 pm
content: I've been eyeing a few VCA chips, such as theTHAT 2180 series, although I'd like to explore cheaper and more commonly available alternatives, if possible.The application will be for audio synthesis, so the bandwidth is not super critical - something like a -3 dB knee at 10 MHz would be ample. The relationship between the gain and the voltage control does not need to be linear. Amp dynamic range should be 90 dB, or perhaps better. However, I do want very good attenuation with the voltage control.If anyone has worked with such ICs in the past, drop me a few hints. Cheers.

author: fcb
author_rank: Super Contributor
timestamp: September 07, 2013, 03:49:11 pm
content: -3dB @ 10MHz... not sure thats necessary for audio-synthesis (unless your trying somesort of down converting trick)THAT218x series is based on the great Blackmer cell and really are very good - but expensive. I use a lot of LM13700's and they have adequate performance, easy to get, forgiving to work with and low-cost. Although a 90dB is dnr is out of the question.
Voltage Controlled Current Source Question - Page 1
Forum section: electronics / projects

author: bobbbyyy
author_rank: Newbie
timestamp: June 09, 2013, 12:03:13 pm
content: I'm trying to use one DAC to control multiple N-channel MOSFETs each with identical loads. The objective is for all MOSFETs to output the same amount of current with respect to each other and have a linear relationship to the DAC's output voltage.I researched voltage controlled current source circuits and simulated the attached circuit I found. It looks like the circuit is doing exactly what's needed but the op amp input voltage is reduced to a range between 0 to 110 mV instead of a wider range (see attachment for op amp input voltage vs MOSFET output current graph).The sense resistor (R3) is set to 1 Ohm. If it's increased, the input voltage range changes but the maximum current that can be sunk from the MOSFET gets reduced (not wanted).How can I get a wider input voltage range for such a circuit (0V to 3V for example)?Is there another circuit that I should look into instead of this one?

author: David_AVD
author_rank: Super Contributor
timestamp: June 09, 2013, 12:14:33 pm
content: Simple voltage divider on the input?

author: bobbbyyy
author_rank: Newbie
timestamp: June 10, 2013, 01:37:26 am
content: Quote from: David_AVD on June 09, 2013, 12:14:33 pmThat works perfectly. Thanks!
Voltage Controlled Oscillator Design ~300MHz 10V Pk-Pk - Page 1
Forum section: electronics / projects

author: Lyuben
author_rank: Newbie
timestamp: December 09, 2024, 04:57:50 pm
content: First a disclaimer, I am not an RF engineer - yet, and my experience is still limited. I am trying to design an oscillator that I can use to apply 10V Pk-Pk voltage-sinewave across a PIN diode in reverse-bias (10V Pk-Pk centered around -5V DC). The frequency of interest is 290MHz, although that due to some uncertainties in my circuit it can be slightly more or slightly less. Therefore, I would like to be able to adjust my oscillator between say 280MHz-300MHz to compensate for the uncertainties.Additionally, it's quite important for my application that the frequency remains stable. I am still figuring out how stable I need it exactly to be but for now I am assuming +/- 0.1MHz from the central frequency (290MHz) should suffice. Furthermore, my PIN diode doesn't have the same impedance at 300MHz, as it does at 280MHz. I'm currently thinking of first designing the oscillator for 50Ohm and then moving on to design some tunable impedance-matching network to put in-between. However, I am curious if this can be implemented in the oscillator design in some smart way.For now, the circuits that I am looking at are a Colpitt's oscillator, and a PLL circuit. However, achieving 10V Pk-Pk seems troublesome. Any ideas, recommendations, or piece-of-advise is more than welcome!

author: Benta
author_rank: Super Contributor
timestamp: December 09, 2024, 05:58:15 pm
content: I'd probably just use a small-signal VCO and amplify the output signal appropriately.Like a MC100EL1648.

author: moffy
author_rank: Super Contributor
timestamp: December 09, 2024, 09:09:58 pm
content: A small RF transformer might help:https://www.minicircuits.com/pdfs/TC16-1T+.pdf

author: Etesla
author_rank: Regular Contributor
timestamp: December 13, 2024, 12:06:39 am
content: Are you making a thing that you can tweak by hand in one off quantities, or would this design be for mass production? And over what conditions (duration and temperature) do you want it's frequency to be 290 MHz +- 0.1MHz?

author: SCSKITS
author_rank: Regular Contributor
timestamp: December 13, 2024, 02:25:16 pm
content: So you need +24dBm into 50 ohms if that is the impedance you are driving. For a "one of" experiment, I would use an RF signal generator and an amplifier to get the required levels, with the output coupled by a transformer with a capacitor in series with the output to isolate from the DC voltage. If your impedance is higher than 50 ohms, then the transformer can be used to directly step up the signal generator output. If a matching network is needed it can be after the transformer.
Voltage Divider Calculator -- Real Resistor Values - Page 1
Forum section: electronics / projects

author: slugrustle
author_rank: Frequent Contributor
timestamp: November 19, 2017, 04:36:05 am
content: I just wrote a Javascript voltage divider calculator that gives answers with real-world resistor values that you can actually buy (EIA E24 and/or E96):https://github.com/slugrustle/voltage_dividerTo try it out, download the code from github (green "Clone or download" button). You only need the file voltage_divider.html; just open this in a browser.In addition to plugging my project, I also want to know if anyone has seen something similar. I've only seen voltage divider calculators that do simple algebra and give you a resistor value that you can't actually buy.

author: prasimix
author_rank: Unknown
timestamp: November 19, 2017, 07:05:46 am
content: This one is online long time:http://jansson.us/resistors.html

author: sainter
author_rank: Regular Contributor
timestamp: November 19, 2017, 11:55:37 am
content: Electrodroid for android a pretty good HQ for such a thing.

author: Gyro
author_rank: Super Contributor
timestamp: November 19, 2017, 12:22:33 pm
content: You might like to try this one out too:https://www.eevblog.com/forum/projects/fun-with-resistors/P.S. Yours looks good, it would be nice to a allow dividers with more than two resistors though.
Voltage divider before a linear regulator? - Page 1
Forum section: electronics / projects

author: DebboR
author_rank: Contributor
timestamp: May 28, 2013, 07:24:21 pm
content: Hello,I am working on a little project that uses an input voltage between 25V and 45V. I also have a very tiny IC that has a nominal voltage of about 5V with a draw of a few µA. To power this IC, I want to use something like a 7805 (as it is available in a small package and is cheap), but the maximum input voltage is around 25V.Now I want to know if I can simply place a voltage divider on the input of the 7805? And if so, what would be good values? 4.7kOhm maybe?Thank you in advanceDebboR

author: CarlG
author_rank: Regular Contributor
timestamp: May 28, 2013, 07:51:05 pm
content: Hi, take a look in the 7805 datasheet, you'll probably find some application for high input voltage.A voltage divider could be used yes, but you'll probably waste more power than some sort of preregulator for the 7805 to ensure stabliity etc.

author: madires
author_rank: Super Contributor
timestamp: May 28, 2013, 08:03:27 pm
content: The 7805 is total overkill for some µA. Maybe a MCP1702 is suited better. Regarding the voltage divider please look up the formula for loaded voltage dividers.

author: mikes
author_rank: Regular Contributor
timestamp: May 28, 2013, 08:45:02 pm
content: This calls for a ~5 V zener and a ~5 K resistor (a few mA through the zener)

author: madires
author_rank: Super Contributor
timestamp: May 28, 2013, 08:50:49 pm
content: Quote from: mikes on May 28, 2013, 08:45:02 pmYep, even better! If a stable voltage is required he could use a zener with a little higher voltage and a MCP1702. Much better than the voltage divider.

author: DebboR
author_rank: Contributor
timestamp: May 28, 2013, 09:02:28 pm
content: Ok, thanks for the quick answers! I didn't think about using the zener. I will probably do that as the output doesn't have to be so stable. Also thanks for letting me know about the MCP1702! I never heard about that one...DebboR
Voltage doubler circuit - Page 1
Forum section: electronics / projects

author: circuithead
author_rank: Contributor
timestamp: April 13, 2015, 03:32:16 am
content: Hi,I'm looking to build a power supply and need 25VDC at 0.3A and 50VDC at 40mA.My plan was to use a wallwart AC - AC adapter for the 25VDC and then use a voltage doubler connected to the same adapter for the 50V.I've found a few different schematics online for similar things but with centre tap transformers.. and although they simulate well, the one that I found that uses a single winding does not...Is this a spice error or my own error?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 13, 2015, 07:57:23 am
content: The half wave doubler circuit would be best here. With a main FWB circuit, you can be sure that each end of the AC winding is alternately banging between +V and -V, each cycle; when and where, you can't be so sure of (because any intermediate voltage is defined by the rectifier diode leakage and capacitance, and not backed up by any kind of current capacity), but that it's going between those points, sooner or layer, means you can use either AC terminal with a HWD.You can also use a cap-coupled FWB, as shown, but this uses extra diodes and capacitors, and doesn't double the voltage on its own. You need to stack the negative side of that rectifier on top of the first one to get your 50V.Tim
voltage doubler for AC adapter - Page 1
Forum section: electronics / projects

author: rocmel
author_rank: Newbie
timestamp: May 04, 2020, 06:56:01 am
content: I need a 30v adapter but my junk box only has up to 24vSo I hacked a HP 18V adapter made by Astec (it's actually 17v) in order to get the 30V outIt will be used to charge 25.2V lithium battery pack.I don't know why they used parts in parallel.I added the circuit shown shaded. I traced the circuit and & left out some ceramic caps.The diode is from EHT supply, high speed from an old TV.Can someone tell me why I'm getting 32v at the added circuit.

author: capt bullshot
author_rank: Super Contributor
timestamp: May 04, 2020, 09:50:00 am
content: Most probably it's because your SMPS uses the flyback topology.With this topology, energy is charged into the magnetic core from the primary and then discharged into the secondary. Voltage regulation is done by adjusting the amount of transferred energy. While the charging phase, the full rectified input voltage is applied to the primary, and the secondary rectifier blocks that voltage. Your additional rectifier works the other way round, so your circuit receives the primary voltage multiplied by the transformer ratio. In a flyback converter, this voltage is not regulated nor has anything in common with the regulated output, it just depends on the input voltage and the transformer ratio (plus ringing).
Voltage doubler question - Page 1
Forum section: electronics / projects

author: CaptDon
author_rank: Super Contributor
timestamp: May 27, 2021, 12:56:46 pm
content: I am building a high voltage supply for an amplifier based around an Eimac 8930, the sort of super 4CX250B. I have two transformers that are stout with low secondary resistance but half the total voltage I need. I can't put the secondaries in series since they are only rated at 1500v insulation. My sustained D.C. output voltage target is 2200 to 2400. I was thinking of running each transformer with one side of the secondary grounded and pushing a voltage doubler circuit to feed a larger 200uf energy storage bank for the plate supply. I would wire the transformers out of phase so that on each half cycle one or the other would be pushing power into the storage bank. My question involves ripple on the capacitors. If my doubler circuit uses a pair of 100uf caps for an equivalent 50uf (since in effect they are in series) and I am pushing energy into a 200uf storage bank with a 300ma. peak load I would guess the ripple on the caps in the doubler circuit would have about 4X the ripple of the storage bank which would also show up as less than expected total voltage on the storage bank. Any thoughts??

author: bob91343
author_rank: Super Contributor
timestamp: May 27, 2021, 11:09:23 pm
content: I am confused. I assume you are using a half wave doubler. Is the output common also one end of the windings?I get very nervous at these voltages - it takes only small glitch to send everything into flames. Were it mine, I would get the correct transformer.Draw a diagram so we can understand what you are about.

author: Ian.M
author_rank: Super Contributor
timestamp: May 28, 2021, 12:17:37 am
content: As Bob has said, we need a diagram + specs for your proposed transformers to be able to comment intelligently.Simulating your proposed circuit inLTspicewould answer your ripple questions. You'd also be able to look at the inrush current, which may be problematic if the secondary resistance is notably low.As an example, here's a sim for a simple capacitively coupled bridge rectifier doubler circuit.Note the use of.opt gshuntto avoid problems when the diodes transition between conducting/non-conducting, leaving some nodes momentarily floating, which would otherwise vastly slow or even stall the sim.

author: james_s
author_rank: Super Contributor
timestamp: May 28, 2021, 02:08:47 am
content: I don't have the circuit in front of me but the basic concept of using a charge pump voltage doubler ought to work fine, that's exactly how microwave oven magnetrons are driven although they forgo a capacitor to smooth the pulsating DC on the output. I agree that simulation is probably the easiest way to evaluate something like this, it's a simple enough circuit that the real world behavior shouldn't be too far out from the simulation and that's a lot safer than poking around on a live HV system of this power level. I've messed with some pretty dangerous stuff and this thing would make me nervous.
VOLTAGE DROP - Page 1
Forum section: electronics / projects

author: madivak
author_rank: Newbie
timestamp: July 30, 2016, 03:24:13 pm
content: Hi i recently updated an evaluation board for AW2042 (http://wiki.iteadstudio.com/Core_AW204x), that i added more functionalities i.e wifi + Bluuettoth and Ethernet. But i have ran into some major Voltage drop issues. Every time i connect a 5V to the system, i instantly record around 4.5V at 5V test points which immediately starts to drop and finally hits 2.8V within 6 seconds or so. Now i need to start isolating the parts to identify where the problem lies. So to start with, has anyone ever had such issues and what are the obvious culprits here. Correct me if am wrong but i think that 6 seconds it takes for the voltage to drop means a component in the system is somehow charging up and causes the voltage to start dropping. Can someone please give me some advice on this?

author: danadak
author_rank: Super Contributor
timestamp: July 30, 2016, 04:00:17 pm
content: Sure sounds like the regulator supplying the 5V is going into thermal shutdown.Add up all the current drains from the motherboard and all the ancillaryboards and see if your 5V supply has the specs to handle it.Regards, Dana.

author: madivak
author_rank: Newbie
timestamp: August 02, 2016, 12:47:41 pm
content: Thanks Dana, Let me check on that.

author: madivak
author_rank: Newbie
timestamp: August 04, 2016, 07:03:05 am
content: Found that the problem was the boost circuit i had connected to the 5V rail.I removed it and the voltage drop issues were gone. Now i have a problem. What solution do i employ to ensure voltage drop is not an issue when i connect either buck, boost regulators?For example i have an AMS1117 3V3 that takes in 5V and a 8V5 boost circuit that also takes in 5V. What design methods should i employ in terms of VIN on both of these 2 circuits to ensure they dont interfere with other peripherals that require the 5V?

author: Fungus
author_rank: Super Contributor
timestamp: August 04, 2016, 07:21:23 am
content: Quote from: madivak on July 30, 2016, 03:24:13 pmYou are drawing too many amps.

author: R005T3r
author_rank: Frequent Contributor
timestamp: August 04, 2016, 10:16:13 am
content: Transport a higher voltage near to them and then conver it to 5V locally via an active regulator...

author: madivak
author_rank: Newbie
timestamp: August 09, 2016, 02:00:39 pm
content: i just learnt a thing or 2 from Dev's video. I think current was was not enough.
Voltage drop and high power consumption in PowerPath circuit with charger? - Page 1
Forum section: electronics / projects

author: Russbo
author_rank: Newbie
timestamp: May 03, 2017, 03:20:48 pm
content: I have a circuit I've put together using an LTC4412, based pretty much directly on the reference circuit on Linear's site.I'm using 2 Pfets to isolate the two inputs in my circuit from eachother (a 24V DC PSU and an 18.5V lion battery). With just the two connected to the circuit, the function works exactly as expected. Battery at the output with no DC PSU, plug the PSU in, the 24V is seen at the output.If I connect a charger (simple eBay CC/CV board set to 21V/2A) between the 24V line and the battery I experience a massive power consumption from the wall (160W) instead of the 40-50W I should see to indicate battery charging. This is with no load connected. There is also a 0.5-0.7V drop at the output of the PowerPath circuit.I feel like the output of the DC PSU is making its way to the battery side of the circuit but I'm not sure.The circuit diagram is on the left in this image, with the charger connected as is seen on the right hand side.Any help would be much appreciated.
Voltage drop detection and battery backup switch - Page 1
Forum section: electronics / projects

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: February 20, 2018, 01:28:24 am
content: Hello i have a pretty basic questions but i do not know how to search for a solution.The circuit is basically a reference crystal with a high frequency that gets divided and then decade counters just count up ms , seconds , minutes , hours , etc. The data gets fed to CD4543 BCD decoder ics that are connected to 7 segment displays for output.Problem is that when the power goes out i want the oscillator and the crystals keep going with the help of a battery and have the decoder ics and 7 segment displays shut down.First questions is : Would a comparator circuit work for this aplication ?2) Can it operate fast enough so the circuit does not lose track of counting3) Will there be a problem in controlling the power delivery of the 7 segment displays and the decoders through a mosfet.Thank you. (if you need more information i would be more than happy to provide it)

author: danadak
author_rank: Super Contributor
timestamp: February 20, 2018, 01:33:32 am
content: If you operate offline on a battery you just use diodesteering to handle this -https://www.allaboutcircuits.com/projects/battery-backup-power-supplies/http://www.instructables.com/id/Simple-5v-battery-backup-circuit/Regards, Dana.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: February 20, 2018, 01:38:43 am
content: I think that should do it.The clock will be wall powered and with this circuit , a big capacitor to smooth the transition and keep the counter running till the battery kicks in i think i should be fine.Thank you.
Voltage follower question / Fan tacho speed signal - Page 1
Forum section: electronics / projects

author: hobbyelectronics
author_rank: Regular Contributor
timestamp: November 22, 2021, 05:34:13 pm
content: Hello,I have a need for a simple circuit to measure the speed of a fan using a PIC MCU but this will be used in an industrial environment.Currently, I have a fan with a open collector RPM output.The output then goes through a 100R resistor, then through a BAT54-S (Tied to 5V and 0V and com on the RPM signal) then through a resistor and cap to ground as a low pass filter.This signal is then tied to 5V through a 10K pull up before going into a PIC input pin. See basic circuit below.This seems to work perfectly without any problems and has been running for sometime.On the board I also have a op-amp as a voltage follower measuring the voltage from a 10K / NTC potential divider, just as an over temp reading for the PCB.Now my question is really, would it be a bad idea to also have a voltage follower to buffer the RPM signal before it goes into the PIC input pin?What about a Schmitt trigger instead? Would that be more suitable as its really a digital signal?Really, this is just a general discussion as the best way to sort of isolate the RPM signal from a 4 wire fan that is maybe a foot away for the PCB but external to the case.Thanks

author: David Hess
author_rank: Super Contributor
timestamp: November 24, 2021, 05:24:41 pm
content: A voltage follower would not really add anything useful, but a Schmitt trigger (after the RC filter) would increase noise immunity.

author: hobbyelectronics
author_rank: Regular Contributor
timestamp: December 16, 2021, 09:05:09 am
content: Hi David,Thanks for your reply. I did think that may be the case but was not sure if it would add any benefit. But what you said makes perfect sense.I now need to find a single channel low cost Schmitt trigger. I am sure I was looking at this option before and found a simple device somewhere.Thanks

author: hobbyelectronics
author_rank: Regular Contributor
timestamp: December 16, 2021, 09:43:16 am
content: Hi,One other thought that comes to mind here is about protecting the FAN Tacho input from high voltage noise. Would it be advisable to maybe use a TVS diode instead of (Or as well as) the BAT54-S pair of diodes to protect against input noise. The fan cable is only about 200mm long but runs through a 400V ac part of the enclosure so may pick up noise. There are also relays switching at 400Vac (2A) (Need to look at FET replacements at some point) but the firmware stops checking the fan when these are being switched. Also as the fan is external to the enclosure, to protect the input form other outside noise would a TVS may also help. Maybe even an opto between the FAN after the filter and the MCU??Any suggestions on this would also be helpful.Thanks