hybridfree/eevblog-posts huggingface dataset:
Using Current Monitoring Relays - Page 1
Forum section: electronics / projects

author: EHT
author_rank: Frequent Contributor
timestamp: May 05, 2023, 09:46:30 pm
content: Hello everyone, I have a question about using current monitoring relays for the purpose of protecting against overcurrent. For exampleSiemensorGeyaindustrial DIN units.I want to use this build a general purpose variable AC supply with overcurrent limit. My question is that whilst these are designed for protecting against overcurrent faults, I’m not convinced they are protected against shorts in the monitoring circuit, which would draw a very high instantaneous current. For instance, looking at the datasheet for a breaker shows it is rated at 10kA for a short (e.g.here). I guess those using a current transformer could be protected but none of the datasheets quote this figure or say they are protected against shorts. I could add a breaker or fuse for the maximum current, but I’m not sure that would act fast enough to protect this relay. Siemens 3UG4622 is a common model but looks like it uses a shunt.Ideally I’d like the setup to behave like a bench DC PSU with OCP, for the purpose of safely bench testing AC mains devices which may have faults. I see a fair few other threads on using variacs and dim bulbs etc. I also looked at the circuit of the Sencore PR570 variable AC supply. This uses a current transformer to monitor and trigger a relay.So far my design includes:• Isolation transformer. I have a 1kVA non-medical type. I will add inrush protection to this (delay relay & NTC).• Variac, which can be bypassed (e.g. not for testing SMPS). I have an 8A Carroll &Meynell.• AC power meter on output. I have PZEM-022, will modify to separate supply and measurement.Alternatively I could just use the low tech dim bulb approach instead or as well, but I quite liked the idea of having variable control and it would be easy with a CM relay.Any views on these CM relays?Related threads:•https://www.eevblog.com/forum/projects/upgrade-of-a-tried-and-true-bench-ac-mains-overload-monitor/msg4430722/#msg4430722•https://www.eevblog.com/forum/beginners/power-meter-for-variac/msg3539250/#msg3539250
Using D2XX and VCP with FT2232H at the same time? - Page 1
Forum section: electronics / projects

author: Boscoe
author_rank: Frequent Contributor
timestamp: July 21, 2024, 08:53:13 am
content: Hi all,I'd like some advice on my project. I have an FT2232H with port A connected to an FPGA for 245 sync operation and port B as an RS232 interface for communicating with and programming an ESP32. Port A have been preconfigured in the EEPROM for the sync mode using the D2XX driver and port B as RS232 and VCP. Both interfaces work perfectly well independently however when I connect to and configure port A using the D2XX driver, port B stops working with no communication and it's not possible to program the ESP32 unless I power cycle the FT2232H putting it back into the EEPROM configuration. When I do configure and use port A using D2XX this works as expected.Does anyone have any experience doing this kind of thing? I have tested this setup on MacOS and Ubuntu with the same results. I'm confident I'm configuring the correct port otherwise I wouldn't get any data from the FPGA. Below is my init code.Thanks!Code:dev_serial = "SE9AJ5P8A"print(f"Connecting to {dev_serial}")dev = ftd2xx.openEx(dev_serial.encode(), ftd2xx.defines.OPEN_BY_SERIAL_NUMBER)time.sleep(0.1)dev.setTimeouts(10, 10)time.sleep(0.1)dev.setBitMode(0xFF, 0x00)time.sleep(0.1)dev.setBitMode(0xFF, 0x40)time.sleep(0.1)dev.setUSBParameters(0x10000, 0x10000)time.sleep(0.1)dev.setLatencyTimer(2)time.sleep(0.1)dev.setFlowControl(ftd2xx.defines.FLOW_RTS_CTS, 0, 0)time.sleep(0.1)dev.purge(ftd2xx.defines.PURGE_RX)time.sleep(0.1)dev.purge(ftd2xx.defines.PURGE_TX)time.sleep(0.1)

author: laminarlade
author_rank: Newbie
timestamp: July 21, 2024, 11:30:49 am
content: Hi Boscoe,AFAIK on Mac and Linux D2XX and VCP are 'mutual exclusive', seehttps://ftdichip.com/wp-content/uploads/2020/08/D2XX_Programmers_GuideFT_000071.pdfcap. 2.But you can try the open source libftdi/pylibftdi combo on Ubuntu.

author: Boscoe
author_rank: Frequent Contributor
timestamp: July 21, 2024, 12:15:07 pm
content: Thanks!I just found that the FT2232H cannot support any other interfaces when sync mode is used
Using dw01 for over discharge protection - Page 1
Forum section: electronics / projects

author: kfir
author_rank: Newbie
timestamp: March 05, 2018, 01:42:48 pm
content: while searcing for li-ion cell charger and protection IC's,i found this combanation recommended, the TP4056 for charging + dw01-p for protection.my concern with the dw01-p is the overdischarge protection voltage is 2.4V (typ).as far as i understand discharging a li-ion battery to 2.4v is damaging to the cell.and from what i have seen this chip is farly common so it make no sense it would damage the cell,so what am i missing here?for this reason i have searched for an alternativ, i found FS312F-G wich has a 3.0V cutoff voltage.but i cant find it for sell so any suggestion for a cell protection IC ?

author: Peabody
author_rank: Super Contributor
timestamp: March 05, 2018, 05:39:13 pm
content: As you say, the DW01 is in very widespread use. In fact, I suspect it is the protection chip installed on most lipo single cells which have embedded protection circuits. When I took one apart, that's what I found.But you have to remember that in most cases that 2.4v will be reached under load. I did a test at about 120 ma, and while it shut down at 2.38V, after an hour of no load recovery, the cell meaured about 2.85V. Of course that's just one example, but you see what I'm saying. So the 2.4V is probably not as bad as it sounds.And if you select the other one, shutting down at 3.0V under load may be leaving quite a bit on the table. But I'm not sure it matters because I couldn't find one either.Something like a MAX809 could be used to trigger a higher shutoff, but that would probably substantially increase costs relative to the DW01.

author: soubitos
author_rank: Frequent Contributor
timestamp: March 22, 2018, 01:08:27 am
content: The combination i use in the 4056 modules i build is TP4056 or TC4056 (Toppower or FM), FS312F-G as protection IC and i am now testing NCE2007N as the dual mosfet part.https://datasheet.lcsc.com/szlcsc/TP4056_C16581.pdfhttps://datasheet.lcsc.com/szlcsc/TC4056A_C84051.pdfhttps://datasheet.lcsc.com/szlcsc/FS312F-G_C82736.pdfhttps://datasheet.lcsc.com/szlcsc/NCE2007N_C169816.pdf
External flash chip – general data reading/writing/erasing principles? - Page 1
Forum section: electronics / projects

author: 3dgeo
author_rank: Frequent Contributor
timestamp: August 16, 2020, 08:11:49 pm
content: Howdy,I want to useW25N01GVZEIGexternal flash memory (for images and other data storage).128KByte block is way too big so I will be switching to NOR flash, something likeMX25L12835F.I've never worked with external flash and I'm trying to grasp general concept on how data reading/writing/erasing works, so correct me if I'm wrong:1.With NOR/NAND flash you can erase only by Blocks (32KByte with MX25L12835F, 128KByte with W25N01GVZEIG).2.With NOR flash you can write by individual Byte.3.With NAND flash you can only write by Block (128KByte with W25N01GVZEIG).3.With NAND flash you can only write by Page (2KByte with W25N01GVZEIG), actually W25N01GVZEIG has 2KB buffer that can be writen by byte and after saved to any Page.4.NOR/NAND can be writen only in erased cells (not on top of old data).
Using HCNR200 for DC-DC Isolation - Page 1
Forum section: electronics / projects

author: ajoseph88
author_rank: Contributor
timestamp: October 29, 2015, 08:30:40 pm
content: Anyone successfully implemented HCNR200 with op-amps for dc-dc isolation, where the output varies linearly with input...can you share the circuit with me please...I tried all the datasheet circuits, but none of them worked....Getting struck too long. cause of this problem...
Using header pins pushed in to a female a female sma adapter? - Page 1
Forum section: electronics / projects

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: July 19, 2016, 07:08:46 pm
content: I have TONS of sma connectors converters board mounts etc.... I tend to try to stick to SMA and BNC only when I need coax connections, there available at radio shack, and even home depot if you dont mind 75ohm BNC terms.Ive been experimenting with home brew wifi antennas for wifi and I have just ordered a Baofeng along with a decent RP-Sma antenna. Although I have some things that use SO239 like a 2meter amplifier and some yagis. I dont own any RP-SMA connectors of either gender. Is it ok to simpy insert a header pin in to the sma jack and cut it? It seems to work fine for short runs of LMR400 and wifi but im not to sure if im incuring any loss by doing this, they are square oins in a round hole, how about using some solid wire out of RG-8 as a pin it seems to fit fine, you dont even need to solder the SMA pin on to connector becuase the RG-8 conductor fits through the whole just fine if you use RG-174 SMA connectors.Im pretty sure at VHF/UHF this probably isnt a huge issue but at 2.4ghz?

author: Kilrah
author_rank: Unknown
timestamp: July 19, 2016, 09:35:19 pm
content: Just get proper adapters. An SMA to RP-SMA adapter costs <$2 on the bay...

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: July 19, 2016, 10:20:40 pm
content: The issue isnt price... its waiting 3 damn weeks for things to come in the mail... I hate waiting on crap like an adapter when I have everything else sitting in front of me. I really do miss brick and mortar sometimes! I use to be able to wait on newegg so I could save 500 bucks on my new gaming rig, but I dont want to wait for a damn connector to save 2 to 5 dollars. I will probably order a few but until they arrive...The better answer may be to rip the few things I have with RP SMA apart and replace the damn connectors, rp sma is such a stupid ass idea.... like you average consumer was gonna go get a god damn 15 element loop yagi for 1200mhz and plug it in to a wifi card....
Using HV9910B as on/off controller for smps - Page 1
Forum section: electronics / projects

author: ocset
author_rank: Super Contributor
timestamp: April 20, 2018, 05:28:12 am
content: Hello,The HV9910B smps controller datasheet doesnt give the delay for the gate driver going low after the PWMD pin is taken low.Do you know it?Also, the delay for the HV9910B gate driver coming back on again after PWMD is taken back high?HV9910B datasheethttps://www.microchip.com/wwwproducts/en/HV9910B

author: RobK_NL
author_rank: Frequent Contributor
timestamp: April 20, 2018, 10:28:40 am
content: Given that it's just an AND-gate, I would expect nanoseconds.But if you *really* want to know, why not just A). measure it or B). ask your local, friendly Microchip FAE.
Using "internetsharing via bluetooth" in an embedded system - Page 1
Forum section: electronics / projects

author: cgroen
author_rank: Unknown
timestamp: October 26, 2018, 04:52:40 pm
content: Hello,I have a project where I have a BLE (CYBLE 212019 module from Cypresshttp://www.cypress.com/documentation/datasheets/cyble-212019-00-ez-ble-creator-module).Now, I would like to somehow use that to connect to a "normal" mobile phone that is set up to share its internet connection thru Bluetooth.I'm having some problems finding the right method for this (to be honest, I'm on deep water)In my system I have the possibility to use LwIP TCP/IP stack (using it in other projects over 3G/4G), but in this particular project I'm wondering if it would be possible to connect the "Bluetooth" world with the LwIP world and utilize the "Internet sharing via Bluetooth" feature on smartphones....Any pointers, experience, good ideas etc ?
Using IRS2186 mosfet driver for Synchronous boost application - Page 1
Forum section: electronics / projects

author: pmadithya
author_rank: Newbie
timestamp: October 30, 2013, 04:32:12 am
content: Hello I'm using IRS2186 mosfet driver soic-8 package to drive a high side and low side mosfet. Now the problem is I have made two separate designs for High side and low side drivers but both are not working separately. I have enclosed the schematic below. I will be using one of these mosfets to replace the diode usually used in Boost converter. So this mosfet will be used as a synchronous fashion. But since both the drivers are not working as of now, there are some hurdles. Can I use the same driver to switch the 2 mosfets because of the synchronous boost design.This mosfet I have used in Synchronous boost converter is IRFZ44 and the Input voltage is from a 20W panel with specs Voc = 20V and Isc = 1.4A and Vmp = 17V and Imp = 1.18A. Also inductor value is L=47uH, Cin = Cout = 100uF. In the driver circuit , C1 = C2 = 0.1 uF, R1=R2=10 ohms,Vcc = 15V, Hin and Lin are fed with microcontroller PWM pulses of 3.3V.
Using LiFePO4 batteries on Maxim MAX1720x - Page 1
Forum section: electronics / projects

author: cgroen
author_rank: Unknown
timestamp: November 05, 2019, 08:27:38 am
content: I'm building a device (charger, fuelgauge etc) that uses some (3 in series) 2500 mA/H LiFePO4 cells. The fuelgauge is a MAX17205, this little device can do cell balancing and fuelgauge. The default parameters of the device is for LiIon cells, if you are going to use (f.ex) LiFePO4 you will need to give it a set of parameters for it to work with that chemistry. I have contact thru a disti with Maxim, but it takes apparently ages for them to react. I have the prototype running here on the desk but can't get most of the fuelgauge stuff up and running as I dont have parameters for the Maxim device for LiFePO4 cellsI know it is a long shot, but have any of you out there done something similar with this device, and, by any luck, used LiFePO4 cells ??

author: cgroen
author_rank: Unknown
timestamp: November 21, 2019, 09:26:26 am
content: Just an update,I managed to get data from Maxim for this, so if anyone ever stumbles across this post with the same request, they know there is hopeBTW, wonderful little device this Fuelgauge !

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: November 21, 2019, 01:03:13 pm
content: Nice chip and reasonable priced!
Using linear regulator as switch  - Page 1
Forum section: electronics / projects

author: itdontgo
author_rank: Regular Contributor
timestamp: December 31, 2020, 09:23:06 am
content: Is it a good idea to connect the adjust pin of a linear regulator to a tri state micro pin and then use it as a switch? So, high-z for normal operation and logic high for off.

author: ledtester
author_rank: Super Contributor
timestamp: December 31, 2020, 10:27:46 am
content: Do you mean like a LM317?Here's a discussion on disconnecting GND from a 7805:https://electronics.stackexchange.com/a/100799Would using a regulator with an shutdown/enable pin work for you?

author: itdontgo
author_rank: Regular Contributor
timestamp: December 31, 2020, 10:51:24 am
content: I got myself mixed up. It would work the other way wouldn't it. The adjustable regulator is basically a 1.25V regulator but connected to a potential divider and not GND. So it would just go to 1.25V minimum which might reset my circuit but might not. I use an AZ1084I'm probably best using a regulator with a enable like you mentioned.

author: exe
author_rank: Unknown
timestamp: December 31, 2020, 03:15:44 pm
content: If it was April 1, I'd suggest short circuit the output with a fet. It's also possible to disconnect the regulator with a fet, but high-side fet would require a level shifter to be controlled from an mcu. It's like two or three parts.
Using LM324 and OP07  for controlling voltage  - Page 1
Forum section: electronics / projects

author: Md Mubdiul Hasan
author_rank: Regular Contributor
timestamp: August 01, 2018, 08:37:20 am
content: Hello there,This post might be a fun for learning, some of you might laugh to see it once!Trying to control old TCA785, a phase control IC,http://images.100y.com.tw/pdf_file/TCA785P.pdf.But before that, take a look my circuit in this attachment ….1. Lets say 0-10 VDC signal in increments of 1 volt or a 0-20 mA signal in increments of 1 mA has given to inverting input ofU1D,pin 13, CVC signal.2. At U1B, pin 5, reference voltage has applied, lets say 3-5 volt dc, its frequency dependent RC parallel feedback resistance contributing gain curve.3. All op-amp has negative feedback.4. Common mode signal is generated from external IC.5. U1A looks like buffer amplifier.6. U2 op07 looks like active low pass filter.7. U1C and U1D positive pins are grounded!!8. Not sure pot R6 and R16 are wrongly connected ?Discuss and advice whatever you like to suggest for further development. i.e stable gain, linearity, impedance, noise!Raise your hand where I am doing wrongCalculation, signal analysis is necessary.
Using LTSpice with Potentiometers - Page 1
Forum section: electronics / projects

author: Ray.B
author_rank: Contributor
timestamp: May 16, 2016, 05:44:57 am
content: Hi DaveThis is my first forum question. You started doing some videos on LTSpice demos, I was wondering if you could explain how to use potentiometers in the designs? The things that I have seen in the example circuits from Linear Technology that they have some pots in their designs, but the parts lists don't show any standard potentiometers.I have gone to the Yahoo Groups-LT Spice and downloaded some potentiometers symbols and .lib files. But these are potentiometer files someone have made, that you have to import into LTSpice.I think that you were doing some basic how to videos with LTSpice awhile ago. I was looking on the forum about potentiometers, but nothing was done.Could you do a video on using potentiometers in LTSpice?Later Ray.B

author: matkar
author_rank: Regular Contributor
timestamp: May 16, 2016, 08:36:40 am
content: Here is a sipmle example with the necessary files. Place asy file in C:\Program Files\LTC\LTspiceIV\lib\sym\MyLib (you will have to create a folder) and place sub file in the same folder your project (asc) is in.Run the example.
Using miminal PCB trace width, too risky? - Page 1
Forum section: electronics / projects

author: zapta
author_rank: Super Contributor
timestamp: October 11, 2014, 04:36:03 pm
content: I am trying to layout out a dense (for me) board and have hard time routing it unless I go with 6mil design rules. 6mil is within Elecrow spec but they recommend at least 8mil. OSHpark can also do 6mil with the standard process.http://www.elecrow.com/2-layer-5-5cm-max-510pcs-color-free-p-418.htmlHow safe it is to use manufacturer's minimal trace width? Am I setting myself for a failure?This is for a hobby project so no mass production yield issues, etc.

author: nctnico
author_rank: Super Contributor
timestamp: October 11, 2014, 04:58:10 pm
content: 6 mil is approx. 0.15 mmThat shouldn't be a problem for a decent PCB house.

author: LukeW
author_rank: Frequent Contributor
timestamp: October 12, 2014, 01:04:42 am
content: If a PCB fab can't reliably deliver boards with intact copper artwork when your layout complies with the minimum widths and other design rules that they specify, they don't deserve your business IMO. If they can't reliably do 6/6 they shouldn't advertise it.I've never had a problem with 6 thou from OSHPark, but I've never used the other one you mention. But 6/6 is nothing to worry about for any decent PCB house, and there are lots of low-cost options around the world that are decent.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 12, 2014, 01:22:21 am
content: Rules are rules, if they can't meet them they wouldn't put them up there.You might want to add 100% electrical test to your order, though, especially if you're going with a cheaper service (needless to say, anyone who won't do that, isn't worth wasting the money on!).Tim

author: Smokey
author_rank: Super Contributor
timestamp: October 13, 2014, 02:51:28 am
content: What everyone said. 6/6 is pretty much standard these days. 0402 component size is pretty standard small component size as well. Pretty much everyone should be able to handle that stuff.

author: tggzzz
author_rank: Super Contributor
timestamp: October 13, 2014, 08:49:20 am
content: Quote from: T3sl4co1l on October 12, 2014, 01:22:21 amIt might be worth checking what each manufacturer's definition of "100% test" includes, and that they actually do it. I've had a 100% tested board containing a large blob of unremoved copper shorting out two tracks. I didn't complain because of the extreme low cost and because I had more boards than I needed.The "100% test" might mean only that each plate through hole is tested for continuity (because those are the probable failure points), or that all combinations of tracks are tested to verify there isn't any bridging. The latter will be more time consuming and therefore expensive.

author: ovnr
author_rank: Frequent Contributor
timestamp: October 13, 2014, 09:20:57 am
content: I've had a dozen boards fabbed at various chinese shops (Seeed, Itead, Elecrow, etc), most with 6 mil traces. No problems whatsoever.
Using Molex computer power connectors for mains? - Page 1
Forum section: electronics / projects

author: ledtester
author_rank: Super Contributor
timestamp: May 21, 2018, 05:15:20 pm
content: Related to my question about favorite wire to board connectors:https://www.eevblog.com/forum/projects/favorite-wire-to-board-connectors-for-power/I'm considering using the Molex power cables you find associated with ATX power supplies for carrying mains power from a power inlet to a PCB. Both the Molex Standard (0.093") and Molex Mini-fit Jr seem to be suitable for this purpose.The advantages I see are (correct me if I'm wrong on any of these):- pre-made cable assemblies using 20 - 18 AWG 300V wire- Molex Standard pins and housings are spec-ed to 250V RMS and 9 A with similar specs for Mini-fit Jr- pins can be extracted and inserted into alternate housings- both male and female crimped wires in 8"+ lengths are readily (and cheaply) availableAre there any caveats I should be aware of? The intended application would be to supply mains power to a low voltage DC power supply / transformer, so the amount of mains current carried would be < 1A.Update:I'm basing the Molex Standard specs on the information availableon this Molex web page. I don't know the part number for the 4-pin housings used with computer power supplies, and perhaps they have different specs.

author: Yansi
author_rank: Super Contributor
timestamp: May 21, 2018, 05:43:09 pm
content: Leave the 4-pin thingy to the PC stuff.The Molex MiniFit (Amphenol MF42) 4.2mm pitch connectors are otherwise OK for mains applications. I would rather like to see 300V rating for these, but 250V may be good enough. have used those before. No fails reported.

author: ajb
author_rank: Super Contributor
timestamp: May 21, 2018, 06:24:57 pm
content: I don't like those 4-pin connectors for mains because there's a slit in the plastic between adjacent contacts. I'd want to leave an empty position between line and neutral. The mini-fit ones are much preferable in that respect, being fully insulated. A lot of unenclosed power supplies use three position JST VH or similar 3.56mm connectors with the center pin removed for mains input.Quote from: Yansi on May 21, 2018, 05:43:09 pmOften the ratings on connectors indicate which standard the manufacturer chose to test them against, not necessarily the levels at which they're safe to use, which is how you get otherwise identical connectors with different ratings depending on which certifying agency's logo is on it. If there's a second source for equivalent components sometimes it's worth looking at their ratings to see if they're any different; this may give a better idea of what the connector geometry actually provides. In some cases it may even be possible to get a manufacturer to re-test to a higher standard if the connector will support it.
Using multiple digital potentiometers to set feedback ratio? - Page 1
Forum section: electronics / projects

author: Korken
author_rank: Regular Contributor
timestamp: November 11, 2014, 10:34:27 am
content: Hi all!I have an step up/down switch-mode IC that I want to control the output of from a microcontroller.How I have done this before is to have an I2C pot as feedback resistors so I can control the voltage divider.However I have now come to the problem that I need more steps in the potentiometer, but the "high tap" ones get quite expensive.So the idea is to use two "low tap" ones. What is the best way use multiple potentiometers to get higher resolution?The only requirement is that the I2C pot only changes the resistance to ground as the voltage on the output can get above the maximum rating.Or is there another way to change the feedback ratio?Thanks!

author: Marco
author_rank: Super Contributor
timestamp: November 11, 2014, 12:32:15 pm
content: Why not change the reference voltage with a dac instead?

author: Korken
author_rank: Regular Contributor
timestamp: November 11, 2014, 03:40:01 pm
content: Hmm, would you care to explain how you mean?Or rather, how would you connect a DAC to do this? Offset the ground reference?

author: dannyf
author_rank: Super Contributor
timestamp: November 11, 2014, 03:47:50 pm
content: No easy solution if you are going after full-range high resolution: digital pots are not meant for those applications.One less-than-perfect solution is to pair two digital pots together - one pot is connected between the wiper and one terminal of another pot. It provides finer resolution on one end of the wiper but not on the other end.

author: Korken
author_rank: Regular Contributor
timestamp: November 11, 2014, 04:10:38 pm
content: I though a bit on the DAC part and I thought this would work (attached image).I add in the DAC to provide a current sink/source to shift the output level.Was this what you had in mind?

author: Charles Creations
author_rank: Contributor
timestamp: November 11, 2014, 05:53:35 pm
content: I don't know what microcontroller your are using, but assuming it doesn't have a true hardware DAC, you can use a pwm function with a low pass filter to achieve a crude DAC. You are limited to your pwm resolution and you have to be sure that you don't load the filter too much or else its output will drop.

author: Marco
author_rank: Super Contributor
timestamp: November 11, 2014, 06:29:35 pm
content: Quote from: Korken on November 11, 2014, 04:10:38 pmNo, that's better though ... should work.

author: Korken
author_rank: Regular Contributor
timestamp: November 11, 2014, 07:02:34 pm
content: Thanks for the replies!All it takes is a new angle and great things happen.I'd like to test it with the PWM as well, could be an easy solution. Thanks for the tip!
using Multiplying DAC to generate variable height pulses - Page 1
Forum section: electronics / projects

author: eliocor
author_rank: Unknown
timestamp: September 02, 2012, 11:52:17 pm
content: I need to generate rectangular pulses with width between 1 and 10us: their output peak voltage can range from +5V to -5v in (at least) 5 mV steps.The original pulse (generated by a PWM microprocessor pin) have a pk-pk output voltage of 5V:What I need is a variable attenuator with at least 10 bits of resolution (better 12 or 14 for linearity reasons).I was thinking to use aMultiplying DAClike theAD5446(14bit) set in 4 quadrant configuration: 13 bit for attenuation and one for sign [seeBipolar Operation, pag. 16].This device is reasonably cheap for my requirements and its reference bandwidth is 12MHz.The output results could be summoned in the following two pictures:output set to 2.7V from the original 0-5V pulseoutput set to -3.3V from the original 0-5V pulseThe output pk-pk voltage need to be changed not more than once per second.- - - - -Based on your experience, do you think my approach can be worthful?Have you different suggestions/solutions on how to solve my needs?

author: jahonen
author_rank: Super Contributor
timestamp: September 03, 2012, 02:13:14 pm
content: I can't say if it is any simpler, but maybe another option would be a normal DAC (connected to have a bipolar output) and an analog MUX to select either zero voltage or the DAC output according to the MCU PWM output?Regards,Janne

author: eliocor
author_rank: Unknown
timestamp: September 03, 2012, 02:28:49 pm
content: It seems interesting: I have to look at the commutation speed of the analog switch, but it should work.Thanks for the suggestion.

author: free_electron
author_rank: Super Contributor
timestamp: September 03, 2012, 02:33:29 pm
content: Jahonen is right.Sending this kind of signal through a multiplying dac will be trouble... The bamdwidth limitation of the dac will heavily distort the edges...

author: Zad
author_rank: Super Contributor
timestamp: September 03, 2012, 07:02:40 pm
content: The AD5444 has a 3dB bandwidth of 12MHz, I can't see 1uS pulses being a huge problem.

author: eliocor
author_rank: Unknown
timestamp: September 03, 2012, 07:36:04 pm
content: Yes, 12MHz bandwidth can be enough, but I like the suggestion of using a "standard" DAC:my project will be open sourced, so I have to care about the possibilities of using different hardware.A "standard" DAC will be easier to get than a Multiplying DAC.In the next days I hope to get some time to test this configuration and see if it can be better than my initial thoughts:my request for comments was for identifying the cheapest and safest way to generate those pulses.Thanks in advance for all of your welcome comments!!!
Using NCT Sensors on the Heating - length of wires? - Page 1
Forum section: electronics / projects

author: kazzle101
author_rank: Contributor
timestamp: March 01, 2025, 10:03:06 am
content: HelloI want to get the assorted temperatures of my central heating in to Home Assistant.I got some of these clip on sensorshttps://www.rapidonline.com/atc-semitec-103ft-7y043-12-15mm-ip67-rated-pipe-clip-temperature-sensor-26-7478and in my testing they seem to work quite well.On my test setup, I am connecting them to the microcontroller an ESP32 board like so:I am also looking to use a couple of these ADS1015 12-Bit ADC to I2C Boardshttps://thepihut.com/products/adafruit-ads1015-12-bit-adc-4-channel-with-programmable-gain-amplifierMy question is, as the pipes will be a couple of meters away from the controller, would losses at 3.3V be a problem or would I be better using 5V and a logic level switcher on the I2C lines?ThanksKarl.

author: moffy
author_rank: Super Contributor
timestamp: March 01, 2025, 12:21:17 pm
content: Use twisted pair cable, as long as the cable resistance is not significant compared to the 10k load resistor, it won't be a problem. Also put a capacitor across the 10k resistor near the ADC.
Using NON-lite version of Compute Module 3/3+ in Lite-like configuration - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: August 02, 2021, 12:35:04 pm
content: Hi,I designed a PCB for a client with the same configuration jumper used in the reference design for the USB Boot Enable and also another jumper connecting/disconnecting pins 4 and 6 (SDX_VDD) of CM to 3V3 rail as show in the attached schematic.My question is, can we use the CM3+ with onboard memory but configured such that it boots from and uses only the external SSD? In other words for it to work like a lite version?I am asking because they have a little bit of stock of the non-Lite version but not of the Lite one.Thank you
Using one crystal for both PAL and NTSC - Page 1
Forum section: electronics / projects

author: c64
author_rank: Frequent Contributor
timestamp: May 10, 2020, 04:16:12 am
content: I'm looking at datasheets for few video decoders (for example ti TVP5150)They all use 14.31818 (or 28.63636) MHz crystal to capture both PAL and NTSC. I guess it's choosen because it's exactly 4x(8x) of the NTSC colorburst. But it's not any fraction of the PAL colorburst frequency. So how does it work for PAL?NTSC colorburst is 3.5795454 MHzPAL colorburst is 4.4336187 MHz

author: Renate
author_rank: Super Contributor
timestamp: May 10, 2020, 01:53:04 pm
content: That's an interesting question and I don't know.NTSC = 4.5 MHz (audio subcarrier) / 286 (harmonic of line freq that hits audio) / 227.5 (color cycles in line)NTSC = 2^3 * 3^2 * 5^7 *7 / 11 HzPAL = 25 Hz (frame rate) * 625 (lines) * 283.75 (color cycles in line) + 25 Hz (offset)If we ignore that pesky 25 Hz offsetPAL = 5^7 * 227 /4 HzSo the ratio between the two is:2^5 * 3^2 * 7 / (11 * 227)2016 / 2497So, in short, I don't know.

author: Bud
author_rank: Super Contributor
timestamp: May 10, 2020, 03:00:42 pm
content: Likely it is done using a PLL ( phase locked loop). You have two oscillators, one is the reference, the other one adjustable (voltage controlled). You divide outputs of both oscillators to arrive to a same common frequency, then feed these outputs to a phase frequency detector. if both frequencies are the same the ouyput of the detector is neutral. If they are not, the detector will produce a positive or negative voltage which is fed back to the adjustable oscillator and adjusts its frequency up or down to equalize the divided frequencies at the detector input. This way you can have two or more oscillators running at different frequencies derived from a common reference, as long as a common PFD frequency can be found for the dividers.Have a read on PLL theory of operation to understand this better. PLLs are widely used in electronics so at some point you will run into it anyways.
Using only positive output of a fully-differential opamp - Page 1
Forum section: electronics / projects

author: fitzgerald
author_rank: Contributor
timestamp: August 31, 2015, 12:16:19 pm
content: Is it a problem to use only the positive output of a fully-differential opamp (in particular the LME49724)? Of course the benefits of a differential signal are lost; but are there any traps to look out for?Note:- The positive output will be connected to a medium/high-impedance input (> 20 kOhm); the negative output is left floating (but with feedback resistor present!). V_OCM is connected to GND. There is a bit of current imbalance between the loads, but it is not a lot (0.25 mA max. @ 5V output)

author: jlmoon
author_rank: Unknown
timestamp: August 31, 2015, 02:36:28 pm
content: I would think this would be a gross misapplication of the part. How do you plan on deriving the feedback loop required for the part to work correctly? I would carefully study the application information section of the data sheet regarding the Vocm pin and the basic differential function in relation to your power supply rails. Best of luck!

author: fitzgerald
author_rank: Contributor
timestamp: August 31, 2015, 05:48:52 pm
content: Sorry for the confusion; there is a feedback resistor from the negative output to the positive input. The load will be connected between the positive output and GND. Internally the Vocm pin is a resistor divider between the two power rails which can be forced to GND if needed (such as in this case). The negative output signal is just not being 'used' / loaded

author: jlmoon
author_rank: Unknown
timestamp: August 31, 2015, 07:40:25 pm
content: On the data sheet, I don't see the internal makeup of this part. Have you made an attempt to breadboard this circuit as you need it? Might answer a lot of your questions.

author: fitzgerald
author_rank: Contributor
timestamp: September 01, 2015, 06:15:52 am
content: Yes; it does work. The opamp doesn't get hot and the scope traces seem OK. I don't have the right equipment to measure distortion and noise.

author: tszaboo
author_rank: Super Contributor
timestamp: September 01, 2015, 08:14:55 am
content: Quote from: fitzgerald on September 01, 2015, 06:15:52 amStill doesnt change the fact, that FDA should be used to drive differential load. You can use an opamp to drive a SE load, so that is a much better solution than an FDA. You need less parts to reach the same performance, for less cost. Offset voltages and stuff is not even specified in the datasheet for SE load.
Using Open Drain Output as Resistor Divider Ground - Page 1
Forum section: electronics / projects

author: Dubbie
author_rank: Unknown
timestamp: August 07, 2018, 11:11:13 pm
content: I have the problem of a very low power device needing to measure the battery voltage which is higher than the VDD for the micro.It is an STM32F0I don't want to leave the resistor divider hooked up all the time as it will drain my tiny battery.My immediate plan was to use an open drain output to switch my resistor divider to ground.then I realised that when everything is off, the voltage at that node will be VBATT which may damage the uC.I only have space on my board for 2 passive components so I can't afford to add a FET for switching.I found this thread:https://www.eevblog.com/forum/chat/resistive-divider-gt-adc-how-to-get-low-parasitic-drain/Does anyone have any other clever solutions?If nobody can come up with any clever tricks, I'll have to redesign my board to fit in a FET. Currently using 0402s, so I could switch a bunch of those to 0201s to save some space.

author: MT
author_rank: Super Contributor
timestamp: August 07, 2018, 11:34:04 pm
content: Quote from: Dubbie on August 07, 2018, 11:11:13 pmF0 resistor bridge at Vbatt pin is 50K i recall that is a tiny current(you didnt mention how much) at 3.3V, ad a resistor to this pin from your battery until voltage suits the pin, else switch in/out, etc.Edit: Nope, Vbat pin max 3.6V.

author: Dubbie
author_rank: Unknown
timestamp: August 07, 2018, 11:51:46 pm
content: Yeah Absolute Max for all pins is 3.9V3.6V max.My batt voltage is 4.2V.

author: lordium
author_rank: Regular Contributor
timestamp: August 08, 2018, 01:11:42 am
content: Since all the ADC pins are protected with diodes from GND and to VDDA, I think if the resistance was large enough, then the current would be small and cause no damage. Maybe you would need to increase your sampling time though to compensate the larger resistance.

author: Dubbie
author_rank: Unknown
timestamp: August 08, 2018, 01:15:29 am
content: I wondered about that... I also was worried that this was very bad engineering practice....I am fine with using say 100K divider. That should be plenty for a reasonably accurate measurement. The purpose is to keep the uC turned off if the battery is dicharged below the min value.

author: lordium
author_rank: Regular Contributor
timestamp: August 08, 2018, 01:51:14 am
content: 6.3.14 I/O port characteristicsLooked it up since I was not sure, but manual mentions functional susceptibility of +-5mA.
Using opto-Triac instead of switch contact for magnetic Run/Stop switch? - Page 1
Forum section: electronics / projects

author: Jester
author_rank: Frequent Contributor
timestamp: April 13, 2022, 06:58:48 pm
content: I'm adding CNC capability to a lathe that uses a magnetic Run/Stop switch. These switches if your not familiar use a small coil that is series connected with one of the run contacts in the F-Off-R switch so that if either the switch is rotated to OFF or if the power fails the switch opens as a safety feature.When operating in CNC mode, the Run/Stop switch will need to be maintained in the run mode by the CNC controller once started by a push. I'm thinking of using an opto-triac (MOC3052 or similar) to maintain the A1 RUN coil current in the switch. The coil requires 40mA.Although the coil appears to have a fair bit of inductance 4.3H (rough estimate), I would think that the inductive kick voltage from the coil would be minimal, because the Triac turns off when the actual current falls to near zero, not the voltage. Does that make sense?Anyone see any issues with this approach?Sketch included. For clarity the 9-10 terminals are closed when in either F or R, and open otherwise.

author: moffy
author_rank: Super Contributor
timestamp: April 13, 2022, 09:45:08 pm
content: The MOC3052 is rated at 60ma and the load is about 40ma, I would use something like Figure 8 in :https://www.onsemi.com/pdf/datasheet/moc3052m-d.pdf to boost the current, to allow for surges. With 4.3H even a small residual current will have significant energy so use the snubbers and MOV shown in Figure 8 as well.P.S. make sure you fuse the Triacs as well.

author: Terry Bites
author_rank: Super Contributor
timestamp: April 14, 2022, 06:41:32 pm
content: Doesn't this defeat the contactor's no volt release fucntion?

author: Jester
author_rank: Frequent Contributor
timestamp: April 14, 2022, 09:34:01 pm
content: Quote from: moffy on April 13, 2022, 09:45:08 pmI thought I would do a quick reality test on the snubber circuit. Keep in mind:1) I used a more inductive relay coil that I had in my bin, because I did not want to remove the switch from my lathe.2) I used an actual switch to open circuit the inductor, I think the Triac would be better in that it should keep conducting, allowing the current to ramp down before actually turning off?Top two images are with just 50V, 840Vp-p with no snubber! and about 1200vp-p @ 170VBottom two are with the snubber and 170V, last one with a 200V MOV. I will probably put a footprint for the MOV, but not actually populate it.

author: Jester
author_rank: Frequent Contributor
timestamp: April 14, 2022, 09:35:37 pm
content: Quote from: Terry Bites on April 14, 2022, 06:41:32 pmActually not because the Opto-Triac drive is only enabled while in CNC mode, and if the power goes down the uC resets and does not come up in CNC mode.Good point though.

author: moffy
author_rank: Super Contributor
timestamp: April 15, 2022, 12:02:41 am
content: Lovely demonstration of the effectiveness of snubbers. I am no great fan of MOVs though they have their place, and if the snubber alone can keep the voltages within reason, that's the way to go.
Using planes as additional capacitor - useless, good or bad? - Page 1
Forum section: electronics / projects

author: eTobey
author_rank: Super Contributor
timestamp: December 26, 2023, 09:34:21 pm
content: I am designing a powerrail, with 2 more powerrails after that (with a AP66300). I was thinking about additionally using big planes of Vin/Vout with oposing GND plane to act as an additional capacitor.Is this a good idea, or a bad one? Or wouldnt it matter at all?

author: ataradov
author_rank: Super Contributor
timestamp: December 26, 2023, 10:18:04 pm
content: It does not matter. Calculate the resulting capacitance, it is negligible. It is a good idea to use power planes in general, and possible additional capacitance is not going to make things worse. But don't rely on it to do anything particular.

author: moffy
author_rank: Super Contributor
timestamp: December 27, 2023, 02:31:55 am
content: The planes can provide electrostatic shielding, and low impedance but as ataradov said "Calculate the resulting capacitance, it is negligible"

author: Someone
author_rank: Super Contributor
timestamp: December 27, 2023, 03:33:31 am
content: "negligible" depends on what you are looking at, but planes only start appearing as a significant factor up above a few hundred MHz:https://resources.system-analysis.cadence.com/blog/msa2021-power-plane-resonance-analysis-in-your-pcb

author: Marco
author_rank: Super Contributor
timestamp: December 27, 2023, 12:56:38 pm
content: Do any of the hobbyiist friendly PCB manufacturers offer planar capacitor layers yet or is it only available for boutique and ridiculously high volume users?

author: DavidAlfa
author_rank: Super Contributor
timestamp: December 27, 2023, 01:21:50 pm
content: Will only provide few picofarads, maybe 1nF at most.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 27, 2023, 06:35:41 pm
content: As others have said, doesn't matter. Use one value of MLCC, first priority being smallest possible package, second priority largest possible capacitance available in that package, sprinkled over the bus as close as the consumers as possible. Additionally, use lossy (e.g. electrolytic) bulk capacitance near power input. Power plane can be full contiguous plane, or segmented fills with different power rails on the same layer, or just bunch of wide traces.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 27, 2023, 09:43:10 pm
content: And if you're looking to save a few cents (and PCB area) on bypass capacitors with the thought that large planes will do it, think again. I don't think that was the idea here, but just saying, I have seen ultra-cheap designs trying to get rid of any part possible even if it's just 1 cent.Apart from the low equivalent capacitance, the inductance and how it is distributed over the board would make this completely unpractical.

author: Marco
author_rank: Super Contributor
timestamp: December 28, 2023, 08:45:04 am
content: Unless you pay for Faradflex or similar.
Using power splitter at lower frequencies. - Page 1
Forum section: electronics / projects

author: Vgkid
author_rank: Super Contributor
timestamp: December 29, 2014, 03:50:30 am
content: I have noticed that there are a bunch of power splitters in the 700-900 Mhz range. What issues would arise if it were to be used at 10 Mhz, at highest 100 Mhz. Or should I bite the bullet and find a lower rated one.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 29, 2014, 07:52:42 am
content: 700-900MHz sounds like a "wideband" splitter, in that, for its design, it works over a relatively wide range... but still, it's a tuned design (perhaps with 1/4 wave elements?), and only works over that range.If that's what it is, I would expect it behaves as a lump of metal at very low frequencies (i.e., all ports shorted together, so the mismatch at all ports sucks, and the coupling coefficient is equal). Or if it's a fractional power splitter, like the kind with coupled 1/4 wave traces, the coupling coefficient will be 1.0 for the "through" ports and 0.0 for the "coupled" ports.The (truly) wideband splitters use transformers with permeable cores to enforce matching over a very wide range of frequencies (several decades).So, the correct answer is: depends on design, but most likely, it's not going to do anything like what it does in the rated bandwidth, and there's probably a good reason why, even if we don't know what's inside the black box.Tim

author: Vgkid
author_rank: Super Contributor
timestamp: December 29, 2014, 11:39:31 pm
content: Thanks for the reply, i figured that much. To bad lower frequencied ones are less numerous.

author: TSL
author_rank: Regular Contributor
timestamp: December 30, 2014, 02:55:51 am
content: What do you need one for ?Are you trying to split high power? i.e. over 1w or more ?Are you feeding antenna's or splitting signals before buffers ?Knowing what you want to do might get you a more detailed responsecheersTim