hybridfree/eevblog-posts huggingface dataset:
Serial connecting of max7219 - Page 1
Forum section: electronics / beginners

author: marekpasek
author_rank: Contributor
timestamp: May 05, 2019, 05:12:22 pm
content: Hello,Is it possible to drive a 8Xn display (where n is a number, which exceeds 8 ) just by connecting a couple of MAX7219 in series? I have a 10-digit seven segment VFD display with common grids for every digit and common anode for coresponding segment of every digit (10-MT-20GY in particular). I would like to use four of these to display data from arduino. Since I am not a programmer I want to use MAX7219, for which there exist dozens of libraries and tons of troubleshooting articles, so every problem with it is easily solvable. I want to use all ten digits, not just eight, so I need to use two 8-digit drivers for each display. And there comes the problem. Is this possible with MAX7219? I would have to connect the common segment pin of both MAX7219 together (not literally shorten them, just use some transistor AND gate to switch the anode voltage!). Since the datasheet tells nothing about timing of pulses on common cathode pins, I do not know, what is really happening on the outputs of serially connected chips. Do serially connected chips count to eight simultaniously or one by one? Could they not interfere with each other then?Thank you very much for any response. If you find anything unclear in the text, please ask. Writing about this problem is for some reason very difficult for me (possibly because English lacks declension and the most of grammatical forms I would use in my native language), so sorry for that.

author: iMo
author_rank: Super Contributor
timestamp: May 05, 2019, 05:17:43 pm
content: Marku, yes you may wire N chips in series. There are libs which support N chips in series.Page 13.https://www.sparkfun.com/datasheets/Components/General/COM-09622-MAX7219-MAX7221.pdfYou load data serially to all N chips (as a X*N bits long bitstream) while they share Clock and Load (low) signal. Din/Dout-->Din/Dout-->Din/Dout..When the Load goes high all chips start to display their own actual data loaded.Mind each 7219 chip makes its own multiplexing (8 anodes x 8 cathodes).So you need separate Anodes and Cathodes for each 7219.

author: marekpasek
author_rank: Contributor
timestamp: May 05, 2019, 06:14:37 pm
content: Well ,that is the problem. I have 8 anodes and 10 grids, therefore a cannot use the circuit shown on the page 13 of the datasheet.Děkuji za odpověď.

author: iMo
author_rank: Super Contributor
timestamp: May 05, 2019, 06:22:32 pm
content: I think a small mcu with a piece of code can do NxM multiplexing easily..

author: marekpasek
author_rank: Contributor
timestamp: May 05, 2019, 07:18:39 pm
content: Agree. Bunch of 74595s and 4017s will do the job.Thank you
Serial data transmission confusion - Page 1
Forum section: electronics / beginners

author: bborisov567
author_rank: Regular Contributor
timestamp: October 22, 2021, 04:08:46 pm
content: Recently i ve been looking into cables for connecting to lpg controllers. Most of them use simple serial communication (RX and TX pins connected directly to adapters with ft232 or pl2303 do the job). But a group of contollersare supposed to use this kind of wiring:On other places on the internet i found a schematic with max232 for voltage level conversion:As far as i understand from the datasheet of the max ic all it does is converting given RX and TX levels to +5V.But then why people are going into all of the hassle of soldering the max232 schematic if you connect it directly?And my second questions is how the communication takes place only through one wire with two resistors at the end?Also if you can recommend me some article on serial communication to shed some light.

author: mon2
author_rank: Frequent Contributor
timestamp: October 22, 2021, 05:03:55 pm
content: If you use the MAX232, the voltage swings will be bipolar with positive & negative voltages on the TX & RX lines. Respectively, if using RS232 levels, you must interface the other side of the wiring with another RS232 transceiver (TX & RX). The transceiver (MAX232 or equivalent) will take your CPU CMOS levels (often CMOS levels are @ 3v3) and shift to +5 / -5V. Typically, these days, RS232 transceivers are operating @ 3v3 but they feature a capacitor voltage doubler for the I/O. So this translates to about +6 / -6 volt swings on the RS232 pins.You CANNOT safely interface RS232 directly to CMOS pins on the CPU. Again, RS232 to RS232 transceivers must be used. With RS232 transceivers you can drive the cable longer than if you do NOT use RS232 transceivers. Varying directly with the baud rate (speed of the serial port) and the quality of your RS232 wiring, you can run say 20-50ft with 9600bps / 19200bps. There are many articles on this topic but if you must run very long cables then consider RS422 or RS485 transceivers instead. With the differential signals of RS422 / RS485 transceivers, you can run upto 4000ft at the slower baud rates.MAX232 is an old school transceiver but a stable one. Consider devices with 15kv ESD protection to protect against carpet zaps, etc. - static does KILL the parts.

author: bborisov567
author_rank: Regular Contributor
timestamp: October 22, 2021, 07:08:19 pm
content: So i need max232 only if i am connecting to a physical RS 232, for example on a old pc and also for protection? According to PL2303's datasheet leves depend on VCC so when using 5v to supply the 2303 i dont need max232? And last what about the one wire and the two 180 ohm resistors, how is the magic happening?

author: Benta
author_rank: Super Contributor
timestamp: October 22, 2021, 07:40:35 pm
content: Quote from: bborisov567 on October 22, 2021, 07:08:19 pmNo magic. Some kind of half-duples X-on/X-off signalling, but this is firmware-related.
Serial Decode Error on Rigol DHO812 - Page 1
Forum section: electronics / beginners

author: Nautiluso
author_rank: Newbie
timestamp: January 01, 2025, 04:52:43 pm
content: Decoding a 1200 baud 7 bit Event 1 stop bit serial protocol via a Rigol DHO812 gives me an "S" and a "P". I guess they are errors but does anyone know exactly what they mean? Thanks and best wishes for 2025!

author: mwb1100
author_rank: Frequent Contributor
timestamp: January 01, 2025, 06:26:14 pm
content: The P indicates a parity error and the S indicates a stop bit error.I think you want 8n1 setting (8 data bits).

author: Nautiluso
author_rank: Newbie
timestamp: January 02, 2025, 11:37:43 am
content: I did various tests - the protocol is 8E1, I had never seen one. Now everything works thanks.

author: mwb1100
author_rank: Frequent Contributor
timestamp: January 02, 2025, 06:53:33 pm
content: Quote from: Nautiluso on January 02, 2025, 11:37:43 amI can see that now in the screenshot. I don't think I have ever come across a device actually using parity in RS232 comms; I can't recall ever having used anything other than 8n1.
Serial disconnect with AND gates - Page 1
Forum section: electronics / beginners

author: tomshirvo
author_rank: Regular Contributor
timestamp: March 31, 2015, 01:55:52 am
content: Just posting to see if this will work. I have simulated and it worked but I just never know.I have a uC that is connected to an Xbee S2 module. Communication will mostly be with the Xbee but there is a need to be able to communicate directly to the uC with another device.I have a bootloader on the uC, when I plug in the external device it will bring IO-1 high which the bootloader will then set IO-2 low which then disconnects the RX and TX lines to the Xbee.I have attached a picture below, will this work??thanks in advance!
Serial display adaptor board to run PC monitor - Page 1
Forum section: electronics / beginners

author: Seekonk
author_rank: Super Contributor
timestamp: January 03, 2015, 12:52:57 am
content: I have an arduino project and would like to send plain old ASCII characters to a PC monitor display. I have searched ebay thinking there must be a $10 board from China to do this but my search words haven't come up with anything.

author: Wilksey
author_rank: Super Contributor
timestamp: January 03, 2015, 01:12:12 am
content: Hi,Have you seen the GameDuino2?http://excamera.com/sphinx/gameduino2/One example of particular interest might be:http://excamera.com/sphinx/gameduino2/samples/helloworld/index.html

author: netdudeuk
author_rank: Frequent Contributor
timestamp: January 03, 2015, 08:24:21 am
content: If composite video would do them this is a nice cheap way to get data out to a screenhttp://searle.hostei.com/grant/MonitorKeyboard/index.htmlProbably not much more than your $10 and you can interface to it in several ways.

author: Seekonk
author_rank: Super Contributor
timestamp: January 03, 2015, 08:32:31 am
content: That is pretty interesting. What I wanted was a simple RS232 type that would turn a standard color PC monitor into screen display like the old LSI Blue Pig (am I showing my age?). I'm building updated electronics for 1950's era SUN distributor machine and a large 80 character display would be ideal. Target board is just a $3 mini. Add all this stuff on and you might as well go with a PC and get data storage. A month ago there was an article on a board here that turned your computer into an AV entertainment center. With remote it was only $15 shipped! I'm sure a simple board is out there though this has possibilities for graphs and control panels. Project keeps growing in scope. With all these snap on boards there is a concern about how many pins they use, you run out of empty pins quick.Now if someone just made that into a board. 40 years ago I had a Z80 demo board and I interfaced it to a S-100 video board to make a word processor for a computer class. The days are over when I had to do that much work. Spoiled by all those under $10 boards from China.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: January 03, 2015, 02:17:49 pm
content: I was running the board on my own Z80 computer last year ...https://hackaday.io/project/182-z80-microcomputer... but now have a Parallax Propeller colour VGA (640 x 480 @ 69Hz settings: 80 x 40 characters) version ...
Serial OLED/VFD - Page 1
Forum section: electronics / beginners

author: sam1275
author_rank: Frequent Contributor
timestamp: September 27, 2015, 11:32:01 am
content: Hi everyone, can anyone recommend me a display that can directly connect to the debugging serial port such as residential gateway, and display the message? Not all serial can do that lol, also, I need a character one of course, and better to be a VFD / OLED, can anyone give me a certain model suggest? Thank you.

author: sam1275
author_rank: Frequent Contributor
timestamp: September 28, 2015, 11:11:48 am
content: Quote from: sam1275 on September 27, 2015, 11:32:01 amlol

author: SL4P
author_rank: Super Contributor
timestamp: September 28, 2015, 10:30:44 pm
content: @sam, to save you the embarrassment of responding to your own posts...Perhaps you'd consider redefining your OP question.Currently it has almost no points that anyone can assist with - without simply re-posting they entire history of digital electronics, Comms, and display.Perhaps starting with the model of gateway (assuming you mean your router?).All 'cereals'cando 'that', but it all depends on what 'that' is...!A character based display won't be as helpful if the 'message' is graph data (usage etc)...
serial to Ethernet IC  - Page 1
Forum section: electronics / beginners

author: alamwte
author_rank: Regular Contributor
timestamp: April 13, 2021, 08:24:34 am
content: Hi,I am looking for an IC that convert serial to Ethernet , and be under the web.But I can not find anything.Would you introduce me an IC ?

author: kripton2035
author_rank: Super Contributor
timestamp: April 13, 2021, 08:55:18 am
content: I have no IC to show you, but a module that just do that. it can do a lot more as it has an esp32 inside.https://www.seeedstudio.com/Ethernet-module-based-on-ESP32-series-WT32-ETH01-p-4736.html

author: Benta
author_rank: Super Contributor
timestamp: April 13, 2021, 03:50:32 pm
content: Never heard of such a thing.General solution would be a microcontroller with Ethernet controller and serial port(s). Plenty of those around, but you'll need one with well-supported TCP/IP stack (if you're lucky, it might be free).

author: fordem
author_rank: Regular Contributor
timestamp: April 13, 2021, 05:10:38 pm
content: Google ethernet terminal server

author: MadScientist
author_rank: Frequent Contributor
timestamp: April 13, 2021, 11:30:37 pm
content: I think wiznet do one.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: April 14, 2021, 02:43:18 am
content: https://www.microchip.com/wwwproducts/en/ENC28J60I bought some of these off of ebay already on a breakout board. I've never used them though.

author: alamwte
author_rank: Regular Contributor
timestamp: April 14, 2021, 05:16:42 am
content: Thank you all to guide me

author: ebclr
author_rank: Super Contributor
timestamp: April 14, 2021, 11:11:31 am
content: http://www.wch-ic.com/products/CH9121.html

author: RoadRunner
author_rank: Frequent Contributor
timestamp: April 14, 2021, 01:41:58 pm
content: Lantronix has few products which are in size of Ethernet jack. Expensive ~70USD, but nice black box solution. Lantronix also has driver for windows to make it look like a serial port.There will be no off the self single chip solution. you can make one in few hours. Take any Ethernet dev board may be microchip or even a Raspberry, have socket open on Ethernet and use a serial port to push data in and out of socket. Make it appear like a serial port in windows would need a driver. Doing custom driver in Windows is hard.

author: Pack34
author_rank: Frequent Contributor
timestamp: April 14, 2021, 02:49:50 pm
content: Quote from: JustMeHere on April 14, 2021, 02:43:18 amI used to use the ENC28J60 a lot with some small 8bit PICs. Seemed to work great but I wasn't sending a lot of data back and forth. Just about a dozen uint16s every 100ms.
Series Capacitor Charge Regulation - Page 1
Forum section: electronics / beginners

author: TheDood
author_rank: Regular Contributor
timestamp: August 29, 2019, 08:49:09 am
content: Hey all, I'm trying to figure out where to attach the comparator inputs in this cct?? The 2 humps resemble a rectified sine wave. Goal is to compare cap V's and execute a procedure based on that comparison, in this instance I'm trying to regulate/bypass 1 cap if it happens to have a greater V than the comparison.OP-Amps would have separate PS. The idea is to use depletion NMOS between capacitors and use enhancement NMOS for bypassing and trigger them simultaneously.Trying to trigger the D-NMOS to turn off at the same time E-NMOS is turned on. I'm trying to initiate this action when there is a difference in V from 1 cap to the other. When they are equal I would want the D-NMOS to conduct and E-NMOS to turn off.I'm thinking that if I attach inputs to each Cap positive plate that ill have a difference in V regardless if the caps are equally charged or not. I can't think of any place to hook up the OP-Amp inputs that would give me the desired outcome, but I'm just learning and figured perhaps someone could help me see a way. Thanks

author: Ian.M
author_rank: Super Contributor
timestamp: August 29, 2019, 09:45:29 am
content: WTF are you actually trying to do? Give an overview not how you think it should be implemented.*IF* what you have shown us represents the whole original problem, then we'd need to know: What is the signal on the left from, what are its characteristics, and what effect do you want your circuit to have on it?http://xyproblem.info/

author: TheDood
author_rank: Regular Contributor
timestamp: August 29, 2019, 11:21:24 am
content: Lol, well, WTF I'm actually trying to do is charge each cap equally. Maybe there's variation in caps so they dont all charge at same rate? How would I compare capacitor charge levels in order to know whether to bypass or not?It's a rectified sine wave, and I don't think the value matters much, so just choose any arbitrary V that you'd like. Let's use 30V, if that works for you then it works for me. It's more or less a dummy cct to help me gain an understanding so don't read too much into it.. Use any capacitor rating or FETs you'd like, how would I compare 2 caps to each other to do step B... We could do a 30V DC source next, I just wanted to learn about a rectified signal as its something I'm not super familiar with though see quite often.. The jyst is.. Compare 2 caps, carry out a procedure accordingly...in this instance step B is bypassing the cap that has a higher V...

author: TheDood
author_rank: Regular Contributor
timestamp: August 29, 2019, 11:44:49 am
content: I'm actually starting to think I'd need (3) OP-Amps for (2) caps, 1 for each cap, and then 1 to compare between the 2?
Series resistor in STM32F4Discovery - Page 1
Forum section: electronics / beginners

author: SolarSunrise
author_rank: Regular Contributor
timestamp: April 16, 2014, 03:30:58 pm
content: I was designing a new DAQ around an STM32F4 so when I checked the STM32F4Discovery schematic for reference, I found something strange in the datasheet (check attachment). The R24 was shown to be a 220 ohm resistor. According to theApp Note AN2867from ST, the series resistors are used as a low pass filter with one of the crystal's load capacitor. This is for when the crystal gets overdriven.However, if we calculate the cut-off frequency with a 220 ohm resistor & 20pF cap, it's 36171577.9754 hz or about 36 Mhz. This is wayy over the 3rd harmonic of the 8 Mhz crystal, thus it will not be useful for attenuating overdriven frequency of the crystal. Shouldn't it be around 1k like in the example in the App Note? - Check attachmentDid ST manually adjust the resistor experimentally? Even so, shouldn't it be close to 1K? Although it is trivial, I'm really confused right now.Thanks in advance!EDIT: I changed the title from "capacitor" to "resistor". Oops.
Series MOSFET circuit - Page 1
Forum section: electronics / beginners

author: usamakr
author_rank: Newbie
timestamp: October 13, 2017, 05:42:06 pm
content: Dear All,A small question. I was studying a reference design and I could not understand a certain part of a circuit. I have highlighted the part in the attachment with an orange rectangle.Any ideas? Even a name or guide what to search for on Google will do.

author: Fgrir
author_rank: Regular Contributor
timestamp: October 13, 2017, 05:51:41 pm
content: I think those are depletion-mode MOSFETS, maybe a current limiter?EDIT: Sort of like a variation on Figure 4 in the following:ww1.microchip.com/downloads/en/AppNotes/AN-D66.pdf

author: eblc1388
author_rank: Frequent Contributor
timestamp: October 14, 2017, 07:33:12 am
content: They look like back-to-back connected common MOSFETs. Because of the internal body diode inside each MOSFET which allows current flow in the reverse direction, this particular configuration will stop current flow from either direction when the MOSFETs are not biased.Try searching "mosfet back to back" in Google images and you'll get lots of examples.

author: David Hess
author_rank: Super Contributor
timestamp: October 14, 2017, 08:47:48 pm
content: It is hard to tell from the image but I agree with Fgrir; those are back to back depletion mode MOSFETs being used as an AC current limiter for input protection. Such a circuit can easily protect a sensitive input up to +/-500 volts.
Series / parallel switching two power supplies? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: October 27, 2016, 02:50:59 pm
content: I have two HP computer 50V server power supplies switched as series or parallel using the switch arrangement similar to the attached image. I get 100V or 50V (at a LOT of Amps....Given I have a 3 way two pole rotary switch can I arrange it so in the third position I get 50V but from just one of the two supplies? Should be easy to work out, but I am having a "senior" moment here <LOL> Thanks.

author: electr_peter
author_rank: Unknown
timestamp: October 27, 2016, 06:50:38 pm
content: Quote from: Chris Wilson on October 27, 2016, 02:50:59 pmI guess you can. Just add small modification to switching arrangement and use either parallel or series or single PSU.

author: Chris Wilson
author_rank: Super Contributor
timestamp: October 28, 2016, 05:29:06 pm
content: Thanks Peter, feeling stupid, but I just got a mental block about it

author: Paul Moir
author_rank: Frequent Contributor
timestamp: October 28, 2016, 06:00:42 pm
content: Make sure that switch is break-before-make!

author: Chris Wilson
author_rank: Super Contributor
timestamp: October 28, 2016, 07:17:17 pm
content: Thanks for the warning, it is, but I won't be doing any hot switching, cheers Paul.
Series pass element - Page 1
Forum section: electronics / beginners

author: JJalling
author_rank: Unknown
timestamp: January 19, 2015, 01:46:22 pm
content: Hi all,please excuse my (probably rather stupid) question, but I can't find a clear answer. I have spend quite some time in the weekend, looking at power supply schematics.What is the advantage of using a LM317 in this schematic (http://www.electro-tech-online.com/attachments/lm317-png.18890/), rather than a NPN transistor (maybe darlington)?BR Jonas

author: digsys
author_rank: Unknown
timestamp: January 19, 2015, 01:56:37 pm
content: The LM317 has integrated short circuit limiting and thermal shutdown for a start.

author: rob77
author_rank: Super Contributor
timestamp: January 19, 2015, 02:56:21 pm
content: and the most important part is that the LM317 itself is doing the regulation... the opamp is there just to provide a "lift" - the output will be regulated to opamps output + 1,25V by the LM317. so if the opamp will output 4V, the output will be 5,25V

author: JJalling
author_rank: Unknown
timestamp: January 19, 2015, 03:58:02 pm
content: Yes ok, I see. This was actually the image I wanted to post. Isn't the opamp doing the regulation in this circuit?BR Jonas

author: tautech
author_rank: Super Contributor
timestamp: January 19, 2015, 05:59:37 pm
content: Quote from: JJalling on January 19, 2015, 03:58:02 pmNo. The 317 is doing the "work", the opamp is just controlling it.Remember a 317 is an adjustable regulator.The ADJ bias is set by R5,6,7 and the opamp is adjusting this like a variable pot.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 19, 2015, 06:57:52 pm
content: No..?Yes, precisely: the op-amp is doing the control. The 317 is serving only as a current amplifier, a voltage follower.The advantage over a BJT is the low input current and negative offset voltage (ADJ = Vout - 1.25V, rather than Vbase = Vout + ~0.7V). Therefore, any general purpose op-amp can be used.The circuit will still have much higher dropout than doing it discrete (such as with a R2R op-amp and high-beta follower transistor, or any op-amp followed by an amplifying / level shifting / current gain stage, which would only need a transistor or two), but this way keeps the parts count down, which is likely important to the editors and readers of whatever magazine I presume this is from.Tim

author: JJalling
author_rank: Unknown
timestamp: January 20, 2015, 08:29:36 am
content: Ok, so partcount and complexity is the general answer as I read it.I don't know if the image is from a magazine or not - i was too lazy to draw my own schematic so found it on google's imagesearch.ThanksBR Jonas
Series Pass Regulator  - Page 1
Forum section: electronics / beginners

author: Simon123
author_rank: Regular Contributor
timestamp: April 21, 2018, 11:44:22 pm
content: I was looking at some ON Semi PDF and this circuit:http://www.onsemi.com/pub/Collateral/HBD854-D.PDF(Page 36.)I was wondering why would they use PNP Error amplifier and reference it towards + output instead of common ground and use NPN?Thanks.

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 22, 2018, 05:49:35 am
content: IDK, but I was just starting to make some basic regulator circuits to learn multi-BJT circuits, and them parts arrived for a SMPS repair, and I've only been at that since. (But that's my backup computer PSU, so I better stay at it)

author: SeanB
author_rank: Super Contributor
timestamp: April 22, 2018, 08:08:23 am
content: I would guess it makes driving the pass element easier from the differential pair, as the collector voltage swing has a much higher gain than using a single transistor to compare the sample with the reference, and the differential pair is inherently temperature stable as well, only needing a good stable reference voltage, and all the temperature drift is cancelled out by the differential pair gain for the rest of the circuit. flipping it around to use NPN differential pair would need another transistor or two to do the level shifting needed to drive the pass element, and this extra stage will add more phase shift and reduce stability of the circuit as well. The first circuit as well can easily have current limiting added to it, as the current sense amplifier can easily feed current into Q3 to control the current in the circuit, using only one extra PNP transistor.

author: Simon123
author_rank: Regular Contributor
timestamp: April 22, 2018, 11:38:36 am
content: What about this then?It uses same darlington pair and shunt transistor.I know this one is using a negative rail, but that is only to get output to 0V, also this one has Linear response opposed to the 1st circuit.But the thing is, it uses NPN, without any extra shifting transistors?Kinda confused now ...So i guess the question is, why would they reference the regulator/comparator to + Output instead of ground?

author: Simon123
author_rank: Regular Contributor
timestamp: April 22, 2018, 03:29:00 pm
content: Ok i see the problem now.The differential pair has a voltage across Emitter resistor and this voltage would bias the "Shunt" transistor.Thanks, forgot about that ...
Series resistor on serial and pwm output - Page 1
Forum section: electronics / beginners

author: AvlKP
author_rank: Newbie
timestamp: August 16, 2024, 06:21:23 am
content: I'm trying to learn by creating a flight controller. Found some reference schematics, and was wondering what is the use of these resistors? I tried to research it and guessed that it was series termination. But, from what I understand, series termination are supposed to be placed near driver. These resistors not only exist on TX but also RX. Can someone explain what are they for and how were the values chosen?

author: PGPG
author_rank: Frequent Contributor
timestamp: August 16, 2024, 08:37:20 am
content: I think all 220R resistors are to limit supply noise.Any IC switching its output stage needs a current pulse from supply to reload the whole capacitance connected to its output. The faster IC the higher current pulse. When near the output you insert some R (I use 47..100R at all my outputs) these pulse at first moment is needed only to reload IC internal output capacity and reloading the connection wires capacity and receiver(s) input capacity is postponed in time making the pulse peak several times lower than when there is no R in serie.PS.As there are connectors than I suppose signals are inserted into cables (don't know how long). Cables (instead of tracks at PCB) like to be the noise emission source in devices. So the other function of these resistors is to limit signal bandwidth in these cables.Values are chosen to not disturb normal circuit operation while make some noise reduction.
Series switch voltages (check on fundamentals)  - Page 1
Forum section: electronics / beginners

author: JourneymanWizard
author_rank: Newbie
timestamp: June 12, 2018, 07:47:28 pm
content: Fundamentals check on rating switches (and switch-like elements):(in fundamentals land, assume ideal elements unless necessary to do otherwise)(There is a picture attached)Imagine two simple switches [S1 and S2] in series, with a resistor  between them. Imagine that a potential is developed across the two opposite unconnected ends of the switch [V1-V2].When both switches are closed, the voltage across each switch is 0V, the voltage across the resistor is [V1-V2], and the current through each switch (and the resistor) is [V1-V2] / R. The switch has to carry that current.When S1 is opened and S2 closed, current drops to zero. The voltage across S1 is [V1-V2]. The voltage across R + S2 has to be zero, as no current is flowing through that branch. The switch S1 has to withstand [V1-V2].When S2 is opened and S1 closed, the situation above is repeated for S2: S2 has to withstand [V2-V1].When S1 and S2 are both opened, no current flows through resistor R; therefore the voltage drop across R is 0. The withstand voltage of S1 + S2 has to be [V1-V2]. If the switches are in all ways equal, the withstand voltage can be [V1-V2] / 2 per switch.... in posting, I think I Rubber Duck'd my original question (what are the minimum voltage ratings for two open switches). Please let me know if you disagree with any of the above.

author: james_s
author_rank: Super Contributor
timestamp: June 12, 2018, 07:58:25 pm
content: The minimum voltage rating of each switch has to be equal to the voltage into the circuit, because if one or the other switch is closed that is the voltage that will be present across the open switch.

author: JourneymanWizard
author_rank: Newbie
timestamp: June 12, 2018, 08:28:56 pm
content: Agreed, unless both switches are always opened/closed simultaneously. I think in that case that the rating can be [V1-V2]/2. That was the point I was puzzling over a bit.EDIT: Found an application mentioned on Wikipedia involving stacking. Will want to think about it, but gives some ideashttps://en.wikipedia.org/wiki/Cascode#Other_applications

author: tpowell1830
author_rank: Frequent Contributor
timestamp: June 12, 2018, 10:09:49 pm
content: Agreed with other posters. However, the voltageratingshould be about 20% higher than V1-V2 for normal applications, but if there is a coil involved, the rating should be even higher (get out the calculator to determine flyback, etc.).Hope this helps...
Series Voltage regulator - Page 1
Forum section: electronics / beginners

author: BayHitchi
author_rank: Newbie
timestamp: June 25, 2018, 09:12:54 pm
content: Hello people, im a begginer in eletronics and my first project is a series voltage regulator with overcurrent protection. For some personal reasons i coud not attend school for some weeks, so im pretty lost in transistors and regulators. I dont ask for anyone to just do it for me, but if ayone could help me out understand how/why to project it woul be amazing!I just have to project the values of all resistors, V(in)max and V(in)min, in this circuit.The target V(out) = 12v and max current = 1A.

author: Seekonk
author_rank: Super Contributor
timestamp: June 25, 2018, 09:54:30 pm
content: At what voltage will the transistor turn on, then solve for resisyance.

author: not1xor1
author_rank: Frequent Contributor
timestamp: June 26, 2018, 04:21:31 pm
content: Quote from: BayHitchi on June 25, 2018, 09:12:54 pmTr2:as soon as the base voltage (ouput voltage divided by the R1+VR1+R2 divider) gets above the zener voltage plus Vbe, Tr2 reduces the base current of Tr1, while it does the opposite if the voltage gets below the reference (Vzener+Vbe).In other words, Vzener + Vbe is the input signal, while the base of Tr2 gets the feedback signal and adjust the amplification of Tr1 in order to keep the output voltage constant.Tr3:as soon as too much current goes through R5 (i.e. I * R5 >= Vbe), it "steals" some base current from Tr1 limiting the output current.If the current is below that threshold (it is a soft knee) Tr3 does nothing (it is off).knowing all the parameters (voltages, transistor features, etc.) you can easily calculate all the resistor values
series&parallel connection of batteries under load - Page 1
Forum section: electronics / beginners

author: chota.sanjiv
author_rank: Contributor
timestamp: July 08, 2017, 07:22:12 pm
content: Hi,I have 15x18650 cells connected in parallel, I have observed that the cells which are near to the terminals are getting much more strained rather than cells at the other end under high load conditions. I tried to solve it by connecting the +tive terminals of each cell with equal length of wire, this seems to work and each cell seems to get equal share of the load.Is there any other was to solve this, I have seen many tutorial of 18650 cells being used for battery pack and are just connected in a matrix, am I missing something here.Also what will happen if these same cells are connected in series which cell be under more stress (assuming are are balanced perfectly) or all will have equal share of the load.thanks,Sanjeev
Serious op amp issue.  - Page 1
Forum section: electronics / beginners

author: Shane1981
author_rank: Newbie
timestamp: November 06, 2017, 08:42:57 pm
content: So I'm using an lm358 op amp as a basic inverting amplifier to test the gain on my scope. I have calculated the resistors for gain of -10. I'm using a 15 volt power supply for the supply pins and a 1volt input signal at 100 hz. The output I'm getting is 160 mV with a clipped off negative sine wave. How can this be? I have checked everything 1000 times. It's only 3 components. The op amp and two resistors. So I can't imagine how it can be a connection error. I should be getting an out put of about 10 volts. I don't know. I have spent days on this. Please help!

author: BNElecEng
author_rank: Regular Contributor
timestamp: November 06, 2017, 08:54:06 pm
content: Have you got a negative supply?

author: tecman
author_rank: Frequent Contributor
timestamp: November 06, 2017, 09:12:52 pm
content: Without a schematic, kind of hard to tell. If you have a single power supply, connected to the op-amp will certainly exhibit problems. if you bias the op-amp to 7.5 volts you could swing about +/- 5 volts. Best solution is to get dual 15 volt supplies (+/- 15)paul

author: w2aew
author_rank: Super Contributor
timestamp: November 06, 2017, 09:31:13 pm
content: Quote from: Shane1981 on November 06, 2017, 08:42:57 pmSounds like your input signal is going beyond the permitted input voltage range of the op amp. As others have said, posting a schematic, including how you're connecting your input signal, would help.

author: Audioguru
author_rank: Super Contributor
timestamp: November 07, 2017, 02:20:48 am
content: He also did not post the detailed schematic nor say exactly what the supply is on the other website forum.
Seriously, does this create a physicacl danger? - Page 1
Forum section: electronics / beginners

author: watchmaker
author_rank: Unknown
timestamp: March 01, 2024, 12:18:37 pm
content: In my pursuit to perfect the ThaiKit Curve tracer, I added a function generator driven VI board on the outside of the case to have variable voltage for testing zeners. Works good, but my AWG only puts out 10V. I realized I have a 25 V AC secondary inside the case.In my simplistic world view, I want to run that 25 volts across a switched 10k ohm pot. Take the center tap and the side that feeds the negative 9just seems right, but...) voltage supply up to my board. This is so I can test zeners up to 25 volts.I also need to find a plastic box bottom to protect the ckt board which will reside on top of my curve tracer box. All will be inside cabinet except where the variable voltage comes up underneath the test board.Because of the low currents used by the boards, I am going to fuse the secondary since the primary side of the transformer would need a fuse that is too small (1/5 that needed to protect the secondary side boards).Thanks.Why is this bad?Thanks!

author: Jwillis
author_rank: Super Contributor
timestamp: March 01, 2024, 04:45:10 pm
content: Not 100% sure what you mean. Are you using an Active VI tracer or an Octopus? If you transformer is 25VAC then drawing voltage from centre tap would only give you 12.5VAC. Or is the transformer 25V-0V-25V. What ever the case may be, adding a voltage divider wouldn't pose any problem.A 1/2W potentiometer should be plenty for the few mA needed to test zeners

author: ejeffrey
author_rank: Super Contributor
timestamp: March 01, 2024, 06:19:24 pm
content: QuoteA fuse on the secondary doesn't help if the transformer develops a short circuit within the windings.Also, the purpose of a fuse isn't to protect your electronics. It can't and won't do that. It's there to prevent your wiring from starting a fire. There is no need to size your fuse to the actual current drawn if that is extremely low. It just needs to be sized to protect the wiring. A 400 mA fuse (which is quite common) is often fine even if normal current draw is only 10 mA.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 02, 2024, 08:21:14 am
content: The pots may want some extra protection, so that a short on the output side would not destroy it.

author: watchmaker
author_rank: Unknown
timestamp: March 02, 2024, 11:19:40 am
content: Thank you all!Yes, I will fuse the pot.JWillis, I am using my scope see the trace of the Zener for which a variable ac voltage is useful. And it is correct that all I have across the full winding is 15 vac.I was dissatisfied with the lack of means for safely checking Zeners on the ThaiKit tracer. And I like having things as compact as possible. Just look at the space I have to work with! My watch shop is 3 times larger and that does not include my machine room.The purpose of the probe pins and the separate zener socket is to allow testing several zeners without messing with the probes. The cover is a watch band case (what else you expect?).
Server PSU current limit? - Page 1
Forum section: electronics / beginners

author: rks96
author_rank: Contributor
timestamp: November 17, 2023, 06:59:12 pm
content: HiHow does the server PSU handle overload conditions? Does PSU use CC mode when max power output is reached or simply cut out?Is there a standalone current limiting PCB module / circuit I could use with a server PSU to achieve current limiting? Maybe I simply dont know the proper term for what I am looking for! Similar to Buck or boost converters without a voltage adjusting feature, only current? I am planing on trying to use / modify PWM DC motor speed controller for this purpose, but before trying I would like to know other thoughts.My goal is to use server psu for car battery charger / starter.

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 18, 2023, 10:32:32 am
content: PC/server ATX power supplies usually use trigger protection, because voltage has to be either stable (12VDC +-10%), or absent at all.To redesign it to a charger you have to find a power supply which is easy to redesign to it has a current limiting mode.

author: rks96
author_rank: Contributor
timestamp: November 18, 2023, 11:41:31 pm
content: Thanks for info!

author: wraper
author_rank: Unknown
timestamp: November 18, 2023, 11:53:01 pm
content: They shut down, the same as 99% of non lab PSUs (power bricks will also try to restart unlike computer PSUs). Also CC is totally useless in computer hardware, reducing voltage will just increase current draw from step-down converters. Also there is no point of keeping powering faulty hardware.
Service manual for BVM Panasonic BT-H1450y  - Page 1
Forum section: electronics / beginners

author: BreakingHard
author_rank: Newbie
timestamp: March 06, 2021, 06:29:53 am
content: Hello, could You please help I am serching service manual or schematic for old broadcast monitor by Panasonic, model BT-H1450y
Service Manual for Schlumberger CRC 5071 Scope - Page 1
Forum section: electronics / beginners

author: Bskitter
author_rank: Regular Contributor
timestamp: August 15, 2016, 11:32:50 am
content: Hello Guys, a friend recently gave me two Scopes that are not working, I am trying to get them both up and running,The one is a telequipment DM63 which I have found the manual for, but the other one (Schlumberger CRC 5071) has almost no information on the net.When I turn the scope on a hear a slight sound that the ray on the tube is on but there is nothing on the screen, If I switch the scope over to storage mode there is some faint green on the screen. If I hit the Manual button on the Storage section the whole screen goes green for a few seconds then fades away.I have tested the power supply and all the output seem good.There was been some work on the PSU and what looks like the power unit for the Screen.So, does anybody have a service manual for one of these things or any recommendations on what to test ?Here are both the scopes.Byron
Service Manuals - Page 1
Forum section: electronics / beginners

author: PerPC
author_rank: Contributor
timestamp: May 05, 2012, 09:26:39 pm
content: where is a good place to find service manuals? i mean i can find the standard user manuals online but not service manuals. Thank you much for your time and responses.

author: free_electron
author_rank: Super Contributor
timestamp: May 05, 2012, 09:28:34 pm
content: service manuals of what ?agilent has most of them onlinethere is BAMA (boat anchor manual archive)there is kurts manualsandmany moreif you are after 'consumer stuff' ... good luck !

author: PerPC
author_rank: Contributor
timestamp: May 06, 2012, 12:15:18 am
content: Thanks FreeElec. Naw not so much after consumer stuff, just fooling around and might need a service manual here and there. Thanks and ill be sure to write those resources down for future reference

author: PerPC
author_rank: Contributor
timestamp: May 06, 2012, 12:16:19 am
content: Oh im a tad slow. And i needed service manuals for laptops and netbooks of all sorts. Pretty much thats it

author: Unknown
author_rank: Unknown
timestamp: May 06, 2012, 12:23:31 am
content: You can usually find them on the website of the manufacturer in the case of brand-name business laptops (like those from Dell, HP and Lenovo). Service documentation tends to be less available for the cheap consumer stuff that no one bothers to repair. You can sometimes find them on third-party websites. Two sites I've seen mentioned on several occasions areElektro Tanyaande-service info.
SERVO MOTOR PWM Frequency  - Page 1
Forum section: electronics / beginners

author: NASK
author_rank: Contributor
timestamp: July 12, 2019, 04:16:24 am
content: Hi guys !I cant understand how to determine PWM frequency for SERVO Motors using datasheet.but this site sayshttps://electrosome.com/servo-motor-pic-microcontroller/it is 20ms.how to find it Hitec HS-425BB and VIGOR VS-10A SERVOs.Hitec HS-425BBVIGOR VS-10A

author: viperidae
author_rank: Frequent Contributor
timestamp: July 12, 2019, 06:18:08 am
content: Hobby servos like those generally accept a 50hz input, with a pulse width between 1 and 2ms. As it says there, Centre is 1.5ms

author: MarkR42
author_rank: Regular Contributor
timestamp: July 16, 2019, 10:31:03 pm
content: Frequency isn't what drives servos, it's the width of the (positive) pulse.The space between pulses, i.e. frequency, isn't important at all. Most servos keep trying to do the same thing until they receive another pulse, but eventually turn off after some delay (e.g. 100ms).This is completely typical with a 1500us pulse for "centre" position.
Servo speed controller swap out - Page 1
Forum section: electronics / beginners

author: TheSniper
author_rank: Contributor
timestamp: August 26, 2018, 12:43:47 am
content: All,I have a Servo that the speed controller is a S49 Linear hall effect sensor.Is it possible to just replace it with a Potentiometer? 10K? wire for wire.?Basically the controller uses a mechanical foot pedal. and I want to control it with a knob.I hoe the question is clear enough.TIA! Sam

author: Signal32
author_rank: Frequent Contributor
timestamp: August 26, 2018, 03:25:27 pm
content: Yes, you should be able to replace it with a circuit that contains a potentiometer. You can't just swap it with a potentiometer and get the exact behavior.Depending on the circuit around it you can design a potentiometer circuit that acts the same as the S49.

author: Vtile
author_rank: Super Contributor
timestamp: August 26, 2018, 06:39:03 pm
content: You should study the point of signal interface at which kind of signal the hall-effect sensor setup gives the rest of the controller.
Servo tuning with a scope..DC brushed motor type - Page 1
Forum section: electronics / beginners

author: golash
author_rank: Contributor
timestamp: February 21, 2015, 03:49:35 pm
content: HiI am attempting to tune my Gecko drives. Just a few days ago I received my new scope.Am wondering if anyone is familiar with the tuning process. Hoping for some direction.Not certain if my scope settings are correct but here is a video of the machine and scopewaveformThis is a thread I started that covers more details.http://www.cnczone.com/forums/general-cnc-machine-related-electronics/243416-new-control-panel-build-looking-advice-layout-5.html

author: ConKbot
author_rank: Super Contributor
timestamp: February 21, 2015, 04:10:28 pm
content: Gecko doesn't have software for their controllers which spits out the relevant plots needed for tuning? Every servo controller I've used had software which could plot commanded position vs actual, motor current vs desired current, etc.Generally when your tuning a drive, tune the current control loop, then the velocity control loop and finally the position control loop. You feed it a square wave (usually a control can generate this itself) and you turn up Kp until you get sight overshoot and ringing, then Kd to damp out the overshoot, and add Ki to shorten the step response.Not all those parameters may be present though, as velocity is the derivitive of position, and current (torque, therefore force) is the derivitive of velocity
Servos and micros and power isolation, oh my! - Page 1
Forum section: electronics / beginners

author: rrinker
author_rank: Super Contributor
timestamp: December 24, 2016, 05:21:55 am
content: Cheap servos = electrical noise. Micros = noise is bad.So - opinions on "is it isolated enough" if there is a common, say 12V DC unregulated power feed and one (for the sake of example, a nice jellybean part, the good old 7805 linear regulator) regulator circuit powering ONLY the servo, and another regulator circuit powering the micro - both sources from the same unregulated supply. Assuming the 7805's were wired up per proper practice with the recommended caps and all that.Would this be enough isolation to keep most of the servo noise out of the micro side of things, or do I really need to run two completely independent power supplies? Anecdotal evidence from a commercial product that I have used that is designed this way (input power goes to two different regulator circuits, one feeds just the servo power, the other feeds the micro, pushbuttons, and indicator LEDs) sees to indicate this type of design is definitely sufficient. The commercial product was and still is quite reliable, and I never had any issues with noise causing spurious operation of the circuit.

author: SeanB
author_rank: Super Contributor
timestamp: December 24, 2016, 06:13:43 am
content: Better is to add some series resistance to the regulator inputs, so the RC filter is more effective at reducing noise. If your current is such that the R is low, then a small inductor ( well damped with a parallel resistor and some lossy ferrite core) will do as well. This adds impedance to the regulator supply, so that you do not have the decoupling capacitors handling the motor ripple current. on the input side you still need adequate decoupling capacitance, but this is more relaxed value and ESR wise then.