hybridfree/eevblog-posts huggingface dataset:
using negative linear reg for positive voltage - Page 1
Forum section: electronics / beginners

author: mianchen
author_rank: Regular Contributor
timestamp: October 09, 2012, 03:09:32 pm
content: i'm making a few (50) identical widgets that require +5v, ~50ma power supply. I only have 5 78l05, but 100+ 79l05. is there any potential problems if I use these 7905 as voltage reg? obviously I will connect the gnd pins of 7905 to the vcc of the widgets, and output pins to ground of th widgets.I've tested it and it worked, but since i'm a noob, I'd like to ask before I design the pcb and start making the lot. thanks

author: Simon
author_rank: Unknown
timestamp: October 09, 2012, 03:11:05 pm
content: It's possible, I can't remember the implications, probably that you loose your common ground but if this is not a problem it might well be ok.

author: SeanB
author_rank: Super Contributor
timestamp: October 09, 2012, 03:56:26 pm
content: No problem just remember a 7905 requires a little more capacitance on input and output, as they can oscillate if there is not enough. Refer to data sheet for recommended values.

author: Short Circuit
author_rank: Frequent Contributor
timestamp: October 09, 2012, 05:29:22 pm
content: Anybody to service these widgets in the future will probably hate you for saving these 10 cents.

author: mariush
author_rank: Super Contributor
timestamp: October 09, 2012, 06:43:57 pm
content: I agree, not worth the price. You can get them the next day from Farnell.You can get 50 of those for less than 9 pounds... maybe not 7805, but these would be just as good, for 50mA it doesn't matter:http://uk.farnell.com/nxp/nx1117ce50z/ldo-5-0v-1-25-sot223/dp/20572867805 are also cheap enough:http://uk.farnell.com/fairchild-semiconductor/ka78l05az/ic-v-reg-5-0v-78l05-to-92-3/dp/1014073
Using noise suppression capacitors on powersupplies? - Page 1
Forum section: electronics / beginners

author: MrZwing
author_rank: Regular Contributor
timestamp: January 17, 2016, 08:36:36 pm
content: HiI'm designing well more like modifying a simple power supply meant to be used in audio and I have some questions about noise suppression capacitors at the AC input.is this mostly to stabilise if you have a motor or something similar that causes fluctuation in the circuit or is it available to put it on the AC side before the transformer and bridge rectifier to gain less noise in the rest of the circuit or is it much work for almost no result?and if it is a ok idea can I gets some pointers where to read up on choosing which values to use?

author: Simon
author_rank: Unknown
timestamp: January 17, 2016, 08:46:18 pm
content: There are "Y" filters on most things to stop noise, but you will find it easier to filter power at low voltage DC where you are filtering the 50Hz out and any switch mode supply noise.

author: MrZwing
author_rank: Regular Contributor
timestamp: January 17, 2016, 08:54:18 pm
content: I will filter the DC part as well i just wondered if adding some caps on the AC side to make it a little bit stable input and for some safety (plus a fuse).or am I just over thinking something. i have a tendency to do just that.

author: Simon
author_rank: Unknown
timestamp: January 17, 2016, 09:00:09 pm
content: No, if you are just trying to get a clean supply for audio stuff then filter on the DC side. Decent power supplies will be well filtered already, power audio generally does not need perfect DC supplies and signal processing is easily filtered with an inductor in series and capacitor in parallel if you want to be paranoid.

author: MrZwing
author_rank: Regular Contributor
timestamp: January 18, 2016, 08:38:46 am
content: Hmm true I have been thinking about putting a filter in to calm my paranoid mind.Have plans on buying a signal generator so i can experiment with filter circuits to get a better grasp around them, already have the oscilloscope.then I will settle for a fuse on the AC side and make everything else on the DC part.

author: tggzzz
author_rank: Super Contributor
timestamp: January 18, 2016, 09:27:06 am
content: Quote from: MrZwing on January 18, 2016, 08:38:46 amI doubt a siggen will be able to simulate the interference from a motor.I have seen motor startup transients cause clicks on an audio circuit. The solution was a common-mode inductior near the interference source; winding the mains cable several times through a toroidal ferrite ring was sufficient in that case. A clip-on ferrite inductor might be sufficient.
Using non-polarised electrolytic in a PSU - Page 1
Forum section: electronics / beginners

author: johnkenyon
author_rank: Regular Contributor
timestamp: June 28, 2018, 11:05:21 am
content: I've just made a purchasing boo-boo, and ordered 100uF/35v, 105degCnon-polarisedelectrolytic capacitors instead of a standardpolarisedcomponent.I only realised when I came to solder the things and noticed that there was no -ve marking or band on the things...Two of these are intended for use as the output reservoir capacitors for a 100mA per rail linear DC power supply (LM317/LM337, one for each rail), which also have a 100nF polyester cap in parallel.This PSU isn't doing 24/7 service, the device gets used infrequently and the PSU is always disconnected from the mains when not in use.A search of t'interweb seems to point to NP capacitors only being used where required (e.g. speaker crossovers) down to the increased cost, and not on the basis of any other characteristic.So my questions to the audience are:1) Is there any reason why I can't/shouldn't use these in my current design.2) Are there any further reasons why the additional spare capacitors I bought for stock() can't be used in any other PSU/reservoir capacitor situation (e.g. 24/7 type stuff, input reservoir use with high ripple, SMPS part replacement etc.)If anyone wants to look more closely the spec sheet is here:http://www.farnell.com/datasheets/1661880.pdfThanks in advance/John

author: Zero999
author_rank: Super Contributor
timestamp: June 28, 2018, 12:48:23 pm
content: They probably will have a slightly higher internal resistance and be physically larger, than the proper polarised capacitors, but will work perfectly, whether it be in a 24/7 application or not.

author: David Hess
author_rank: Super Contributor
timestamp: June 28, 2018, 01:25:06 pm
content: They will work fine.

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 28, 2018, 01:40:22 pm
content: A non-polarized electrolytic is really two regular electrolytics back to back.So, as the others said, it will work with the mentioned caveats.

author: johnkenyon
author_rank: Regular Contributor
timestamp: June 28, 2018, 04:19:46 pm
content: Thanks for the feedback.The job's now stuck waiting for a small package which actually contains the advertised LM337 instead of a useless P-channel MOSFET... (And before you ask, the incorrect part was shipped from Leeds or Preston, not Shenzhen)./John
Using old linksys cases for other stuff  - Page 1
Forum section: electronics / beginners

author: Ludvig82
author_rank: Contributor
timestamp: January 18, 2016, 10:15:40 pm
content: I have some old Linksys wrt54gl routers and some switches with same form factor cases on them lying around. Some working, some don't. Since they stack nicely, I was wondering of repurpose the cases for other electronics. My first idea was for 2.5 hdd as a backup disc. But there has to be more stuff I could use them for which can come in handy in my "office" at home. Maybe a USB hub?Anyone got any suggestions for me? This would be some nice projects for me to work on while I am away for my work weeks out on the sea (work at a fish farm, I live on a barge every second week)Sent fra min London via Tapatalk

author: Monkeh
author_rank: Super Contributor
timestamp: January 18, 2016, 10:21:25 pm
content: Shove a 5V supply in and make one a USB charging box (with bonus hub).I do like those stackable cases, I wish more stuff was built that way.

author: Ludvig82
author_rank: Contributor
timestamp: January 18, 2016, 11:27:50 pm
content: I have been toying with the idea of making a USB charge station with high amp ports, since some of my stuff need 2a 5v. Maybe I could do that in a linksys caseSent fra min London via Tapatalk

author: Ludvig82
author_rank: Contributor
timestamp: January 18, 2016, 11:30:05 pm
content: And yeah, I like the stackable cases too, and since I've used a lot of these routers, they bring back memories. I saw the new linksys routers have adapted the colour, and kinda copied the looks of the old ones but more modern. Didn't see if they where stackable, if they are I know what router I will buy next Sent fra min London via Tapatalk
using on semi C5 process with electric - Page 1
Forum section: electronics / beginners

author: kzomran
author_rank: Newbie
timestamp: May 25, 2019, 10:05:01 pm
content: Hello,i am trying to use electric vlsi tools to make a chip with on semi C5 process to submit it to mosis for manufacturingmy question is for On Semi C5 process>what is the sheet resistance of n-well resistor and what is the minimum width>also what is the sheet resistance of poly1,poly2 and minimum width>when we say sheet resistance do we mean one lambada width and one lumbada length that is w=0.3 um l=0.3 um or what are the dimensions of the sheet>when designing a capacitor with poly1 and poly2 so what is the capacitance of the area of each poly> and since poly1 has different capacitance per area than poly2 so do i have to use different areas of poly1 and poly2 to have matching capacitancethank you

author: jmelson
author_rank: Super Contributor
timestamp: May 25, 2019, 11:39:38 pm
content: Quote from: kzomran on May 25, 2019, 10:05:01 pmAre you sure this process is still available? They seem to have only one run this year, and not a lot of time left to submit.QuoteDo you have the design kit? If not, your chances of producing anything are essentially zero.You can get the design kit for the process from MOSIS, but there is a LOT of paperwork involved.But, it will have very detailed information on these parameters, although they may be encoded into device models. It probably wouldn't be hard to extract this from the models, but once you have models you may not actually need these parameters.Jon

author: kzomran
author_rank: Newbie
timestamp: May 26, 2019, 10:01:49 am
content: thanks i got the idea now. the first were to start is to sign NDA with On Semi

author: amyk
author_rank: Super Contributor
timestamp: May 26, 2019, 06:37:03 pm
content: You can find some of the info here:https://www.onsemi.com/pub/Collateral/C5-D.PDF
using op07 below its 0 deg C limit - Page 1
Forum section: electronics / beginners

author: asap70
author_rank: Newbie
timestamp: January 19, 2021, 10:27:52 am
content: Hello.Does anyone have an idea as to the feasibility of using an opamp (OP07,say) at -25 deg. C, when it is rated for 0 deg. C min? Anyone who has done it? Possible pitfalls, change in parameters perhaps, bias starvation, or failure with extended use? Would appreciate your opinions and data.thanks and regards,asap

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 19, 2021, 10:36:08 am
content: Where do you get the 0c value?The datasheet I have specifies it to -55c.

author: Zero999
author_rank: Super Contributor
timestamp: January 19, 2021, 11:09:50 am
content: There are different versions of the OP07, with different temperature ratings. As far as I'm aware, the only difference is the package. The OP07E is only rated down to 0°C. To work at -25°C, use the OP07C, which is rated down to -40°C.https://www.analog.com/media/en/technical-documentation/data-sheets/OP07.pdf
Using photoresistor with decorative lights - Page 1
Forum section: electronics / beginners

author: Phillipthegreat
author_rank: Newbie
timestamp: December 08, 2017, 09:18:12 pm
content: Hello, all!I want to use a small string of decorative lights for a Christmas present thing (this is the idea:http://livingstontowncenter.com/canvas-light-up-wall-art.html/delightful-decoration-canvas-light-up-wall-art-charming-17-best-ideas-about-light-up-canvas-on-pinterest), and I'd like them to turn on when the room gets dark. I've seen multiple types of photo resistors/ photocells, and I'm wondering what the best solution would be. I'm planning to use led strips such as those in pc cases, but that might change. Does what type of light I use matter to the photoresistor? So, I'm thinking of using a photoresistor like this:https://vetco.net/products/photoelectric-switch-25w-125vac-on-at-dark?gclid=CjwKCAiAjanRBRByEiwAKGyjZVcCn8kLHYvQGnAN9DGJC9jPad2JVZhqfptcRrYbeFL7jgqrKfaArhoC-AMQAvD_BwE. Would this guy work best for me? The only thing I need the resistor to do is detect when a room is lit up. I know some beginner level electronics, but I'm still plenty new, so I thought I'd ask here first.Thanks!

author: danadak
author_rank: Super Contributor
timestamp: December 09, 2017, 01:01:19 am
content: Looks like switch operates in hot side AC line, and is rated fortotal acceptable load power. So do not exceed that.Be careful doing the wiring, you are working with lethal voltages. Noexposed wiring. Consult online house wring/color code DIY sites.https://www.doityourself.com/stry/identifying-house-electric-wiring-colorshttps://www.angieslist.com/articles/what-do-electrical-wire-color-codes-mean.htmRegards, Dana.
Using phototransistor to disable RX/TX LEDs - Page 1
Forum section: electronics / beginners

author: dagnum
author_rank: Newbie
timestamp: February 11, 2023, 08:43:48 pm
content: Hi,I'm designing a very low power data logger and thought I was being clever by powering the RX/TX LEDs through a phototransistor. The idea is that when the logger is deployed inside a dark enclosure the lights don't use power, but when someone opens it up to check if it is working the lights will flash to let us know it is still alive. It's my understanding that the RX/TX LEDs light up when the lines are driven low by the interface chip (CH340 here), and that anything I do with the LEDs should not affect the communication. I have spun up 50 of these boards and noticed a couple weird things I'm not understanding.If I placed my finger over the phototransistor during upload the code upload fails. Can anyone explain why this is different than if I had no LEDs at all?When I cover the phototransistor completely there is still a very faint light. Is it not possible for this to turn completely off?In retrospect a more flexible design would be to have the microcontroller read a signal from the phototransistor and then code a threshold for powering the LEDs. I thought this would be a simple analog design though.edit: Here is a link to the specific phototransistor if it is helpful.https://www.digikey.com/en/products/detail/everlight-electronics-co-ltd/PT17-21C-L41-TR8/2675873

author: ataradov
author_rank: Super Contributor
timestamp: February 11, 2023, 09:38:47 pm
content: This ptototransistor specifies 100 nA for Collector Dark Current. And you are probably not completely covering the sides and all. Modern LEDs are stupid efficient and might be visible even at that current. And I would not be too concerned by this extra consumption.I run all my indication LEDs for indoor use at single uA typically and this is plenty for stuff on the development boards. They are blinding otherwise.Look with the scope at the RX/TX lines and see what exactly fails. You may be touching some pins while covering it and inducting some noise or something like this. I don't see why this would not work.And for a cleaner test, just remove the transistor on one of the board and see if you still have an issue.

author: dagnum
author_rank: Newbie
timestamp: February 11, 2023, 11:33:12 pm
content: Thanks, I'll look into the uploading issue more. Glad to hear there isn't a huge mistake here.Future revision may just exclude the phototransistor entirely and just have higher value resistors. You're right about the efficiency of these LEDs and how little current you really need.
Using PIC Capture Compare Module For Frequency Measurement - Page 1
Forum section: electronics / beginners

author: khatus
author_rank: Regular Contributor
timestamp: November 24, 2019, 01:55:18 pm
content: Hello guys i am a beginner in pic micro controller programming. i have a code for frequency measurement using pic 18f4550 microcontroller.but the problem is although the code sometimes works in real hardware but it did not simulate i Proteus simulation software. This code is very important for me since I want to understand how capture module works in pic.Can any guys fix this code as well as post the simulation file in this forum so that i can download them and simulate it.Or provide some alternative code for Testing capture module functionality of pic 18f4550.Code:// some random garbage uncommented code found on forum// 20MHz external crystal with no PLL to give 20MHz system clock// a 5 kHz test square wave is provided on RC1 - link RC1 to RC2 to test operation#define f_timer 5000000 // T1 clock is Fosc/4sbit LCD_RS at LATB4_bit;sbit LCD_EN at LATB5_bit;sbit LCD_D4 at LATB0_bit;sbit LCD_D5 at LATB1_bit;sbit LCD_D6 at LATB2_bit;sbit LCD_D7 at LATB3_bit;sbit LCD_RS_Direction at TRISB4_bit;sbit LCD_EN_Direction at TRISB5_bit;sbit LCD_D4_Direction at TRISB0_bit;sbit LCD_D5_Direction at TRISB1_bit;sbit LCD_D6_Direction at TRISB2_bit;sbit LCD_D7_Direction at TRISB3_bit;void main ( void ){unsigned long signal_period,data1,data2;char frequency_Hz;float Frequency;Lcd_Init();TRISC.TRISC1 = 1;OSCCON = 0b1110000;PIE1.CCP1IE = 1;PIR1.CCP1IF = 0;CCP1CON = 0x05;CCPR1 = 0x00;PIR1.TMR1IF = 0;T1CON = 0x80;T1CON.TMR1ON = 1;TRISB = 0;TRISA = 0; // all outputsLATA = 0; // all low to start withTMR1H = 0;TMR1L = 0;PWM2_Init(5000); // provide test frequency output on RC1PWM2_Set_Duty(127); // square wavePWM2_Start();while( 1 ){while(!(PIR1.CCP1IF));PIR1.CCP1IF=0;data1 = CCPR1;while(!(PIR1.CCP1IF));PIR1.CCP1IF = 0;data2 = CCPR1;if(data1 < data2){Lcd_Cmd(_LCD_CLEAR); // clear out old informationsignal_period = data2 - data1;Frequency = ((float)f_timer / (float)signal_period);FloatToStr( Frequency,frequency_Hz );///LongWordToStrWithZeros(Frequency, frequency_Hz);Lcd_Out(1, 1, frequency_Hz); // display new frequency valueTMR1H = 0;TMR1L = 0;}Delay_ms(500); // Limit display rate to reduce flicker}}

author: Ian.M
author_rank: Super Contributor
timestamp: November 24, 2019, 02:32:17 pm
content: Duplicate:https://www.eevblog.com/forum/beginners/testing-capture-module-functionality-in-pic-18f4550/
Using PNP to Switch Negative Voltage - Page 1
Forum section: electronics / beginners

author: braden_sun
author_rank: Newbie
timestamp: March 15, 2020, 01:34:59 am
content: Hello,I would like to use a transistor to switch a negative voltage and found the following circuit. Is there any issues with using this (Aside form the ~.6V offset when switching to 0V)? Or would I be better off just using a relay?I am also having some trouble fully understanding the circuit. I understand when the 3.3V input turns off, the transistor is off and the output gets pulled to -5V. But then when the transistor and 3.3V input turn on, is the way to think about it like two Kirchhoff Current Loops? One from the 3.3V through the base and one from the 3.3V through the collector?Thanks for the help!

author: greenpossum
author_rank: Frequent Contributor
timestamp: March 15, 2020, 03:40:51 am
content: It's anemitter followercommon base configuration. I've seen this used to good effect in other circuits.Edit: basically it's operating as a level shifter.

author: fourfathom
author_rank: Super Contributor
timestamp: March 15, 2020, 05:56:06 am
content: Quote from: braden_sun on March 15, 2020, 01:34:59 amSure, the two current loops are one way to look at it. But there is also a significant current flowing through the base-emitter junction that you ought to consider. It sometimes helps me to understand these "upside down" circuits by flipping them over: substitute a NPN transistor and swap the voltage polarities, then draw it positive on top, negative on bottom. This lets me look at a more "normal" configuration. Of course you still need to implement it with the PNP!Quote from: greenpossum on March 15, 2020, 03:40:51 amNot an emitter follower (which is a common collector configuration), but it is a common base design. As long as the collector load is a high resistance (as it is in the circuit shown) it's going to work well enough for level shifting.

author: greenpossum
author_rank: Frequent Contributor
timestamp: March 15, 2020, 05:58:37 am
content: >Not an emitter follower (which is a common collector configuration), but it is a common base design. As long as the collector load is a high resistance (as it is in the circuit shown) it's going to work well enough for level shifting.You're right, had a brain fart. Common base it is.OP, it's fairly easy to work out even in your head. You only need to consider the on and off states of the level shifter.Here's one place I've seen it before. This the low end of an anode driver for a 7-segment plasma display panel. The NPN transistor is a MPSA42 and the high end is a PNP MPSA92. Only one base resistor is needed because only one digit is on at any time.
Using polarized capacitors in place of bi/uni/non-polar electrolytic capcitors - Page 1
Forum section: electronics / beginners

author: drewt86
author_rank: Newbie
timestamp: November 22, 2017, 05:25:36 pm
content: Hi gang,My name is Drew and while I've been watching EEV on youtube for years, this is my first time on the forum. I'm still learning and recently took on a project to repair a device of mine that stopped working.After a power supply issue I had with a Presonus Central Station, I decided to order all new caps. There were only 30 on the board and figured it couldn't hurt while I had it apart. Since I'll be receiving the parts on Friday, I came in today to remove the capacitors from the board and document the layout/orientation, etc. As I was desoldering them, I discovered that although they are electrolytics, some of them or nonpolarized. I didn't notice it until I went to look for the minus. My bad, if I had discovered this earlier, I would have replaced it with poly caps.Here is a spec sheet one type of capacitor on the board in question.http://www.vek-online.de/files/4188/upload/Elektrolyt/CD71H.pdfThe ones on the board are made by the Chang Yang company...and to be clear, I didn't make that name up. That's what they say on them...Anyway, my question is, is it possible to use a polarized capacitor in place of it? I know you can't go the other way around but this is the first time I've thought of this. Is there something special about how I should orient it? Most of these bipolar caps appear to be filtering outputs of the MC33079 all over the board. Each cap is in series with a 50ohm resistor from the output and ends up at some relays on a different board. Sadly, there is no schematic to be released.While I've been learning a lot in the past few months, I still have many gaps in my electronics knowledge and I just found one. Any help is appreciated.

author: danadak
author_rank: Super Contributor
timestamp: November 22, 2017, 05:38:03 pm
content: Without seeing the schematic , in general. a polar cannot replace anon polar. Exception is use of two polars used in series, like polarityconnections, eg. + to + or - to -, to create a non polar.Regards, Dana.

author: Zero999
author_rank: Super Contributor
timestamp: November 22, 2017, 06:58:51 pm
content: Yes, use the same value capacitors, connected back-to-back. The capacitance will be half of the original capacitor value.https://www.quora.com/What-is-the-difference-between-AC-and-DC-capacitorshttp://www.electronicecircuits.com/electronic-circuits/crossover-network
Using powerbank to power projects - Page 1
Forum section: electronics / beginners

author: aiq25
author_rank: Regular Contributor
timestamp: May 16, 2018, 10:22:44 pm
content: Hi. I would like to use a powerbank to power some of my projects and have a basic. From my understanding, a port on a powerbank that is rated for 2.1A can provide that much current correct? Reason I ask is because I recently came across some topics and there were some disucssion that talked about having resistors on the D+/D- lines but from my understanding that is on the charger end (so this case the powerbank) and I just want to make sure.I'm working on a LED board that will require about 800mA @ 5V and I'm looking to use a powerbank to power the board. I just want to make sure the board can get at least 1A of current.

author: Wimberleytech
author_rank: Super Contributor
timestamp: May 16, 2018, 11:46:29 pm
content: Somewhere on the powerbank it should say something like: 5V -- 2.1 AYes, you can draw 2.1 amps. Your 800mA board will be just fine.

author: aiq25
author_rank: Regular Contributor
timestamp: May 17, 2018, 12:27:55 am
content: Thanks!
Using Probes with different bandwidth on same scope Yay or Nay? - Page 1
Forum section: electronics / beginners

author: noidea
author_rank: Unknown
timestamp: June 03, 2015, 04:20:09 pm
content: This may be a dumb question but I have searched the forum and net and can't seem to find an answer so here goes. I'm a scope newb and know that your probes should have a higher bandwidth than what you are trying to measure but if you have a two channel scope does it make a big difference if your probes are different bandwidth?The scenario is I have a Fluke 106C 100Mhz scopemeter and one of the VPS210 200MHz probes is dead (it's open circuit, I'm happy to try and take it apart for the forums enjoyment if you want)Fluke accessories are "rather expensive" in Oz and a VPS210-G 200MHz probe is $399 ex GST from RS components but the probe for a 190 Series II Scopemeter VPS410-G which is a 300MHz probe with higher CAT ratings is only $293 ex GST. I then did a bit of searching for other isolated probes and worked out the Fluke Probes are about 99.999% to really be Multi Contact Isoprobe III series and I can buy a 300MHz or 500MHz probe from RS for around the $150 mark, which seems like the way to go.At the moment the signals I am measure are in the range of 10kHz with a 10V peak to peak so all of these probes are way more than I need but if I use a 200MHz probe in one channel and a 300 or 500 MHz probe in the other channel is it going to make a huge difference? I would rather not have to buy two new probes if I only need to buy one.

author: c4757p
author_rank: Super Contributor
timestamp: June 03, 2015, 04:23:41 pm
content: You're fine. The probes have a higher bandwidth than the scope anyway, so they have practically no effect on the overall bandwidth. If that weren't the case, the bandwidth of each channel would just be determined by the bandwidth of the probe on it.

author: tggzzz
author_rank: Super Contributor
timestamp: June 03, 2015, 04:47:08 pm
content: You should be OK.Sanity check: put all the probes on the same point, and see if the displayed signals are identical.

author: w2aew
author_rank: Super Contributor
timestamp: June 03, 2015, 07:50:42 pm
content: The only gotcha you might run into when using higher BW probes on a slow scope is that the compensation range might be insufficient to properly compensate the probe. If you're able to properly compensate the probe, then you'll be fine.

author: noidea
author_rank: Unknown
timestamp: June 04, 2015, 12:16:32 am
content: Thanks all for the information and heads up about compensation I think it might be wise to stay with the 300MHz options.I'll report back about the probe compensation when I get the new probe.

author: tggzzz
author_rank: Super Contributor
timestamp: June 04, 2015, 08:35:28 am
content: Quote from: noidea on June 04, 2015, 12:16:32 amPut the probes on the same point and see if there is any difference; subtract one signal from the other. If no difference then you don't have a problem.
Using PWM motor controller for LED strip - Page 1
Forum section: electronics / beginners

author: hyperknot
author_rank: Contributor
timestamp: July 17, 2023, 02:54:50 pm
content: Hi,I'd like to dim a 24V single white LED strip. My problem is that I'd like to avoid using PWM frequencies in the audible range, so I'm looking for a LED controller over 20 kHz. My problem is that it's almost impossible to find one, except from some specialized brands made for movie production. For example this is one:https://store.waveformlighting.com/products/filmgrade-flicker-free-dimmer-for-led-stripOn the other hand, I found cheap motor controllers on Ali / Amazon, for example the popularZK-MGone. It can do adjustable frequency between 1-99 kHz.Would it be equally good to use such a motor controller for controlling a LED strip? I mean it seems cheap, made for higher currents and has the adjustable frequency range. It has a physical knob, which I prefer over any of the "smart" solutions.

author: DavidAlfa
author_rank: Super Contributor
timestamp: July 17, 2023, 03:33:26 pm
content: PWM in audible range is rarely a problem for leds, only when powering devices that can act as audio transductors, like coils in motors.Lots of everyday things using led dimming work between 100Hz and 10K without problem.Having said that, there's no reason why the motor controller would not work with leds, seems a very simple device just toggling a MOSFET.
using PWM signals to control variable power supply. - Page 1
Forum section: electronics / beginners

author: TechJunkie97
author_rank: Contributor
timestamp: July 25, 2017, 05:34:21 am
content: I have a DIY 0-30v 0-3amp power supply with 10k potentiometers to control the voltage and current with voltage dividers from 0 to 10v. I am planning to use the chip from Arduino Uno ( Atmel atmega328p ) for driving these voltages. The circuit diagram of the power supply is attached below.The power supply has 24v for a fan but I do not intend to cross 1 amp so I don't need a fan. I am describing a couple of options that I came up with:OPTION 1:Use 8705 regulator to drop down from 24v to 5v for chip operation and use that 24v supply again to power op-amp for converting the signal from 0-5v to 0-10v. Please see the attached circuit diagram for more details.OPTION 2:Use USB cable to power the chip and 24v from power supply for powering the op-amp for converting 0-5v signal to 0-10vOPTION 3:Use a 9v volt battery for the op-amp. Use 5V regulator to drop voltage for the chip, however, the max op-amp voltage will be less than 9V. I think this option prevents heat losses but also sacrifices some output voltageAll my knowledge here is solely from Dave's videos and I have never used a voltage regulator or op-amp before. So, please point out if anything is wrong. I would like to know your opinion about which option seems most reasonable or if there is a better approach to this problem. Also, do I have to worry about limiting current in these circuits?
Using RCA audio cables with old RCA WO-91A oscilloscope? - Page 1
Forum section: electronics / beginners

author: bgrebel9
author_rank: Newbie
timestamp: November 14, 2017, 10:45:44 pm
content: Hello,I just recently purchased a RCA WO-91a oscilloscope, and I was wondering if you could help me with a quick question.Is it possible using a BNC/RCA-adapter to plug in music into this oscilloscope?If this RCA brand uses a different plug-in than a BNC plug, is it possible to attain a different adapter that would allow me to hook in RCA audio cables?I would really appreciate any help you can provide!Kind regards to you,Brandon

author: helius
author_rank: Super Contributor
timestamp: November 14, 2017, 11:10:26 pm
content: This is a very old scope from before BNCs were invented. It probably has a SO-239 (also known as UHF) input socket.You could use a BNC-PL259 adapter together with a RCA-BNC cable.

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 14, 2017, 11:59:27 pm
content: The RCA WO-91a oscilloscope appears to use the old Amphenol coaxial "microphone connector" input.So you could use a RCA to Amphenol adapter like this:https://www.ebay.com/itm/Heathkit-EICO-Microphone-to-RCA-Adapter/182892305142Or you could simply replace that antique connector with BNC or something modern.

author: bgrebel9
author_rank: Newbie
timestamp: November 15, 2017, 01:04:29 am
content: Thanks so much! Just to confirm, would the BNC-PL259 adapter also work in addition to the amphenol-rca adapter or would it not fit? Or would the amphenol-rca simply be best to use because it cuts out the BNC adapter. I really appreciate your help—please forgive my ignorance!

author: bgrebel9
author_rank: Newbie
timestamp: November 15, 2017, 01:07:46 am
content: I appreciate your kind reply very much. Thank you!!

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 15, 2017, 01:45:48 am
content: No, that old scope uses the old Amphenol coaxial connector.The PL259 is a completely different connector that is not compatible with that oscilloscope input.

author: helius
author_rank: Super Contributor
timestamp: November 15, 2017, 02:15:26 am
content: I appear to have misidentified the connector on that picture of the scope. I can see now that it is not UHF.The mating connector would be theAmphenol 75-MC1or else one of the connectors fromSwitchcraft like the 2501F. I'm not sure if these are compatible, they appear to be the same design but the diameters or threads may differ.I never heard of these connectors before, but they are really interesting because they are hermaphroditic without any weird protuberances. You just reverse the nut to turn "female and male" plugs into "male and female".

author: Brumby
author_rank: Unknown
timestamp: November 15, 2017, 02:16:05 am
content: Quote from: Richard Crowley on November 15, 2017, 01:45:48 amIndeed. The PL259 has a centre pin which the scope connector cannot accommodate:
Using relays at their rated current? - Page 1
Forum section: electronics / beginners

author: cpitman
author_rank: Newbie
timestamp: September 02, 2023, 04:36:13 pm
content: In the US, the NEC requires wiring/breakers/etc to be rated for 80% of the current for continuous loads (3+ hours). So if I want a 12A load on a circuit, I need the wiring/breaker to support 15A.Does any of this apply to electrical components? The main example I have now is relays. If I need to switch a 12A load (and keep it closed for 3 hours or more), would a relay rated for 12A work? Or do I need one rated for 15A and have it loaded at only 80% of capacity?

author: BrokenYugo
author_rank: Super Contributor
timestamp: September 02, 2023, 05:18:25 pm
content: I'm not qualified to answer regulations wise, but it is generally considered poor form to run any electrical component at or near it's maximum rating.

author: bdunham7
author_rank: Super Contributor
timestamp: September 02, 2023, 05:33:52 pm
content: The NEC does not apply to electrical components other than those used in your building wiring. How much you derate a relay or other component in your device is an entirely separate question and the answer could range from 'none' to 'a lot'. 80% is not a good universal answer. Also the NEC 80% rule only applies to standard configurations and breakers--there are systems and breakers that are rated for use at 100% continuously.

author: cpitman
author_rank: Newbie
timestamp: September 02, 2023, 05:48:55 pm
content: Thanks, "derating" is the keyword I needed! Is there a resource you would recommend for understanding derating?I see quite a few "high spec" standards like NASA and the military, are those considered "standards"? Or are they more conservative than needed for normal commercial uses?

author: floobydust
author_rank: Super Contributor
timestamp: September 02, 2023, 06:48:46 pm
content: First classify the relay's load - is it resistive, tungsten lighting, inductive ballast or an electric motor etc. ? You have to take into account the inrush currents.There are UL and IEC approvals for relays as a component for use in a product. Not at the NEC level unless it's a device like a motor starter I believe.Many relays have no formal approvals and a "12A" rating is vague for how long it will last with certain loads or if it's fit for purpose.Example part to look at is popular T9,T90appliance relay approvals. It's current rating varies depending on the load/lifetime.
Using same power supply for two devices? - Page 1
Forum section: electronics / beginners

author: dog80
author_rank: Regular Contributor
timestamp: December 18, 2013, 07:18:18 pm
content: I have two credit card POS machines. They are identical models but programmed to accept different cards. The label on the power supplies says 9 Volts, 4 Amps but the actual voltage is around 9.2I tested the one of the machines and it draws about 100mA when idle and 2 to 3 amps when printing.Due to space constrains and since only one of them will be printing at any given time, it would be nice if I could power both using the same power supply and get rid of the other one.Is it safe to do or am I missing something?

author: minime72706
author_rank: Frequent Contributor
timestamp: December 18, 2013, 07:27:42 pm
content: I think you should be fine, but it would be a right pain in the ass if you managed to blow the fuse in the power supply, assuming it has one. You might consider putting a secondary fuse in series with each of the two POS terminals just in case, but if it were me, I'd just risk it. You wouldn't exactly be hard-pressed to find a replacement for the power supply and if it's a switch-mode with a fuse, you can usually open them to fix it.What type is it? A black box with a cable coming out of each end? A wall wart? etc.
Can a damaged op-amp output DC voltage? (Headphone circuit) - Page 1
Forum section: electronics / beginners

author: Mp3
author_rank: Frequent Contributor
timestamp: May 05, 2020, 10:22:20 am
content: I got a broken usb audio interface in the mail, it had a failed capacitor for one of the two stereo audio channels (not sure which) which took out the negative side pad with it. So i replaced the capacitor and ran a wire from the negative leg to the nearest component on the pcb trace.I plugged some headphones to test and noticed only one side worked, distorted very easily, so i disconnected and found some DC voltage on the headphone output i thought was unusual. The headphones sounded broken after trying on another device, so i think it got fried with DC voltage.However the speaker outputs sound just fine and I am not measuring DC on them.The headphone circuit has its own op-amp, and I am not sure if the output capacitor that i replaced affects both the speaker and headphone outputs. I am quite certain I will need to replace this headphone op-amp to get it working again, but I was wondering if such a thing is possible from a capacitor going bad...? (I suppose it could have shorted one of the power rails to the op-amp?)
Using SmartThings sensors with a RPi - Page 1
Forum section: electronics / beginners

author: graffitici
author_rank: Newbie
timestamp: July 04, 2014, 02:20:39 pm
content: Hi,Has anyone tried using the SmartThings sensor with an RPi? I believe they all use Zigbee. The XBee line of products are the common way tinkerers interface with Zigbee devices, but AFAIK there are many Zigbee-like standards. So even series-1 XBee modules cannot interface with series-2 XBee modules. I was thinking about getting the XBee USB dongle for this purpose, but I figured I'd ask around before investing in it.It would be cool to have access to these sensors directly, skipping the rather expensive SmartThings hub.Thanks!
Using SN75176 line drivers in one-to-many configuration - Page 1
Forum section: electronics / beginners

author: spectral
author_rank: Newbie
timestamp: September 20, 2014, 04:35:10 am
content: Hi,Just discovered this forum, and am very excited to have a new place to learn!I currently have a setup where I am sending TTL serial data from a Raspberry Pi to an Arduino, over around 25 ft, using two SN75176s to transmit/receive over the distance. I have limited understanding of the mechanism the SN75176s use, but I understand they utilize a current loop by sending inverse signals to transmit the data. In my setup I am using two 200ohm resistors bridging the data pairs on either side, but I must admit I am a little unclear on their purpose!My goal is to use a similar setup to allow the Raspberry Pi to send an identical signal to many Arduinos, (maybe ~30 for my long-term goal for this project). From the datasheet, this component can handle outputting 60mA, so I assume simply splitting the data lines to put many receivers in parallel will violate this restriction. There is probably a simple solution to the problem, but I'm not sure where to turn at this point. Perhaps this component isn't a good fit, or there is a concept I am missing here, so any help would be awesome!Edit: Here's a link to the datasheet just in case that makes it easierhttp://www.ti.com/lit/ds/symlink/sn75176a.pdfThanks!- Eric

author: David_AVD
author_rank: Super Contributor
timestamp: September 20, 2014, 06:56:03 am
content: Do a Google search for RS485 and multidrop in particular.RS485 works best when you loop in/out of each node (chain) instead of a radial (star) topology, but depending on the data rate you can get away with quite a bit.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 20, 2014, 08:15:55 am
content: It is not a current loop. The resistors are to terminate the ends of the line to reduce reflections, and should be at each end of the line, not at each node. You should also have biasing resistors to make sure that the line stays in an idle state when not driven - e.g. 1k from d+ to +5v and 1K from D- to 0V. Again only at one point, not at each node.Standard RS485 transceivers are designed to drive about 32 nodes plus the termination, but you can get ones with lower receiver load to allow larger node counts
Using soldering tweezers - Page 1
Forum section: electronics / beginners

author: Kfire778
author_rank: Contributor
timestamp: May 05, 2019, 09:40:36 pm
content: I just acquired my first set of hot soldering tweezers, the hakko fm 2023 run off of a fm 202, any advice, or links to read to learn to properly use these tools would be greatly appreciated.
using Spi arduino library  to drive max6675 - Page 1
Forum section: electronics / beginners

author: amateur_25
author_rank: Regular Contributor
timestamp: December 26, 2016, 12:28:22 pm
content: hI GUYSI need some help to ensure my understanding of how this is supposed to work.I have found a sketch online to drive my max6675 using the spi library i.e. hardware spi bus on the uno.I want to know given the attached serial timing diagram which spi mode should I use?Based on my newly found knowledge I believe it should be mode 1Is this correct?Code:void setup(){pinMode(9,OUTPUT); // configure MAX6675 CS pindigitalWrite(9,HIGH); // tell MAX6675 to read sensorSPI.begin();Serial.begin(9600);}int readTemp(){SPI.beginTransaction((SPISettings(1000000, MSBFIRST, SPI_MODE1))); // configure the SPI for this devicedigitalWrite(9,LOW); // I am now talking to the MAX6675uint16_t reading=SPI.transfer16(0); // read 16bitsSerial.println("current reading:");Serial.print(reading);digitalWrite(9,HIGH); // I am done Talking to the MAX6675SPI.endTransaction(); // release the SPI bus for others to use (i.e. SD, ethernet)if (reading & 0x0004){// sensor disconnectedreading = -1;}else {reading = reading >>3; // the reading is in bits 14..03, get rid of bit 2,1,0}return reading;}void loop(){readTemp();}
using storage ic with other pendrive - Page 1
Forum section: electronics / beginners

author: electricenthusiast
author_rank: Contributor
timestamp: December 21, 2022, 02:42:40 pm
content: I got a 1gb pendrive. When i plugged it in my pc, it said usb not detected. After long testing i found out, the pendrive is damaged but the storage ic didn't. My files are in it. is it possible to move that storage chip into other pendrive with another brand by replacing the ic to other working pendrive?

author: bidrohini
author_rank: Regular Contributor
timestamp: December 22, 2022, 11:26:36 am
content: The following videos may help you.
Using the LKM1638 with ATTiny45 help - Page 1
Forum section: electronics / beginners

author: zastil
author_rank: Newbie
timestamp: November 23, 2012, 03:27:31 pm
content: I am trying to get the LKM1638 to a attiny45 chip I know how to program it with the arduino and it works on the arduino but it's not working with a attiny45 now I am kinda new to connection pins i.e. clock, pwm and strobe. And I wonder if I cam using the right pins I have put below the pins and if you can help me match them up even if they can be, I would appreciate the help.

author: zastil
author_rank: Newbie
timestamp: November 23, 2012, 03:29:15 pm
content: I should add the only 1 unit of LKM is used so only need STB0 connected and not the other STB's.

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 23, 2012, 04:02:46 pm
content: I'm not familiar with either the LKM or the ATTiny but here is how I see it:VCC and GND are clear enough I hope.If you want to talk to the module (pseudo code):set data to outputmake STB lowFor bits is 1 to 8make CLK lowset data to bit you want to sendmake CLK highnext bitmake STB highif you want to read from the module (pseudo code):set data to to inputmake STB lowFor bits is 1 to 8make CLK lowread bit from datamake CLK highnext bitmake STB highSo what you need is 2 output pins on the ATTiny for STB and CLK, and one pin you can switch from input to output for data.Hope this makes sense...
Using the PM 6303 RCL Meter - Page 1
Forum section: electronics / beginners

author: watchmaker
author_rank: Unknown
timestamp: May 09, 2024, 06:01:40 pm
content: The owner and service manuals seem to suggest that these either work or they do not. Nothing to adjust; just replace.So other than zeroing the C before use, these are self regulating? Is there anything I should know about its use?It does agree with my Shannon Tweezers and hits the nail on resistance with both the ST and my Fluke 45.This was miscategorized in the Health and Dental section and I got it cheap, with the Phillips 4 wire Kelvin alligator clip adapter. i figured since I was starting capacitors and inductors, what the Hell.I presume I will learn how to measure capacitance manually at which point I will verify its reliability.THANKS!

author: aliarifat794
author_rank: Regular Contributor
timestamp: May 12, 2024, 08:37:01 am
content: Is your RCL meter working fine?

author: watchmaker
author_rank: Unknown
timestamp: May 12, 2024, 11:16:00 am
content: Quote from: aliarifat794 on May 12, 2024, 08:37:01 amAs far as I know, yes it works. R agrees with FLuke and Keysight 1252, and Shannon's tweezers. C agrees with Shannon's Tweezers.I zero it with the clips open to where it alternates between 0.0 pF and L on Cp.Not sure if it would have been smarter to use the money for the Deere or if it is "better" than the Tweezers, but since I am a wathcmaker, I like toys and I like to confirm measurement instruments (which I know is different than calibrate). In my old life as a statistician, the motto was "if you can't be right, be consistent".
using tp4056 moduals - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: August 20, 2021, 09:56:36 am
content: Hi all,i have a 17ah 13s 9p battery im trying to balance while waiting for a smart bms to arrive,a few cell groups are low,ie 3.8v while some are at 4.1v,i am using a tp 4056 modual at the moment to charge the cells powered from a lab psu,its realy slow tho,i want to know if i can parellel 3 or 4 tp4056 moduals together to increase the charge current?,or would all the grounds being common be a no go?

author: m3vuv
author_rank: Super Contributor
timestamp: August 21, 2021, 06:43:33 am
content: can anyone answer this?,i dont think its rocket science!

author: grrmachine
author_rank: Contributor
timestamp: August 21, 2021, 08:20:30 am
content: Are you building a 13s battery pack? Assuming you're charging a single (1S) balanced (Multiple P) cells with TP4056. Looking at a CC/CV charger architecture you could technically have them in parallel provided that the leads are extremely short and have no potential drop over the cables that don't vary the feedback on multiple TP4056's and doesn't do trickle charge at different intervals. :/ I wouldn't do that.If you have a bench power supply, you could use its CC mode to charge cells. First balance parallel cells within 0.2V of their potential. Or make a parallel pack with alike cells. Set the current limit to 0.5C of the rated pack and monitor the I, V, and charge time.Dave's got a video on this:Good luck