hybridfree/eevblog-posts huggingface dataset:
Resistor Setup.. - Page 1
Forum section: electronics / beginners

author: Ranger14
author_rank: Regular Contributor
timestamp: January 31, 2016, 02:24:01 pm
content: I have picked up a couple 1% resistor kits off ebay and they work really nice.. But I am looking to get a 5% resistor kit so I don't have search through all the 1% and makes prototyping easier.. My issue comes as I am still learning electronics and I am not sure what should be the min and max resistor value .. Cause I see they have a couple ohm resistors to mega ohm's and trying to find the right values to pick up and do they have a kit already available with quality parts ??

author: SeanB
author_rank: Super Contributor
timestamp: January 31, 2016, 03:11:36 pm
content: Don't bother with 5% resistors, just use the 1% ones, as they are all standard values in any case. Just remember than in many cases a resistor value can be quite a bit different from the value in the parts list and the project will still work. The exceptions are for gain setting, where you will be expected to use the correct value, and in many of these cases the resistor value in the parts list will call for a 1% or better part in any case.For most use cases a resistor of nominal value 1k can be any resistor from 800R to 1k5, and it will still work. This is often true for things like pull up or pull down resistors, or rersistors used for led indicators or transistor base current limiting.

author: uncle_bob
author_rank: Unknown
timestamp: January 31, 2016, 04:25:03 pm
content: HiOne resistor kit is plenty. That's true regardless of the precision of the kit. There are only a few times you need an exact resistor value "right now". When you do, a kit is a handy thing to have. That of course *assumes* you keep it stocked. What normally happens is that there are some values you use far more often than others. You run out of those and start using the ones in adjacent bins. Soon you have whole ranges of resistance values missing.The answer is not quite as simple as it may seem. You can replace resistors as you use them, one at a time. This is cost prohibitive and a total waste of time. You also can replace the entire set. Now you start building up piles and piles of odd value resistors. The third alternative (since you have cash on hand) is to buy a stock of the "normal values" and use them for most stuff. Here's what I would get:100K10K4.7K2.2K1K470 ohm220 ohm100 ohm47 ohm10 ohmThat's ten values. Not many bins to keep track of. I'd probably double up on 1K and 10K. Use these for your "normal stuff" and save the assortment for things that need it. At 1 cent per resistor, $10 will buy you a hundred of each ($12 if you go overboard on the 1K and 10K). Unless you go builder crazy, it will be a while before you need more resistors.Bob
Resistor substitution box circuit - Page 1
Forum section: electronics / beginners

author: M0BSW
author_rank: Frequent Contributor
timestamp: February 23, 2013, 07:42:04 pm
content: Hi Everyone , I've lost the circuit for a Resistor sudstitution box, does anyone know of a good no frills circuit.thanks in advancePaul

author: FenderBender
author_rank: Super Contributor
timestamp: February 23, 2013, 11:13:18 pm
content: They are all pretty much the same. Get 10-position rotary switches. Then you get 10 resistors per switch. So you'd get 10 of each type (1M, 100k, 10k, 1k, 100, 10, 1, 0.1 etc.) And then you put one of each of these resistors between the 10 pins of the switch so that each time you move the switch, you add (or subtract) a resistor to the circuit.Dave also did a video on his own and a assembled unit.You can use standard rotary switches or thumbhweel switches. There are cheap thumbwheel switches on eBay (quality is unknown, though they will probably work fine). You can also get BCD switches (binary coded decimal) which might seem trickier to setup but they are actually just as simple as a 10 position switch.

author: Circuitous
author_rank: Unknown
timestamp: February 24, 2013, 12:02:31 am
content: For a diagram and example, see:http://kripton2035.free.fr/LabTools/lbt-resistordeca.htmlDecade switches like the ones in the example are available on ebay. If you're in the US, an easy place to order these from is Adafruit.comHere's a link to the large sizehttp://www.adafruit.com/products/1082$7.50 for a pack of 5.

author: george graves
author_rank: Super Contributor
timestamp: February 24, 2013, 01:41:59 am
content: Here ya go.....http://www.digitalunderpants.com/?p=219

author: M0BSW
author_rank: Frequent Contributor
timestamp: February 25, 2013, 04:16:26 pm
content: Hey thank you everyone kind enough to answer, I thought they were more complicated than that , really appreciate your helpPaul

author: M0BSW
author_rank: Frequent Contributor
timestamp: February 27, 2013, 05:00:00 pm
content: I got a thumbwheel set on the way, and all the resistors I need , weekend project

author: pspgeek
author_rank: Contributor
timestamp: March 14, 2013, 02:55:12 am
content: QuoteHow would this be setup?

author: Nakitxu
author_rank: Contributor
timestamp: March 14, 2013, 08:26:53 am
content: Yoy have a full post explaining this in:https://www.eevblog.com/forum/projects/diy-cheap-resistor-decade-substitution-box/

author: M0BSW
author_rank: Frequent Contributor
timestamp: March 14, 2013, 07:48:36 pm
content: Quote from: Nakitxu on March 14, 2013, 08:26:53 amThis is the one I've built , & its perfect for my needs , thanks for the help
Resistor TCR in parallel and series - Page 1
Forum section: electronics / beginners

author: nukie
author_rank: Frequent Contributor
timestamp: July 25, 2011, 08:12:32 am
content: I am trying to make a 102K 5PPM resistor by soldering a 100K+2K 5PPM in series. Is this a feasible method? Does the TCR increase when resistors are connected in series?I searched high and low, all I can find on the net is this formula no.1http://rsi.aip.org/resource/1/rsinak/v79/i12/p123304_s1?view=fulltext&display=print&bypassSSO=1But then it doesn't really help because I am a maths idiot and it isn't really what I am after. Can someone please point me out in the right direction?

author: IanB
author_rank: Super Contributor
timestamp: July 25, 2011, 08:26:11 am
content: If the TCR of each of the resistors is the same, then when you connect the resistors in series the TCR of the combination will be the same as any resistor individually. You can visualize this by imagining the 100k resistor to be made up of 50 identical 2k resistors in series (divide the 100k track into 50 equal segments). Since the TCR is a property of the track width and not of the track length, then any length of track will have the same TCR including a length of 102k made from 51 equal segments.If the TCR of each of the resistors is different, then the situation is more complicated and you will have to use the formulas given in the link you referenced. If you do not understand the math then try to find someone who does. Sometime mathematics and formulas are the only answer to certain questions. (I'm sorry but I do not have time to go into it here as it is well after midnight for me, but maybe someone else can assist.)

author: nukie
author_rank: Frequent Contributor
timestamp: July 25, 2011, 12:48:24 pm
content: Thanks heaps Ian, that's what I need to know. I was worried if there's a pitfall for something simple like that but TCR is new to me.

author: ejeffrey
author_rank: Super Contributor
timestamp: July 25, 2011, 01:49:48 pm
content: The other thing to remember is that if you have one resistor much bigger than the other, the TCR will be mostly determined by the large resistor. This is simply because 100 PPM of a 100 k resistor is a lot more than 100 PPM of a 1 K resistor.This is useful because it means you can use large fixed resistors with low TCR in series with a small trimpot with a larger TCR and still get an accurately trimmable resistor with a low TCR.
Resistor to reduce voltage for motor - Page 1
Forum section: electronics / beginners

author: steveggz
author_rank: Contributor
timestamp: March 19, 2018, 01:33:32 am
content: I need to power a small 20mm mini 5v fan. I have a 5v mean well power supply but I want to use a resistor to lower the voltage to 2.80v. I tested the fan at 2.80 volts (with a vaiable power supply) and it was the quietest while giving enough air. Is it possible to just put a resistor before the fan to lower the voltage to 2.80v? Everything online talks about using a resistor for LED's. I don't get it, can you only use a resistor with constant current?My power source is 5v 6AMy mini fan is rated at 5v .150 but I want it to run at 2.80v (Its draws around 50mA at that voltage according to my variable ps)

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: March 19, 2018, 02:37:16 am
content: No problem and Ohms law will solve it for you. You can use a series resistor to reduce any voltage source AC or DC. That statement comes with BUTs, but it is still true.If it is true that your fan draws 50 mA when driven by 2.8V then the resistor needs to drop 2.2V at 50 mA. So the resistor value you need is 2.2 / .05 = 44 Ohms and it needs to handle ( 2.2V )^2 / 44 = 0.11 Watts of power.The closest standard value available is 43 Ohms and a 1/4 Watt resistor would do fine. You can get it almost anywhere electronic components are sold.DK has them for $0.10 for just one but I'm sure that you can get it many, many other places.https://www.digikey.com/product-detail/en/yageo/CFR-25JB-52-43R/43QBK-ND/2121

author: chrisl
author_rank: Regular Contributor
timestamp: March 19, 2018, 02:38:17 am
content: you can try using 3 diodes in series or a 43 ohm 1/2 w (or even a 1/4 w) resistor..

author: fourtytwo42
author_rank: Super Contributor
timestamp: March 19, 2018, 09:23:15 am
content: These fans often require more current to start so the diode solution maybe better than a resistor, trial and error is king
Resistor tolerances - Page 1
Forum section: electronics / beginners

author: MattHollands
author_rank: Frequent Contributor
timestamp: March 08, 2015, 02:15:33 am
content: Hi! I'm new here!I was wondering about resistor tolerances. Imagine I were building a high precision one off device, but only had 5% tolerance resistors. Chances are if I measured enough resistors I would find one at exactly the right resistance. Would this be as precise as buying 1% (or better) tolerance resistors, or is there something intrinsically inaccurate about high tolerance resistors e.g. Will they naturally vary over time more than an lower tolerance resistor?I hope I have been clear in what I am asking!Thanks

author: cosmicray
author_rank: Frequent Contributor
timestamp: March 08, 2015, 02:23:27 pm
content: Quote from: MattHollands on March 08, 2015, 02:15:33 amThis is like a rabbit's hole, in how precise your device needs to be, etc, etc. There are extreme examples on eevblog of resistor precision, and they usually are needed because the device/project needs that level of precision. Unless you have a calibrated DMM, you may have to question what value your DMM is presenting vs what resistance is actually present. Matched sets of resistors can, to some extent, be determined via a whetstone bridge.What resistor value are you trying to obtain ?

author: MattHollands
author_rank: Frequent Contributor
timestamp: March 09, 2015, 12:15:53 am
content: Thanks for the replies! I don't have any particular value in mind right now, I am just thinking about potentially building my own (basic) LCR meter. I haven't decided what values I would put in series with the DUT but I guess the accuracy of this resistor is quite important to the overall accuracy of the LCR reading. However I suppose as it is only a one-off I could just measure the true value of whatever resistor I use and use that for the calculations instead

author: wraper
author_rank: Unknown
timestamp: March 09, 2015, 12:41:08 am
content: With higher tolerance, likely you'll get higher temperature coefficient too and increased resistance change with ageing. Should be aware of carbon resistors too which will come with 5%+ tolerance. Of course there are low tempco high initial tolerance resistors in the wild but this is special case.

author: MattHollands
author_rank: Frequent Contributor
timestamp: March 09, 2015, 12:48:14 am
content: Ok, I have contacted where I bought my resistors from to see if I can get the datasheets for them. I suspect they won't be brilliant and will end up buying some specially for my case.Looks like I need to buy some more electronics trays so I can keep my high tolerance resistors from my low tolerance ones!
Resistor value - Page 1
Forum section: electronics / beginners

author: andrufg77
author_rank: Newbie
timestamp: May 08, 2020, 08:17:35 pm
content: Could you tell me the value of this resistor, it is from a 450w PC power source, it is located next to the large capacitor

author: Cubdriver
author_rank: Unknown
timestamp: May 08, 2020, 08:32:52 pm
content: I read it as 0.27 ohm, 5%, 20 PPM/*C Perhaps some kind of current viewing resistor in the circuit, given its low value?-Pat

author: andrufg77
author_rank: Newbie
timestamp: May 08, 2020, 08:38:46 pm
content: Quote from: Cubdriver on May 08, 2020, 08:32:52 pmOk thank you, on the circuit it says nothing, the second image shows its location and on the multimeter it does not measure any value

author: Cubdriver
author_rank: Unknown
timestamp: May 08, 2020, 08:49:18 pm
content: Quote from: andrufg77 on May 08, 2020, 08:38:46 pmI'm wondering if it might be a fusible resistor, given the pink body and that it appears to have burned open. What units are on the scale its next to - cm or inches?-Pat

author: andrufg77
author_rank: Newbie
timestamp: May 08, 2020, 08:52:32 pm
content: Quote from: Cubdriver on May 08, 2020, 08:49:18 pmThe resitor measures 1.5cm

author: Cubdriver
author_rank: Unknown
timestamp: May 08, 2020, 09:41:11 pm
content: Quote from: andrufg77 on May 08, 2020, 08:52:32 pmIn that case it appears to be a 3w resistor and this Yageo at Digi Key looks close:FKN3WSJR-73-0R27-Pat

author: andrufg77
author_rank: Newbie
timestamp: May 08, 2020, 10:13:42 pm
content: Quote from: Cubdriver on May 08, 2020, 09:41:11 pmThank you that´s very helpful

author: Cubdriver
author_rank: Unknown
timestamp: May 08, 2020, 10:19:20 pm
content: You are most welcome.

author: ArthurDent
author_rank: Super Contributor
timestamp: May 09, 2020, 03:07:21 pm
content: The question is what caused this fusible resistor to fail. If you just replace it, the replacement may fail as well unless whatever the resistor is connected to is functioning properly. You may want to carefully check the rest of the power supply and buy a few extra replacement resistors, just in case.

author: drussell
author_rank: Super Contributor
timestamp: May 09, 2020, 03:44:21 pm
content: Quote from: ArthurDent on May 09, 2020, 03:07:21 pmIndeed. While it ispossiblefor something like this to fail during some random transient and the rest of the supply to be OK, the vast majority of the time something like the input fusible resistor would be murdered by something downstream rather than dying on its' own.Check carefully for shorts, especially whatever switching transistor is actually doing the power, etc. and seriously consider powering it up on a dim-bulb and/or Variac if you have one available. Anyone can make a dim-bulb "tester" but not everyone has a Variac on hand to master-control it.

author: andrufg77
author_rank: Newbie
timestamp: May 10, 2020, 02:12:58 am
content: Quote from: ArthurDent on May 09, 2020, 03:07:21 pmOk thank you i will do that
Resistor Value Calculation for Hysteresis - Page 1
Forum section: electronics / beginners

author: wbspathum
author_rank: Newbie
timestamp: September 27, 2015, 07:42:19 am
content: Hi All,i already asked this question inhttp://electronics.stackexchange.combut they didn't helped me to solve it, they just bulling on me. im asking this because i don't know. if i knew i wont be here asking this question.ok... this is my problem.i need a Comparator with Hysteresis circuit for the project im currently working on. and i found a circuit in LM393 datasheet (i have attached a screen shot of it) but i don't know how to solve that equations.i really appreciate if someone can show me the steps to solve the equations to get all resistor values..my upper threshold voltage(TH1) should be 2.3Vand lower threshold voltage(TH2) should be 0.3Vand V out High should be 5V and Low should be 0Vi hope im clear enough. if you need more details, please comment.

author: KJDS
author_rank: Super Contributor
timestamp: September 27, 2015, 08:11:31 am
content: What are you using the output for? That will determine RL.Set R1 to 10k as a starting point and Vref to be 1.3V. Then you should have enough known parameters to calculate R2 and Rs.If it doesn't work out, change R1

author: wbspathum
author_rank: Newbie
timestamp: September 27, 2015, 08:14:30 am
content: Quote from: KJDS on September 27, 2015, 08:11:31 amim sending it to a Micro controller.
Resistor value on schematic shown as "S.A.T" What does it stand for please? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: December 04, 2012, 08:20:54 pm
content: Reading a schematic for an EIP frequency counter a resistor is shown as 2% S.A.T It might be 5.A.T Can anyone tell me what it stands for please?Schematic attached, resistor outlined in pink. Thanks

author: Smokey
author_rank: Super Contributor
timestamp: December 04, 2012, 08:36:06 pm
content: Not sure what that means, but there is usually another page somewhere that has a table of reference designators, values, and package sizes. You might want to look up the number there.

author: Fraser
author_rank: Super Contributor
timestamp: December 04, 2012, 08:47:12 pm
content: I believe this is the same as "Select on Test" (S.O.T), likely 'Select At Test'.This is a component whose value is chosen during testing using a substitution box or resistors. It's a 2% tolerance part so the exact value is likely important to the operation of the circuit in which it operates.From the circuit it would appear that this resistor works with R122 at the Mixer 1 LO input to set a DC level at that point.Fraser

author: Chris Wilson
author_rank: Super Contributor
timestamp: December 04, 2012, 09:04:50 pm
content: That might figure as I am having trouble with region of the circuit, maybe a biasing issue. If I warm Q12 the counter works on a particular range. I changed it for a brand new one with the same issue. I believe Q12 itself is fine, but warming it *may* alter its biasing needs, perfectly normally? If I measure the collector voltage referenced to ground I see 0.22 volts. If I warm Q12 even slightly I get a slowly, smoothly rising voltage, collector to ground, and at about .52V the counter starts reading on Band 2. Continue to warm Q12 (within very conservative bounds, not mad hot), I see up to 11.9V.As Q12 is allowed to cool to ambient the collector to ground voltage drops smoothly and slowly again, at around 0.5V the counter stops seeing the 10MHz input at 50mV, and reads zeros again. By the time Q12 is back to ambient I see 0.22V again. I am admittedly out of my depth, but feel the problem is local to this section of the circuit.Base V is about 11.66V Emitter V is about 12.07V

author: w2aew
author_rank: Super Contributor
timestamp: December 05, 2012, 04:33:39 am
content: Fraser has it right - S.A.T. means "Select At Test" - a value was adjusted/chosen at the end of the manufacturing line to make the circuit perform properly. Usually this is done where a trimmer won't do, due to physical or performance reasons...

author: Chris Wilson
author_rank: Super Contributor
timestamp: December 07, 2012, 07:55:35 pm
content: Thanks for the info.
Resistor values for non linear DAC - Page 1
Forum section: electronics / beginners

author: Jaunedeau
author_rank: Regular Contributor
timestamp: May 29, 2023, 10:14:02 am
content: Hi,for some project*, I need to ouput a value out of 64 different possible ones. I'd like to do this with a resistor ladder**. But my values are not distributed linearly. Using a N^2 resistor ladder, I would need 9 bits to get the precision I need (1/350), versus 6 if the values where linear.I do not have enough GPIOs available on my MCU, so I could either :- lower my precision requirements- find non linear values for the resistors that would allow me to reduce the number of resistors with less diminution of the precisionI was going to write a program to explore resistors combinations from the E series to find the best solution for a given cost***, but then I thought I might not be the first one to encouter this problem and solutions or algorithms might already exist. Does someone know of such a thing ?Thank you,J.* : analog rgb video output from an mcu** : because it's cheap, easy to source, delay is ok and I'll learn more than using an I²C DAC*** : number of GPIOs + number of resistors

author: Picuino
author_rank: Super Contributor
timestamp: May 30, 2023, 01:54:57 pm
content: You can combine a linear ladder resistor network fed with a PWM signal and filtered output to increase the resolution of the DAC.Edit:https://www.edn.com/hybrid-pwm-r2r-dac-improves-on-both/

author: Picuino
author_rank: Super Contributor
timestamp: May 30, 2023, 02:20:03 pm
content: Another solution you could think of is to use a linear resistor ladder and, at the output, perform a non-linear signal transformation like the one you are looking for (such as a gamma correction).

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 30, 2023, 04:00:45 pm
content: Quote from: Jaunedeau on May 29, 2023, 10:14:02 amSo, how about you specify the relative values you do need, between 0.0% and 100.0%?Or is it just the typicalgamma correctionof 1.8, 2.2, or 2.8?

author: Jaunedeau
author_rank: Regular Contributor
timestamp: May 30, 2023, 05:19:10 pm
content: I have have palettes I want to reproduce. On "modern" computers (e.g. the Atari ST or the Amiga) they are basically evenly spread, but some that come from chroma + lum analog generation + uncontrolled effects (e.g. atari 2600) or even some ancient forgotten black magic (C64) can be harder to explainPWM is unfortunately not an option with 10 mcu cycle per pixel.
Resistor watt rating for high power opamps - Page 1
Forum section: electronics / beginners

author: sean87
author_rank: Regular Contributor
timestamp: May 31, 2017, 08:40:41 am
content: Let's say you want to use a power opamp to amplify a small signal into a big one. The opamp would output something like 50V@2A.In this case, does the resistors of the feedback/input (e.g. R1 and R2 in the above picture) stage need to be of a high watt rating? Or I can get away with normal resistors or even SMD 0806 resistors? which are maybe around 250mW rated or less?

author: danadak
author_rank: Super Contributor
timestamp: May 31, 2017, 09:39:56 am
content: Generally speaking no, The Power OpAmp inputs "look" electrically likea normal hi-z input, so no significant current is drawn, and input and fdbkRs just function as a voltage divider to set loop feedback factor.Regards, Dana.

author: dmills
author_rank: Super Contributor
timestamp: May 31, 2017, 09:45:19 am
content: R2 power dissipation is set by the maximum output voltage P=E^2/R in the obvious way.R1 power dissipation is set by the maximum input voltage (same eqn).This follows from the observation that the inverting input of the opamp is a virtual earth node.Note that resistors have a maximum voltage as well as a maximum power rating, both must be respected.Regards. Dan.
Resistor Wattage Rating - Page 1
Forum section: electronics / beginners

author: mcintire265
author_rank: Newbie
timestamp: June 05, 2016, 02:44:38 am
content: First of all been watching the YouTube channel for a long time. First post however here.Found a bunch of resistors in a box I forgot I had and was wondering the easiest way to tell the rated Wattage. They are smaller 4 band so it's not readily identifiable.Any suggestions greatly appreciated.And yes by my post you can probably tell I'm an American haha. Flood city area Pennsylvania.Sent from my SM-G930V using Tapatalk

author: Brumby
author_rank: Unknown
timestamp: June 05, 2016, 03:32:35 am
content: First suggestion is to take some photos - decent quality and reasonably close, please. It would be good to have a ruler in the picture for scale.Then we could offer some ideas.

author: Simon
author_rank: Unknown
timestamp: June 05, 2016, 06:56:11 am
content: The wattage loosely relates to the physical size of the component. Most resistor materials can only work up to a certain temperature and given the same sized component to dissipate more power you would need to increase the temperature. So in order to have the same maximum temperature for any given wattage you need to increase the size of the resistor. There are some exceptions where you get some older and poorer components that are larger for same wattage or on the flip side you get some modern resistors which are more expensive and more compact that can dissipate more power in the same package size. It's never a good idea to use any component at its maximum rating anyway and even a resistor datasheet can make for interesting reading. If you post the dimensions someone can cross-reference with some known stock and give you a rough idea.

author: Ammar
author_rank: Regular Contributor
timestamp: June 06, 2016, 11:06:19 pm
content: A typical through hole resistor will be rated at 1/4 W. If they are smaller than that they are probably rated at 1/8 W. However, as stated before pictures with some kind of scale would be useful as this is just a stab in the dark.
Resistor  ???? - Page 1
Forum section: electronics / beginners

author: K.primdahl.8270
author_rank: Newbie
timestamp: April 25, 2024, 08:54:12 pm
content: I'm puzzled by this resistorCan anyone help please

author: Zero999
author_rank: Super Contributor
timestamp: April 25, 2024, 09:32:15 pm
content: 1 Ohm.It looks fine.Have you measured it using a mutimeter?

author: Herschel
author_rank: Regular Contributor
timestamp: April 27, 2024, 12:26:35 pm
content: https://www.digikey.in/en/resources/conversion-calculators/conversion-calculator-resistor-color-code?_gl=1*1d14nck*_up*MQ..&gclid=EAIaIQobChMI-LiPqK_ihQMVaYbCCB22yA3REAAYASAAEgI6OPD_BwE80 ohm 1% ?is the second band grey or silver? i have never seen a resistor with 2nd silver band like this before...just use a mulimeter...

author: soldar
author_rank: Super Contributor
timestamp: April 27, 2024, 03:06:33 pm
content: blk-grey-blk-blk?180?

author: Ian.M
author_rank: Super Contributor
timestamp: April 27, 2024, 04:59:35 pm
content: Quote from: soldar on April 27, 2024, 03:06:33 pmThe value wouldn't start with black unless the multiplier band was silver, and 180 would be BROWN grey black black. The grey/silver band has a sheen to it that differs from the pigment bands so is probably metallic silver rather than grey. Perhaps this color-balanced zoomed in view of it will help.Its a tossup between:Brown (1) Black (0) Black(0) Silver (/100) Black () = One ohm, with a mystery black final band (as black isn't a tolerance color)and:Brown (1) Black (0) Black(x1) Silver (10% Tol.) Black (250ppm TC) = Ten ohms, 10% tolerance 250ppm temperature coefficient.

author: soldar
author_rank: Super Contributor
timestamp: April 27, 2024, 05:31:33 pm
content: Quote from: Ian.M on April 27, 2024, 04:59:35 pmYou are correct, of course. I had a brain fart there. I blame it on the flu I am undergoing.

author: Herschel
author_rank: Regular Contributor
timestamp: April 28, 2024, 05:22:19 pm
content: if the second band from the nearest ist band is silver, it would be a 10ohm resistor. So what about the last black band? that depents from where you got that resistor. if its from a cheap chinese powersupply, that makes sense. i have seen a lot of things like this before...or if the second band is grey, which makes the last(Tolerance band brown making it an 80 ohm resistor with 1% tolerance)anyway check your resistor here:https://www.digikey.in/en/resources/conversion-calculators/conversion-calculator-resistor-color-code?_gl=1
Resistors: 0.4W size compared to 0.25W size - Page 1
Forum section: electronics / beginners

author: tron9000
author_rank: Frequent Contributor
timestamp: May 26, 2016, 10:34:52 am
content: (I did think of this until now)So just doing a bit of stock taking and found a box of 0.4W resistorsnow compared to a 0.25W one they are noticeably smaller. They are both metal film type, same resistance, same tolerance, but the one that takes more power is SMALLER?Does anyone know why this is? You usually associate larger size with more power don't you?

author: cowana
author_rank: Frequent Contributor
timestamp: May 26, 2016, 10:48:29 am
content: It all comes down to the maximum temperature.For a given power dissipation, the smaller one will get hotter - but as long as it can cope with that, there isn't an issue.So although they're both metal film, I'd imagine there are some subtle differences in the materials used which allow the 0.4W one to have a much higher maximum temperature.Andy

author: RogerRowland
author_rank: Regular Contributor
timestamp: May 26, 2016, 10:49:53 am
content: ... either that, or you mislabelled the boxes

author: tron9000
author_rank: Frequent Contributor
timestamp: May 26, 2016, 11:38:11 am
content: Quote from: RogerRowland on May 26, 2016, 10:49:53 amnope I checked the part number on the suppliers site!

author: freddy114234
author_rank: Newbie
timestamp: June 01, 2016, 09:44:21 am
content: mainly due to the thermal conductivity of ceramic core(as the same size, the percentage of aluminum oxide is proportional to the power rate ).

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 01, 2016, 10:55:17 am
content: The specification of max. power dissipation of a resistor is always coupled with its max. body temperature and in turn with its stability.These parameters also depend on the technology (Thin Film, Thick Film, or others), and the case size.For SMD components, the cooling pads on the PCB play an overwhelming role in the cooling aspect.Small resistors can not transfer as much heat over their soldering junctions, than bigger ones, and heat up more, reducing their max. power, although the naked components may have the same specification.Here's an example for leaded resistors, with randomly chosen values:If you have a thin film (precision) resistor of a certain case size, you may apply 0.25W for 125°C max. hot spot temperature, which gives 0.1%/yr. stability, and 0.4W for 155°C hot spot temperature and 0.5%/yr. stability ("Power Mode").Thick Film resistors of the same case size may even allow higher power dissipation, first due to the higher robustness of the "Thick" film, and second, because thick film resistors are mostly less stable, anyhow.The specification of the manufacturers are mostly valid for the naked component only, but do not account for the cooling problem by air flow or by PCB cooling areas.These arguments may well explain the characteristics of your resistors.Frank
Resistors - carbon composition vs carbon film vs metal film? - Page 1
Forum section: electronics / beginners

author: prefabpeti
author_rank: Newbie
timestamp: February 09, 2022, 01:43:09 pm
content: Hello all, I'm working on my 1989 Pioneer laserdisc player still.I'm trying to source several resistors but I seem to have opened up a can of worms as to what type to get.I'm led to believe this age of appliance will have carbon composition resistors and I should try to go like-for-like.From what I can find, carbon composition can handle spikes in power better compared to newer types - but are susceptible to damage from moisture and over time can go outside of tolerance.Carbon film and metal film appear to be better in most ways.Can anyone offer advice on whether I should stick with original type or not?For reference I've attached a photo of the area of one of the boards in question.

author: Gyro
author_rank: Super Contributor
timestamp: February 09, 2022, 01:53:05 pm
content: Carbon composition (and it's ceramic composition replacement) is relegated to high pulse applications these days, as you say. They really have no place in normal analogue circuitry (they also have bigger package sizes.The resistors that you have circled all appear to be carbon film, 1/8W and 1/4W. There is no point in changing them, unless they have failed. All of the ones shown look to be in perfect condition. You are likely to risk more damage to the PCB in changing them for metal film than any likely benefit.The best policy is to leave things alone unless they are faulty.

author: prefabpeti
author_rank: Newbie
timestamp: February 09, 2022, 03:08:07 pm
content: Thank you @Gyro!Something to bear in mind is this is a circuit that has been shorted. I believe the short has been resolved (as this particular appliance has lots of wiring looms connecting the different boards - the wires are quite fragile and reassembly damages them easily. I've repaired a number of crimped wires already). I'm looking at replacing any resistors near the two transistors that getting overheated.Perhaps I need to go back to the drawing board - if the transistors are still getting hot, perhaps the short is still there.

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 09, 2022, 04:43:39 pm
content: A failed or over stressed resistor usually gives a lot of visual clues, you can overheat them to a point of blackening the body and they'll often still work.

author: TimFox
author_rank: Super Contributor
timestamp: February 09, 2022, 04:46:38 pm
content: If you have good reason to suspect an individual resistor (such as the visual clues for overheating mentioned above), a relatively mild overload can result in a measurable change in value, without outright failure. To test the resistance, however, you need to disconnect one side of the resistor from the circuit, which must be done carefully (also mentioned above).
Resistors question - Page 1
Forum section: electronics / beginners

author: 10101
author_rank: Contributor
timestamp: August 02, 2015, 04:35:00 pm
content: I need help finding the voltage in the voltmeter please (image below).Could you please explain how to solve it ?Thanks in advance

author: IanB
author_rank: Super Contributor
timestamp: August 02, 2015, 04:43:09 pm
content: Find any node or nodes in the circuit where the voltage is not already stated. Label these unknown voltages with names, such as V1. Now use Ohm's law to write equations relating the unknown voltage(s), the resistance values, and the currents through those resistors. Do a current balance (all currents into and out of a junction must sum to zero). Solve the resulting equations for the unknown voltage(s).

author: PSR B1257
author_rank: Frequent Contributor
timestamp: August 02, 2015, 04:53:38 pm
content: QuoteApart of the explanations above, it's just a voltage divider. The resistor across the supply is irrelevant, if you have an ideal source (i.e. no internal series resistance)

author: 10101
author_rank: Contributor
timestamp: August 02, 2015, 05:00:35 pm
content: Thx to bothmy doubt was the 2nd parallel resistor added to the voltage divider,but since it's irrelevant, great !

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 11, 2015, 06:58:59 pm
content: true, it is a trick resistor. So to finish your homework, if the supply reads 86volts then the meter reads 11v
Resistors, Resistor chips, Resistor networks/strips - Page 1
Forum section: electronics / beginners

author: banedon
author_rank: Regular Contributor
timestamp: August 25, 2013, 04:07:51 pm
content: Hi guysCan someone advise what (if any) are the benefits of using resistor networks & resistor chips over just resistors. Is it simply space saving/simplcity of design? And should a strip or chip be used?Examples:Chip -http://uk.farnell.com/bourns/4814p-t01-472lf/resistor-network-4k7/dp/9357432Strip -http://uk.farnell.com/bourns/4609x-101-472lf/resistor-network-9-pin-4k7-2/dp/9357025Also, are there any downsides of using such devices?Many thanks for any advice!Mike

author: ConKbot
author_rank: Super Contributor
timestamp: August 25, 2013, 04:22:02 pm
content: For the resistor networks, you can save on space, where you need a lot of resistors in of the same value in a small space, I.e. a 1206 sized network can have 4 resistors, and it lowers your part count for assembly, plus you don't need to break out the tiny tips for the pick and place like if you were using 0402's or 0201s. Or the strip that you linked can provide a 4.7k pull up/down for an 8-bit bus with one device, so for automated assembly, the pick and place would just stuff that and be done, rather than having to pick, form, cut and stuff 8 separate through hole resistors.The resistors in an IC package depend on the specs, but you can get some where there are matched pairs, or matched sets of resistors (I.e they may be within 1% of the nominal value, but match each other within 0.1%) Or for thermal coupling, so that when one resistor heats up, and the resistance changes, the other ones mostly match. This would be used more in a precision amplifier application.

author: banedon
author_rank: Regular Contributor
timestamp: August 25, 2013, 04:51:59 pm
content: Many thanks, ConKbot.My next (2nd) project is trying to design an EEPROM programmer and so I need to use some pull up resistors for both the 8 bit data and 13 bit address buses and wondered if these would do the trick - it seems so.Again, many thanks!Mike

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 25, 2013, 05:43:20 pm
content: In SMD manufacturing, each pick 'n place action is calculated to cost 5 Cents, where the single components cost tenths of Cents and perhaps a few cents for the array.Arrays of 4 (or 7-8) independent resistors are used in the PCB layout for µC bus lines for EMC measures.The other leaded array with a common connection is used for pull-up of transistor / driver arrays, but there is no convenient SMD counterpart.That's a similar problem like SMD capacitor arrays with common ground.Frank
Resistors with unknown purpose - Page 1
Forum section: electronics / beginners

author: sonnytiger
author_rank: Frequent Contributor
timestamp: April 30, 2015, 08:38:08 pm
content: I understand how the circuit works for the most part (micro controller pulls pin low or high to turn on one or the other led) but I don't get why the 330 ohm resistor is there just sucking up current for what seems like no reason. And it is directly connected across the supply (albeit through the SIP resistor array).Thanks for any help!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 30, 2015, 08:40:00 pm
content: Surely you mean to ask if the 150 ohm resistors are there for no apparent reason...??The 330 ohm resistors are current-limiting the LEDs. When the MCU pins are high or low, the LED to GND (via 330 ohm) or to VCC (via the other, not shown) lights up.And, the 150 ohm resistors I believe are there to shunt the LEDs when the MCU pins are tristated, so that the LEDs don't quite light up. 150 seems awfully low for this, but I think that is the purpose.Tim

author: sonnytiger
author_rank: Frequent Contributor
timestamp: April 30, 2015, 09:07:19 pm
content: yes sorry, the 150 ohm onesthat makes sense, otherwise they would probably dimply light up, eh?

author: dom0
author_rank: Super Contributor
timestamp: April 30, 2015, 09:16:57 pm
content: A little bit, yes, eh?

author: sonnytiger
author_rank: Frequent Contributor
timestamp: April 30, 2015, 09:59:16 pm
content: You're not using it right!
Resolver sensor with stm32 - Page 1
Forum section: electronics / beginners

author: baksuz
author_rank: Newbie
timestamp: March 12, 2019, 02:53:23 pm
content: Hi everyone,I am just interested did any one ever find a way to connect resolvers outputs directly to microcontroller and was able to sample them.Resolver has sin and cos negative and positive modulated signal.Even if that is impossible is there any why with minimal hardware to connect it to microcontroller and do sampling in it, where the output will be a envelope signal of that modulated one.Thank you for your time

author: capt bullshot
author_rank: Super Contributor
timestamp: March 12, 2019, 03:20:12 pm
content: I didn't do that in that particular way, but why not?To my knowledge, one can convert resolver output to digital in some ways:- Resolver to digital style (this is kind of a PLL tracking the speed and position). There are some chips operating this way.- Synchronously rectifying the output, then sampling the resulting sin / cos tracks like any other encoder that has the typical sin / cos output- Sampling the resolver signal at the peak voltage.All of these methods require access to the excitation signal to generate either the synchronous rectifier control or the sampling signal. Depending on the particular resolver and its cable length, one might need some phase shift here.Typical exictation frequencies are within the 400Hz ... some kHz range, modern MCUs (including the STM32) should have enough computing power to do at least the third mentioned method.You should provide the excitation reference to a timer input to create the phase shift and ADC trigger, and convert the resolvers output signal to a voltage range suitable to the ADC (one might get away done with some resistors),.Using the second mentioned method (synchronous rectifiying) provides some more level of noise / disturbance suppression. By providing some oversampling (e.g. about 10 ... 20 samples per excitation frequency period) a MCU should also be able to achieve this.So my answer is: No, I haven't done that this way yet, but from my experience I'd say it's achieveable.

author: jmelson
author_rank: Super Contributor
timestamp: March 12, 2019, 07:00:08 pm
content: Quote from: baksuz on March 12, 2019, 02:53:23 pmA resolver is a pair of transformers whose magnetic coupling varies with shaft angle. There is no simple way to read the position. A very good chip to do it is the Analog Devices AD2S1200, but it is a tad bit expensive. I make a board that is mostly the reference circuit for that chip, used in motion control applications.Jon

author: Benta
author_rank: Super Contributor
timestamp: March 12, 2019, 07:25:32 pm
content: In principle you can, but it needs damn fast ADCs.Much easier and cheaper to do an analog demodulation and just read the sin/cos with the ADC.
Resonance problem between switchmode power supply and electronic load - Page 1
Forum section: electronics / beginners

author: skysurf76
author_rank: Regular Contributor
timestamp: October 11, 2018, 09:27:30 pm
content: Its been my job over the last couple of months to come up with a test/adjustment procedure for MVP8 switch mode power supplies (datasheet attached). When I started all we had for loading was a bunch of 250 watt wire wound resistors of various (usually inconvenient) values. I needed an electronic load for my lab at home so I ordered a KL238 300 watt DC electronic load from ebay and took it to work.The model of supply we use has 6 modules with 7 voltages. (-24/-2.2)(12/-5.2)(24)(-12)(5)(5)The DC load was working great for every module. I could load them up their rated power and the supply would regulate the voltage to its specification. When I got to the -5.2 volt output everything changed. The voltage started at -5.2 and with only a 1 amp load the voltage would drop to below -6 volts, after about 4-5 amps the voltage would then jump into the low -4's. I could also hear a high pitched whining coming from the module. After verifying this behavior across several supplies I almost convinced myself that there was a serious design problem with the -5.2 volt module. Then it hit me and I realized the voltage output as I increased the load was that of a resonant circuit. I took one of the available 250watt wire wound resistors and put about a 2 amp load on the -5.2 volt rail and its voltage held steady, and with no whining.I'm assuming the control circuitry in the load has a frequency of operation similar to the switching being done on the -5.2 volt output. My question is if there is anyway to verify my theory and overcome it. If this were a resonant LC circuit I would just add capacitance to change the resonant frequency, but seeing as how the control circuits in both devices are causing it I don't think a capacitor would change anything.I really do find this phenomenon very interesting and would love to hear any knowledge or advice anyone might have on the subject.

author: exe
author_rank: Unknown
timestamp: October 12, 2018, 10:59:08 am
content: Two control loops (in psu and in the load) got in conflictI'd try a resistor in series/parallel with the load, this should move operating point of the load and may help. But this will affect readings and settings.PS I had the same with my DIY load which I use as a resistor (no chopping / step response / etc). I just slowed down its response with a 10nF cap in feedback loop, but that was an invasive change.BTW if your load has 4-wire measurement you can add external compensation.
Resonant choke V conventional capacitor smoothed HV supplies. - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: August 30, 2012, 09:13:42 pm
content: If I were to convert a high voltage (tube linear amp) power supply unit from using a big resonant choke and a 4uF oil filled cap for smoothing a bridge rectifier circuit on the secondary of the HV transformer to a conventional capacitor smoothing on the bridge output, using either 2 big oil filled caps in series (60uF each, so 30uF at doubled the single caps WV rating), or an array of electrolytics giving a similar or gretaer capacitance figure, the output voltage will rise. Is this solely due to losing the resistance of the resonant choke's winding? Or is it more complex? Thanks. The PSU is commercially made by Henry Electronics, USA. The PSU is 3 phase, I am told quite a lot of people have done a "remove the resonant choke, up the microfarads substantially, alter the bleeder resistor values, and run off the outer two of the three transformer windings on single phase" mod. I don't doubt it's possible, just need to get a grasp of what the implications of removing the choke are. As standard the choke is resonated for smoothing the UK's 50Hz mains cycle with the 4uF smoothing cap (oil filled).Original circuit (3 phase, albeit a higher voltage transformer than mine ,but circuit wise identical) and the circuit I have seen with the modded phases and smoothing circuit, Thanks