hybridfree/eevblog-posts huggingface dataset:
Resistive touch panel - image distortion - Page 1
Forum section: electronics / beginners

author: aleksey_au
author_rank: Newbie
timestamp: May 18, 2016, 12:40:40 am
content: I have bought Fujitsu Feather Touch resistive NC01111-T222 touch panelit works very well but I see some image distortion:the screen is like covered by millions of very small dots that shimmer by different colors if viewer moves.I attached the photo, on the left lighter side the grid is actually the borders between physical pixels of LCD,it is visible that the borders and pixels are distorted.Is it the effect of spacer dots or what?Is it possible to find the resistive touch panel without image distortion?Where is the good opto-electronics forum about touch panels?
Resistor and capacitor on mosfet gate? - Page 1
Forum section: electronics / beginners

author: fubar.gr
author_rank: Unknown
timestamp: February 24, 2015, 03:42:17 pm
content: What is the purpose of R4 in parallel with C3 driving the mosfet gate in this desulfator circuit? I've seen resistors in series with the gate before, but never with a capacitor in parallel.

author: nuno
author_rank: Frequent Contributor
timestamp: February 24, 2015, 07:29:44 pm
content: I think it's an old technique to help in fast turn off. When you have the FET ON, the voltage across the cap is 0V (R4 ensures that by shorting C3 and we're assuming some time for things to stabilize); then you switch the half-bridge to 0V (2N3904 -> off, 2N3906 -> on) which puts the capacitor in parallel with the FET's gate-source capacitance which is charged to Vcc, thus discharging it quickly to some point "in the middle" by having charge move from G-S to C3 without resistance (well, almost, there's the BJT + parasitics in the path). The faster the FET switch off, the higher the voltage transient obtained from the coil (dv = L (di/dt)).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 25, 2015, 02:11:09 am
content: As should be expected for the purpose and mechanism, the circuit itself is also voodoo, so don't read too closely into it.An R||C is actually useful for driving BJTs, in many cases, because of the lower input voltage. Example:Tim
Resistor and capacitor paralleled across LEDs in car instrument cluster - Page 1
Forum section: electronics / beginners

author: jono80
author_rank: Newbie
timestamp: June 23, 2021, 02:12:45 pm
content: I’ve been looking at car instrument clusters (this one’s out of a 2010 Toyota Hilux). The circuitry to drive some indicator LEDs (eg. for low oil pressure, check engine, brake etc.) is a common 12v positive supply with the ECU (or sensor) providing the path to ground via a current limiting resistor (on another part of the PCB, not shown in the pic). There is a capacitor and resistor in parallel with some of the LEDs and I’m curious as to what this would be for? For some LEDs there is no capacitor or resistor, for others there are both or only the capacitor or resistor.If I was guessing it might be ESD protection? Or to prevent capacitive coupling causing the LED to light from neighbouring traces (unlikely at this voltage?)Anyone know or care to hazard a guess? It might be related to how each LED is driven (eg. by ECU or by a simple switch like oil pressure)…

author: sigma_xi
author_rank: Contributor
timestamp: June 23, 2021, 02:39:36 pm
content: Could be a snubber to protect the LED from the large transients that can occur in car supply rails (e.g. load dump). The parallel resistor discharges the capacitor in case there is no path to ground. Although usually TVS diodes are used to protect circuits from these transients.

author: Benta
author_rank: Super Contributor
timestamp: June 23, 2021, 04:05:15 pm
content: It doesn't even have to be a load dump (which is worst case).A car is an incredibly "dirty" environment when it comes to spikes and other noise.If the indicators are incandescent bulbs it's no problem. But with LEDs, flashing or ghosting from noise is an issue.The wire harness from ECU to dashboard can easily be a meter or longer, plenty for picking up noise.

author: Roverfan
author_rank: Contributor
timestamp: June 25, 2021, 09:22:17 am
content: My guess is its purely for aesthetics, softer user experience. The capacitors turn off leds slower. This is expected in the modern world, as a led going off instanly is too much of a shock.On some circuits it would be expected that the light turns off instantly, others would need to be soft close.

author: bigk1
author_rank: Newbie
timestamp: June 25, 2021, 11:53:58 am
content: Quote from: Roverfan on June 25, 2021, 09:22:17 amThis ^ If you notice, the capacitor / resistor are for the LED's with user functions (cruise, 4wd etc). The one's without are for errors (diesel low, engine oil etc). User functions are a normal notification, but you want that "shock" to draw attention to problems.Cars are dirty environments but most things now communicate over CAN bus with the power filtered at every major electronic device such as instrument clusters, HVAC ECU etc.

author: krzysssztof
author_rank: Contributor
timestamp: June 26, 2021, 06:41:40 pm
content: Resistor might be there to bleed residual current (potentially induced by other circuits in the proximity?).Even microamps can cause LEDs glowing what would be irritating, especially at night.
Values needed for 15A 110v RC network - Page 1
Forum section: electronics / beginners

author: Psburg
author_rank: Newbie
timestamp: September 13, 2020, 04:29:26 am
content: What resistor and wattage rating is needed for connecting this to 110v 15A outlet, and what capacitor should be used? Do I just use Ohm's law to get the resistor value (=7.3Ω)? and the wattage rating, V x I (1650W?)? (or even just open ended without the inductor)
Resistor Array orientation - Page 1
Forum section: electronics / beginners

author: relax
author_rank: Newbie
timestamp: March 27, 2019, 12:53:37 am
content: Hi,today was the first time that i had a few resistor networks in my hand and of course i ran into the orientation trap. I thought "resistors, direction won't matter". Well, I've learned my lessonBut there is one thing i don't understand yet.In the project there are Bourns 102 circuit resistor networks (isolated) and 101 circuit bussed resistor networks with a common pin.From my beginner understanding the orientation of the resistor array should only matter on the 101 version with the common pin, but why does the 102 one has the little dot to mark pin 1 as well? Why does it matter if they don't have a common pin?Thanks in advance

author: David Hess
author_rank: Super Contributor
timestamp: March 27, 2019, 03:49:54 am
content: Quote from: relax on March 27, 2019, 12:53:37 amThey have the same common pin even though it does not matter on the 102 version because they use the same mold for the packaging.

author: Brumby
author_rank: Unknown
timestamp: March 27, 2019, 06:55:34 am
content: It is actually rather uncommon for multi pin packages to be insensitive to orientation. The need for pin identification is, thus, pretty much universal.The molds used to encapsulate devices will have the identification indicator included. Since these molds aren't cheap to make, using onewitha pin indicator for a device which doesn't need it is simply good economics.

author: Daixiwen
author_rank: Frequent Contributor
timestamp: March 27, 2019, 07:17:09 am
content: For regular electronics it doesn't matter but for top audiophile gear you need to take into account the fact that the electrons, having a negative charge, prefer to flow from a high number pin to a lower one and not the other way round. Putting the package in the correct orientation will give you deeper bass and a better spatial definition (did I get this right?)

author: babysitter
author_rank: Frequent Contributor
timestamp: March 27, 2019, 08:32:39 am
content: Quote from: Daixiwen on March 27, 2019, 07:17:09 amExcellent advice, dear audiophool-oriented friend!And also forget the poor lady that does optical inspection for 8,50€/hr who has to strain her neck for reading the marking if placed the wrong way.

author: magic
author_rank: Super Contributor
timestamp: March 27, 2019, 08:42:26 am
content: It's not funnyI always install THT resistors so that conventional current flows in the same direction as the color bands (if possible).And sure, you got it backwards, as evidenced by opamp pinouts. The 101 network posted by OP is a pulldown network, for pullups please get one with common on pin 14Besides, making fun of audiophools on an engineering forum is boring. If you want to be funny, go actually convince them of that and post screenshots
Resistor color code help... - Page 1
Forum section: electronics / beginners

author: casp3rtech
author_rank: Newbie
timestamp: November 20, 2016, 11:37:18 pm
content: I can't seem to find this thing no matter what.. Resistor fried on a TV power supply and I can't seem to make out the color code using the colors I see.. Maybe I am doing something wrong. From what I can see its red, black, gold, orange, black... All code generators are giving me an error and even if i do it manually, it makes no sense.

author: Yansi
author_rank: Super Contributor
timestamp: November 20, 2016, 11:54:54 pm
content: If the left most band is RED (really cannot tell for sure from a photo with incorrect white balance), then it is 0.2ohm resistor. Err.... was.

author: Andy Watson
author_rank: Super Contributor
timestamp: November 21, 2016, 12:00:29 am
content: I think the left band is brown. The gold band is a 0.1 multiplier, so it's a 1.0 ohm.

author: Yansi
author_rank: Super Contributor
timestamp: November 21, 2016, 12:06:51 am
content: Yeah youre right. My mistake.Guess that was a current shunt from a switchmode power supply. If this one is fried, the mosfet and/or the controller IC might be as well.

author: Brumby
author_rank: Unknown
timestamp: November 21, 2016, 12:19:05 am
content: If you take the bit of gunk on the left end of the body as a reference, the white balance wasn't too far off.Here's my effort at rebalancing...

author: casp3rtech
author_rank: Newbie
timestamp: November 21, 2016, 12:20:47 am
content: I have added two more while changing light settings on camera. This part is from a TV power supply that was damaged from power surge. So far I have found 3 bad capacitors, one fuse and this resistor. The power supply is massive and I can't find it anywhere! The model is BN44-00744A

author: casp3rtech
author_rank: Newbie
timestamp: November 21, 2016, 12:27:20 am
content: The bad components locations so far...

author: Brumby
author_rank: Unknown
timestamp: November 21, 2016, 12:32:57 am
content: Quote from: casp3rtech on November 21, 2016, 12:20:47 amFor the lighting conditions - and my assumption that the gunk is white (or at least neutral) - your first photo was closest to correct white balance.As such, I see the first band as brown. The extra photos support this.
resistor color code wheel - Page 1
Forum section: electronics / beginners

author: jobog
author_rank: Regular Contributor
timestamp: March 24, 2016, 07:15:56 pm
content: For ages I've had a little 3 wheel resistor color code calculator. I know Elenco has these 3 band units but does anyone know if there is a 4 or 5 band calculator like this available. I know you can look up the code on your computer and I even have an app for my phone that gives this info but it would be handy to have something similar to the 3 band. I've searched and I find all kinds of printable charts but nothing with the little wheels.

author: daybyter
author_rank: Frequent Contributor
timestamp: March 24, 2016, 09:40:17 pm
content: http://www.electronics-tutorials.ws/resistor/resistor-colour-code-wheel.html

author: jobog
author_rank: Regular Contributor
timestamp: March 24, 2016, 11:03:53 pm
content: Quote from: daybyter on March 24, 2016, 09:40:17 pmThanks for the link, that will work just fine.
Resistor color code - Page 1
Forum section: electronics / beginners

author: Strand17
author_rank: Contributor
timestamp: March 16, 2021, 07:45:10 pm
content: Hello,Please excuse a basic question, but I am struggling to figure out the value of a resistor based on its color code(!).As far as I can tell the color rings are silver, black, purple, red and silver (see picture). The color balance in the picture is a bit off, but the middle ring surely is violet (not gray nor blue). The rings at both ends are the same color and have a bit of a metallic sheen to them, so gray is unlikely.Using my normal color-chart for resistor values, this makes no sense. Can someone help, please?The circuit is a low noise amplifier. There are two of these resistors, There appears to be one in series with the +12V and one with the -12V supply to the input OP (AD797). However, I could be wrong here.Thanks in advance!Jonas

author: TimFox
author_rank: Super Contributor
timestamp: March 16, 2021, 07:51:30 pm
content: My guess is 17 ohms, 10% tolerance. I don't know what the wider silver band represents, but black is never a leading digit in this code. That is not a normal +/- 10% value (E12 series). Is it possible that your "violet" is a color-shifted grey, giving 18 ohms? Neither violet nor blue fits the E12 series for 10% resistors.Sometimes, inductors are color-coded and can be confused with resistors.

author: Benta
author_rank: Super Contributor
timestamp: March 16, 2021, 08:05:36 pm
content: More probably a small inductor. Your description of its placement would support this.

author: floobydust
author_rank: Super Contributor
timestamp: March 16, 2021, 08:14:38 pm
content: That looks like an inductor, not a resistor.Double Silver-Brown-Grey-Black-Silver might be 18uH +/-10% DCR 17 ohms.Vishay Dale IM-2 series looks like that.edit: if Double Silver-Red-Violet-Black-Silver might be 27uH +/-10% DCR 25 ohms.

author: boffin
author_rank: Unknown
timestamp: March 16, 2021, 08:36:11 pm
content: Yup, looks like an inductor:https://media.digikey.com/pdf/Data%20Sheets/Vishay%20Dale%20PDFs/IM_Series.pdf

author: Strand17
author_rank: Contributor
timestamp: March 16, 2021, 08:52:29 pm
content: Excellent!It has to be one of the Vishay inductors.With your suggestion about inductor I found a key to the color-code at:https://www.rfcafe.com/references/electrical/inductor-color-codes.htmDouble width silver for MIL-Spec and then red, violet, black and silver makes 27 uH, +/- 10%.Thanks a lot to everyone!Jonas
Resistor colour code camera app? - Page 1
Forum section: electronics / beginners

author: Xykon
author_rank: Newbie
timestamp: June 09, 2015, 07:44:36 am
content: Hello,I'm colourblind and I used to have an app on my iPhone that would photograph a resistor and tell me the value.Unfortunately that app I had is no longer maintained and doesn't work with latest iOS versions.I've been searching quite a while for a replacement but no luck so far. Last night I was trying to debug a power supply and suspected a resistor. In the end I gave up and will ask a colleague at work today to give me the colour codes.Does anyone have any alternate suggestions for an iPhone or Windows PC app that can identify resistor colour rings for me?Thanks a lot.Sent from my iPhone using Tapatalk

author: McBryce
author_rank: Super Contributor
timestamp: June 09, 2015, 08:37:12 am
content: Have you tried this?http://labrigger.com/blog/2012/03/05/optical-recognition-of-resistor-codes/McBryce.

author: Xykon
author_rank: Newbie
timestamp: June 09, 2015, 08:58:07 am
content: QuoteThis seems to be a common problem with these types of apps unfortunately... still looking for a working one

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: June 09, 2015, 09:06:46 am
content: http://armageddon421.de/?p=279Might be of some interest, although wont be simple to get running

author: Zero999
author_rank: Super Contributor
timestamp: June 09, 2015, 09:59:58 am
content: Why not use a multimeter?

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 09, 2015, 10:16:40 am
content: Quote from: Hero999 on June 09, 2015, 09:59:58 amTo check if the resistor is within spec?

author: Xykon
author_rank: Newbie
timestamp: June 09, 2015, 12:11:26 pm
content: Quote from: PA0PBZ on June 09, 2015, 10:16:40 amYes... it's the only part in the power supply you could call dodgy... the PCB under it is slightly discolored although this could also just have been from heat. I need to know if the resistance I measure with the multimeter matches what it's supposed to do.Quote from: RobertHolcombe on June 09, 2015, 09:06:46 amThanks, this looks promising. I'll have to check it out tonight to see how well that works.
Resistor Colour codes - Page 1
Forum section: electronics / beginners

author: keynaboutradios
author_rank: Contributor
timestamp: November 27, 2017, 06:15:13 pm
content: Hi Everyone!Please be gentle with me.I have a resistor with five bands, Brown Black gold gold Yellow, I thought I knew how to read resistor bands, but obviously not!! can anyone shed some light on this for me.

author: drussell
author_rank: Super Contributor
timestamp: November 27, 2017, 06:28:52 pm
content: Quote from: keynaboutradios on November 27, 2017, 06:15:13 pmThis is probably one of those oddballs that is a 3-band value with tolerance and temperature co-efficient or something. The best question is, what value does it read when you measure the resistance with a meter?I expect it is likely a 0.15% with a temperature coefficient of 25 ppm/K...though it could be some other oddball code types too, of course, so I'd measure it to see if it is even close to something that makes sense from the colors.Quote

author: Seekonk
author_rank: Super Contributor
timestamp: November 27, 2017, 07:03:57 pm
content: Don't feel bad, I've been in electronics 50+ years and I can no longer figure out what the colors are. I have to get the meter out to figure out what the color is supposed to be.

author: keynaboutradios
author_rank: Contributor
timestamp: November 27, 2017, 08:06:16 pm
content: Thanks for replies everyone.It was burnt out drussell, I did see the yellow band on capacitor markings for Temperature coefficient but no mention for resistors.Thanks again

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: November 27, 2017, 08:09:42 pm
content: +1 for temperature coefficient. However, I think it should read 1\$\Omega\$ 5% 25ppm because:BrownBlackGoldGold10x0.1\$\Omega\$5%

author: janoc
author_rank: Super Contributor
timestamp: November 27, 2017, 08:34:11 pm
content: Quote from: Seekonk on November 27, 2017, 07:03:57 pmI haven't even bothered to memorize them - the bands are often faded, dirty or you don't have enough light to read them so you don't save much time by doing that. The resistance could be well off as wellevery time, or at least one of those cheap eBay testers for a quick check.

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: November 27, 2017, 08:37:52 pm
content: Quote from: janoc on November 27, 2017, 08:34:11 pmIt is still handy to memorize the basic colors when you need to dig through a pile of unsorted resistors, looking for something specific

author: janoc
author_rank: Super Contributor
timestamp: November 28, 2017, 01:42:28 am
content: Quote from: frozenfrogz on November 27, 2017, 08:37:52 pmFor that a little reference chart stuck to a wall is enough. OTOH, I am keeping my resistors sorted, so rarely have this issue

author: drussell
author_rank: Super Contributor
timestamp: November 28, 2017, 04:16:32 am
content: Quote from: frozenfrogz on November 27, 2017, 08:09:42 pmIndeed... I believe you are correct, sir....In my haste, hurredly posting a reply before lunch, I do believe I did, indeed mixmultiplexmymultipliers...I revise my guess to 1.0
Resistor Decade Box: Are RC models useful for learning? - Page 1
Forum section: electronics / beginners

author: Cliff Matthews
author_rank: Unknown
timestamp: September 08, 2016, 03:23:45 pm
content: I have been eying the thumbwheel decade thread for a while.. since my kids are burning-out my old round decade wheel. I have a couple good multi-gang rotary switches, so I'm looking for ways to use them first. Searching for ideas, is saw Global Specialties discontinued a model called the RC-10 but the manual had a schematic and it looks novel enough to clone.Would anyone have any ideas to improve this for kids? One idea I was thinking of was to use another SPST switch in the series path to insert the secondary winding of a speaker transformer. The primary winding would connect to a BNC jack and back-to-back 5.1v zener's for a way they can safely modulate signals passing through the box without killing my AF generator.
Resistor decade box, component power rating - Page 1
Forum section: electronics / beginners

author: nikodemus
author_rank: Newbie
timestamp: July 04, 2013, 10:25:28 am
content: I'm thinking of building a resistor decade box.Something that confuses me is that the designs I've seen seem to use resistors of all-the-same power rating, typically around 1W.I was thinking of speccing mine for up to 10V voltage instead -- so for dialed in 1 Ohm, that resistor would have to be able to handle 100W, for 2 Ohms the second series resistor would need to handle 50W, for 3 Ohms the third 33W, etc.Seems that a fixed-voltage specced box would just be much easier to use when working on eg. battery powered devices.Am I missing something? Is it just assumed that these boxes are used only with current-limited power supplies, or is there another reason why a max-power spec instead of max-voltage spec is typical one?

author: george graves
author_rank: Super Contributor
timestamp: July 04, 2013, 11:25:42 am
content: Do you know how big a 100W resistor is?The reason why you can get away with smaller resistors is that you generally only use it to set up low current devices. Setting up op-amps and voltage dividers, led brightness.https://www.tindie.com/products/redrocketlabs/resistance-decade-box-resistor-substitution-box/If you're looking for something that you can use to put a "load" on a battery - take a look at Dave's "dummy load" project. It's a easy and fun build for a beginner.

author: nikodemus
author_rank: Newbie
timestamp: July 04, 2013, 01:47:49 pm
content: Thanks for the response!Even more pertinently, now that I actually think about it, ... no matter the size of the resistor, I really don't want to think about the heat sink something able dissipate 100W would need!
Resistor difference  - Page 1
Forum section: electronics / beginners

author: steveggz
author_rank: Contributor
timestamp: October 20, 2017, 06:10:52 pm
content: Is there a actual difference between a resistor and a current limiting resistor? Or is it the same resistor except being applied in series or parallel?

author: ataradov
author_rank: Super Contributor
timestamp: October 20, 2017, 07:59:06 pm
content: This is a really strange question. Current limiting is one of the jobs resistor can do in a circuit. Series or parallel is irrelevant here.Resistor is resistor regardless of its use.

author: Nusa
author_rank: Super Contributor
timestamp: October 20, 2017, 08:47:23 pm
content: Resisting, or limiting, current is all a resistor does. So strictly speaking, a current-limiting resistor is a redundant phrase, but it often gets used when that's the sole role the resistor is serving.Similarly, when we call something a pull-up or pull-down resistor, its primary role is to provide a stable default state to a floating or unconnected circuit.Read up on fundamentals:http://www.resistorguide.com/what-is-a-resistor/

author: Ian.M
author_rank: Super Contributor
timestamp: October 20, 2017, 09:22:25 pm
content: The only exception would be using a fusible resistor as a current limiter as fusible resistors are designed to burn open circuit if overloaded, without catching on fire. Replacing a fusible resistor with an ordinary one is a *BAD* idea, as even though most small metal film resistors will go open-circuit on overload without *much* flaming of their surface coating, the resistance may drop as the surface coating carbonizes.

author: TimNJ
author_rank: Super Contributor
timestamp: October 20, 2017, 09:36:56 pm
content: Similar to what others have said...I think the term "current limiting resistor" is frequently used when talking about LEDs and the series resistor used to limit the current through the LED. Physically nothing different about that resistor compared to any other resistor. Speculating that you are talking about LEDs, the reason you need a "current limiting resistor" is because an LED is basically a current-driven device. It's the current through the LED which affects how bright it is.
resistor divider calculator/selector - Page 1
Forum section: electronics / beginners

author: jsquaredz
author_rank: Contributor
timestamp: May 30, 2015, 02:33:37 pm
content: Does anyone know of a resistor divider calculator that allows you to enter an input voltage, a range for the output voltage, and the resistors such that you can enter in some values and get equivalent resistor selections from standard E* series?Hope this makes sense.

author: fubar.gr
author_rank: Unknown
timestamp: May 30, 2015, 03:24:51 pm
content: This one is the best:http://mustcalculate.com/electronics/automaticresistivevoltagedivider.phpThere's also this one:http://jansson.us/resistors.html

author: jsquaredz
author_rank: Contributor
timestamp: May 30, 2015, 03:44:38 pm
content: Quote from: fubar.gr on May 30, 2015, 03:24:51 pmExcellent. Exactly what I needed.

author: Zero999
author_rank: Super Contributor
timestamp: June 27, 2015, 06:23:21 pm
content: Here's my favourite one:http://sim.okawa-denshi.jp/en/teikokeisan.htmIt works with potential dividers with three resistors.

author: schwarzrmsu
author_rank: Contributor
timestamp: June 28, 2015, 10:06:41 pm
content: Great links. Who needs math these days.

author: coldrunning2002
author_rank: Newbie
timestamp: March 02, 2016, 08:28:02 pm
content: Quote from: fubar.gr on May 30, 2015, 03:24:51 pmThis one produces spread sheets showing the results to your problem, and the tool keeps a log book of all your problems; and you can keep it on your computer.Written in c++ for a dos console.down load from here:goo.gl/CW4qg8orwww.goatelectronics.com

author: adamlewerin
author_rank: Newbie
timestamp: March 02, 2016, 08:44:39 pm
content: I actually prefer Electro Droid, an Android app with different calculators, references and connector data.It can calculate most thins that you need including voltage dividers, LED-resistors, NE555-setup, RC-filters and many other things, as well as containing most common connectors and a number of reference sheets for connectors, maximum current for cable dimensions and component footprints
Resistor divider network calculation for buck converter - Page 1
Forum section: electronics / beginners

author: newtekuser
author_rank: Frequent Contributor
timestamp: November 02, 2024, 06:33:32 am
content: I'm using the MP8765 switching IC to down step 12V to 5V. According to Ti documentation for calculating the power stage for a buck converter, the formulae for calculating R1 and R2 are:R2 = VFB / IR1/2, where IR1/2 needs to be 100 times as big as IFBR1 = R2 ((Vout-VFB) -1)In the MP8765 data sheet, I have selected VFB to be 600mV (0.6V) and IFB for the same is 10nA (0.00000001A).If I plug these values into the formula for R1 and R2 I get:R1 = 440Mohm and R2 = 60Mohm.Something does not look right to me, the values are huge! What I'm I missing?https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MP8765/document_id/777https://www.ti.com/lit/an/slva477b/slva477b.pdf?ts=1730500800156

author: rteodor
author_rank: Frequent Contributor
timestamp: November 02, 2024, 07:09:59 am
content: I_R12 should beat least100 times bigger than I_FB.1uA in your case but I would put, if requirements allow, something like 100uA.For example: 47K + 6K4.

author: ArdWar
author_rank: Frequent Contributor
timestamp: November 02, 2024, 07:27:04 am
content: 1) Pick worst case scenario for IFB. For example 50nA for MP8765.2) That will be your upper limit for RFB2selection. Using the 100x rule of thumb that will be RFB2(MAX)= 600mV/5uA = 120k3) Of course you may pick lower resistance than the upper limit (duh)...4) You may even deliberately pick significantly lower resistance if you have other consideration. e.g. leakage, noise immunity, BOM consolidation, etc. or even just because you don't particularly mind the increased quiescent draw.5) Through the magic of my proprietary calculation, 220k : 30k sounds about right for 5VOUT

author: newtekuser
author_rank: Frequent Contributor
timestamp: November 02, 2024, 05:35:20 pm
content: Thank you all, it's clear now!
Resistor help - Page 1
Forum section: electronics / beginners

author: Crambone
author_rank: Frequent Contributor
timestamp: February 23, 2024, 08:47:34 pm
content: I have a board that has a resistor marked 4R70 it measures 2.22mm long. Is this 4.7 ohms? What case code is that size?Drew

author: Wil_Bloodworth
author_rank: Regular Contributor
timestamp: February 23, 2024, 08:56:19 pm
content: Can you post a photo of the resistor?- Wil

author: selcuk
author_rank: Frequent Contributor
timestamp: February 23, 2024, 09:02:16 pm
content: It can be 0805 4.7 ohm. You may refer to the first table in this link:https://eepower.com/resistor-guide/resistor-standards-and-codes/resistor-sizes-and-packages/

author: Crambone
author_rank: Frequent Contributor
timestamp: February 23, 2024, 09:05:57 pm
content: Yes sorry I thought I posted it but forgot.It’s on a LAMBDA Power supply

author: Wil_Bloodworth
author_rank: Regular Contributor
timestamp: February 23, 2024, 09:31:55 pm
content: Yes. 4.7 Ohms.- Wil

author: tooki
author_rank: Super Contributor
timestamp: February 24, 2024, 07:00:04 pm
content: Quote from: Crambone on February 23, 2024, 08:47:34 pmMeasure thewidthof the chip cap, so that you have at least one dimension whose length is not affected by the thickness of the solder joints.

author: BillyO
author_rank: Super Contributor
timestamp: February 24, 2024, 08:28:47 pm
content: They are 0805.
Resistor keeps dying...  - Page 1
Forum section: electronics / beginners

author: mortos360
author_rank: Regular Contributor
timestamp: July 07, 2014, 11:10:56 am
content: I am trying to fix a plasma tv power supply, that I killed few days ago by accidentally discharging the caps with a short to chassis.after that accident I found a dead fuse and power resistor (F501 and R501)... after replacing them, the resistor keeps dying as soon as I connect the PS to the mains, even tho nothing is connected to it.. no load or anything. I can't find any short on the board.. everything looks ok to me. Maybe someone has an idea why that power resistor (5W) keeps dying?Thanksps: here is the schematic:

author: mij59
author_rank: Frequent Contributor
timestamp: July 07, 2014, 11:22:12 am
content: Check if there is a short in D501, D504, IC501 (TP3, TP4)

author: Strada916
author_rank: Frequent Contributor
timestamp: July 07, 2014, 11:25:09 am
content: Sometimes you need to load the psu output so it doesn't kill it self. As it tries to regulate against no load ie no feedback.

author: mortos360
author_rank: Regular Contributor
timestamp: July 07, 2014, 11:30:21 am
content: Quote from: mij59 on July 07, 2014, 11:22:12 amD504 is dead... but I am sure it wasn't dead 2 days ago when I checked all the diodes.Is it possible that it died because of no load (as Strada916 mentioned)?

author: mij59
author_rank: Frequent Contributor
timestamp: July 07, 2014, 11:49:58 am
content: Quote from: mortos360 on July 07, 2014, 11:30:21 amYes could be, but why did the psu fail in the first place ?The feedback is done with an optocoupler, it could be the course .

author: mortos360
author_rank: Regular Contributor
timestamp: July 07, 2014, 01:15:44 pm
content: Quote from: mij59 on July 07, 2014, 11:49:58 am1 of my test hooks was hanging on TP4 and the end of the cable touched the chassis and discharged the caps from the main board... there was a lot energy, the first 5mm of the test hook was completely vaporised.

author: mortos360
author_rank: Regular Contributor
timestamp: July 08, 2014, 09:55:41 am
content: Any idea what kind of diode that D504 is?Seem like its a Panasonic part and ppl charge 20$ for it online... but it can't be that special, or?

author: rs20
author_rank: Super Contributor
timestamp: July 08, 2014, 10:17:37 am
content: Judging from the schematic the D504 is a zener diode back-to-back with a standard diode. In a pinch, you could just use two separate parts (a zener diode, and a normal diode) with appropriate ratings. Can you find a datasheet?

author: mortos360
author_rank: Regular Contributor
timestamp: July 08, 2014, 10:25:23 am
content: Quote from: rs20 on July 08, 2014, 10:17:37 amNah.. at least not with standard google search. the only thing I have is the panasonic part no. VXST3D82BL3 but this doesn't got me anything yet.

author: mij59
author_rank: Frequent Contributor
timestamp: July 08, 2014, 10:46:10 am
content: Quote from: mortos360 on July 08, 2014, 10:25:23 amThis may be a starting point.https://www.shindengen.co.jp/product_e/semi/list_detail_NEW.php?category_id=06&sub_id=02&product_id=ST03D-82
Resistor Maximum Working Voltage - Page 1
Forum section: electronics / beginners

author: jpalicke
author_rank: Unknown
timestamp: March 16, 2015, 04:37:14 am
content: I had a question about the maximum working voltage rating on resistors. Is it defined as the maximum voltage across the resistor, or the maximum voltage with respect to ground? Seems like it should be the former, but I've seen people say it's the latter. Which is it?Joe

author: free_electron
author_rank: Super Contributor
timestamp: March 16, 2015, 04:48:45 am
content: Volage across the resistor.

author: jpalicke
author_rank: Unknown
timestamp: March 16, 2015, 04:50:53 am
content: Many thanks!Joe

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 16, 2015, 07:07:55 am
content: Quote from: JoeN on March 16, 2015, 04:39:47 am^

author: SeanB
author_rank: Super Contributor
timestamp: March 16, 2015, 07:01:52 pm
content: For power resistors there are also ratings for the voltage between the resistor leads ( any of them) and the case if it is a metal case for cooling, and if there is a water cooling connection. Ceramic resistors also have a rating for hot and cold use, as when they are at full power dissipation they are no longer usable as insulated case resistors, the case must be considered as conductive as the ceramic can carry current if it is red hot. You often get them with a steel mounting, which must be connected to one lead in operation, or soldered to the board and isolated.

author: TimFox
author_rank: Super Contributor
timestamp: March 16, 2015, 07:20:16 pm
content: For a given series of resistors, (e.g., 1-watt carbon) especially ones designed for high voltage, there is a resistance value often specified for that series where the resistors are limited by voltage (lead to lead) above that resistance, and by power rating below that resistance.

author: katzohki
author_rank: Frequent Contributor
timestamp: March 16, 2015, 08:43:42 pm
content: Usually most people are concerned with the power rating of the resistor, but voltage is a good thing to keep in mind. Since I work with high voltages in my circuits (up to 10kV) I have to get special resistors that are high voltage rated.

author: cosmicray
author_rank: Frequent Contributor
timestamp: March 16, 2015, 09:46:46 pm
content: Datasheets for resistors will commonly show a maximum DC Working Voltage, and a maximum DC Overload Voltage. A couple of datasheets I looked at, showed an overload voltage that was 2x the working voltage (for axial resistors).

author: Zero999
author_rank: Super Contributor
timestamp: March 16, 2015, 10:05:18 pm
content: It's not just blowing the resistor up which you risk by exceeding the voltage rating: at higher voltage the resistance often drops below the rated value.

author: Neilm
author_rank: Super Contributor
timestamp: March 16, 2015, 10:08:43 pm
content: Quote from: cosmicray on March 16, 2015, 09:46:46 pmI have seen short term overloads of 5 or 10 times the rated voltage, depending on the resistor construction and the length of time of the overload.
Resistor notation. - Page 1
Forum section: electronics / beginners

author: sahko123
author_rank: Frequent Contributor
timestamp: February 25, 2021, 02:10:01 pm
content: I want to know what the difference between these resistors are and why it has that circled drawing and what it actually means?

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: February 25, 2021, 02:17:34 pm
content: Mf may mean metal film.

author: Terry Bites
author_rank: Super Contributor
timestamp: February 26, 2021, 06:02:28 pm
content: I've seen this in 70's Japanese schematics where both symbols are used. It seems to appear where a precise low drift part would be expected and may well be metal film types. The keyboard divider chain in a Korg Mini for example.
Resistor Power Rating - Page 1
Forum section: electronics / beginners

author: paul23
author_rank: Regular Contributor
timestamp: October 08, 2014, 03:33:28 pm
content: This is a question I really should know the answer to, but I'm not sure, so thought it is best askI am using a Microchip fan controller IC in a circuit I'm working on and I am not 100% sure on the power rating for the resistor Rsense. The fan motor is 12V 0.1A so 1.2W. The voltage drop across the resistor is 900mV so I think a 1W resistor is more than adequate, but I'm not 100% sure I am correct and if I should add the 1.2W from the fan and use a 2W resistor instead.Thanks

author: grumpydoc
author_rank: Super Contributor
timestamp: October 08, 2014, 04:39:47 pm
content: QuoteThedatasheethas a table of nominal fan currents vs sense resistor which suggests about half that. At 500mA a sense resistor of 1ohm is suggested - dissipation in the sense resistor would be then be 0.25W, at 100mA 4.7 ohms is suggested giving a dissipation of 47mWHTH.

author: paul23
author_rank: Regular Contributor
timestamp: October 08, 2014, 05:37:32 pm
content: Thanks, it was more the method than actual numbers I was confused with. I tested with a 10 Ohm resistor (the smallest I have available) to try and prove them method and that's why I had 900mV. So I am right in my original question then and the power dissipation of the resistor is just the voltage drop across it + the fan current + the 4.7 Ohms for the resistor? I don't include the 1.2W from the fan?

author: suicidaleggroll
author_rank: Super Contributor
timestamp: October 08, 2014, 05:46:09 pm
content: The power dissipated in any device is the voltage drop across it multiplied by the current through it.The 1.2 W from the fan is being burned off in the fan, not the resistor.

author: paul23
author_rank: Regular Contributor
timestamp: October 08, 2014, 05:59:12 pm
content: Thanks that is exactly what I thought, I just wanted to make sure.
Resistor red red gold gold silver - Page 1
Forum section: electronics / beginners

author: oliver602
author_rank: Regular Contributor
timestamp: January 24, 2015, 04:20:51 pm
content: Hi,I am replacing 2 damaged parts on a TV power supply. One of these is a resistor with the colours red, red, gold, gold, silver. Best guess based on squinting at a chard resistor and images online. I don't understand the workings of this power supply so I'm just blindly replacing these visibly damaged parts. The schematicavailable heresays 2.2ohm 1/2 watt. R7920 on primary side at top left near STBY CONTROLLER market in red.My question is, what do the bands mean on this resistor? Is this really a 4 band resistor? Is the last band a temperature coefficient? Could it be something else?

author: SeanB
author_rank: Super Contributor
timestamp: January 24, 2015, 04:22:16 pm
content: 2R2 0.5W fusible resistor.

author: oliver602
author_rank: Regular Contributor
timestamp: January 24, 2015, 06:50:57 pm
content: Thats great thanks SeanB.How do you know it is a fusible resistor?

author: SeanB
author_rank: Super Contributor
timestamp: January 24, 2015, 06:55:30 pm
content: The texture normally is a give away. Most resistors are shiny dipped with a clear varnish, but almost all fusible resistors will be coated with a cement film to make them flame proof, so will look matt finish on the body.As well it is in a SMPS primary side, as a safety device, so it will most likely be a fusible type placed there to provide a safety function along with being a plain resistor in the circuit.
Resistor required at base of pass transistor? - Page 1
Forum section: electronics / beginners

author: Clear as mud
author_rank: Regular Contributor
timestamp: November 13, 2013, 02:30:34 am
content: I understand why a resistor is required to limit base current in a transistor switch or amplifier, but my question is what happens when the transistor is driven by an op-amp in a negative feedback configuration? Is it helpful to put a resistor between the op-amp output and the base of the transistor? Why?I searched for an answer to this question, but didn't find anything. I found this page regarding constructing voltage regulators from op-amps:http://tangentsoft.net/elec/opamp-linreg.htmlIn the first schematic on that page, there is no resistor between the op-amp and the transistor, but the final three schematics all have 10 ohm or 47 ohm resistors. Each circuit on the page is supposed to provide improved performance (in terms of output stability and noise) than the preceding circuit, but there is no explanation of how the resistors at the base of the pass transistors help.

author: Frenchie
author_rank: Regular Contributor
timestamp: November 13, 2013, 05:40:05 am
content: The resistor is there to protect the op amp and limit the output current it can supply.As an extreme example, if you think about what happens when you short the output, you have a base-emitter PN junction (ie a diode) going to ground. The output voltage will be lower than the set point & negative feedback will drive the opamp output to the positive rail (or as close as it'll go). Without a resistor there, you're essentially shorting the positive rail to ground through your opamp and a diode. If you're lucky the opamp's short circuit protection should kick in and save it, but it's not exactly the nicest thing to do to it.Unfortunately you can't just stick a big value resistor there either. The current flowing through the emmitter is the sum of the current through the collector and the base. The transistor's base sees a current of Ib = 1/(1+Beta)*Ie (Approximately Ie/Beta). If you are trying to pull a 1A load through a power transistor with a Beta of say 50, you'll end up pulling ~20mA through the base. If you try and drive that with a 1k resistor on the base that's an additional 20V your opamp will have to source in addition to the (Vout + 0.6V) it has to supply to drive the transistor.This and the fact that your op-amp has to supply a relatively big load to drive the transistor on its own is why you'll usually see Darlington output stages with much larger gains or alternatively a FET output.

author: KJDS
author_rank: Super Contributor
timestamp: November 13, 2013, 10:45:50 am
content: A transistor amplifier without a small resistor in the base is usually called an oscillator.
Resistor selection for instrumentation amplifier - Page 1
Forum section: electronics / beginners

author: AQUAMAN
author_rank: Regular Contributor
timestamp: October 05, 2016, 11:56:26 am
content: I have an LT1167 instrumentation amplifier, which requires an external resistor to set the gainhttp://cds.linear.com/docs/en/datasheet/1167fc.pdfThis is for a precision application and I need very low temperature dependence. I need a gain of less than 10 so will be buying a 10k resistor. The gain is not important but the repeatability of the measurements isDoes anyone have any recommendations on what resistor to buy?I would buy an AD624 which has set gains and tells your the temp coefficient of each gain setting, but its €35 and a huge package

author: trophosphere
author_rank: Frequent Contributor
timestamp: October 05, 2016, 02:49:49 pm
content: Can you quantify "low temperature dependence" or rather how much are you able to tolerate? There is a wide range from 100ppm/C for thick film to that of 2ppm/C for thin film (Ex. Susumu or Caddock). If that is not enough then try Vishay as they have some speced for 0.05ppm/C.

author: AQUAMAN
author_rank: Regular Contributor
timestamp: October 05, 2016, 03:45:15 pm
content: Quote from: trophosphere on October 05, 2016, 02:49:49 pmHave just seen the vishay ones, thanks

author: Brutte
author_rank: Frequent Contributor
timestamp: October 06, 2016, 06:43:24 am
content: Quote from: AQUAMAN on October 05, 2016, 11:56:26 amIt says:G(Rg) = 1 + (49.4k/Rg)So that means:"dG/dRg"=-49.4k/Rg^2(where the thingy in quotes is the differentiation symbol)which at your 10k attains:"dG/dRG"(10k)=4.94e-4 [1/]so you can approximate your G with affine function of dRg.G(Rg+dRg)~G(Rg)+"dG/dRg"*dRgGoing further we know that Rg is a function of temperature:Rg(T+dT)~ Rg(T)+"dRg/dT"*dTwhere T is temperature and dT is the deviation from T.The "dRg/dT" is also known as TCR (linear temperature coefficient of resistance)Concluding:G(T+dT) ~ G(T)+"dG/dT"*dT

author: David Hess
author_rank: Super Contributor
timestamp: October 06, 2016, 04:36:41 pm
content: The datasheet says that the gain drift with a perfect resistor is 20ppm/C typical and 50ppm/C maximum so using a perfect resistor may only halve the gain drift versus a 20ppm/C or 50ppm/C resistor. In the error budget analysis, they use a 10ppm/C resistor.

author: rob77
author_rank: Super Contributor
timestamp: October 06, 2016, 06:28:16 pm
content: a vishay foil resistor would be a waste of money... simply just go ahead with a 15ppm/C smd resistor there.

author: bson
author_rank: Unknown
timestamp: October 07, 2016, 12:04:06 am
content: If the thermal response is repeatable and not particular fast changing you could also calibrate for temperature, then co-measure the temperature and factor it out from the measurement for a thermally linearized data point. This of course assumes minimal thermal hysteresis and an error manifesting itself as a repeatable value deflection rather than noise. (Although you can always characterize the hysteresis - the real key is predictable repeatability.)