hybridfree/eevblog-posts huggingface dataset:
Single pulse generator using discrete components - Page 1
Forum section: electronics / beginners

author: Yaroooo
author_rank: Regular Contributor
timestamp: April 16, 2021, 02:31:26 pm
content: Hi all!I've a problem with a schematic and I'd like to have some support. I've a commercial board like this:What I want to do is to drive LEDs with OUTPUT pin. This LEDs are used like flash source, so I turn them ON for a very small amount and then off for a relative long time.I have a button to manually drive the flash, so I must limit ON time by external hardware to avoid LED damage.What I've done is this schematic:What this circuit should do is:- Circuit is 24V powered -> Button is randomly pressed -> Flash ON for RC time (about 2ms) -> Time finished Flash goes OFF -> Button is released -> C de-charge -> Button is randomly pressed..etc..I've tested on breadboard and circuit actually works. But I've found some problems:1) When button is released, OUTPUT take some time to go HIGH again. Actually not a real problem, but if there's a way to solve I'll able to control better ON time length;2) Very rarely circuit freezes with OUTPUT to LOW, happened 1 or 2 times after pressing Button and some more times when circuit is connected to power for the first time;3) ON time sometimes doubles or triples, sometimes OUTPUT stay LOW for 4ms or 6ms instead of 2ms;I attach an oscilloscope image about problem 1) .Any help is appreciated!

author: Kleinstein
author_rank: Super Contributor
timestamp: April 16, 2021, 04:46:21 pm
content: The part with the slow ramp looks a little like there is some oscillation. It looks like the circuit does no go cleanly from on to off, but kind of oscallates for some time.The case with stuck on could be a kind if sustained oscillation.One point that could cause troulbe is that not many MOSFETs like some 24 V at the gate. Some added resistance at the drain sides could reduce the voltage and als redue the tendency for osciallation by reducing gain.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 16, 2021, 06:16:24 pm
content: If you insist on discrete circuits, you might do something like the high side here.The gate has a ton of capacitance, so you need to pull it up with something stronger than a 10k resistor.This uses a 680 ohm into an emitter follower, which effectively reduces its value by hFE. So, the pull-up resistance is close to 5 ohms at the gate, for typical transistor choices. This will swing the gate in the ballpark of 100ns. (Instead of 2N4401/3, also good are higher current duals like ZXTC2045E6TA or ZXGD3003E6TA, note that the latter is crudely spec'd as a "gate driver" but yeah it's just two damn transistors in a pack, treat it as such.)Tim
Single-row 6-pin DuPont 1.27mm female into 2.54mm male ribbon cable - Page 1
Forum section: electronics / beginners

author: jj5
author_rank: Unknown
timestamp: November 01, 2023, 06:58:44 am
content: Hi there. Me and a mate of mine are looking for a cable to do a job. We have a board with single-row 6-pin 1.27mm pin header and we want to change that into 2.54mm pin header so we can attach our stuff, but it's really hard to find a cable that meets those specifications. If we could get a single cable that would be best, but if we need a cable and a separate adapter that would be okay too. Can anyone suggest where we could find such a thing, or what we should search for and where?The 1.27mm headers we want to attach to look like this:

author: Dan123456
author_rank: Regular Contributor
timestamp: November 01, 2023, 09:23:50 am
content: If you only need the one, I would probably just make a custom cable if I were youGrab some hook up wires that have the 2.54mm connectors already attached (you can get a pack of 100 or something from Jaycar for like $10), then snip the other end off and attach the 1.27mm connector you needI’m sure you probably can find something ready made if you really search but imagine they will probably want an arm and a leg for it due to it being specialEdit: they are called jumper leads, not hook up wires. My bad!These are the ones I was thinking of and they come as a ribbon so would still look fairly professional toohttps://www.jaycar.com.au/150mm-plug-to-socket-jumper-leads-40-pieces/p/WC6028?pos=3&queryId=388d8103fbf956ae5a4f9ef282c8f09e

author: Ian.M
author_rank: Super Contributor
timestamp: November 01, 2023, 09:34:27 am
content: 1.27mm pitch connectors are a **** to assemble without the correct crimp tooling, clone crimpers are mostly a pile of cr@p, and the official crimpers will cost you an arm and a leg, so follow Dan's advice but the other way round. Buy a six way cable with 1.27 mm pitch connectors, cut off one end and either solder it to a 2.54 mm pitch header, and reinforce and strain relieve with a bead of epoxy over the joints, or crimp on 'duPont' pins and fit to a six way shell (clone crimper kits to do 2.54 mm pitch 'duPont' style connectors are affordable and if used with care give reasonable results).Another option would be to make an adapter using this pitch adapter PCB:http://www.proto-advantage.com/store/product_info.php?products_id=3800052You don't appear to have clearance round the 1.27 mm pitch header so cant simply fit a female 1.27mm pitch header socket to go straight onto your board's header. You probably need to get a 1.27 mm pitch cable as above, but instead of cutting the end, simply put the mating header on the pitch adapter PCB.
single sided pcbs to test spray paint and laser method - Page 1
Forum section: electronics / beginners

author: farmerni
author_rank: Newbie
timestamp: January 03, 2018, 03:31:47 pm
content: Just want some simple useful pcbs to test pcb etching using black spray paint, a K40 laser cutter/engraver, 1 A4 sheet FR4 and ferric chloride etchant. Any and all advice welcome. Especially interested in a through hole design for a plcc44 breakout using a socket as I tried to make one in Kicad but it seemed to tight to etch properly. I've never tried any surface mount, but would like to try, just not with the plcc as its a z80 for a future project

author: phil from seattle
author_rank: Super Contributor
timestamp: January 03, 2018, 05:25:52 pm
content: what are you asking for? someone to design test boards for you?

author: farmerni
author_rank: Newbie
timestamp: January 05, 2018, 10:20:49 am
content: just asking if anyone has some cool designs already done

author: Detzi
author_rank: Regular Contributor
timestamp: January 05, 2018, 11:01:18 am
content: Quote from: farmerni on January 05, 2018, 10:20:49 amHi, farmerniis use this method on a regular basis to save me time. I upgradedan K40 with a Arduino Mega2560, a ramps 1.4 and the Drivers, running now marlin, because the crap driver board that was inside (especially this Moshi shit) is unusable.Since then i can produce pcbs with pitches down to 0.4mm. The bottom layer is used as ground plane without traces and i try to use smd wherever possible to save me most of the drilling.The Layout is produced with KiCAD, the CAM processor is Estlcam which generates gcode from a .dxf.Total time from a layout to solerable PCB is about an hour (no rush).But this won't be cheap. In fact the plain Material costs are higher than a PCB shipped from China

author: farmerni
author_rank: Newbie
timestamp: January 05, 2018, 12:31:35 pm
content: thanks mine is standard with coreldraw and it is reasonably easy to put in dxfs, so might draw up a board later and test
Single stub conjugate matching non unity conductance circle - Page 1
Forum section: electronics / beginners

author: optic37
author_rank: Newbie
timestamp: March 29, 2025, 11:50:02 pm
content: I'm working on an interstage matching network for an amplifier design, aiming for a conjugate match between stage 1 output (source) and stage 2 input (load) using a single shunt stub and the Smith Chart.My understanding of the standard single-stub procedure for matching a load (ZL) to the system impedance Z0 is typically: (when working on a smith chart with both Z and Y traces)Convert ZL to normalized impedanceRotate clockwise on its constant |Γ| circle.Stop rotation when intersecting the G=1 circle.Calculate the length of the transmission line from the distance to the intersection.Now graphically look at the admitance to find the susceptance.Add a shunt stub to cancel the resulting susceptance.However, when applying this to interstage conjugate matching, my target admittance isn't necessarily 1+j0, but rather the conjugate of the source's output admittance (Y_source). Using the standard procedure above (stopping at G=1) doesn't seem right because it doesn't incorporate any information about Y_source. I only plot the load admittance (YL) and rotate to G=1.My question is: For interstage conjugate matching, should I still rotate ZL until I intersect the G=1 circle? Or is the correct procedure to rotate ZL until the conductance G matches the real part of the target conjugate admittance (G = Re{Y_source})*, which might not be 1?Using G=1 feels incomplete because the source information isn't used, but I'm having trouble finding clear graphical examples demonstrating rotation to a non-unity G circle specifically for this conjugate matching case.Any clarification on the correct procedure would be greatly appreciated.Thanks.
Single Supply Comparator - Page 1
Forum section: electronics / beginners

author: dfox416
author_rank: Contributor
timestamp: May 28, 2014, 02:31:14 am
content: I am trying to use an LM311 comparator with a single supply but I cannot get it to work and can't find any examples online. I want it to take a sine wave as input and output a square wave. Any help is greatly appreciated. Thanks!

author: IanB
author_rank: Super Contributor
timestamp: May 28, 2014, 02:51:27 am
content: Can you post a schematic of your circuit and explain why it's not doing what you expect it to do?

author: dfox416
author_rank: Contributor
timestamp: May 28, 2014, 02:59:25 am
content: i attached a schematic. i know it is not right because i need to apply a DC offset to the input since i want it to detect the zero crossing but i am not sure how to do that. if i use the same voltage divider for both inputs, it effectively shorts them together. should i use separate voltage dividers for each input?

author: IanB
author_rank: Super Contributor
timestamp: May 28, 2014, 03:03:28 am
content: Are you simulating it, or building it on a breadboard?If you are only simulating it you can bias the sine wave at half the supply voltage in the source block.If you are building it for real you need to use separate bias resistors for the sine wave input and couple the input signal through a capacitor.

author: Fank1
author_rank: Regular Contributor
timestamp: May 28, 2014, 10:49:27 am
content: Your reference, ie the - input, is at 4.5 V the input must exceed this for the output to go positive.Duplicate the voltage divider ( R2 - R3 ) on the + input and couple the signal from V1 with a capacitor.

author: MrsR
author_rank: Regular Contributor
timestamp: May 29, 2014, 09:55:26 pm
content: Quote from: IanB on May 28, 2014, 02:51:27 amIf you want to simulate first Try LTspice IV a Comp. like a LT1018 should do it and in real life a LM393 worked OK! (it was a lot cheaper) on a Breadboard and now the PCB is nextI just finished designing a Brushed motor controller and in some ways the output is similar I used Triangle waveform but the input was a square wave that I made a Integrator for A input and B input is the Triangular wave form.HAVE FUNRachael

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 29, 2014, 11:48:28 pm
content: Check out the schematic inthis post. It is pretty much exactly what you are looking for.
Single Supply Integrator Questions - Page 1
Forum section: electronics / beginners

author: eev_carl
author_rank: Regular Contributor
timestamp: January 02, 2018, 12:25:35 pm
content: Hi,I built this single-supply integrator amplifier but am not getting the output on the scope I expected. From the specification in the lower-right of the book image (Vin=+-2.5V, 2000Hz, Vout=+=1.3V), I was expecting a triangle wave at +1.3V/-1.3V. However, I got a curved triangle at a much smaller amplitude. See the first scope image which shows a lower amplitude than what the book asked for. It shows a +-1.25V Vin, but I got similar results with the +2.5V/-2.5V input. My V+ is 9V and I've tried 5V and 15V as well.Also, there is a lot of overshoot at the square wave transitions and was wondering if this was in spec. See the second image. I'm using a Rigol 1054Z scope and DG1022 function generator.Thanks in advance,Carl

author: Zero999
author_rank: Super Contributor
timestamp: January 02, 2018, 02:35:29 pm
content: Try increasing R2 to 470k.

author: orin
author_rank: Frequent Contributor
timestamp: January 02, 2018, 08:53:59 pm
content: The scope trace looks fine to me. See attached ltspice run (Using LT1013 as the op-amp. I scaled and offset the traces; the rectangular wave is actually 2.5V pk-pk).The curved triangle is due to the R1-C2 time constant of 470us which is significant considering the pulse width is 250uS. The R1-C2 time constant must be much greater than the pulse width, or C2 charges, reducing the current into the integrator. Remember that this circuit is integrating the current into the inverting input node, so as C2 charges, there is less voltage across R1, less current into the integrator and the triangle becomes an exponential curve.If you exclude the effect of C2, then 2.5V for 250uS will put 2.5*250E-6/4700 charge on the integrating capacitor; applying Q=CV, that's about 1.3V as originally claimed.Edit: corrected component designation (C2, not C1).

author: Zero999
author_rank: Super Contributor
timestamp: January 03, 2018, 08:44:14 am
content: Quote from: orin on January 02, 2018, 08:53:59 pmYou're right. I overlooked C2. I erroneously assumed the circuit looked like a resistive load at the input, but it doesn't, it's a constant current load. The circuit is both a differentiator and integrator, depending on which capacitor is larger. To make it more of an integrator, C2 could be a 10µF electrolytic capacitor, with the anode connected to R1.
single supply op amp PSRR - Page 1
Forum section: electronics / beginners

author: electrolust
author_rank: Unknown
timestamp: October 15, 2015, 07:03:00 am
content: http://www.edn.com/design/analog/4347861/Demystifying-single-supply-op-amp-designIn the first section, 4th paragraph,"This simple circuit has some serious limitations. The first limitation is that the op amp's power-supply rejection is almost entirely missing, because any change in supply voltage directly changes the VS/2 biasing voltage, which the resistor divider sets. ... Because a 1V change on the supply line causes a 0.5V change at the output of the divider, the circuit's power-supply rejection is only 6 dB."I don't get it. AIUI, PSRR is the op amp's ability to ignore/attenuate Vs changes so that the effect on the output is minimized. But in a single supply design, if the bias voltage can track the supply voltage perfectly as Vs/2, then doesn't that effectively completely ignore ripple in Vs? ISTM the author is not considering that a change in Vs is also a change in the virtual ground.My math (perhaps bad) says that 500mV change in signal for 1V change in Vs is indeed 6dB as the author claims. However in this circuit we aren't changing thesignalby 500mV, we are changing thebiasby 500mV, which we NEED TO DO because we are tracking the change in Vs.

author: Performa01
author_rank: Super Contributor
timestamp: October 15, 2015, 09:00:50 am
content: Here the problem is, that the load is referenced to real circuit ground (there is no virtual ground in this circuit).I didn't read that article, but in order to cure this problem, I'm pretty sure the author will suggest a stabilized bias voltage for the OpAmp later on...

author: Zero999
author_rank: Super Contributor
timestamp: October 17, 2015, 01:46:43 pm
content: Yes, the author talks about adding a capacitor and another resistor to the bias point to filter out the ripple.The first circuit would be fine run off a smooth power supply such as a battery or if any noise/ripple on the power supply is well below the lower cut-off frequency of RC circuit formed by the AC coupling capacitor and load.

author: Tim F
author_rank: Regular Contributor
timestamp: October 17, 2015, 02:00:03 pm
content: The problem with Figure1 is that if the supply voltage changes, the voltage at the non-inverting input changes by exactly half that amount and opamp has to change it's output in order to bring the inverting output to the same voltage as the non-inverting input - voila, noise on the supply rail just made it directly to the output at a level of -6dB plus the gain you have configured.What I usually do is this, it's easier for newbies to understand. I like to think of it as creating an R-C filtered reference voltage from the powersupply, and you use that as your ground reference for the opamp. The PSRR will still rise to -6dB at DC, but you can choose R and C values which give you suitably low PSRR in the passband you are interested in.Once you have that worked out, consider how this changes things:
single supply op amp signal bias error - Page 1
Forum section: electronics / beginners

author: electrolust
author_rank: Unknown
timestamp: October 14, 2015, 06:48:14 pm
content: When running an op amp with single power supply, I'm reading that you need to bias your input signal. Makes sense.Is there a problem due to the bias being wrong by a few percent? Because now the zero crossing of an AC signal is offset from the virtual/effective ground. Wouldn't this cause that part of the signal that is within the offset error to be amplified in the "wrong direction"?I'm looking at a datasheet that suggests to use a resistor divider to add bias to the input signal. However due to resistor tolerance the bias isn't going to land right at +Vs/2.

author: homebrew
author_rank: Frequent Contributor
timestamp: October 14, 2015, 07:10:23 pm
content: Yes, that would definitively be a problem. And that's why you don't do it that way :-)On the bottom of the page you will find the appropriate schematic:http://www.radio-electronics.com/info/circuits/opamp_non_inverting/op_amp_non-inverting.phpThe whole idea is to use the capacitor (C2 in this case) as a way to auto-adjust the virtual ground.

author: dan3460
author_rank: Frequent Contributor
timestamp: October 14, 2015, 07:41:15 pm
content: Interesting, could someone explain how this is calculate:QuoteThis quote comes from the end of the article when describing the values for each part.My ohms law calculate that two 100K resistors in parallel will be 50k and not 50ohms. I'm missing something?

author: electrolust
author_rank: Unknown
timestamp: October 14, 2015, 08:03:42 pm
content: Seems pretty obvious that the missing 'k' is just a typo.I am more confused about other seeming typos (or not?) on the page. EG the discussion on AC coupling. They talk about the possibility to DC couple the circuit and describe how to handle that, but proceed to show a circuit that is AC coupled.I'm also lost on how to select C2 but I suspect that is more my lack of knowledge than some error.

author: John Coloccia
author_rank: Super Contributor
timestamp: October 14, 2015, 08:14:14 pm
content: Quote from: electrolust on October 14, 2015, 08:03:42 pmWell, the way that particular schematic is drawn is not exactly how I'd do it, but nevermind that. The way it's drawn, C2 is there so that you don't amplify the DC offset. It determines the low frequency response of the circuit. With the resistors, it essentially creates a high pass filter. Choose it large enough that it gives you a linear enough response through the range of frequencies you need to amplify.
Single supply op amps - Page 1
Forum section: electronics / beginners

author: dfox416
author_rank: Contributor
timestamp: March 12, 2014, 05:41:19 am
content: Hello,Here is what I want to do: operate an op amp single supply (9V and ground) and allow for maximum positive and negative voltage swing (bias at 4.5V). I would like to know how to do it in inverting and non inverting configurations. I have been messing around trying to make this work but I haven't seen a definitive fool-proof way to do it. Some of the circuits I've seen online don't even work in simulation. Can someone post schematics of the correct way to implement an inverting and non inverting op amp in this configuration, AC coupled and DC coupled? Any help would be much appreciated!

author: Bored@Work
author_rank: Super Contributor
timestamp: March 12, 2014, 05:55:29 am
content: http://www.ti.com/lit/ml/sloa091/sloa091.pdfhttp://www.ti.com/lit/an/slod006b/slod006b.pdfhttp://www.ti.com/lit/ds/symlink/lm124-n.pdf

author: dfox416
author_rank: Contributor
timestamp: March 12, 2014, 06:14:04 am
content: I simulated the circuit given on page A-5 of the first link and I got microvolts on the output from a 200mV sine (picture attached). What am I doing wrong?

author: awallin
author_rank: Frequent Contributor
timestamp: March 12, 2014, 06:21:17 am
content: Quote from: dfox416 on March 12, 2014, 06:14:04 aminput also needs to be biased at 4.5V? i.e. sine swings symmetrically around 4.5V - or AC-couple the input with a capacitor after the signal-generator.

author: dfox416
author_rank: Contributor
timestamp: March 12, 2014, 06:31:03 am
content: Thanks. Works perfectly with the capacitor!
Single to differential ended - circuit - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: January 22, 2015, 11:55:21 am
content: I have attached a circuit. Since I have to measure the voltage using ADS1248.Now ADS1248 is connected to second board & it have single supply. (AVDD = DVDD = 3.3V)Output of INA121 in attached circuit is single ended. So I had used THS4521 to convert it to differential signal.1. I have selected gain = 1 for THS4521.2. Ground of both boards is common.3. I have left Vocm of THS4521 open . Will it put the signal to mid level of supply voltage to that its in Vocm range of ADS1248or I have to additionally connect 1.67V to THS4521.

author: eejake52
author_rank: Contributor
timestamp: January 22, 2015, 04:45:11 pm
content: Quote from: Vindhyachal.takniki on January 22, 2015, 11:55:21 amBased on the examples shown in the datasheet for the THS4521, I think it will seek to the midpoint with just C1 connected.But now you've got me curious. What is the application? Is that a strain gauge? You have DC coupled the INA121 to the THS4521, so I guess you are measuring a slowly varying signal; but are you sure that P1 is always positive w.r.t. P2?Jake
Single Transistor Amplifier Design - Page 1
Forum section: electronics / beginners

author: Mattjd
author_rank: Regular Contributor
timestamp: March 04, 2019, 12:33:29 am
content: Hi,I'm trying to design an amplifier with the design specifications shown in the first image of the link.Now I wanted to try a single common source amplifier. We're directed to use a specific nmos within cadence. Nmos4I performed the simulations also shown in the imgur link to obtain the followingConsidering the gain required is 10. I was going start by choosing a Q point from the graphs shown in the imgur link.I chose, (11.112mA,2) @ Vgs = 2 as my Q point. This provides a transconductance gm of 10.621 mS. As well as...Early voltage Va = 20.2 volts ... Va = ro*Id = 1818*11.112mA = 20.20Channel Length modulation lambda= 0.0495 ... lambda = 1/Vaconduction parameter Kn = 11.97 mA/V ... Kn = 2*Id/[(Vgs-Vt)^2(1+lambda*Vds)]Additionally you can see from my Id vs Vgs graph that Vt is roughly .7 volts.Since I chose a 4 resistor CS design, I was going to pick R1 = 300k Ohms and R2 = 200k Ohms. To calculate Rd I had planned on working backwards from this-10 = -gm*(ro||RL||Rd)*(Rg/(Rsig+Rg) (Rs isnt necessary bc i had planned on including by pass cap in parallel with it)...Rg = R1||R2as I know gm, ro,RLOnce I calculated Rd, I was going to back calculate the necessary Rs value to give the proper Vgs and Vds as they're both known.I get a negative resistance for Rd, im assuming something is wrong with my simulations OR i simply dont have a large enough gm to get the desired amplification.I was hoping someone could point out my mistake.

author: Audioguru
author_rank: Super Contributor
timestamp: March 04, 2019, 01:19:19 am
content: What is the part number of your Mosfet that has a 'typical" threshold voltage of only 0.7V? or did you design the Mosfet?Did you know that graphs in a datasheet are only for a "typical" one but the range from minimum to maximum are wide and are written in text?

author: Mattjd
author_rank: Regular Contributor
timestamp: March 04, 2019, 01:33:18 am
content: Quote from: Audioguru on March 04, 2019, 01:19:19 amIts nmos4 in NCSU_Analog_Parts of cadence

author: bson
author_rank: Unknown
timestamp: March 04, 2019, 01:48:18 am
content: Quote from: Mattjd on March 04, 2019, 12:33:29 amGiven,-10 = -gm*(ro||RL||Rd)*(Rg/(Rsig+Rg)I get:-10/(-gm*Rg/(Rsig+Rg)) = ro||RL||Rd = 1/(go + gL + gd)gm*Rg/10(Rsig+Rg) = go + gL + gdgd = 1/Rd = gm*Rg/10(Rsig+Rg) - 1/Ro - 1/RLRg =2/(2+3) = 0.4Ω= 200k||300k = 120kΩRsig = 1kΩRL = 500ΩRo = 1818Ω1/Rd = 10.621m*0.4/10(1k+0.4) - 1/1818 - 1/500 = 0.42246Rd = 2.37ΩEDIT: Oh wait, Rg is 200k||300k, not a divider. Sorry.Yup, corrected for that I get a negative Rd also; -668Ω.

author: Mattjd
author_rank: Regular Contributor
timestamp: March 04, 2019, 01:58:55 am
content: Quote from: bson on March 04, 2019, 01:48:18 amyour Rg is wrongRg is the parallel resistance of R1 and R2, which is 120k, so Rg/(Rsig+Rg) = 120k/121k ...approx 1, which is why that part of the gain is typically ignored when Rg is much much larger than Rsig
Single transistor amplifier project  - Page 1
Forum section: electronics / beginners

author: CarlS
author_rank: Newbie
timestamp: May 18, 2018, 06:29:35 pm
content: I want to do a project for end of school year - a single ( power ) bipolar transistor amplifier with source from a CD player and driving a small speaker. I do not understand and maybe you can explain :1. How come the very small input signal ( can be milivolts ) will "beat" the ground to base voltage ? How does that work ?2. If my speaker is 32 Ohms how do I select the voltage and current going through the transistor ? I see in the datasheet some curves - how are they used ?

author: rstofer
author_rank: Super Contributor
timestamp: May 19, 2018, 02:32:27 am
content: 1) You bias the base with a pair of resistors between power supply and ground. This causes the transistor to conduct even with no signal. For a class A amplifier, you will adjust the bias such that the collector voltage (given the current flowing through the collector resistor (load) is about 1/2 of the power supply.This allows the collector voltage to swing from Vcc to Gnd.You capacitively couple the signal into the base.2) I have never tried to drive a low value load like 32 Ohms. If the power supply was 12V and it was all dropped across the speaker, the current flow would be 375 mA and that seems like a lot. I'd have to think about that...Watch the videos by W2AEW - he does a magnificent job explaining how these things work. For simplicity, not energy efficiency, you want to look at Class A operation. You can Google for circuits as well.

author: rstofer
author_rank: Super Contributor
timestamp: May 19, 2018, 03:08:50 am
content: You might find this interesting. One way to resolve the low load impedance is to use a transformer - maybe 20:1 as mentioned in the comments. So, the collector will see 20 * 32 ohms or 640 Ohms, just like w2aew's video.Expect a bunch of heat.You can also check around for capacitively coupled speakers. That eliminates the transformer but usually requires quite a high value capacitor.
Single transistor as level shifter - Page 1
Forum section: electronics / beginners

author: austnais
author_rank: Contributor
timestamp: February 15, 2016, 04:13:20 pm
content: Hi guys!Yes, the question is in the title! Is this socially accepted for real circuits (safety-critical)?I'm translating both from 5V to 24V and 5V to 15V with one discrete NPN-transistor.Please, if you have something to say regarding this topic, speak! It can be anything from other ways to do it, improvements, draw-backs and so on,Thank you,

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 15, 2016, 04:17:08 pm
content: - 5V logic cannot be directly connected to the base. Use a current limiting resistor (and usually a B-E resistor as well, to keep it fast).- The output won't pull up to full +V, due to the LED. This might not be a problem (is there another pull-up on the connection?).- The output is not short, overvoltage or reverse protected, so I don't think I would call it "safety critical".- What kind of "safety critical" application do you have in mind? I sincerely hope you aren't doing something like medical life support or mission-critical, andasking questions to the internetabout it. I would seriously suggest spending real money talking to consultants about "safety critical" systems.Tim

author: austnais
author_rank: Contributor
timestamp: February 15, 2016, 04:23:16 pm
content: Quote from: T3sl4co1l on February 15, 2016, 04:17:08 pmThank you T3sl4co1l for your reply!Sorry! I should have included more of the circuit...-There is of course a base-resistor (but it is outside the snapshot)-There is also a separate pull-up on the 24V side, so no worries.-There is also a current-limit resistor on the output, which actually goes to the base of an PNP.Safety-critical was wrongly put, or wrongly understood. What I mean is robust. For example, is it more robust than using a dedicated chip?Don't worry, you wont see this in a pacemaker or any medical...

author: mstoer
author_rank: Contributor
timestamp: February 15, 2016, 05:37:20 pm
content: I am assuming you wanted it to be unidirectional? I mostly do level shifting for I2C communications (bidirectional) and use logic level MOSFETs for it. Nothing wrong with a unidirectional BJT level shifter if that's all you need though.

author: Audioguru
author_rank: Super Contributor
timestamp: February 15, 2016, 06:55:40 pm
content: Please postthe entire schematicwith the resistors and PNP transistor so we can see if the "separate pullup" prevents the LED from lighting and if there is anything that turns off the PNP.

author: austnais
author_rank: Contributor
timestamp: February 15, 2016, 07:45:02 pm
content: Quote from: Audioguru on February 15, 2016, 06:55:40 pmThanks for reply, but there is no reason to post the rest. The pullup is connected in parallel with the led and the resistor. The whole circuit is tested and works as intended. All I wanted input on was is if this is the typical way to do it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 15, 2016, 11:30:08 pm
content: Alright, then yes, that's the correct way to do it.Tim
Single transistor with 7 pins!? - Page 1
Forum section: electronics / beginners

author: MrZwing
author_rank: Regular Contributor
timestamp: February 20, 2017, 09:02:05 pm
content: http://www.wolfspeed.com/downloads/dl/file/id/145/product/1/c3m0065090j.pdfWhy does this transistor have several "source" pins and what are the uses for it? i have been scratching my head quite a bit over this one.does anyone have an answer for me why so many source pins? is there a special application for it?/MrZ

author: Benta
author_rank: Super Contributor
timestamp: February 20, 2017, 09:13:33 pm
content: It has 5 source pins to keep resistance low. Drain is the tab, which is big enough.

author: MrZwing
author_rank: Regular Contributor
timestamp: February 20, 2017, 09:15:46 pm
content: so you hook up all 5 of them to source so the elektrons can pick and choose their way?

author: Benta
author_rank: Super Contributor
timestamp: February 20, 2017, 09:28:30 pm
content: Quote from: MrZwing on February 20, 2017, 09:15:46 pmYes. It's called "paralleling". A lot of us engineers use it in practice. If you grind off the top of the device, you'll also see 5 parallel bond wires.

author: MrZwing
author_rank: Regular Contributor
timestamp: February 20, 2017, 09:39:16 pm
content: ahh nice good to know sounds like a good practice.

author: Phoenix
author_rank: Frequent Contributor
timestamp: February 21, 2017, 01:33:20 am
content: One of the source pins is also called driver source. It's purpose is to provide a dedicated gate driver return path. This helps stop the gate driver being effected by the power current.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 21, 2017, 01:48:36 am
content: Pins have equivalent inductance, and when you're switching, let's see, about 30A in 10 nanoseconds, every nanohenry counts.Each pin on a D2PAK sized device has about 4nH inductance. (For a regular D2PAK, that's all you need to know. For this one, the pins are connected in parallel, so the inductances also act in parallel. You can ignore coupling between them, for a wave-of-the-hands analysis.)The Kelvin source connection, for gate drive, is very nice as well.Homework 1: given the numbers I just wrote, how much voltage error, or overshoot, do you expect? Where does that error appear in the circuit? Why would it be important? How much difference is there, using one pin versus all in parallel?Homework 2: draw out the equivalent circuit of a transistor, including its pin/lead inductances, stray trace/wiring/PCB inductance, and so on for everything else in the power switching circuit. Show us your schematic, and reflect on its meaning.Tim
Single-Wire EEPROM Implementation Problem (AT21CS11) - Page 1
Forum section: electronics / beginners

author: Sarcarean
author_rank: Contributor
timestamp: October 14, 2018, 10:07:38 am
content: So I am banging my head against the keyboard now. I am trying to read a SWI EEPROM (AT21CS11) using PB7 of ATMEGA32U2. I have that line connected to VCC (3.3V) with a 2Kresistor. I am not sure what the problem is, but I have noticed that the reset and discover event does not look correct.The RESET and DISCOVER event should look like this: PB7_LOW, wait 200uS, PB7_Release, wait 10uS, PB7_LOW, wait 1uS and release, then check if bus is being pulled down by AT21.Here is what the correct waveform looks like:However, here is what mine looks like:Does anyone have any ideas of what I did wrong?
Sink or Source Input - Page 1
Forum section: electronics / beginners

author: sımışka
author_rank: Contributor
timestamp: January 30, 2020, 06:21:36 pm
content: Hi everyone,I am trying to design an I / O board. It has the following features:4-20ma, 0-10v input2 relay outputs,4 standard opto inputs4 high speed opto inputs. ( +24v)I have a question about high speed inputs. I use is a single photo diode optocoupler . HCPL-M601. What connection should I make for the polorite to be correct according to the sink or source input connection status? The signal can be sink or source.

author: Kirill V.
author_rank: Regular Contributor
timestamp: January 31, 2020, 01:27:14 am
content: Source means that current flows into the optocoupler led? Then you just need to limit the amount of input current.Sink means that current must flow from the optocoupler? Then the led can't provide this and you will have to add an external diode.Do I understand you correctly?

author: sımışka
author_rank: Contributor
timestamp: January 31, 2020, 05:22:18 am
content: Actually, Inputs and outputs in PLCs can be made according to source or sink connection. For example, when the COM of the inputs is connected to +24, our signal must be - triggered so that the input is triggered. The input polority is important now that the opto I use is single photodiode. How can I automatically connect the optocoupler to the anode or cathode by understanding that the terminal that connects to the COM is + or -? Or is there a high-speed dual-color optocoupler?

author: Kirill V.
author_rank: Regular Contributor
timestamp: February 02, 2020, 12:38:19 am
content: Does your board know which input mode is currently being used - sink or source? Is there some indicator of the current mode that it accepts?
site problems - Page 1
Forum section: electronics / beginners

author: ME
author_rank: Frequent Contributor
timestamp: April 05, 2025, 03:15:05 pm
content: why am i getting either error 504 bad gateway or file not found ??.

author: BennoG
author_rank: Frequent Contributor
timestamp: April 05, 2025, 03:42:02 pm
content: Same problem over here. Netherlands KPN.Benno

author: incf
author_rank: Frequent Contributor
timestamp: April 05, 2025, 03:47:17 pm
content: Quote from: ME on April 05, 2025, 03:15:05 pmAbout an hour ago someone posted a reply linking to my thread on the same topic under the correct board. But then their post disappeared?https://www.eevblog.com/forum/news/forum-intermittently-producing-file-not-found-and-bad-gateway-errors/

author: PascalNE
author_rank: Regular Contributor
timestamp: April 05, 2025, 03:50:53 pm
content: I'm also getting file not found UK.

author: Grandchuck
author_rank: Super Contributor
timestamp: April 05, 2025, 03:57:56 pm
content: https://www.eevblog.com/forum/chat/website-error-reports/msg5871648/#msg5871648Reported about 4 hours ago.
Sites with decent MCU parametric search? - Page 1
Forum section: electronics / beginners

author: Mechanical Menace
author_rank: Super Contributor
timestamp: September 10, 2015, 06:07:53 am
content: Is there any site where every combination of peripheral or connectivity of an MCU doesn't have it's own filter but single options do? Say I want look up options with an EBI and DMA I don't have to go through selecting every list of options that include EBI/EMI and then DMA but can just select both separately?Thanks.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 10, 2015, 06:28:24 am
content: Not that I know of.But you can download excel parametric files from almost all manufacturers. Then you can filter inside each manufacturer, and the remaining lines can be combined to a new sheet.

author: AndyC_772
author_rank: Super Contributor
timestamp: September 10, 2015, 07:20:47 am
content: One of the reasons I use PICs is that Microchip's "advanced part selector" is such a powerful tool for finding the right part for a given design.http://www.microchip.com/maps/microcontroller.aspxI know what you mean about bad parametric searches. One particularly irritating example of laziness is if, say, I want an MCU with at least 2 SPI interfaces. Sure, there's an option for "2xSPI", but 3 or 4 SPIs would be fine too; it's not as though I have to use them all."2 x SPI", or "2xSPI/I2C" need selecting too.
sixthhd hd-1 mystery chip - Page 1
Forum section: electronics / beginners

author: ker2x
author_rank: Regular Contributor
timestamp: October 21, 2019, 05:14:27 pm
content: Friendly greetings !i bought a 7" screen branded "Koolertron".Since it's for an FPGA project i, teared it down but found a weird chip with the model erased and rewritten : "SIXTHHD HD-1"My google-fu found this japanese videoI don't speak japaneseBut thanks to him, it pointed to a Realtek RTD2660.Well, the photo and spec he got was a RTD2660 but he ended up witht he same weird chip as me.The screen i bought, look like the same board, do not mention any chipset at all. i can only assume it's a RTD2660.This is the datasheet i found :http://aitendo3.sakura.ne.jp/aitendo_data/product_img/lcd_controller/Xs/RTD2660.jsp.pdfmarked CONFIDENTIAL FOR GMI ONLY.Apparently it support a whole bunch of stuff (eg : downscaling 1920x1440 input to the 1024x600 output)Anyone have experience with this mystery chip ?Can i assume it's really a RTD2660 ? Any way to confirm ?It even have a 8051 MCU with 256KB of flash ^^ (for the OSD i assume)thank you.PS : we can see on the full photography there is a little bit of a non-erased logo than can possibly be part of the realtek logo.

author: amyk
author_rank: Super Contributor
timestamp: October 22, 2019, 02:15:46 am
content: You can check the pinout. I suspect RTD2660 or 2662 is correct, and you can find (Russian only, unfortunately) a firmware project for them:http://openrtd2662.ru/
Sizing mosfet for smps (220v to 40-30v)  - Page 1
Forum section: electronics / beginners

author: nandoanalog
author_rank: Contributor
timestamp: October 20, 2016, 09:26:10 am
content: I need a power supply capable of delivering at least 20 amps at 30-40v continuously. When stepping down 220v dc to my desired voltage, how do I rate the switching mosfet amperage wise?

author: Ammar
author_rank: Regular Contributor
timestamp: October 20, 2016, 10:42:47 am
content: First thing is to choose a topology and then look at the design equations for it.

author: rob77
author_rank: Super Contributor
timestamp: October 20, 2016, 11:19:27 am
content: Quote from: nandoanalog on October 20, 2016, 09:26:10 amstepping down 220V DC ? what's the AC input ?

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: October 20, 2016, 11:21:05 am
content: I would start with a bigger package size that a to220. Next, consider the size of the heat sink. Think about how fast it must switch to produce the desired output. You must consider if you need more than one of these. Think if it needs dropping resistors on the input to limit the current if using more than one. Last, do a practical test to see if it meets you needs before building and manufacture.

author: JS
author_rank: Frequent Contributor
timestamp: October 20, 2016, 04:31:29 pm
content: Quote from: nandoanalog on October 20, 2016, 02:08:22 pmThats over 310VDC once rectified and properly filtered, even if you don't filter it properly you should be able to handle those 310V peaks.The voltage rating of the components doesn't mean much more than, "it's less than this" but you already knew it for both since you started with 32VAC to feed them.How do you know and what do you mean by the welder eats up 505 of the power? where does the other 50% goes?JS

author: poorchava
author_rank: Super Contributor
timestamp: October 20, 2016, 07:44:45 pm
content: If the OP is asking questions like that he or she should not try to design an 800W+ mains psu as they obviously lack the basic knowledge of the matter.Sent from my HTC One M8s using Tapatalk

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 20, 2016, 11:59:52 pm
content: http://www.mouser.com/Power/Power-Supplies/Switching-Power-Supplies/_/N-axgkh?P=1yxt68iZ1yxt6euZ1yxt778Z1yxt6q2Z1yxt76mZ1yxt7fgZ1yxt6evZ1yxt64rZ1yxt6f8Z1yxt619Z1yxt656Z1yaq8r3&Rl=axgkhZerbiZ1z0wc7vZ1yot873SGT&Keyword=meanwell&FS=TrueEven if you're an expert, you won't beat them on price. Or reliability. Or regulatory approval. Or...I say this as an expert at switching supply design.Tim

author: poorchava
author_rank: Super Contributor
timestamp: October 21, 2016, 06:37:57 am
content: Quote from: blueskull on October 20, 2016, 10:26:06 pmI guess that depends on requirements such as cost effectivity, design time and efficiency. IMO Full bridge requires more time to design and is more expensive in production but more efficient. I think in most cases here a half-bridge would be more optimal.
Sizing snubbed MOV for pump motor. - Page 1
Forum section: electronics / beginners

author: JustMeHere
author_rank: Frequent Contributor
timestamp: April 24, 2019, 02:45:14 am
content: I want to control a 240v 8A AC watre pump motor with a relay. My research suggests I use a MOV to protect the relay contacts. I can't figure out which MOV to use.Thanks in advance for any help.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 24, 2019, 12:59:29 pm
content: Very little energy is required, compared to the energy a MOV can handle. A 7mm dia. THT, or 2820 size SMT chip, will do. Maybe even a 1206 or 1806, if they make one in that voltage.Tim
SK6812 RGBW type LED what's inside? - Page 1
Forum section: electronics / beginners

author: davebullock
author_rank: Contributor
timestamp: August 05, 2022, 03:47:39 pm
content: Hi experts,I have a string of SK6812 RGBW/ WS2812 LED's and have had a ESP32 controller and motherboard failure.The 5V led supply was accidentally increased to 24V which had the result of destroying the 3v3-5V level shifter on the ESP32 motherboard and subsequently the ESP32 via the associated I/O pin.When returned to 5V all the LED's still work exactly as expected with no ill effect noticeable.My question is :-What is inside the controller 'chip' that allowed the overvoltage to be routed out of the LED's data pin and destroy the level shifter etc?Having scoured the internet I can find plenty of datasheets on these programmable type LED's, but non give any clue as to their internal architecture and if they contain data input protection diodes etc.I assume that the overvoltage event caused a reverse breakdown (maybe non-destructive) of the data input protection diodes which routed 24V out the serial data line into the output of the level shifter?A stupid accident (and maybe the longevity of the LED strips are compromised) but, switching to the spare channel on the motherboard and fitting a fresh ESP32 has all the LED's working as expected.So how did the overvoltage get to come back out the serial data input without destroying the LED's?Answers on a postcard......ThanksDave

author: AndyBeez
author_rank: Frequent Contributor
timestamp: August 05, 2022, 04:06:55 pm
content: Was 24V also applied to the onboard level shifter's Vout rail?

author: thm_w
author_rank: Super Contributor
timestamp: August 05, 2022, 09:47:21 pm
content: So the 5V LED supply was ONLY powering the LEDs and the level shifter, and was not powering the ESP32 at all?What is the part number of the level shifter? If it was an IC, it could have passed through that as well.
Skip or keep? - Page 1
Forum section: electronics / beginners

author: abaxas
author_rank: Regular Contributor
timestamp: June 16, 2014, 06:18:56 pm
content: Hi all,Been having a sort out and found my old electronics kits from 20+ years ago. Obviously I'm going to keep all the semiconductors but bin most of the rest... so the question is.... skip or keep?Electrolytic caps.....skip or keep?Polyester film caps....skip or keep?Ceramic caps....skip or keep?My mind thinks skip the electrolytics but keep the rest, anyone agree?

author: w2aew
author_rank: Super Contributor
timestamp: June 16, 2014, 06:48:51 pm
content: I'd say keep it all. Certainly there is no issue with the film or ceramic caps. If the electrolytics are from a decent manufacturer, never been used, and stored in a reasonable environment, they are most likely just fine.

author: abaxas
author_rank: Regular Contributor
timestamp: June 16, 2014, 06:58:54 pm
content: They are all circa 1990/1(ish) vintage gemcon caps.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 16, 2014, 07:31:41 pm
content: Certainly keep the poly and ceramic caps.There is no significant time/temperature related degradation process as there is for electroltics.Get one of those $20 LCR/Transistor testers and check the ESR of the electrolytics.They may all be still good as well, but testing will confirm one way or the other.

author: wraper
author_rank: Unknown
timestamp: June 16, 2014, 08:09:37 pm
content: Throw away those electrolytics. Even if they measure OK now, they may die a bit later. Also if voltage was not applied on the electrolytic cap for a very long time, oxide layer becomes thinner. So if you power such a cap with a higher voltage (e.g. half of the rated), there may be huge leakage current. Therefore it may get hot, electrolyte starts to emit gases, and cap may blow up before the oxide layer gets formed. I experienced it myself with some large NOS capacitors.

author: deth502
author_rank: Frequent Contributor
timestamp: June 16, 2014, 08:49:40 pm
content: ive had odd value caps that i salvaged from vintage 1970's electronics and had/still have them working fine after years of use. not to mention i have vintage 60's and 70's electronics with the original caps in them still working fine.i side with "double check them with a cheap esr meter before hand" and go option.

author: Aspiringloser
author_rank: Newbie
timestamp: June 18, 2014, 07:32:38 am
content: You could send them to me.