hybridfree/eevblog-posts huggingface dataset:
Driving a high-power SCR via triac and opto-isolator - Page 1
Forum section: electronics / beginners

author: Tujmin
author_rank: Newbie
timestamp: May 29, 2025, 10:45:30 am
content: Hi, could you please tell me if I can use the following cirquit to drive SCR assembly MTC200A1600(max gate trigger current = 180mA)?Thank you in advance!

author: SuzyC
author_rank: Frequent Contributor
timestamp: May 29, 2025, 12:54:52 pm
content: Sould work with a resistive load and transient voltqge protection if operation is well within max temperature limits..but where's the load?R80 would trigger the SCR's unless R82 and R83 are reduced to ~100-ohm.

author: Zero999
author_rank: Super Contributor
timestamp: May 30, 2025, 12:35:20 pm
content: R80 & C19 should be across U17 & U18, not Q9.
Driving a high-side mosfet as a switch for a DC application - Page 1
Forum section: electronics / beginners

author: niehu3s
author_rank: Newbie
timestamp: November 29, 2022, 06:17:48 pm
content: TL;DR: The most broke college student needs to drive a high-side MOSFET that will replace a relay, being ON for a long period. What is your suggestion?Hi, I'm developing an open-source automotive Power Distribution Module for my undergraduate thesis. Briefly, a PDM replaces the relay/fusebox of a car with solid-state switches and current sensing, thus providing real-time diagnostics, the ability to interface with CAN Bus directly and enables to customize the behavior of the power distribution by code.eg:https://www.ecumaster.com/products/pmu/;https://www.holley.com/products/data_acquisition/power_distribution_modules/As a proof of concept, the PDM will have 4 12V/20A and 4 12V/10A channels. Each channel is made up of: a high-side current sensing amplifier and its shunt resistor; a N-Channel Mosfet and its high-side gate driver. As shown in the image below, where GATE_LC0 is the signal coming out of a STM32 BluePill:However, I'm a broke (and Brazilian, which means everything is expensive) and can't seem to find a way to cheaply implement this gate-driver. There are ICs like the LTC1155, which are 2 Ch. high-side gate drivers, however they cost 6 dollars each, and I make only 95 dollars a month working a part-time job, so you can see how significant 30 dollars just in gate drivers would be XD.Thus, my question is: What is your suggestion on how to drive 8 high-side NMOS cheaply? Remembering that it won't be used with high frequency switching and more like a conventional relay, staying ON for a long period.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 29, 2022, 10:53:32 pm
content: One way is to use an P-channel fet. Then you can just pull the gate to GND (if the max Ugs allows that).Another way is to build a charge pump from a few diodes and capacitors that can lift the gate above the power supply voltage. In a more "advanced" form the MOSfet itself is made part of the charge pump, and this is called "bootstrapping". With that magic word you can find many examples. This is one of them:https://www.malabdali.com/mosfet-bootstrap-for-high-side-driver/Yet another way is to use a small auxiliary power source and "stack that on top" of your power supply. You will still need some kind of level converter to get upto that higher voltage.
driving a high voltage transformer? - Page 1
Forum section: electronics / beginners

author: electronics man
author_rank: Frequent Contributor
timestamp: October 31, 2015, 06:26:06 pm
content: Hi, i have made a high voltage transformer, i have been driving it with a power mosfet and my function gen, while this works it keep it keeps tripping my power supply probably from voltage spikes how do I stop this?

author: Simon
author_rank: Unknown
timestamp: October 31, 2015, 06:27:37 pm
content: Where do you think these voltage spikes are occurring? It sounds like you might need a TVS diode. You may need some sort of back EMF diode but I am no expert on this, posting your schematic might be a good idea.

author: electronics man
author_rank: Frequent Contributor
timestamp: October 31, 2015, 06:45:35 pm
content: here it is, i was thinking a diode but i dont know where to put it

author: Simon
author_rank: Unknown
timestamp: October 31, 2015, 06:55:56 pm
content: presumably you are feeding it a square wave. I do not know if negative back emf on the primary is a good thing, it would in any case get shunted into the power supply by the mosfets body diode, you could try a back emf diode, or a bidirectional TVS.

author: SeanB
author_rank: Super Contributor
timestamp: October 31, 2015, 07:13:56 pm
content: A mix of a TVS diode on the supply, some local bulk decoupling and across the transformer a snubber network of a resistor, capacitor and diode to clamp the turn off spike to a level the power device can handle.

author: electronics man
author_rank: Frequent Contributor
timestamp: October 31, 2015, 07:34:54 pm
content: could you give me a schematic for the snubber network?

author: SeanB
author_rank: Super Contributor
timestamp: October 31, 2015, 08:02:56 pm
content: Quote from: electronics man on October 31, 2015, 07:34:54 pmhttp://www.smps.us/12volt-powersupply.htmlD5 R9 C10 are the snubber, you will have to change the values slightly for 12V, R9 would likely be 150R 2W and the others would remain the same.

author: mij59
author_rank: Frequent Contributor
timestamp: November 01, 2015, 04:47:56 am
content: There is no load on the secondary winding, what are application do you have in mind ?
Driving a Magnetic Buzzer - Page 1
Forum section: electronics / beginners

author: Luchik
author_rank: Newbie
timestamp: August 23, 2016, 08:10:51 am
content: Background:I want to drive a magnetic buzzer from a 3V source.I use a BJT and a microcontroller connected to the BJT's Base pin. The microcontroller is also powered by the 3V source.A square wave of 50% duty is generated by the microcontroller in order to drive the buzzer.Now to my problem:Some people say that I have a problem with the driving voltage, since the BJT will take about ~0.2V of the buzzer voltage, leaving ~2.8V for producing sound. I am considering whether a design change is necessary or not. Also, I prefer using a transistor that is already in the BOM (I have a NPN: PDTC123JT and a PMOS: DMP2100U).Questions:1. Should I use a MOSFET instead of BJT? Will it really help?2. I noticed (in other designs) that a buzzer is always toggled to GND and not to VCC. Why is that?I'm thinking about using a PMOS and changing the design. What do you think?3. Is the 0.2V voltage drop critical to performance?Buzzer Datasheet:http://www.quartz1.com/price/techdata/BOT-03D.pdfTransistor Datasheet:http://www.nxp.com/documents/data_sheet/PDTC123J_SER.pdfSuggested PMOS:http://www.diodes.com/_files/datasheets/DMP2100U.pdf

author: leeatljs
author_rank: Contributor
timestamp: August 23, 2016, 08:18:55 am
content: The voltage rating of the buzzer is 2-4V so you are well in there.I notice the buzzer will draw about 100mA, that transistor is rated at 100mA.IMHO you will need a beefier transistor, the 2N7002 would do nicely.

author: Zero999
author_rank: Super Contributor
timestamp: August 23, 2016, 09:01:12 am
content: 1) Either a MOSFET of BJT will work. BJTs tend to be better at lower voltages though.2) The 0V is often switched because it can be done with NPN/NMOS devices which are easier to get hold of and cost less for the same rating PNP/PMOS device. You can use PMOS if you like but it will have a higher on resistance than an NMOS device with everythinh else being equal.3) It won't make much difference.

author: Whales
author_rank: Super Contributor
timestamp: August 23, 2016, 12:17:39 pm
content: 1 and 3) The best thing to do is try it. These parts should be cheap (in comparison to your microcontroller).2) Sometimes it's convenient to turn it on and off in reverse. If you have no reason to do so, then there is no difference other than P-type parts generally being more expensive (as Hero999 states).
Driving a relay directly from the output of a 555? - Page 1
Forum section: electronics / beginners

author: dog80
author_rank: Regular Contributor
timestamp: December 12, 2012, 10:21:45 pm
content: I got a kit similar to this one:http://www.velleman.eu/downloads/0/illustrated/illustrated_assembly_manual_k2579.pdfIt is a 555 in monostable mode, with a trim pot to adjust the output ON time. At the output there's a transistor that drives the relay coil.But the 555 is capable of 200mA output and that specific relay coil draws only 100mA. So why not ditch the transistor and drive the relay coil directly from the 555 output?

author: w2aew
author_rank: Super Contributor
timestamp: December 13, 2012, 12:04:03 am
content: Probably the main reason is that the output can only source that kind of current (can't sink it), and at that output current, the V(OH) will be 2-3V below the supply rail. Since that's a 12v relay, it may not give enough drive.

author: Simon
author_rank: Unknown
timestamp: December 13, 2012, 09:01:04 am
content: I have done this before and it worked but I can't remember the coil current draw. I also got away with no back E.M.F. diode as the sinking transitor on the 555 output presumably took care of that. I'd not recommend it thought for a permanent installation and it will depend on the particular 555 mutant you have.

author: SeanB
author_rank: Super Contributor
timestamp: December 13, 2012, 05:29:32 pm
content: Most will do the full 200mA. I drove a piezo tweeter from one at 40kHz as a pest repeller. Good thing I used a TO100 can version, as it did need a clip on heatsink, it was drawing close to 500ma from the supply. I was running hot to the touch without, and just warm with a small clip on heatsink. 2 555IC's with one being the power oscillator and the other being a modulator for it.
Driving a single 3W LED - Page 1
Forum section: electronics / beginners

author: Drake122
author_rank: Contributor
timestamp: March 09, 2018, 07:30:56 pm
content: Hey guys!Its a noobie question againDo I need some super complicated circuitry to drive a single 3W LED from 12V ? I know I could use a power resistor that wouldn't fry over the higher current, but that wastes a lot of energy. So, what is the simplest circuit to drive that thing?

author: SeanB
author_rank: Super Contributor
timestamp: March 09, 2018, 08:20:22 pm
content: Simplest is to order some 3W led driver boards on line, and use them. There are plenty that are tiny and have all the required circuitry on there, the input bridge rectifier ( so it will work on AC or DC supply), the buck converter and the current sensing, all in a small $1 part. I bought a couple of them as part of another order, and they are about the easiest solution as a plug in part.
Driving a small DC motor directly from a LiPo - Page 1
Forum section: electronics / beginners

author: prebs
author_rank: Newbie
timestamp: August 16, 2013, 01:26:58 pm
content: I remember very vividly a day back in 2008 when a LiPo battery got shorted and exploded. So understandably, im a bit nervous around them. I want to drive a small 5v DC motor, and it would be nice to do this through a 3.7 LiPo battery (motor should work even at 3.7). I am only worried that the motor might draw too much current, and upset the battery. I was thinking of adding a diode between, but would that have any safety effect at all ?Please advice if I can power a motor from a LiPo battery safelyThanks

author: cowana
author_rank: Frequent Contributor
timestamp: August 16, 2013, 01:44:06 pm
content: Hi prebsIn 99% of cases you'll be fine - a typical DC motor draws <1A, and a typical lipo can happily supply >5A. However it does depend on exactly what motor an battery you're talking about - can we have some more details?A diode would help slightly in reducing the voltage available to the motor (thus reducing current) - however this isn't a great way to protect the batter as you'll reduce the torque available. A fuse (or thermistor or polyfuse) would be a much better solution.Cheers,Andy

author: digsys
author_rank: Unknown
timestamp: August 16, 2013, 01:54:08 pm
content: They're not much different than any other type of battery chemistry. Forget the diode, and use a Polyfuse as suggested.Depending on chemistry, you can draw between 2C and 20C from the LiPO. If you don't know what type of chemistry it is,be safe and limit it to 2C. The only other precaution you might add, is not to let it drop below ~2.8 - 3.2V under full power.It just reduces the #cycles a bit. Can you post a pic of the battery?

author: redben
author_rank: Contributor
timestamp: August 16, 2013, 09:29:32 pm
content: You should also put a small capacitor in parallel to give more current when the motor is stopped or slowed down. It will help the battery to absorb current spikes and keep everything running with noises as low as possible.It will also prevent from magnetic and RF issues due to the sparks created at the brushes contacts.
Driving a speaker ??? - Page 1
Forum section: electronics / beginners

author: KM4FER
author_rank: Regular Contributor
timestamp: February 01, 2015, 07:11:03 pm
content: A simple beginner's question.I have a speaker from an old transistor radio. It is marked 8ohm, 0.3W.Using power formulas and Ohm's law I calculate that to get 0.3W from 8ohms I need about 1.5V and 193mA.OK, no problem.......so far.......But would that be Peak voltage/current or RMS?My thinking is that the heating effects of 0.3W would be averaged over many cycles and therefore RMS is the correct answer.But then there is this niggling thought that with 0.3W RMS the peaks are going to exceed that and since there is probably very fine wire in the speaker which could heat up and melt quickly I should be thinking in terms of the peaks of the cycle.Or, I guess I could just use the engineering practice of derating for safety's sake and limit input to about 0.15W?Any guidance?Thanks...earl...

author: Zero999
author_rank: Super Contributor
timestamp: February 01, 2015, 08:39:28 pm
content: Speakers are normally specified at the RMS power which is half the peak power for a sinewave.You need a peak voltage of 2.2V to get 0.3WRMS out.Unless the amplifier is bridged the supply voltage needs to be double that, before losses are taken into account so that's 4.4V but in the real world it needs to be higher than that.

author: IanB
author_rank: Super Contributor
timestamp: February 01, 2015, 08:46:37 pm
content: If you power your amplifier circuit from a small 9 V battery it is unlikely to have enough power to damage the speaker. This is possibly the kind of battery the old transistor radio originally used.

author: KM4FER
author_rank: Regular Contributor
timestamp: February 01, 2015, 09:00:43 pm
content: RMS seemed the most likely to me so I'll go with that.This is purely a learning experience for me so now I'll try to design an amplifier with 0.3W RMS output as one of the criteria.Thanks again.

author: MacAttak
author_rank: Unknown
timestamp: February 01, 2015, 09:25:12 pm
content: Quote from: Hero999 on February 01, 2015, 08:39:28 pmIs that correct? I thought RMS power for a clean sine wave was square root of two over two? (roughly 0.707)

author: lutkeveld
author_rank: Regular Contributor
timestamp: February 01, 2015, 10:46:29 pm
content: P=U^2/RVrms=Vpeak/sqrt(2)sqrt(2) squared is 2. So Vrms is indeed half Vrms

author: lutkeveld
author_rank: Regular Contributor
timestamp: February 01, 2015, 10:51:08 pm
content: The ratings of speakers are often thermal ratings. With average music power being at least 10-12db below peak, the excursion limit is more a problem. I would use a PAM8403 or similar powered by a single li-ion cell.

author: Zero999
author_rank: Super Contributor
timestamp: February 02, 2015, 08:52:00 pm
content: Quote from: MacAttak on February 01, 2015, 09:25:12 pmThat's the voltage.RMS power is half the peak power for a sinewave.
Driving a SSR from 110VAC ? - Page 1
Forum section: electronics / beginners

author: Dave Wave
author_rank: Contributor
timestamp: October 16, 2012, 10:11:39 am
content: I have a device that outputs a control signal (110VAC at 1 amp max). I need to use that signal to turn a larger load on/off. I want to use a SSR to do this, so I got this one from Amazon:http://www.amazon.com/25A-DC-AC-Solid-State-Relay/dp/B005KPGPU4/ref=sr_1_1?ie=UTF8&qid=1350381679&sr=8-1&keywords=LightobjectMy first thought was to use a xformer and FW rectifier to get a DC control voltage, but that seemed a bit clunky.I remember reading about driving an LED from 110V:http://homemadecircuitsandschematics.blogspot.com/2012/03/how-to-make-simplest-1-watt-led-driver.htmlI am assuming the SSR is something like a fancy optocoupler, so can I drive it just like a led?Thoughts?Any help appreciated!-Dave

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 16, 2012, 10:25:28 am
content: I found the following info:Input Data:Operating Voltage 3~32VDCMin. ON / OFF Voltage ON > 2.4V , OFF < 1.0VTrigger Current 7.5mA / 12VSo it is certainly not "like a LED"

author: Rerouter
author_rank: Super Contributor
timestamp: October 16, 2012, 10:32:45 am
content: why not use an AC relay? or is zero crossing a feature you are chasing?

author: SeanB
author_rank: Super Contributor
timestamp: October 16, 2012, 03:40:17 pm
content: You get SSR's with mains input specially for this use. You might find the input spec is typically 60-265VAC at 30mA, and the output is isolated and typically is able to switch 25-30A.You just have to be careful that the output you have is not a SSR itself, as then you will have to make sure the off state current is not going to trigger the power switch module. Normally you just use a 10W power resistor across the power switch inputs such that it draws 50ma or so to make sure the off state voltage is well below the power SSR minimum switch voltage.
Driving a transducer at 20 kHz  - Page 1
Forum section: electronics / beginners

author: igo762
author_rank: Newbie
timestamp: November 13, 2020, 05:34:37 am
content: I would like to drive this speaker/transducer by supplying a 20 kHz signal.https://www.mouser.com/ProductDetail/Visaton/MHT-12-8-Ohm?qs=%2Fha2pyFaduhbtYBJfXbwF%252B02doGhFiAGgrRzwnHRKw%2F3jhBv7qax1A%3D%3DMy first idea was to use something like a MP111FD amplifierhttps://www.mouser.com/ProductDetail/Apex-Microtechnology/MP111FD?qs=TiOZkKH1s2SckWaBxt%252B7Wg%3D%3DWould that work? I am very green so I appreciate any feedback as to what the best approach might be here.

author: Zero999
author_rank: Super Contributor
timestamp: November 13, 2020, 11:39:00 am
content: Quote from: igo762 on November 13, 2020, 05:34:37 amThat will work, but why not just use an ordinary audio amplifier?

author: igo762
author_rank: Newbie
timestamp: November 13, 2020, 08:43:53 pm
content: I am hoping to send a 20 kHz signal at 100 W of power. Could you suggest an off-the-shelf model amplifier that can do that?

author: MasterT
author_rank: Frequent Contributor
timestamp: November 13, 2020, 09:25:59 pm
content: TDA7293120-volt, 100-watt, DMOS audio amplifierwith mute and standbyhttps://www.arrow.com/en/products/tda7293v/stmicroelectronics

author: Benta
author_rank: Super Contributor
timestamp: November 13, 2020, 10:23:41 pm
content: https://www.ti.com/product/TPA3116D2

author: Zero999
author_rank: Super Contributor
timestamp: November 13, 2020, 10:45:29 pm
content: Quote from: igo762 on November 13, 2020, 08:43:53 pmYou'll need relatively high voltages.V = √(P✕R) = √(100✕8) = √800 = 28.3VBut the above calculation will giver the peak power, presumably you want 100W RMS? In that case you need double the voltage, which is 56.6V. Add a bit of headroom and you need a power supply of 60V. Note that this is assuming it's bridged, otherwise you need +-60V, a total of 120V.Changing to a 4Ohm tweeter would reduce the voltage requirements considerably.

author: BrianHG
author_rank: Super Contributor
timestamp: November 13, 2020, 10:55:04 pm
content: Quote from: Zero999 on November 13, 2020, 10:45:29 pmWhy not 2 of those 3$ amp chips in bridge mode.Now you only need a +/-30v supply.A good 32v+32v toroid for power would work fine.Or, 2 cheap off the shelf 48v switchers which support bridging would also be fine giving you some good headroom.
Driving AC contactor coil with DC - Page 1
Forum section: electronics / beginners

author: e100
author_rank: Frequent Contributor
timestamp: February 21, 2023, 02:35:26 pm
content: While researching how to drive a 24vac contactor coil with DC I stumbled upon this posthttps://www.quora.com/Can-the-coil-of-contactor-work-with-DCWhich contains the quote, "I have used DC drive for AC coil contactors for many years. I drive them with a short pulse of high voltage, usually about 15 ms and 140% of the rated voltage, followed by a holding voltage about 10% of the rated voltage."Unfortunately they don't go onto say how they achieve that voltage shift.So how do you do it? Is there a generic circuit or IC that is used for this purpose?

author: Grandchuck
author_rank: Super Contributor
timestamp: February 21, 2023, 02:40:32 pm
content: Not recommended but can be done at reduced coil voltage:https://www.te.com/usa-en/products/relays-contactors-switches/relays/intersection/operating-dc-relays-ac.html?tab=pgp-story

author: BillyO
author_rank: Super Contributor
timestamp: February 21, 2023, 04:02:05 pm
content: You need to limit the current through them if using DC, but then they might not pull in. I have used a resistor to limit the current and then parallel that with a capacitor to provide a decent pulse to pull the contactor/solenoid in.

author: TomKatt
author_rank: Frequent Contributor
timestamp: February 21, 2023, 04:31:52 pm
content: Many DC motor driver chips double as solenoid drivers... Most are PWM current limiting, allowing the high energy pulse needed to pull in the solenoid, followed by reduced hold-in current.

author: pardo-bsso
author_rank: Frequent Contributor
timestamp: February 21, 2023, 05:08:31 pm
content: I don't recall if it was Jim or Bob who described the circuit but the easiest way to achieve that is to have a current limiting resistance in series with the coil and a big electrolytic cap in parallel with that resistance.At turn on the cap behaves mostly like a short and you get a brief high current impulse. After the cap has charged the coil ends up with the resistor in series that drops the current to a lower value (that should be greater than the minimum holding current).(Add protection diodes and such where needed)
Driving an RGB LED Strip - Page 1
Forum section: electronics / beginners

author: aussieW
author_rank: Newbie
timestamp: February 07, 2019, 12:22:20 am
content: HiI am building a circuit to control some 12 volt RGB LED strips that I bought on AliExpress (https://www.aliexpress.com/item/SMD-5050-RGB-LED-Strip-Waterproof-5M-300LED-DC-12V-24V-CCT-RGBCCT-RGBW-RGBWW-WHITE/32903257649.html). I am controlling each of the R, G, B channels through a mosfet which in turn is being controlled by a PWM signal from an ATMega328. The LED strip and ATMega are being powered using a 12 volt linear bench power supply. The LEDs seem to behave as expected, however, when I looked at the PWM signal on the scope (probing the Gate pin) I was surprised to see spikes in voltage of ~22 volt . That seems strange to me as I would expecting to see a nice clean square wave with a max voltage of 5 volts, but as I am a newbie I am seeking guidance from experts as to whether this is normal behaviour, whether I may potentially do damage to my LEDs, what I may have done wrong in my circuit, etc. I have attached a circuit diagram and a screenshot from the scope for reference.Any advice/assistance would be most appreciated.

author: ogden
author_rank: Super Contributor
timestamp: February 07, 2019, 02:13:49 am
content: Could be layout problem, could be probing problem. Most likely both.First thing to ensure - proper probing (of high speed signals) so what you see on the scope screen is what actually happens in your circuit. Use spring clip, not ground "crocodile tail" and measure between two pins of the transistor (gate/ & source). Never connect ground of your scope probe at random ground point, always pick ground connection as close to probe tip as possible. For slow signals "crocodile tail" is ok, but for fast and hi-current spikes in nearby (ground?) wires - it acts like antenna.

author: aussieW
author_rank: Newbie
timestamp: February 08, 2019, 01:20:53 am
content: Thanks for the tip. My probing method was obviously the problem. After I got the probes as close as I could the wave form was a much cleaner square wave ranging from 0 to 5v.

author: StillTrying
author_rank: Super Contributor
timestamp: February 08, 2019, 12:48:11 pm
content: Having the trig level right near the level of the 5V noise is a bad position, moving it down onto the pulses, or up onto the spikes would be better.
Driving an SCR with a Arduino - Page 1
Forum section: electronics / beginners

author: ZeroResistance
author_rank: Frequent Contributor
timestamp: February 28, 2018, 11:24:24 am
content: I want to control an SCR (on /off) with an Arduino Nano.The SCR is connected to 300 to 400V DC derived from mains but this is isolated from the mains.Currently I have just connect an I/O pin of the Arduino to the gate through a 220ohm resistor but this was not working properly I could measure voltage above 5V coming back into the I/O pin then I added a 1N4148 diode in series with the 220ohm resistor but even this setup doesn't seem to work out and the work at the I/O pin seems to drop to around 2.5V.I'm using Pin D2 to drive the gate of the SCR.Is is mandatory to drive the SCR via a opto coupler? Are there any other drive circuits that will work reliably.

author: retrolefty
author_rank: Super Contributor
timestamp: February 28, 2018, 11:48:10 am
content: Normally one doesn't utilize an SCR for controlling DC source voltages as once you turn on the SCR you lose the ability to turn off the SCR. Perhaps a schematic drawing would help us help you?

author: danadak
author_rank: Super Contributor
timestamp: February 28, 2018, 12:13:01 pm
content: Post a schematic as this sure sounds like you are potentially setting upUP for latchup because of Voltages applied to pins outside its permissiblerange allowed. Series R can allow driving I/O pin parasitic diodes but has tobe limited to prevent CMOS latchup due tro parasitic SCR structure inherentin CMOS.https://en.wikipedia.org/wiki/Latch-uphttps://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjY75Lry8jZAhWnuFkKHXGKCagQFggnMAA&url=https%3A%2F%2Fwww.fairchildsemi.com%2Fapplication-notes%2FAN%2FAN-339.pdf&usg=AOvVaw0N7NnjfjppHF0Vl4H16wJmIf SCR driven by mains then it will turn itself off on polarity half cycle reversalwhen its current drops below holding value.This shows some mains applications -http://www.learnabout-electronics.org/Semiconductors/thyristors_62.phphttp://www.nutsvolts.com/magazine/article/scr_principles_and_circuitsRegards, Dana.

author: ZeroResistance
author_rank: Frequent Contributor
timestamp: February 28, 2018, 12:20:17 pm
content: Basically the SCR discharges a capacitor that is charged to around 300VDC.
Driving an ultrasonic piezo transducer for TOF flow measurement - Page 1
Forum section: electronics / beginners

author: FrankT
author_rank: Regular Contributor
timestamp: January 19, 2016, 01:58:06 am
content: I got some junk email from digikey advertising a reference design that measured fluid flow using ultrasonic transducers...http://www.digikey.com.au/product-search/en/programmers-development-systems/evaluation-and-demonstration-boards-and-kits/2622039?k=max35101A bit pricey, but I was wondering if I could cobble together something cheap.The MAX35101 (or the cheaper MAX35102 $9) with a couple of transducers ($?) and a bit of plastic pipe is still cheaper than impeller type flow sensors that I use on my water tanks - and they wont gunk up.However, I'm not sure what type of transducers I need and how to drive them.The MAX3510X can drive them at 125kHz to 1MHz, but when looking at them (eghttp://au.element14.com/multicomp/mcusd25p200b10-7rs-30c/transceiver-200khz-25mm-plastic/dp/2362686) it talks about a drive voltage of 500V perk to perk (yes, that's what it says in the datasheet). The reference design connects the IC directly to the transducer.Am I looking at the wrong type of transducer? Or is it fine to run off lower voltages for the small distance ranges (less than 10cm)?Thanks,Frank

author: coppice
author_rank: Super Contributor
timestamp: January 19, 2016, 05:16:17 am
content: Piezo transducers for sending 1MHz through water usually require only a few volts. The loses through water at that frequency are low, so you get a good strong signal at the receiver quite easily.If you are measuring through gas you need a strong signal at the transmitter to keep the signal above the background noise at the receiver. Some of those transducers require quite a high voltage - tens or hundreds of volts.
Driving BBD from MCU - Page 1
Forum section: electronics / beginners

author: ErnstHot
author_rank: Newbie
timestamp: January 21, 2015, 10:54:48 am
content: I need to drive the clock inputs on a MN3207 bucket brigade device from an MCU. The clock voltage needs to be 14/15 of the MN3207's Vcc and the input capacitance is relatively high, so I need to provide enough current to overcome that at high frequencies.This circuit(PDF) uses a CD4049 to buffer the clock signals, but that needs a higher input signal voltage than an MCU can provide on it's own and so I'm wondering if there's any reason I can't use a transistor to drive the MN3207 directly from the MCU? What would such a circuit look like, other than obviously the transistor? Is there a simple and clever way to get the inverse clock as well without using an extra pin on the MCU?(All this is subject to my possibly flawed understanding)Thanks

author: HalfSpace
author_rank: Regular Contributor
timestamp: January 23, 2015, 08:51:25 pm
content: Hi ErnstHot,You could drive the MN3207 with a mosfet driver IC like the TC4428A or a lower power one. They are 3.3V compatible inputs, inverting and non-inverting outputs and can output up to 18V at high capacitive loads.HalfSpace
Driving bigger fans in my 3D printer... - Page 1
Forum section: electronics / beginners

author: Bug2k17
author_rank: Contributor
timestamp: July 23, 2019, 04:18:12 pm
content: The board in my ctc 3d printer has a port for adding an extra fan, I've used it with a small 40mm 24v fan without problems for a while.I am trying to power 2 80mm 12v fans (in series) from this output. It does work but heat and smell produced tells me this is not going to work long term.Measuring the voltage at the socket with the fan off gives, +24.2v and +22.3v, with the fan switched fully on gives +24.2 and ~+0.4v.I though perhaps something like a tip120 or tip125 (as I already have some of these!) might be able to drive the fans, but I really can't get my head around how this is going to work. I would appreciate any advice on how drive the fans from an output like this.Thanks.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 23, 2019, 04:59:13 pm
content: You can't drive fans (or any motors, for that matter) in series. The current never balances properly, and one ends up getting too much voltage.Use two 24V fans in parallel instead.

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2019, 06:23:12 pm
content: While it's generally not advisable, I don't think that's the problem here. It sounds to me like the driver is overheating due to the current draw of the larger fans. Do you have a schematic? What controls the fans in the existing setup?

author: Bug2k17
author_rank: Contributor
timestamp: July 23, 2019, 07:39:25 pm
content: This socket has the part 7R030 next to it, a quick google brings up thishttps://www.nexperia.com/products/mosfets/power-mosfets/PSMN7R0-30YL.htmlwhich looks like the correct package.That spec looks like it should handle a couple of fans easily?

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2019, 09:12:13 pm
content: Assuming it's being driven into saturation it should. Is that the part that's getting hot?

author: Bug2k17
author_rank: Contributor
timestamp: July 24, 2019, 09:36:45 am
content: Ok, I've run the printer with the board out, it seems the cause of the heat seems to be an adjacent connector starting to melt! This one drives the heated print bed. It seems the extra cooling is causing the print bed heater to work much harder in order to keep it at target temperature. I've taken the connector sockets off the board and soldered the wires for the heater directly onto the board. After running a small print, there appears to be no overheating and it works fine.It does seem that these boards are not capable of adjusting the fan speed, the gcode to run them works with an M106 S0 switching it off and other values 1-255 just power it on a full speed.Thanks for the help, much appreciated. My fault finding skills need work!
Driving capabilities of MPU - Page 1
Forum section: electronics / beginners

author: nnills
author_rank: Contributor
timestamp: April 17, 2020, 07:55:24 am
content: Hi,I am planning on building a computer based on a 6809(NMOS). While reading the datasheet I came across this:[ Attachment Invalid Or Does Not Exist ]I understand what it says but not what it doesn't. It only talks about TTL inputs. Does this mean that it can it drive an "infinite" amount of NMOS/CMOS inputs?Nils

author: nnills
author_rank: Contributor
timestamp: April 17, 2020, 07:58:57 am
content: The picture:

author: Manul
author_rank: Super Contributor
timestamp: April 17, 2020, 10:42:52 am
content: Two things. First, it states maximum capacitance, for example 90 pF. That is the limiting factor of how many inputs it can drive in case of CMOS. Also PCB trace capacitance must be included. So it will for sure be not infinite, maybe 5 or so. Second, output levels seems to be TTL and that is not directly compatible with CMOS inputs. So then the answer is zero.
Driving Darlington Transistor array from Shift Register - Page 1
Forum section: electronics / beginners

author: talvor
author_rank: Contributor
timestamp: September 12, 2013, 03:43:01 am
content: Hi all,I don't have the chips yet to test this but I would like to know if a shift register can be used as the input to a Darlington Transistor array like the UNL2803A?Thanks

author: David_AVD
author_rank: Super Contributor
timestamp: September 12, 2013, 04:56:02 am
content: A very common combination is the 74HC595 shift register and ULN2803A driver.

author: talvor
author_rank: Contributor
timestamp: September 12, 2013, 05:20:50 am
content: Quote from: David_AVD on September 12, 2013, 04:56:02 amThanks for the response.I have some 74HC595 chips on the way. I will grab a couple of ULN2803A drivers and testthis out.

author: oPossum
author_rank: Super Contributor
timestamp: September 12, 2013, 03:13:58 pm
content: Single chip solution:http://www.ti.com/lit/ds/symlink/tpic6a595.pdfhttp://www.ti.com/lit/ds/symlink/tpic6b595.pdfhttp://www.ti.com/lit/ds/symlink/tpic6c595.pdf
Help requested - Driving LED matrix? - Page 1
Forum section: electronics / beginners

author: Xephlon
author_rank: Newbie
timestamp: April 28, 2020, 11:12:06 am
content: Hey there,Recently I have decided to get some of these P4 LED matrixes for a home project of mine:- Two of these:https://de.aliexpress.com/item/32633386488.html?spm=a2g0o.detail.1000023.9.433d7ff7mxEtLX- One of these:https://de.aliexpress.com/item/33023473536.html?spm=a2g0o.detail.1000023.8.433d7ff7Divn59&storeId=933144I would then want to arrange the matrixes so that they were all landscape (Making a 160x32 display)My issue is that for my project I need to send video from my computer to the matrix so that it acts as a second monitor. I have looked for so long and have found no solution that will decode any video source (HDMI/DVI/VGA) for the LED matrix. There are 'sender' and 'receiver' cards which will send the decoded video signal for the matrix (originally DVI) and distribute it to the matrixes at the receiver card, but this totals a cost of over £100 and is not cost-effective for my small project.Sender card is called TS802D and receiver card is called RV908M if you want to lookI also saw this GitHub project where an HDMI signal is decoded by a Spartan6 FPGA, but I can hardly program an Arduino so I am not confident taking that path.https://github.com/ncortot/fpga-led-matrixCan anyone more experienced with this suggest any ideas? Help is greatly appreciated.Thanks

author: mayor
author_rank: Regular Contributor
timestamp: April 29, 2020, 10:08:16 am
content: If you are not an experienced programmer, you will need to buy a prebuilt solution, imho. Even if you were able to put a program together, these panels aren't the easiest to drive, and require fairly beefy hardware. You will have to spend money to get them hooked up to the VGA or DVI output of a computer.
Driving LED with PWM speed controller or step motor driver? - Page 1
Forum section: electronics / beginners

author: zappedy
author_rank: Regular Contributor
timestamp: November 04, 2015, 08:58:55 am
content: Can I do that? I have 3x 3W LED stacks that take 700mA each, but no means to drive it. I haveone of these however (or approx. the same)But I was also going to get a step motor controller, can I use that instead, like anEasyDriver?So, I put a small inductance in series?I realize a DC-DC power module would be the right thing, I'm just curious if motor drivers would work.Just asking before trying so I don't burn anything.

author: tron9000
author_rank: Frequent Contributor
timestamp: November 04, 2015, 09:04:30 am
content: having trouble viewing those links

author: zappedy
author_rank: Regular Contributor
timestamp: November 04, 2015, 09:17:43 am
content: fixed

author: tron9000
author_rank: Frequent Contributor
timestamp: November 04, 2015, 09:30:51 am
content: Stepper drivers and simple PWM drivers work differently.Stepper drivers typically have a H-bridge to drive the motor coils. This allows current to flow in either direction through its coil.The PWM driver looks like some sort of astable chip, whose output is adjustable by the pot, and there's another chip that could be a MOSFET in SOIC package.I would say you can use the PWM driver board and hook it straight up without additional inductance, but your input voltage must be the same as the voltage to drive your LED strip, otherwise if you wind the wick up too far you could blow your string.

author: zappedy
author_rank: Regular Contributor
timestamp: November 04, 2015, 09:42:09 am
content: Thanks!The EasyDriver step motor driver has current limiting though, wouldn't that work, if I set it to slightly below 700mA?

author: tron9000
author_rank: Frequent Contributor
timestamp: November 04, 2015, 09:50:52 am
content: well yes, but that is $15 a board and you'd be only using 1/2 of the h-bridge and all that capability would be going to waste.its like putting a Ferrari F40 engine in a generator.if you want to limit the current to protect your string you could put an in-line fuse with your string.
Driving LEDs with 74LS logic - Page 1
Forum section: electronics / beginners

author: sci4me
author_rank: Regular Contributor
timestamp: July 08, 2015, 03:36:04 pm
content: Hey guys. So I want to add indicator LEDs to different parts of my logic circuits so I can see what it's doing as it runs. Looking at the spec sheets, the high level output currents are like <1 mA... so... what's the right way to drive an LED (and other gates) with that? Can I just add a transistor to drive the LED?

author: SeanB
author_rank: Super Contributor
timestamp: July 08, 2015, 04:02:22 pm
content: TTL is better at sinking current, so run the LEd's from the 5V rail with the logic low turning them on. Use 5mA as a current and most modern LED devices will be very bright at this current. Typically this means a 470R resistor per LED.

author: retrolefty
author_rank: Super Contributor
timestamp: July 08, 2015, 04:04:04 pm
content: A typical 74LS00 output pin can sink significant current to drive a standard LED. Just wire the cathode to the output pin through a suitably sized series resistor (calc for maybe 10 ma, plenty bright) to then to +5vcc. You just have design for circuit so that a LOW output is the active (lite) state.

author: sci4me
author_rank: Regular Contributor
timestamp: July 09, 2015, 02:50:39 am
content: Quote from: retrolefty on July 08, 2015, 04:04:04 pm*sigh* I suppose I have to switch to using 0v as 1 instead of 5v instead of 1... I really wish I had done this from the start...Hmm...

author: Mr.B
author_rank: Unknown
timestamp: July 09, 2015, 02:54:46 am
content: If you don't want the LED to indicate the reverse logic you could use logic level N-Ch FETs, but its going to get busy/messy...

author: edavid
author_rank: Super Contributor
timestamp: July 09, 2015, 03:23:05 am
content: You could use 74HCT where you want to drive LEDs... it can drive about 5mA in the high state.

author: MarkF
author_rank: Super Contributor
timestamp: July 09, 2015, 09:18:15 am
content: Quote from: sci4me on July 09, 2015, 02:50:39 amUse a SN74HC240 or SN74HC244 to drive your LEDs depending on which logic level you want to light the LED. The '240 inverts and the '244 does not.
Driving Leds - Page 1
Forum section: electronics / beginners

author: FlyMario
author_rank: Contributor
timestamp: August 27, 2018, 05:35:55 pm
content: Hi, for Halloween I have several props that are going to use about 350 to 400 LED's each. About 1000 LEDs are going to be 2v 20ma. Instead of soldering so many resistors, I am wondering if I just used a Buck converter putting out 2V at 2A could I just drive a lot of LED's straight off that or would that be LED suicide. Of course, I know I am only going to drive 2A worth of LED's max. As long as I stay under 2A pull from the Buck Converter should I be ok?Thanks,Pete

author: Benta
author_rank: Super Contributor
timestamp: August 27, 2018, 05:55:01 pm
content: No. What you do is connect the LEDs in series and give each series string 20 mA. Depending on your supply voltage, you can decide how many LEDs to each string. Allow for extra voltage for current limiting (~5 V).

author: Brumby
author_rank: Unknown
timestamp: August 28, 2018, 02:24:36 am
content: As Benta has said, series strings are the way to go.50 strings of 20 LEDs; 20 strings of 50 LEDs; 23 strings of 42 LEDs plus one string of 34. There are a lot of ways to go about this. How many LEDs in each string will depend on the capabilities of the power supply you have available and safety considerations of the voltage applied.Running LEDs in parallel isn't the best idea anyway as there will be small differences in their Vf- so some will be brighter (ie drawing more current) than others. There are some products that do this out of cost reduction objectives, but these tend to work because the LEDs are well matched, having come from the same batch. However, I would expect than in a thousand LEDs, you wouldn't be so lucky.

author: FlyMario
author_rank: Contributor
timestamp: August 28, 2018, 12:30:11 pm
content: Yeah thanks guys, I was trying to be lazy. I have so much soldering to do as it is for these monster heads. Just don't need to focus on how many I need to do but instead on how good it will lookFlyMario
Driving MOSFET in my circuit - Page 1
Forum section: electronics / beginners

author: laurence.fourie
author_rank: Newbie
timestamp: June 12, 2024, 07:05:10 pm
content: Hello everyone. I am an electronics hobbyist and have designed a board with an ESP32 micro to use as an alarm panel around my home. The idea is to be able to take a wide range as input voltage into MOSFETs that will switch the LED in an optocoupler. The transistor side of the opto triggers an input on the ESP32. I would appreciate it if you can advise what is wrong with my circuit. Without any input on the MOSFET gate, I measure 2V on the MOSFET's gate. Circuit attached. Thank you in advance for your time and comments.

author: Victorman222
author_rank: Regular Contributor
timestamp: June 13, 2024, 12:12:54 am
content: Hello Laurence. It seems that there is an undefined voltage on MOSFET gates because there is no pull down resistor between gate and source. The MOSFET gate looks like a capacitor from the input side, and it may pick up voltage from various interference sources.Also, what wide range of input voltage are you considering? MOSFET gates typically can handle only +- 20V.

author: CaptDon
author_rank: Super Contributor
timestamp: June 13, 2024, 12:51:51 am
content: Really, the gate is just floating and you expect to get some meaningful reading? As another poster stated, install a pull down resistor or show us what you intend to connect to the gate. "A wide range of voltages"Like what? 0-10vdc? Do you know how a mosfet works and at what gate threshold voltage the mosfet begins to conduct? A "wide range of voltages" could be 0 to 10 kilovolts, define it a little more.

author: xvr
author_rank: Frequent Contributor
timestamp: June 13, 2024, 09:44:05 am
content: QuoteMOSFET is not right device to handle 'wide range' of input. Use resistors and zeners (or TVS).

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 13, 2024, 10:56:23 am
content: Why do you need MOSFET to drive opto anyway? This is practically backward compared to most common implementation. Especially where you need robustness like those in PLC input modules.For one, unprotected MOSFET input areverysensitive to ESD, and can't tolerate overvoltage at all. Optos also usually don't need that much current to operate anyway. Overspecifying series resistor to cope with wide expected input voltage usually won't hurt.

author: kevin.gibbs
author_rank: Regular Contributor
timestamp: November 13, 2024, 12:33:47 pm
content: First, I would move the resistors from the source circuit to the drain circuit.Secondly, suppose the transistors will not always be connected to the signal source (floating gate). In that case, resistors are needed between the gate and the source so that the transistor is initially closed.

author: PGPG
author_rank: Frequent Contributor
timestamp: November 13, 2024, 03:21:26 pm
content: Quote from: kevin.gibbs on November 13, 2024, 12:33:47 pmDo you think, after 5 months OP is still waiting help in solving his problem?