hybridfree/eevblog-posts huggingface dataset:
555 square wave help - Page 1
Forum section: electronics / beginners

author: electron_misfire
author_rank: Contributor
timestamp: April 05, 2014, 06:13:50 am
content: I'm designing a simple square wave generator.I'm using a 555 timer in astable mode.My problem is that whenever I power the circuit it turns on the after a few seconds turns off and never goes back on again.Would anyone have some advice or help?

author: Simon
author_rank: Unknown
timestamp: April 05, 2014, 06:18:12 am
content: Is the top resistor value 1R ?1000uF ? you need to read the datasheet thoroughly, there is a limit to the discharge current allowed in pin 7

author: electron_misfire
author_rank: Contributor
timestamp: April 05, 2014, 06:48:43 am
content: Ok I've swapped the 1r resistor and 1000uf cap. It's working now thanks

author: Simon
author_rank: Unknown
timestamp: April 05, 2014, 07:00:38 am
content: I think that 1R needs to be 1K minimum (check the allowed discharge current) and with 1000uF and 4K that would have given a 4s discharge time.Datasheets have all the formulas, give it a thorough read.
555 timer - Page 1
Forum section: electronics / beginners

author: TheDood
author_rank: Regular Contributor
timestamp: September 23, 2019, 05:30:36 am
content: I keep seeing people bash on the 555 timer for PWM applications and was wondering if someone could explain why, and/or suggest a cheap, widely used, but more relevant option(s)?If using batteries to power the cct, are certain timers less needy for power than others?

author: Nusa
author_rank: Super Contributor
timestamp: September 23, 2019, 07:07:24 am
content: The 555 is a jack of all trades type of chip that's extremely versatile in the right hands. PWM is one of the things it can do, but without getting specific about the application, it's hard to say how suitable it is for it.In todays the digital world, hardware pwm support is common in microcontrollers at all price levels. Software pwm is also practical. Which means anything that already requires a processor typically already has pwm capability on hand.

author: Zero999
author_rank: Super Contributor
timestamp: September 23, 2019, 02:54:08 pm
content: One of the downsides to the 555 timer doing PWM is it can't go all the way down to 0% or up to 100% duty cycle, which a microcontroller can.Another solution is to use a comparator IC, such as the LM393, but it requires more components.
555 timer cap charge question - Page 1
Forum section: electronics / beginners

author: DuncanSteel
author_rank: Contributor
timestamp: October 02, 2016, 07:06:33 am
content: HiI am wondering how is it possible that this cap is being charged?1. Initial condition is cap=0V2. R-Op-Amp3. If we apply 0V to (+) and 6V to (-) input = 0V output4. S-Op-Amp5. If we apply 3V to (+) and =V to (-) input = 9V output6. From flipflop we get 1 as output that is inverted & we get 0V thus cap can not start charging to begin with thus the cycle can not begin.Now I tested this circuit, it works as a dimmer. I don`t get how it is possible?

author: Zero999
author_rank: Super Contributor
timestamp: October 02, 2016, 06:13:48 pm
content: The capacitor is both charged and discharged via the, potentiometer, diodes and the output (pin 3) of the 555 timer. Adjusting the potentiometer alters the resistance on the charge and discharge cycles, thus varying the duty cycle.Bipolar 555 timers such as the NE555 & LM555 have an asymmetrical output stage so won't give a 50% duty cycle when the potentiometer is in the centre and both the frequency and duty cycle will vary depending on the supply voltage. Use a CMOS 555 timer such as the ICM7555 or TLC555 which has a symmetrical output stage and will not suffer from either of the aforementioned issues.
555 timer frequency increasing/decreasing - Page 1
Forum section: electronics / beginners

author: just5554
author_rank: Contributor
timestamp: February 18, 2016, 04:23:38 pm
content: Hi, I want to make circuit with 555 timer, that when i press one button frequency increases, and when i press another, freq. decreases.I need that for my LM317 project, so I could control voltage with buttons. Thank you! Sorry for my maybe awful English. Just say something where to find or what components I should use.

author: Dave
author_rank: Super Contributor
timestamp: February 18, 2016, 04:28:26 pm
content: Get a microcontroller.

author: just5554
author_rank: Contributor
timestamp: February 18, 2016, 04:34:28 pm
content: I also though about something like arduino, well i think i will have to use it

author: Zero999
author_rank: Super Contributor
timestamp: February 18, 2016, 07:31:35 pm
content: Yes, a microcontroller will be able to do that.Just wondering; what does this have to do with an LM386?

author: Leestons
author_rank: Contributor
timestamp: February 18, 2016, 07:47:11 pm
content: Quote from: Hero999 on February 18, 2016, 07:31:35 pmWho mentioned a LM386?

author: Zero999
author_rank: Super Contributor
timestamp: February 18, 2016, 07:53:22 pm
content: Quote from: Leestons on February 18, 2016, 07:47:11 pmSorry, I meant LM317.What does a variable frequency 555 timer oscillator have to do with an LM317?

author: Aodhan145
author_rank: Frequent Contributor
timestamp: February 18, 2016, 09:26:08 pm
content: Quote from: Hero999 on February 18, 2016, 07:53:22 pmMaybe he was going to control the adjust pin with PWM and a filter?Only thing I can think of.

author: Zero999
author_rank: Super Contributor
timestamp: February 18, 2016, 10:10:06 pm
content: Quote from: Aodhan145 on February 18, 2016, 09:26:08 pmThat's PWM which is different to just changing the frequency.It will work but the microcontroller will need to be powered from a fairly accurate power supply voltage and the filtering must be good enough to avoid noise being coupled to the LM317 output.
555 timer issue - Page 1
Forum section: electronics / beginners

author: IvoS
author_rank: Frequent Contributor
timestamp: December 22, 2013, 09:25:16 pm
content: I am having problem with 555 timer. Everything looks nice when channel is put to DC coupling, pic #1.When I switch to AC coupling (pic #2) on my Rigol scope, I see nasty non-square like waves. I am not sure what's going on. What I don't understand is the falling edge goes to -8.8V. I would expect it to be around -5V when AC coupled, kind of symmetrically distributed from the center 0V point, my PSU is set to single +10V. Why don't I see top and bottom edge flat anymore? Any idea?

author: Zero999
author_rank: Super Contributor
timestamp: December 22, 2013, 10:06:27 pm
content: It's what you should expect to see when you switch to AC coupling. The capacitor and resistor on the 'scope input form an integrator which causes the classic exponential decay when the capacitor charges and discharges. If you increase the frequency of the 555 to something like 1kHz, the weird curves and spikes will disappear.

author: IvoS
author_rank: Frequent Contributor
timestamp: December 22, 2013, 10:25:54 pm
content: I thought that pin 3 output is just a flip-flop output and therefore should still maintain reasonably square wave. ?

author: grumpydoc
author_rank: Super Contributor
timestamp: December 22, 2013, 10:47:55 pm
content: QuoteNothing to do with pin 3's output.Hero999 is right - you are seeing the effect of AC coupling on what the 'scopeshows- usually when you switch in AC coupling the lower frequency response tails off below about 10Hz and this will affect the display of slow square wave signals.

author: M0BSW
author_rank: Frequent Contributor
timestamp: December 23, 2013, 07:46:48 pm
content: Quote from: grumpydoc on December 22, 2013, 10:47:55 pmI use pin 3 as a trigger pulse output for scope, showing the triggering pulse on the scope, which I learned from a W2AEW video, and I've used it on several other projects . I agree with the others from my limited experience.

author: IvoS
author_rank: Frequent Contributor
timestamp: December 23, 2013, 09:17:57 pm
content: Thanks guys. Had no idea that scope input can mess it up to that extent. So there is nothing wrong with the output and the waves are still reasonably square. I was surprised how quick rise and fall edges were. If I remember correctly the rise time was 130ns and fall time around 15ns in my slow speed configuration.

author: Zero999
author_rank: Super Contributor
timestamp: December 23, 2013, 10:57:35 pm
content: It's a high pass filter so the high frequency parts of the signal (rise and fall) are not changed, only the low frequency parts (where the signal is high or low for a long period) are suppressed.
555 Timer problem - Page 1
Forum section: electronics / beginners

author: electroniceddy
author_rank: Newbie
timestamp: June 05, 2019, 10:33:50 am
content: Hi guys,im in no way a pro, but a hobbyist, and i have been trying to create a 555 timer wihtout the use of a microchip (ie just with transistors) i have built the following circuit 4 timesand have added some stuff to the front in order to make an a-stable 555 timer, however on every occassion all im getting is a continuous output of on.. 4 different times, (first 2 on breadboard, the second two on circuit board)is this actually a correct schematic for the 555 timer.?im using2n2222 Npn transistors2n3904 Pnp transistorsand1n4002 diodescheers

author: virtualparticles
author_rank: Regular Contributor
timestamp: June 05, 2019, 11:43:56 am
content: OMG, this is very ambitious. Keep in mind that some of the transistors are used in strange ways because it is easier to fab a transistor than a resistor. If I were you, I would load this into LTSpice and analyze it there. The 3904 is one of the transistor choices and any old diode is fine. The 3904 might not have the needed properties for this though. You should be able to troubleshoot it that way.

author: mikerj
author_rank: Super Contributor
timestamp: June 05, 2019, 12:02:54 pm
content: Trying to recreate an IC with discrete components using the original schematic is somewhere between difficult and impossible. There is already a well proven discrete 555 design availableas a kitand thedatasheet pdfincludes the schematic.

author: Wimberleytech
author_rank: Super Contributor
timestamp: June 05, 2019, 12:25:02 pm
content: May be an issue with your flip flop. Try changing the 5k connected to the diode, to 15k as shown in the schematic linked above by mikerj.Also, put a resistor in series with the output LED.

author: Achu
author_rank: Contributor
timestamp: June 05, 2019, 12:29:33 pm
content: I think you could build each sections like comparators, flip flop using transistors and connect them together at last.This modular approach will have more chance of success I believe.A wise man once said nothing
555 timer pwm dimmer for higher voltage - Page 1
Forum section: electronics / beginners

author: Martichoke
author_rank: Newbie
timestamp: March 18, 2019, 10:56:48 am
content: Hi all,My plan is to add some dimming to my 2835 led strip.The strip is powered from 240v(ish)ac into GBU810, off memory putting out 220v(ish)dc.I really like the idea of making my own dimmer and would like to know if its okay to use a 555 timer pwm as a base schenatic and simply change the components for higher rated equivalents.1. Is this even possible/ the safest and most practical path?If yes,How/where can i easily find a higher rated benchmark equivalent? (a 555 timer that is higher rated than 15v, etcIf no,Can you please point me in a good directionOn a side note, I'm an electrician and can safely practice with higher current.Thanks,Choke

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2019, 01:31:22 pm
content: It's a bridge rectifier, so you really have nearly 240√2 = 340V peak, unfiltered DC, not 220VDC.https://www.diodes.com/assets/Datasheets/ds21227.pdfThe 555 timer circuit could theoretically be run off a 12V power supply and drive a transistor rated to >400V to PWM the LED strip, but it's not a beginner project. The whole 555 circuit would float at the mains voltage, thus would need to be treated with the same precautions as the mains.

author: Martichoke
author_rank: Newbie
timestamp: March 18, 2019, 08:03:47 pm
content: Ah thanks for the correction, i was to lazy to bring up the datasheet and i installed it months ago so couldnt quite rememberThanks for the transistor idea, ill try that.

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2019, 09:53:00 pm
content: Quote from: Martichoke on March 18, 2019, 08:03:47 pmI don't think I made myself clear, regarding the danger. The whole 555 timer circuit, including anything connected to it: the 12V power supply, potentiometer which must be plastic, by the way, etc. will all be live at mains voltage. Observe all of the usual precautions when working with mains voltages.Why not simply dump 240V LED strip and replace it with 12V LED strip? The 555 timer circuit will safely work off 12V, with no problems and there's no need to worry about getting a shock off it.
555 Timer PWM without diodes! - Page 1
Forum section: electronics / beginners

author: ali6x944
author_rank: Frequent Contributor
timestamp: May 13, 2016, 01:41:12 pm
content: Hi everyone,I was playing around with the all time favorite 555 Timer, to be more exactly pin 5 of the timer, then bang I pwm signal that increace in duty cycle as the voltage increase and do the opposite as the voltage decrease but I shall admit it needs a very quiet supply because any voltage change will effect the duty cycle, so I tried to reduce this effect by adding caps between the middle pin and and the supply voltage .See schematic :https://drive.google.com/file/d/0B5vW-k7HbsL4eGlRekc5UmwzaE0/view?usp=drivesdk

author: ali6x944
author_rank: Frequent Contributor
timestamp: May 13, 2016, 04:21:16 pm
content: Did it work with anyone else or a bug I got?

author: edavid
author_rank: Super Contributor
timestamp: May 13, 2016, 04:33:03 pm
content: It's shown in the datasheet.http://www.ti.com/lit/ds/symlink/ne555.pdf

author: ali6x944
author_rank: Frequent Contributor
timestamp: May 13, 2016, 05:15:47 pm
content: So why people use the two diode design then?

author: Aodhan145
author_rank: Frequent Contributor
timestamp: May 13, 2016, 05:24:01 pm
content: Quote from: ali6x944 on May 13, 2016, 05:15:47 pmLess components by adding two diodes you don't need 2 resistors and 2 capacitors from your circuit.

author: ali6x944
author_rank: Frequent Contributor
timestamp: May 13, 2016, 05:44:31 pm
content: The caps are not necessarily plus the use of one resistor is possible to change the duty cycle

author: Zero999
author_rank: Super Contributor
timestamp: May 13, 2016, 10:02:01 pm
content: Yes it works. I've done it before.The frequency also varies, along with the duty cycle.With the diode variant, the frequency remains constant. The diode can also be a dual diode package.

author: edavid
author_rank: Super Contributor
timestamp: May 14, 2016, 12:49:27 am
content: Varying the duty cycle using a pot is not the same thing as PWM

author: ali6x944
author_rank: Frequent Contributor
timestamp: May 14, 2016, 04:07:25 am
content: Quote from: Hero999 on May 13, 2016, 10:02:01 pmThanks for clearing that for me

author: Aodhan145
author_rank: Frequent Contributor
timestamp: May 14, 2016, 10:26:21 am
content: Quote from: edavid on May 14, 2016, 12:49:27 amHow so?

author: Raj
author_rank: Frequent Contributor
timestamp: May 14, 2016, 11:53:06 am
content: I could never get my 555 projects working...until i realized that touching them is something that makes them halt
555 Timer question - Page 1
Forum section: electronics / beginners

author: stev.dk
author_rank: Regular Contributor
timestamp: July 27, 2014, 03:32:51 pm
content: Okay, so be prepared - anyone with an iq above 10 will be goingorwithin a few lines of this question, but im a at loss, and need some help here.I have an alarm on my moped... so far so good. I want to make a red LED flash, like on cars, to show the alarm is active. I want it to blink for like 10ms and stay off for like 2 sec or something like that (didn't calculate the exact values yet). I'm using an astable configuration, with a diode going across R2, to get a lower duty cycle than 50%. Everything seems to be working BUT the led dosn't shut completely off, it dims to about 10% maybe. Why is this, and how to fix it? I tried using higher resistors, and running at 5v and not 12v, but it still dosn't turn off... I must be missing something.I have it set up like this.

author: rob77
author_rank: Super Contributor
timestamp: July 27, 2014, 03:35:00 pm
content: where and how is your LED connected ?

author: stev.dk
author_rank: Regular Contributor
timestamp: July 27, 2014, 03:41:34 pm
content: Its connected pin 3 --|>- resistor ---|> GND

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: July 27, 2014, 03:54:54 pm
content: can you give the component value you used in you prototype ?

author: stev.dk
author_rank: Regular Contributor
timestamp: July 27, 2014, 04:15:05 pm
content: Okay, i dont know what i did wrong... I took it apart and assembled again, and now it works as it should.Same values... must have connected something up wrong... don't know what would cause the LED not to turn completely off... but assembled correctly, it works.

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: July 27, 2014, 04:20:56 pm
content: happen all the time
555 triggering? - Page 1
Forum section: electronics / beginners

author: dteck
author_rank: Contributor
timestamp: March 23, 2016, 07:48:29 am
content: Hi everyone,So this is probably a silly question but I've never used a 555 before so I'm hoping someone who knows better can help me. I want to make a simple 5 minute timer circuit attached to a pir motion detector (Your basic security light setup) But what I want to know is so you pull the trigger low to start the timer. What happens if you pull it low again during its countdown? does it restart the 5 minute countdown? or does it simply ignore the second trigger while the countdown is running?Thanks in advance

author: matseng
author_rank: Frequent Contributor
timestamp: March 23, 2016, 08:25:26 am
content: Nothing happens if you re-pull the trigger low during the 5 minute window. The output will be off after 5 minutes regardless what you do with the trigger input - you can even keep the trigger low constantly and the output will go off when the time is up anyways.Falstad simulation here:http://goo.gl/hVhuCqOn my machine the 555 in the simulation timeout is set to about 6 seconds.... Singe click (or click and hold the "H" do the left to take if low.

author: dteck
author_rank: Contributor
timestamp: March 23, 2016, 08:34:53 am
content: Quote from: matseng on March 23, 2016, 08:25:26 amThank you Matseng. That was very helpful.

author: Audioguru
author_rank: Super Contributor
timestamp: March 23, 2016, 02:44:11 pm
content: Quote from: matseng on March 23, 2016, 08:25:26 amAbsolutely NOT. The Falstad simulator is wrong.The datasheet says, "The trigger input must be returned high at least 10?s before the end of the timing interval." Or it will never time out.An applications note from Philips (they bought Signetics who invented the 555) shows a coupling capacitor used to feed a negative-going pulse to the trigger pin and a pullup resistor:
555pwm motor driver - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: December 11, 2019, 02:42:21 pm
content: hi all im building this for a small drill motor,only trouble is i only have a 1meg pot,not a 100k one,any idea if it will work?,cheers Paul.

author: Wimberleytech
author_rank: Super Contributor
timestamp: December 11, 2019, 03:09:00 pm
content: "work" (without any qualifiers) is pretty binary. Yes it will work. You will need to adjust the capacitor accordingly to get the frequency you want.

author: Zero999
author_rank: Super Contributor
timestamp: December 11, 2019, 05:46:09 pm
content: Change C2 to 10nF and the frequency will be the same.
5mm Diameter Cylindrical Li polymer Battery - Page 1
Forum section: electronics / beginners

author: jonovid
author_rank: Super Contributor
timestamp: October 29, 2020, 07:13:30 am
content: 3mm or 5mm diameter cylindrical 50mA or 20mA Li polymer batterieswhere do you find affordable wireless earbud cylindrical 50mA Li polymer batteries.i was looking using a pen as a case. for test probe idea I had,ok so getting SMD electronics to fit inside a pen case is not a problem.but try to find a 3mm or 5mm diameter cylindrical battery?were are the surplus electronics parts from wireless earbuds?. not listed on aliexpressor even e-cigarette cylindrical battery will do if its under 5mm in diameter.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 29, 2020, 08:07:51 am
content: Harvest from a disposable e-cigarette

author: jonovid
author_rank: Super Contributor
timestamp: October 29, 2020, 08:55:28 am
content: Quote from: blueskull on October 29, 2020, 07:24:09 amit's all in thenamethank you
5mm LEDs in chains - are they all manufactured this way or are these special? - Page 1
Forum section: electronics / beginners

author: badrequest400
author_rank: Contributor
timestamp: April 22, 2022, 06:46:44 pm
content: Does anyone know what these weird-lookin' LED chains are (see attachment)? Is this how all LEDs are manufactured and they just haven't had those bottom bits cut off or are these specially-manufactured to be like this?

author: mariush
author_rank: Super Contributor
timestamp: April 22, 2022, 07:31:57 pm
content: Resolution's a bit low, but you can see here similar leads :

author: Benta
author_rank: Super Contributor
timestamp: April 22, 2022, 07:58:11 pm
content: It's for automatic pick-and-place PCB assembly.In 99% of the cases, the LEDs have cut leads and are taped to a self adhesive band at the end of the leads and then be wound on a roll (or an "ammo-pack").The PaP machine will unwind the roll, cut each LED and insert it into the PCB.In this case the manufacturer opted for a simpler solution with a special leadframe instead of the tape. Cheaper? No idea.

author: langwadt
author_rank: Super Contributor
timestamp: April 22, 2022, 08:43:29 pm
content: Quote from: Benta on April 22, 2022, 07:58:11 pmthe leadframe maybe how they are produced, before being cut to be put in ammo-pack or bagsmakes sense to not handle them individually when molding the plastic, and the series string might be used for a quick test

author: thm_w
author_rank: Super Contributor
timestamp: April 22, 2022, 10:08:29 pm
content: Quote from: mariush on April 22, 2022, 07:31:57 pmSame channel they are bonding the dies:Good article here:https://learn.sparkfun.com/tutorials/how-leds-are-made/all

author: eugene
author_rank: Frequent Contributor
timestamp: April 23, 2022, 12:09:22 am
content: Seems that handling the strips could be dangerous for the LEDs. If you were to roll the strip it would put torques on the leads. Leaded LEDs seem pretty rugged, but still.

author: thm_w
author_rank: Super Contributor
timestamp: April 23, 2022, 12:15:39 am
content: Quote from: eugene on April 23, 2022, 12:09:22 amWhy would you roll the lead frame strip? Or are you talking about the paper ones.

author: floobydust
author_rank: Super Contributor
timestamp: April 23, 2022, 12:20:38 am
content: Nothing goes to waste in china, they'll sell any rejects, blemishes etc. A few 5mm LED's I've bought are marked backwards polarity and OP's looks like the leads are uncut.It doesn't mean they are unusable for hobby stuff.

author: xrunner
author_rank: Super Contributor
timestamp: April 23, 2022, 12:36:56 am
content: Quote from: mariush on April 22, 2022, 07:31:57 pmMy Gawd can you imagine doing that all day long every day?
5V dimming circuit to control 24V LED strip - Page 1
Forum section: electronics / beginners

author: sd02720
author_rank: Newbie
timestamp: July 06, 2023, 04:05:08 pm
content: I have a simple dimming circuit from a 5V LED lamp which controls light level and color temp. The original lamp has two strings of LEDs, one warm, and one cool. The 5V inputs directly to the circuit. There is a power button, a plus button, minus button, and a button to control different levels of each color temp to result in a proportional mix.I would like to swap out the LEDs for my own LED tape, which requires 24V.Is there a relatively easy way for me to use this circuit to control the 24V LED tape? I don't need the color changing, I simply want to use the dimming functionality (I have a single-color LED tape...the circuit seemingly outputs a PWM signal in response to hitting the dim + or - buttons)Any insights appreciated...relative newbie here but good at soldering, learning to use oscilloscope. Thanks! Pics attached of existing circuit for reference.

author: Manul
author_rank: Super Contributor
timestamp: July 06, 2023, 05:18:34 pm
content: It seems to me that the IC on the PCB must be some kind of MCU, which controls 2 N-Channel mosfets (low side switches) to PWM LED strips.If the above is correct, then you could take a 5V linear regulator (like a 7805) and use it to power the PCB. Feed the anode (+) side of your LED strip with 24V, with only cathode (-) connected to the PCB (N-Channel mosfet drain). In that case LED strip and PCB is powered separately: LED strip directly from 24V and PCB through 5V regulator. Hope the explanation is clear. Just be sure to check things and confirm assumptions first.Note: It might be that the mosfets are too low voltage for 24V LED strip. Or they could be too little current. In that case they might get damaged and they might also damage the MCU. So you might need to replace them with more powerful ones.

author: sd02720
author_rank: Newbie
timestamp: July 06, 2023, 05:54:27 pm
content: Wow, that makes sense. Thank you very much...I will give it a try and report back. Too bad there are no more Radio Shacks around, I need to order the regulator.It looks like such a simple circuit, I wish I knew enough to build it from scratch. The functionality is perfectly what I need....single pushes on the buttons create a stepped dimming effect up to a minimum and maximum. A continuous hold on either button gradually dims (or brightens) the LEDs. It's magic to the uninitiated!But anyway, it's a throwaway circuit but I only have one shot to make it work. Either way I'll report back with either a success or a smoke-show. Thanks!

author: sd02720
author_rank: Newbie
timestamp: July 07, 2023, 05:57:24 pm
content: Manul, it worked perfectly. Thank you
5V LDO immediately going into current limit - Page 1
Forum section: electronics / beginners

author: chrismec
author_rank: Newbie
timestamp: March 31, 2021, 12:37:33 am
content: Hello all, first post here. I've recently run into an issue that I have never come across before. I have an MIC29501 (https://www.microchip.com/wwwproducts/en/MIC29501) that I am using to power a raspberry pi 4. It is a 5V 5A regulator that can handle 24V continuous on the input. The problem I am having is the regulator immediately goes into current limit upon power up and starts generating a lot of heat and eventually goes into thermal shutdown. This is with an input voltage of 24V. With a lower input/output differential things start acting correctly. It seems this device cannot deliver 5A with a max continuous input voltage of 24V. How would I know this looking at the datasheet? I knew the differential would be an issue with a linear regulator but felt I was pretty safe in choosing an LDO. Can anyone point me to where in the datasheet I should have know this? Thank you : )

author: MikeK
author_rank: Super Contributor
timestamp: March 31, 2021, 12:42:14 am
content: (24V - 5V) x 5A = 95W!!!!How big is your heatsink?

author: Dubbie
author_rank: Unknown
timestamp: March 31, 2021, 12:46:32 am
content: What temp do you think the core might reach in a second or so given 95W dissipation?Check out the table in the datasheet.

author: chrismec
author_rank: Newbie
timestamp: March 31, 2021, 12:55:24 am
content: booooooo, what a dummy I am.Don't know why I was thinking LDO had some magic sauce for large differentials. Ima switch to a proper buck converter. Thanks!

author: Brumby
author_rank: Unknown
timestamp: March 31, 2021, 01:01:55 am
content: Quote from: chrismec on March 31, 2021, 12:37:33 amLDO = low drop out. This means theminimumdifference between input voltage and output voltage can be low and you can still have regulation. It does not define the operating principles - which is what you seem to have assumed.You worked that out.

author: Dubbie
author_rank: Unknown
timestamp: March 31, 2021, 01:03:57 am
content: Just to make the most of this lesson you have learned,check out this video from Dave showing how to run the numbers.
5V LDO regulator @ <5V, behavior? - Page 1
Forum section: electronics / beginners

author: ok_cool
author_rank: Contributor
timestamp: October 11, 2015, 02:30:04 pm
content: Can anything common be said about how LDO regulators behave when, say, 5V fixed regulator is fed with less than that? Circuit requires voltage regulation, but will tolerate if it is less than 5.Editanswering to my own question, but it seems something can go horribly wrong:

author: SeanB
author_rank: Super Contributor
timestamp: October 11, 2015, 03:02:48 pm
content: Dropout voltage will be around 200-400mV ( from the datasheet) so it will simply feed through the input less that. A big caveat though is the current drawn by the regulator through the ground pin will suddenly be a lot higher than the typical current, as it will be drawing the maximum current possible to turn on the output PNP pass device as hard as possible trying to stay in regulation. This can be an issue as it may be 100mA or more, and will often be the highest current in the circuit. If you can get a LDO that uses a MOSFET to regulate the ground pin current will not be as high when it drops out of regulation.

author: ok_cool
author_rank: Contributor
timestamp: October 11, 2015, 03:15:02 pm
content: Quote from: SeanB on October 11, 2015, 03:02:48 pmSo that's where it comes from. Thank you. Did not realize it would do that.Already seemed that by picking low powered regulator I had accidentally picked one that works more sensibly and simply drops to 0:
5V logic to energize 220v contactor? - Page 1
Forum section: electronics / beginners

author: tekati
author_rank: Contributor
timestamp: May 27, 2015, 01:55:09 am
content: Would this be as simple as using a TRIAC? I could use a relay to turn on the contactor but that is just another mechanical point of failure.

author: N2IXK
author_rank: Frequent Contributor
timestamp: May 27, 2015, 02:09:58 am
content: I would use a small solid state relay (SSR). Available as a prepackaged module to do exactly what you need.

author: tekati
author_rank: Contributor
timestamp: May 27, 2015, 02:15:42 am
content: That makes sense.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 27, 2015, 02:21:20 am
content: If you are going to use a triac, be sure to use proper isolation between your logic circuits and the mains voltages.For example the MOC3022:http://www.allelectronics.com/make-a-store/item/moc3022/opto-isolator-triac-output/1.htmlYou would be much better off using a solid-state relay (SSR) as N2IXK suggested.For example:http://www.ebay.com/itm/Relay-Solid-State-For-PID-Temperature-Controller-25A-SSR-25-DA-Output-24V-380V-/221777641731Or perhaps a PowerSwitchTailhttp://www.powerswitchtail.com/Pages/PowerSwitchTail240vackit.aspx

author: Paul Moir
author_rank: Frequent Contributor
timestamp: May 27, 2015, 07:20:03 am
content: A caveat is that a SSR will more commonly fail on then off.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: May 27, 2015, 07:30:50 am
content: Quote from: Richard Crowley on May 27, 2015, 02:21:20 amThey're really cheap and I've been wondering how safe they are. I've often thought that Dave ought to do a teardown to check. Has anyone else looked inside ?

author: matseng
author_rank: Frequent Contributor
timestamp: May 27, 2015, 07:34:36 am
content: Quote from: Richard Crowley on May 27, 2015, 02:21:20 amI love that this seller also sells stuff like "New Womens Silk 3/4 Sleeve Nightdress Sleepwear Nightgown Nighties Pyjamas Set" :-)

author: N2IXK
author_rank: Frequent Contributor
timestamp: May 29, 2015, 01:33:31 am
content: Quote from: Paul Moir on May 27, 2015, 07:20:03 amSo will a triac, in my experience. Semiconductors of all kinds tend to fail short rather than open....
5v Overvoltage protection - Page 1
Forum section: electronics / beginners

author: Tianfeng
author_rank: Contributor
timestamp: June 21, 2019, 02:35:35 pm
content: I need to design add some over voltage protection for a 5v circuit. I was thinking of trying to use a crowbar circuit but I haven't built one before. I need something that can handle higher currents up to possibly 8 or 9 amps on the 5v. I have seen things online likehttps://circuitdigest.com/electronic-circuits/crowbar-circuit-diagrambut . don't really get how the parts relate to each other. I undertsand that the zener diode could be chose at 5.1v or 5.6v and if it goes over that the current will be pulled to ground but I don't get how the fuse is blown to protect the circuit.

author: Zero999
author_rank: Super Contributor
timestamp: June 21, 2019, 02:53:02 pm
content: The fuse is blown, when the thyristor is triggered, because a large current flows through it, causing the fuse wire to melt and go open circuit.

author: Tianfeng
author_rank: Contributor
timestamp: June 21, 2019, 03:51:06 pm
content: Ok so let me see if I am tracking this rightWhen selecting a fuse and thyristor pair the fuse should be above the current draw level of the circuit and the thyristor should be able to output a current level high enough to blow the fuse. And the the schottky diode needs to be rated high enough for the circuit current as well.

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 21, 2019, 04:18:03 pm
content: Quote from: Tianfeng on June 21, 2019, 03:51:06 pmYes. This may be useful as well:https://www.eevblog.com/forum/beginners/actual-fuse-current-rating/Also..your power source should be able to drive enough current to blow the fuse. If it can drive enough current to hurt your (fuse protected thing) but not enough to blow a fuse, fusing may not be the solution here.

author: Tianfeng
author_rank: Contributor
timestamp: June 21, 2019, 04:45:03 pm
content: I was reading that earlier. Interesting. Current is being drawn from arcade boards. They vary in current requirements and some are very high. My goal is really to make sure no one is able to put the wrong voltage in and damage their equipment. I had my buck converter circuit fail and 12v got shot through the 5v line. It fired my arcade board, cables (ther have a built in rgb to ypbpr converter) and the game pcb attached to it.

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 21, 2019, 04:57:27 pm
content: Quote from: Tianfeng on June 21, 2019, 04:45:03 pmMaybe instead of a fuse a back-to-back N-ch mosfet switch would be better. Much faster and doesn't need to be replaced if it blows. Could also be cheaper then fuses and fuse holders. Can have custom voltage limits with comparators and nice terminal blocks for hookup.But the fuse idea could work. Just make sure the fuse can be blown by the power supply short circuit current.

author: Tianfeng
author_rank: Contributor
timestamp: June 21, 2019, 05:59:49 pm
content: Thanks, I will look at n-ch mosfet switches as well.
5V to 100V control with SCR - Page 1
Forum section: electronics / beginners

author: little_carlos
author_rank: Regular Contributor
timestamp: May 28, 2018, 04:37:07 pm
content: Hi, im making test to control a 100V signal (That goes to another transistor to control a Relay) with an SCR and the SCR signal is 3.3V from a microcontroller.The problem is that the output voltage in the SCR is only 3.3V, same as the gate. The SCR acts ON and OFF as it should but the voltage is not 100V, yes, the Anode is connected to 100V (DC, since comes from batteries in series). And the output is the Cathode.Should I be getting 100V in the cathode or im mistaken? Any suggestions?The SCR im using is the C106B.Im controling the SCR using a PUSH-PULL NPN-PNP config at the gate.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: May 28, 2018, 05:24:25 pm
content: An SCR can only turn ON when powered from DC. Nothing you do to the gate can turn it off. It stays on until the power is interrupted.SCRs do not lend themselves to 'cathode follower' arrangements, if that is what you mean. The load is typically in the anode side.If you need to switch the live side of the 100VDC, then you need two transistors, one to 'level shift' the control signal and the other to handle the power switching.

author: capt bullshot
author_rank: Super Contributor
timestamp: May 28, 2018, 05:48:16 pm
content: The way you describe your circuit makes me think the SCR will just destroy the driver stage (or the micro or both) when it turns on. Because the gate will follow the cathode potential once it really turns on.To use the SCR in that configuration, you should use a suitable pulse transformer to isolate the gate/cathode from the driver, so the cathode can go to 100V without harming the driving circuit.Otherwise, a schematic or a simple sketch will help us to understand your problem and give you hints.
opamp - Page 1
Forum section: electronics / beginners

author: Kajover
author_rank: Newbie
timestamp: February 09, 2016, 10:51:36 am
content: Hi,could you please help me design a circuit and choose the best parts for an operational amplifier that has +/-5V as an input an 1A as output? Thank you very much.Kind regards

author: awallin
author_rank: Frequent Contributor
timestamp: February 09, 2016, 10:54:20 am
content: Quote from: Kajover on February 09, 2016, 10:51:36 amneed more specs. what is the source that should generate +/-5V? what ripple/noise is acceptable? what cost is acceptable?

author: Kajover
author_rank: Newbie
timestamp: February 09, 2016, 10:57:09 am
content: Source: do not know (+/-5V)Ripple/noise: low noise would be preferablecost: lower than 10€ for the op amp

author: awallin
author_rank: Frequent Contributor
timestamp: February 09, 2016, 11:01:25 am
content: still not sure what you are asking for...I've used an opa569 for a +/-1A TEC-drivehttp://www.ti.com/lit/ds/symlink/opa569.pdfthe circuit is explained here:http://www.anderswallin.net/2014/09/tec-drive-v2/

author: Kajover
author_rank: Newbie
timestamp: February 09, 2016, 12:31:32 pm
content: thank you... for i_limit, where does 9800 and 1.18V come from?

author: awallin
author_rank: Frequent Contributor
timestamp: February 09, 2016, 12:39:53 pm
content: Quote from: Kajover on February 09, 2016, 12:31:32 pmpage 3 towards the end "current limit"http://www.ti.com/lit/ds/symlink/opa569.pdfkeep in mind this is a linear device so it will dissipate P=U*I power and may need cooling (heatsink and/or fan)

author: Muxr
author_rank: Super Contributor
timestamp: February 09, 2016, 03:10:37 pm
content: Quote from: Kajover on February 09, 2016, 10:51:36 amOp amps are sort of the do it all parts of the analog world. They can do all sorts of things, but sometimes they aren't the best or the most economical part to use for a given task. There are so many different types of op-amps. Without really knowing even some of the basics of what you intend to do with them, it's really hard to recommend a good one for your application. For one 1A op-amps are pretty special, as 1A is a lot of current. Most op-amps drive much less than that.

author: Morgoroth
author_rank: Regular Contributor
timestamp: February 09, 2016, 03:25:55 pm
content: and what about an opamp and a mosfet ?, both cheap and very flexible on design.
5v to 500v DC Convertor - Page 1
Forum section: electronics / beginners

author: odessa
author_rank: Regular Contributor
timestamp: October 14, 2017, 04:14:37 pm
content: Hi,I'm a bit of noob with this stuff but trying to learnI'm trying to make a supply for a Geiger counter tube. I have 5v in, a 450Hz PWM signal running a logic level mosfet switching through the secondary of a small audio transformer. Then 2 caps and diodes charging to 500v.Everything works fine till I add the 10m resistor for the Tube, the voltage before the resistor is 500v, after is 232.Also, is connecting the 0v of the primary and secondary Ok ?What am I doing wrong here please

author: Rbastler
author_rank: Frequent Contributor
timestamp: October 14, 2017, 04:43:58 pm
content: Were are you measuring ? At the tube it should be around half the voltage, with the 10M resistor for the geiger tube. The meter has 10M input impedance.I recomend building a circuit using a MC34063A. Works great.

author: odessa
author_rank: Regular Contributor
timestamp: October 14, 2017, 04:48:03 pm
content: Hi,I'm measuring at the + side of R5, so my meter is acting as a voltage divider ?I have a load of MC34063A, I'll have a look at that.Thanks for the reply

author: Rbastler
author_rank: Frequent Contributor
timestamp: October 14, 2017, 04:55:12 pm
content: Quote from: odessa on October 14, 2017, 04:48:03 pmCorrect. By putting your meter after the 10M for the tube, its acts as a voltage divider. For measuring voltages directly at geiger tube or high impedance HV supplys, like the one for my gamma spectrometer, I use 90M in series with the meter. So I get roughly a division of 1:10.When using the MC34063A just look at some nixie tube supplys. You need to change some parts, but you can start from there.

author: odessa
author_rank: Regular Contributor
timestamp: October 14, 2017, 04:57:42 pm
content: Great, thanks for the advice
5v to 65mv with offset of 2.5v conversion - Page 1
Forum section: electronics / beginners

author: koba30
author_rank: Contributor
timestamp: August 04, 2023, 06:26:13 pm
content: Good day, what could be a good way to convert 0-5v to 0-65mV with a offset of 2.5V?, the purpose is to simulate the output of a pressure transducer that uses a Wheatstone bridge

author: Berni
author_rank: Super Contributor
timestamp: August 04, 2023, 06:32:08 pm
content: Resistor divider of a ratio of 0.013 where the top is connected to the 5V signal while the bottom is connected to a bias voltage of 2,5325 V. Middle of the divider is the voltage you want.

author: TimFox
author_rank: Super Contributor
timestamp: August 04, 2023, 07:10:45 pm
content: With some algebra, you could design a similar network with an input resistor feeding the junction of two resistors between +5 V supply and 0 V, if the +5 V supply is available.The Thévenin equivalent of the latter two resistors is equivalent to Berni's suggestion of a resistor to a +2.5325 V bias supply.You may need a variable resistor element to calibrate this if your +2.5 V offset is critical.

author: rstofer
author_rank: Super Contributor
timestamp: August 05, 2023, 03:46:02 pm
content: Chapter 4 of "Op Amps For Everyone" deals with linear equations of the form: y = m*x + b where m is the gain and b is the offset.https://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf

author: Terry Bites
author_rank: Super Contributor
timestamp: August 05, 2023, 04:35:56 pm
content: All opamp scaling and offsets sorted. See attached.Alternatively, for more precision, use an instrumentation amplifier.The have the function (Gain*(a-b))+Ref.eg INA156 see fig 2 of data sheet.
5v to/from 3.3v level ic suggestions ... - Page 1
Forum section: electronics / beginners

author: voidptr
author_rank: Contributor
timestamp: May 01, 2012, 04:11:39 am
content: i'm looking for suggestions for level converter ic , if possible available in dip and SMD.im waiting on few BSS138 mosfet to try this solution who seems to be a standard for bidirection...but is this the best way to go ?right now i did my matching level between an Amega328 spi interface and a 23K256 SRAM with resistor dividers and diodes, this is good for more than 1Mbits, that is fine with my prototype.

author: free_electron
author_rank: Super Contributor
timestamp: May 01, 2012, 01:24:58 pm
content: Are we talking serial buses like spi and i2c or parallel buses ?For i2c there is the pca9603.For spi you can use the bss138 trickFor parallel buses you can use 74lvcx4245. Those chips have two power pins. One tied to 5v one tied to 3.3 volts

author: olsenn
author_rank: Frequent Contributor
timestamp: May 01, 2012, 01:46:27 pm
content: A buffered volatge divider should work fine, but you can certainly get 3.3V regulators as well for next to nothing

author: voidptr
author_rank: Contributor
timestamp: May 02, 2012, 03:03:12 am
content: thanks all :-)
5V tolerant I/O - Page 1
Forum section: electronics / beginners

author: Udayan Sinha
author_rank: Regular Contributor
timestamp: May 04, 2014, 11:46:10 am
content: Many devices working on 3.3V logic have I/Os that are 5V tolerant. Are these robust enough that they can withstand exposure to 5V on a continuous basis or do their performance degrade over time? I am talking about long term usage- regular exposure to 5V signals for say 5 years atleast.

author: amyk
author_rank: Super Contributor
timestamp: May 04, 2014, 12:26:46 pm
content: Continuous.

author: Jeroen3
author_rank: Super Contributor
timestamp: May 04, 2014, 08:28:03 pm
content: Yes, but not on unpowered chips.Also the leakage current will increase and analog operation is prohibited.Read your datasheet/manual about IO topology and maximum ratings.
6 Degrees of Freedom Breakout - LSM6DS3 sparkfun  - Page 1
Forum section: electronics / beginners

author: Aztlanpz
author_rank: Regular Contributor
timestamp: August 31, 2015, 09:37:35 pm
content: anyone know what value L1 is in the schematic is?

author: JoeN
author_rank: Frequent Contributor
timestamp: September 01, 2015, 08:54:40 am
content: Found this in their eagle library:https://github.com/sparkfun/SparkFun-Eagle-Libraries/blob/master/SparkFun-Passives.lbrCode:<device name="30OHM,1.8A" package="0603"><connects><connect gate="G$1" pin="1" pad="1"/><connect gate="G$1" pin="2" pad="2"/></connects><technologies><technology name=""><attribute name="PROD_ID" value="RES-07859"/></technology></technologies></device>That would be this:http://www.digikey.com/product-detail/en/MPZ1608D300BTA00/445-2986-1-ND/1084529This is just a ferrite bead to filter out high frequency power supply noise. Good practice to include it, probably will work fine without.
60  Hz generator or  motor - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: July 17, 2017, 12:00:07 pm
content: Hi everybody,Does a 60 Hz generator or motor exists? Or does a 50 Hz to 60 Hz generator exists?RegardsJPD

author: Zero999
author_rank: Super Contributor
timestamp: July 17, 2017, 12:50:53 pm
content: The shaft speed and number of pole pairs determines the frequency of an alternator.What are you trying to do? Convert 50Hz mains to 60Hz or vice versa? In the old days a motor generator set (basically a motor mechanically coupled to an alternator, via a suitable gear ratio) would be used to do this. Nowadays a rectifier and inverter will do this with no moving parts.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 17, 2017, 01:01:29 pm
content: pick...http://www.ebay.com.my/itm/3-SUN-M321C5-Electric-Motor-Hobbies-Cars-Planes-Trucks-12V-DC-DIY-3600RPM-/291465112723?hash=item43dcacac93:g:1VkAAOSwrklVVRFchttp://www.ebay.com.my/itm/5-HP-3600-RPM-230-VOLT-AC-184TC-LEESON-131632-00-MOTOR-10-2887-/381921835631?hash=item58ec50ba6f:g:fHwAAOSwEzxYd8Q3http://www.ebay.com.my/itm/PORTABLE-PETROL-GENERATOR-4-STROKE-2700-W-6-5HP-SCHEPPACH-SG3100-/162382432172?hash=item25cebf47ac:g:tVsAAOSwCkZZSpvLhttp://www.ebay.com.my/itm/BrandNew-30Kw-Single-Phase-50-60hz-Diesel-Powered-Generator-Free-Ship-WorldWide-/132105255960?hash=item1ec2163c18:g:eWIAAOxyKsZRr3Fk