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1. RAVEESH HP says

   Sir I have AC-DC SMPS module with 24 volts 4 amp DC output. It has CR6842S smd 8 pin control IC which drives FQPF 20N60 Mosfet on the primary side and 24 volts DC out put is regulated by TL431 IC on the secondary side. I want to make this module a variable power source from 12 to 24 volts at 4 amp rating to use with my hand drilling machine and temperature controlled soldering Iron.
   TL 431 is fed with 20K and 2K3 resistor divider. I tried to vary its out put replacing 20K resistor with 22K pot the module works up to 18 volts only and below that output voltage floats. What I have to do to vary the voltage from 10 to 24 volts on this module.

   I checked it for its current handling capacity with 15 ohms 5 watts resistance the short circuit protection kicks in and the module will not output any voltage. Is it the sign of module under current rated or is there any other method to check its current handling capacity.

   Hope you advise me at your earliest.

   With regards

   Raveesh

   • Swagatam says

     Raveesh, I have already have posted a detailed related article in this article, which you can investigate:

     https://www.homemade-circuits.com/how-to-make-variable-current-smps/

     For checking current capacity, you can use two 12V car headlamps in series and an ammeter in series to get a rough idea regarding its maximum current handling capacity.

2. Jerry says

   I know nothing about drivers and led strings,But with that said I have a lot of time in researching and studying.I am interested in several of your designs but i not know about the drivers, how many i need ? 1 for both front and Back? I can’t find any info on this anywhere.
   for my application and I am wondering if only one of these is necessary for what I am doing?
   Let me explain ,,I am getting some boards made, there will be (6) total with 134 Led Lights Total
   2-Tail Light,Stop,Signal 27 Leds /Board=54
   2-Front Running,Signal 26 Leds/Board =52
   2-Side Light 14 Leds/Board =28 w/Blinking in sequence when signaling
   Leds are :20mA Voltage Forward @3.4 +0.068
   134*0.068=9.112
   12 volt battery
   All my strings are in Parallel I would like to have blinkers chase or some fancy display but not do that with stop light.
   can you suggest me with some help please? I am a DIY er anyway’s on most of my projects I will take any suggestion if you have better idea.
   I just want something that looks cool

   • Swagatam says

     Hi, you can refer to the following article for all the required info. However, you will have to do some hard work to learn the details,

     https://www.homemade-circuits.com/how-to-calculate-and-connect-leds-in/

3. John says

   Hello.

   The circuit I am thinking of would be for personal use, although if it works as it should I might produce them for others for a profit…. just being honest here.
   I know just enough about electronics to admit that I know next to nothing. I don’t know if you know anything about fireworks/pyrotechnics, but that is what this project is all about. I would have to provide more details, I know, but would you be willing or able to design the two circuit boards? If I do put these in the market, I’d be willing to pay you a certain amount for each unit sold, which would help with the upkeep of this wonderful web site.

   Thank you for your time.
   John

   • Swagatam says

     Hi, I think I have a related circuit design already posted in this website:

     https://www.homemade-circuits.com/how-to-build-pyro-ignition-circuit/

4. Ron Hoag says

   Mr. Swagatam i’ve been working on a motor/gen for sometime which uses 6 magnets mounted in a aluminum disk that rotates surrounded by 3 coils where one of them has a trigger winding. The trigger signal is converted to a sharp 10volt square wave to turn on the IGBTs which are connected to the coils which connect to the 12 volt battery supply.when the IGBTs turn off I get a big inductive kick which pushes the magnets hard as they are just parting. The problem is that at the cut off of the trigger signal i get positive spikes greater than 20volts which destroys the IGBTs gates. I have tried zener diodes and low pass curcuit which also helps but reduces the inductive kick. I need to send you pictures of wave forms and schematic. Do you have an email I can send it to?

   • Swagatam says

     Hello Ron, I have understood your question, I think you could try the below shown protections for the IGBT, these should be enough to keep the IGBT safe from the spikes:

     
     

     • Ron Hoag says

       Thanks I will let you know how it works.

       • Swagatam says

         No Problem!

5. oseas says

   hi mr swag my name is oseas i live angola luanda and i really apreciate your site congratulations you have been doing a great job. This is my problem when use the option save page as om my computer to save something from your page after a while the ictures with the schenmatics figure desapear staying just a small rectangle can u plesae tell me if there is a way i can see them again or avoid this from happening tks waiting for replay.

   • Swagatam says

     Thank you oseas, may I know which browser are you using? Please use Google chrome and check again.

6. Jim Snodgrass says

   Hello There,
   I’m seeking help designing a simple low voltage low current relay contact OPEN detector circuit (which I’ll put in a project box). I need a circuit that can detect when a relay contact that is normally closed, opens across it’s two output pins. Once the circuit detects this new OPEN state at the input, I need to (using your new transistor or opto-isolator? circuit) provide a contact closure as an output which will simply pass a GND signal thru its relay contacts in another unit I’m controlling.. If the Input then contacts then close the output relay contacts of the circuit need to OPEN again. I want to use a small 5 volt Normally Open contact relay

   to provide the output contact Closure when its detected and activated but am not sure of a simple way to detect when a relay contact opens. I can provide it either +5 or +12vdc to power the Open Contact Detector circuit. Thanks in advance .. JimS

   • Swagatam says

     Hi, I am not sure if I correctly understood your requirement, still I have made an effort to solve it through this diagram, please check it out…

     https://www.homemade-circuits.com/wp-content/uploads/2019/10/relay-detect.png

     • jim snodgrass says

       Thank You I think the Open switch Contact detector you provided at the link above will work if I give it a Vcc power source so I will try it with the +5.5 vdc supply I have via 10K ohm potentiometer connected to the BC557 Emitter across it to the Vcc RTN line at the bottom and see if that will allow the 160 ohm relay coil to actuate as the input switch contact opens, if not, I will lower the pot-resistance till it does.. I’d send a image of this minor mod if I could but the site won’t accept it. Thanks for your help

       • Swagatam says

         No problem…The best way to show an image is to upload it in any “free image hosting site” online, and then provide the link to me here, so that I can check it. You can also do the same through Google drive. Remember not to include the https, or http, otherwise the comment will be moved to SPAM.

         • Jim Snodgrass says

           Ok I think I understand.. Can you help me find a web site that will allow me to create simple schematics (like yours) ( ideally for free) then post them to a free image hosting site as you suggest? By the way, is there any easy way to find my posts here again later ? I’m not sure I’m posting in the proper locations on the site either but this “About Us” area was the only one I found would allow me to enter the question I’ve posted above. I see no way to put in in a more appropriate group/topic area.. is that all process managed / and filtered by your moderators?

           • Swagatam says

             You can post under any article involving relays or transistors.

       • Jim Snodgrass says

         Ok so set up an account on imagur and believe this may be the link to the Rev 2 DRAFT schematic update..

         imgur.com/LvgoaD7

         Please tell me if this will work and if I can simplify it.. I do need a simple contact closure only (not an open collector driver) output when it detects the NC contact Opens at the input J4.. But, I don’t think I need all the resistors as shown, nor know what values they should be. I have a A928A PNP and a digikey PN 725-1354-ND Reed Relay in hand but can substitute parts. Thanks again for the help .. JimS

         • Swagatam says

           The diagram is not correct, I have shown you the correct diagram previously. It should be exactly as I presented, as per your design specs.

           • jim snodgrass says

             Mr Swagatam,
             could you take another look at the diagram you sent previously? I hate to disagree but don’t see how can work with absolutely no Vcc or Return reference. That is the only reason I tweaked that modification into it, to add a voltage source, that and to try to bias the transistor properly with it added in. I have a 5.5 vdc and RTN I could use to provide a potential across the transistor but right now all we have is a NC contact that will OPEN to trigger the event, and a Normally Open pair of input pins on the circuit’s OUTPUT side that need to see a contact closure (and I can’t use an open collector driver or apply any voltage to them, I need a contact closure at the output but don’t understand how or why the BC557 ( or any other PNP like the A928A I substituted) can work without some difference in potential to drive the relay’s coil current. Can you explain that please? Thank you again for the assist. I can try to move this over to a transistor or a relay thread if you wnat me to try, but I did not see any open “Comment” dialogue for any new entry when I looked there before submitting it here in the “About” thread.

           • Swagatam says

             Hello Jim, it is obvious that the upper line or the emitter of the PNP must be connected to Vcc, I just forgot to show it in the diagram. If there’s no supply then how will the relay operate?
             Similarly the lower line which is connected with the 1N4148 and relay is the 0V line and must be connected to the Vss or the negative of the power supply

7. John Mullinex says

   I am 60 years old and just getting interested in this kind of stuff. You may already have this on your site and I missed it. I would like to build chaser lights that stay lit until the end of the sequence then either blink or flash then start over. I would like to use them as turn signals on my Jazzie. Thank you. John

   • Swagatam says

     Thanks, I’ll try to figure it out and post the idea soon for you!

8. Danish says

   Hello sir,
   I want some help from you. In my project where i stuck. The problem is – I want a 3 phase sequence detector using microcontroller (Atmega-32) without neutral. I referred https://www.researchgate.net/publication/301478340_Micro-controller_Based_3-phase_Sequence_Indicator . But I didn’t understand programming logic of phase AB(); phase Bc(); phase CA(); Please help me.

   • Swagatam says

     Sorry Danish, I am not good with microcontroller coding, so I won’t be able to help you in this regard.

9. Aabhishek Sharma says

   Sir swagatam, can we earn money for writing article on your blog?

   • Swagatam says

     Hi Aabhishek, I am sorry, presently I am not publishing contributions from writers, in future I may surely consider about this and then I may contact you.

10. Heru Wibowo says

    Hai Swagatam,
    apakah Anda memiliki rangkaian led sequential dengan menggunakan IC 74LS164 ?
    Thank You

    • Swag says

      Halo Heru
      Anda dapat merujuk pada artikel berikut: https://www.homemade-circuits.com/knight-rider-led-scanner-circuit/ Ini dapat menyelesaikan kebutuhan Anda