Circuit for single pulse to electromagnet (9-24vdc)

Thread Starter

fire41fighter

Joined Feb 25, 2024
6
Greetings - I have a lot of experience assembling circuits...just not designing them. I am looking for a circuit that will send a single pulse of 9-24vdc to a small electromagnet. I need the pulse to be faster than a momentary switch...thus the circuit. The circuit will eventually be triggered by remote control. I can do this with an arduino and relay, but there must be an easier, more compact way. Any help is appreciated.
 

MaxHeadRoom

Joined Jul 18, 2013
28,684
You could use a DC supply and bridge rectifier followed by an SCR, the SCR can be triggered for as many of the 120hz pulses as you need, from a 555 etc
 

panic mode

Joined Oct 10, 2011
2,746
there is only one relay. its NC contact is in series with input and it will open when relay coil is energized (almost instantly). the inductor L is the load (electromagnet) that you are sending pulse to. this way you will get short pulse to electromagnet regardless of how long the button is pressed.

is this clearer?
1708896703605.png
 
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panic mode

Joined Oct 10, 2011
2,746
here is another variant if the button cannot handle the load current.
it uses capacitor which also makes it possible to extend the pulse
if course the whole thing can be done without relay, just don't know what your comfort level is....
1708897319348.png
 

k1ng 1337

Joined Sep 11, 2020
960
If you are triggering remotely, why not generate the pulse with the microcontroller? If the shortest pulse you can produce in software is still too long, you can shorten it with something like this. Adjust R2 to change duration of the output pulse.

Keep in mind this is a barebones approach. The timing of this circuit is a function of a number of variables. For example, changing the GPIO voltage from 3.3V to 5V will increase the pulse duration so you'll have to adjust R2 accordingly.

Untitled.png
 

k1ng 1337

Joined Sep 11, 2020
960
Here is an improved version with shorter turn on and turn off times for the MOSFET. Now it's a nice square pulse. Minor adjustments to R4 change the output pulse duration.

Untitled1.png
 

MisterBill2

Joined Jan 23, 2018
18,477
A simple way that might work quite well, given that I do not know the required current or the coil resistance. The circuit in post #9 is what I recommend. But an alternative is to have the capacitor in series with the contact and the coil, so that the capacitor charge current will power the coil. You will probably need to experiment with the value of the capacitor to provide the function the magnet is supposed to provide. The series capacitor has worked well for a lot of folks. Yo may also need to add a high value resistor (47K ohms) across the capacitor if repeated operations over a short time are required.
 
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