Introduction: DIY Short Circuit (Overcurrent) Protection

Picture of DIY Short Circuit (Overcurrent) Protection

In this project I will show you how to create a simple circuit that can interrupt the current flow to a load when the adjusted current limit is reached. That means the circuit can act as an overcurrent or short circuit protection. Let's get started!

Step 1: Watch the Video!

The video gives you all the information you need to recreate the protection circuit. In the next steps though I will give you some additional information.

Step 2: Order Your Components!

Picture of Order Your Components!

Here you can find a parts list with example seller:

Amazon.com:

1x Relay (12V one with 2 changeover contacts): http://amzn.to/2v8vHyT

2x PCB Terminal: http://amzn.to/2uKP6VG

1x LM358 OpAmp: http://amzn.to/2v8RfLx

2x BC547 NPN Transistor: http://amzn.to/2u9yW4y

1x 5mm green LED: http://amzn.to/2hdv4OQ

1x 1N4007 Diode: http://amzn.to/2hdAAAU

1x Tactile Switch (NC): http://amzn.to/2uNZBpm

6x 1kΩ, 2x 20kΩ Resistor: http://amzn.to/2eYvgAA

1x 10kΩ Trimmer: http://amzn.to/2eYBArS

1x 0.1Ω Resistor: http://amzn.to/2eYRsdK

Ebay:

1x Relay (12V one with 2 changeover contacts):http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

2x PCB Terminal: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x LM358 OpAmp: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

2x BC547 NPN Transistor:http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 5mm green LED:http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 1N4007 Diode:http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x Tactile Switch (NC):http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

6x 1kΩ, 2x 20kΩ Resistor:http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 10kΩ Trimmer: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 0.1Ω Resistor: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

Amazon.de:

1x Relay (12V one with 2 changeover contacts): http://amzn.to/2uK2t8g

2x PCB Terminal: http://amzn.to/2viTnkl

1x LM358 OpAmp: http://amzn.to/2uNMsN6

2x BC547 NPN Transistor: http://amzn.to/2vj6qCy

1x 5mm green LED: http://amzn.to/2vbPfSn

1x 1N4007 Diode:http://amzn.to/2uO2kiL

1x Tactile Switch (NC): -

6x 1kΩ, 2x 20kΩ Resistor: http://amzn.to/2uNJ4BH

1x 10kΩ Trimmer: http://amzn.to/2uKc9j5

1x 0.1Ω Resistor: http://amzn.to/2eY98qa

Step 3: Build the Circuit!

Picture of Build the Circuit!

Here you can find the schematic of the circuit along with pictures of my finished perfboard layout. Feel free to use them as a reference for your own circuit.

Step 4: Success!

Picture of Success!

You did it! You just created your own short circuit (overcurrent) protection circuit!


Feel free to check out my YouTube channel for more awesome projects:

http://www.youtube.com/user/greatscottlab

You can also follow me on Facebook, Twitter and Google+ for news about upcoming projects and behind the scenes information:

https://twitter.com/GreatScottLab
https://www.facebook.com/greatscottlab

Comments

MarinoH1 (author)2017-09-29

hey scott, i want to adapt this circuit into my lm317 variable power supply, how do i keep the value the same while still being able to change the voltage of my supply??
also how do yo make your circuit's? i tried eagle, fritzing and my head but i can't nice PCB's

VEGEteK (author)MarinoH12017-10-10

If you design a lab psu then you should add current limit feature which will serve you as short circuit limit as well.

meisl.sprax (author)2017-09-17

Hi, I tried to adapt your circuit to 5V. The main problem is that the LM358 requires "head room" of 1.5V to Vcc on its output, which isn't of much concern with 12V but becomes a major issue at 5V.

I ended up putting the 0R1 sense resistor between the load and GND rather than between Vcc and the load, and used a simple non-inverting amplifying configuration for the first op-amp instead of a differential amplifier. This approach should work equally well at higher Vcc, and it even saves a few parts.

Have I missed something? What do you think?

Aristarco (author)2017-08-03

Excellent!! I'm putting this in the To Do list. One question: why do you push the reset button twice? I've been watching the video and still don't understand why you push it twice. Isn't it supposed to be a one-touch reset?

Camoman619 (author)Aristarco2017-08-04

It's because he is using a switch that acts as a toggle switch but as a button so when he presses it once it breaks the connection and stays that way so he has to hit it again to reset the switch back to the closed state which it will keep until he touches it again.

Aristarco (author)Camoman6192017-08-07

Heheh, you're right. I see now it's a push-on/push-off button. Thanks!

itsmescotty (author)2017-08-01

not beyond my capability to make but...

Is this limited to 12vdc? Is it capable of being scaled for use with a 30vdc LED for example.

Yes, that is possible. You just need another relay.

madhavdivya (author)2017-08-01

Great video and educational too. Keep up the good work, God bless.

DenM3 (author)2017-08-01

You make the best videos, and your circuit drawings are text book perfect. Judging from your accent and penmanship, I would say German. I spent 7 years in Germany. Mannheim, Baden Wuerttemberg to be exact. Best time of my life. Whenever I hear the German language or accent, I'm reminded of that beautiful country. Great work as always.

chingada (author)2017-08-01

neat project , coll willbe on my list to do , please some specs for voltage , amps safe ratings

hernytan (author)2017-07-31

I've been working on something similar, it uses an NE555 timer and a P-channel MOSFET instead of a relay to break and latch the circuit. Thought it might be another way to solve this circuit breaking problem (other than the fixed solution of using a resettable fuse). What do you think?

JULIOC136 (author)2017-07-31

Thanks.

tytower (author)2017-07-30

Im wondering if you can explain the circuit board connections in more detail please. The circuit is fine but where does it all fit on the board?

RafaelC179 (author)2017-07-30

As always, perfect. Useful and practical circuits. Now we just need to put an Arduino and an LCD to display the current limit and have an adjustable source. Scott congratulations from Spain.

EdwardF2005 (author)2017-07-30

Great Scott ,I have a sugestion for you , could you make a CNC drawing machine!

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