Author Topic: Current limit tutorial  (Read 3118 times)

Jason

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Current limit tutorial
« on: June 23, 2013, 06:55:31 PM »
Hi Martin

I was just wondering if you could do a tutorial on a current limiting circuit. There are literally no good tutorials on how to current limit a circuit. The videos I have found basically say to put a resistor in series but that is only good for a fixed load output.  What I would like to see a tutorial on is current limiting a circuit with a dynamic load ie. The first half of your circuit needs between 0 - 1 amp on 12 volts (lets say  its a servo motor) but the second half cannot exceed 250ma on the same circuit (this could be a display or something). Sure you can use an LT3013B but 1. good luck finding one to buy and 2. how do I know if it could handle trimming a 1amp load down to 250ma? If not Martin, then please someone make a YouTube tutorial on how to current limit a dynamic load thanks   :-\

As always Martin keeps up the great work ~ Jason
If it ain't broken, let's open it up and see how it works.

Strada916

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Re: Current limit tutorial
« Reply #1 on: June 24, 2013, 05:15:53 AM »
electronic dummy load in serires?

Mr Eastwood

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Re: Current limit tutorial
« Reply #2 on: June 24, 2013, 06:25:51 AM »
I was just wondering if you could do a tutorial on a current limiting circuit. There are literally no good tutorials on how to current limit a circuit.

Have you watched this one?

EEVblog #221 - Lab Power Supply Design - Part 1
http://www.youtube.com/watch?v=CIGjActDeoM

Hey! Frisbee! Far out!

Jason

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Re: Current limit tutorial
« Reply #3 on: June 24, 2013, 07:12:55 AM »
Yeh, the issue is if you put an LM317 into the circuit then you immediately lose 1.25 volts which you might need when you are not current limiting. Where as if you were to use an LT3013 you would only loose 400mV. The component also has the circuitry in it already to sense when it does and doesn't need to limit the circuit. Sure I could check the schematic and rebuild the circuit with through hole parts but I don't have enough electronic know how to determine what does what. Like if I wanted it to now limit to 400ma. It just seems that YouTube in general lacks a good quality tutorial on limiting dynamic loads. Would a  dummy load not be intelligent enough to automatically activate the limit?
If it ain't broken, let's open it up and see how it works.

MJLorton

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Re: Current limit tutorial
« Reply #4 on: June 24, 2013, 02:38:54 PM »
Hi Jason...

I did a series on building my DIY electronic DC load which might provide some value: https://www.youtube.com/watch?v=u_TKfW8ahFQ&list=PL0793201A72D90BE4&index=14

If not..let's see if we can help.
Play, discover, learn and enjoy! (and don't be scared to make mistakes along the way!)