current follower

[Newz2000]

I know this is 1st year EE stuff, but I'm not too familiar with analog and this is definately analog...

I want an LED to turn on when current reaches a set amount, something like 750ma. I have a motor controller chip that puts out a voltage proportional to the current draw... I thought this would be a cool concept to mimick, because I could use a comparitor or schmidt trigger to turn on the LED when the voltage (which represents the current draw) gets high enough.

Can anyone suggest useful search terms or maybe point towards a link that explains how to build this type of circuit?

I'm cool with either turning an LED on or off when current threshold is reached, or making the LED brighter as the current threshold is reached, however I think the on/off is more useful.

[Gorgon]

Hope you can get some ideas from this http://www.allaboutcircuits.com/vol_6/c ... comparator

TOK

[MrAl]

Hello there,

Normally you would insert a very small value resistor (like 0.1 ohms)
in series with the motor and amplify the voltage across it, then
use a comparator (can be op amp on same chip) to trip when the
voltage gets higher than a certain amount.
With 750ma though a 0.1 ohm resistor you get 0.075 volts across it,
amplified 20 times (gain=20) gives 1.5 volts. You could set the
comparator to trigger at this point to turn the LED on.