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How can I get amperage input?


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#1 sampa999

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Posted 17 April 2011 - 08:17 AM

I'd like to be able to read how much power is being drawn by a servo. I'd like to be able to see if it is stuck and unable to move for some reason. I'd be using an external power supply. Is there an IC that will output measured amps as a signal? I'm thinking on the the order of 1-2 amps. Thanks, Sam

#2 MicroEmb

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Posted 17 April 2011 - 09:18 AM

You can use an IC current sensor like Allegro "ACS756SCA-050B-PFF-T" search on that "partnumber" on google. With that you can measure voltage drop over the sensor in about 20 - 40mV / AMP, with use of a analogue input on the microcontroller.

#3 Rod Lopez

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Posted 17 April 2011 - 10:56 AM

Hi Sam,
One way you can do it is by adding a very low resistor (a shunt resistor as they are usually called) between the ground and the servo's ground. An increase in current will increase the voltage dropped across the resistor.
I have been using a 0.1Ohm and an op amp (just to make the voltage easier to read from the Netduino) and it's been working like a champ.

Just for reference you can check Shunt resistors, look for "Use in current measuring"




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