DC Motor Current Sensing

Thread Starter

ashish19183

Joined Sep 16, 2009
13
Hi all,

i need to check DC current of following circuit . This is 24VDC , 5A DC motor
with both direction movement.
my query is this how can i measure current with this circuit for both
direction of motor movement. in circuit i have put 24VDC on both side to
show that which ever side get that voltage motor will run in that direction.
means at a time only one path will get voltage. and i want to put resistor in
one path only not in both paths. if my motor get voltage on path which
having resistor then current sensing i can do by instrumentation amp, but
how to measure current when voltage comes to other path ?????
 

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Thread Starter

ashish19183

Joined Sep 16, 2009
13
@ Artikbot - yaar i dont want to measure current by multimeter
it is like to amplify that voltage drop across that resistor by op-amp or some thing, my problem is how i can measure bidirectional current with only one resistor in one line.

Regarding hall effect sensor.... i didnt use earlier ..i will check but right now looking for some simle solution any op- amp circuit or some thing......
 

Artikbot

Joined Nov 7, 2010
45
Hall effect sensors are very precise, but hard to set up and not quite easy to find.

Although if you want precision, it's the best option ;)
 

Thread Starter

ashish19183

Joined Sep 16, 2009
13
Thanks BillB3857

But from that circuit i didnt get how can i feed voltage across resistor in to Op-Amp as in circuit of full wave precision rectifier it use only single i/p line, where in my case i have two voltage lines and wanna amplify that voltage diff.

please if you have any suggestion provide me.......
 

BillB3857

Joined Feb 28, 2009
2,570
Most current sense resistors are between the ground lead of the motor (or reversing switch) and ground. The input to the op-amp would be taken from between ground and the ungrounded end of the sense resistor. Or you could use a differential amplifier as an input stage.
 

Thread Starter

ashish19183

Joined Sep 16, 2009
13
Ya i got your point but i have to sense bi-directional current and in one direction its fine but again for other direction it will be between motor and source,
i just wanna make configuration which can solve these two problems.......
 

BillB3857

Joined Feb 28, 2009
2,570
If you are stuck using the circuit shown in your first post, you need to use an isolator module. They allow transfer of low level signals with different base references. This an industrial version of what you are looking for. http://dynapowerstore.com/eug7100990006--dual-feedback-isolat7100990007.html

Can you post a schematic of what comes before your original post. There is probably a much cheaper way around your problem.
 
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