Author Topic: H-bridge current sense  (Read 1933 times)

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Offline SenSeS

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H-bridge current sense
« on: February 18, 2015, 12:57:30 pm »
Hi all,

I need an H-bridge that is capable of controlling a DC-motor and measuring the current it uses. The problem is that it’s hard to find H-bridges that have a
current sense pin and that aren’t overkill for my application (I only need 2 inputs and 2 outputs and I need a low voltage one since my DC runs at a maximum of 6V). This is why I thought about using an H-bridge without current sense pin and instead measuring the current that returns from the DC-motor to GND. Are there any drawbacks to this as opposed to having a special purpose current sense pin on the H bridge itself? If not, then why do these current sense pins even exist?

Thanks in advance!
SenSeS
 

Offline hamdi.tn

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Re: H-bridge current sense
« Reply #1 on: February 18, 2015, 01:05:53 pm »
L298 , it has 2 H-bridge

you can always build your own single H-bridge as you said and put a resistor between it and the ground it's the same thing.
i personally use L298 even if i need only one bridge.
when used with motor, current sense can detect if the rotor is blocked , can be used to detect limit without using a limit switch.
 

Offline SenSeS

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Re: H-bridge current sense
« Reply #2 on: February 18, 2015, 05:43:27 pm »
Thanks for the info, however I don't really like the idea of only using half the in/outputs of the H bridge, cause lets say I'd want to make multiple PCBs, or that I need small PCB's, then there really is a cost to having such an H-birdge. I'm sort of surprised that the kind of H bridge I need seems hard to find because it seems fairly standard. Or are H-bridges only used by hobbyists? Do all commercial products implement their own H-bridge? And if so, why? Doesn't this take up more space than a small simple 8pin H bridge? It also seems more error prone.
 

Offline max_torque

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Re: H-bridge current sense
« Reply #3 on: February 18, 2015, 07:18:38 pm »
Remember that, depending on where the current is sensed, that current is not necessarily the loads current!  IE if it is sensed on the output of the H bridge to gnd, as is often the case, it is only the same as the load current at 100% duty!

Check your devices datasheet to understand where the current is measured before assuming anything  :bullshit:
 

Offline K1JOS

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Re: H-bridge current sense
« Reply #4 on: February 19, 2015, 01:23:45 am »
Look at Pololu.com they have sevferal reasonably priced high current H drivers with built in bidirectional current sensing

https://www.pololu.com/category/82/pololu-high-power-motor-drivers

 

Offline DutchGert

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Re: H-bridge current sense
« Reply #5 on: February 19, 2015, 01:12:55 pm »
Try the VNH5180A-E from ST or one of there other VNH series H-Bridges.

Also, Polulu sells boards that use those chips
 


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