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Trouble understanding a V+ description on a motor driver

rasen58

Apr 30, 2021
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Apr 30, 2021
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Hi I'm connecting a Pololu 36V15 motor driver (https://www.pololu.com/product/760) to a motor.
On the left side of the board, we connect the OUTA and OUTB pins to the actual motor, and the V+ and GND go to our power supply.
I have a question on the V+ pin on the logic side of the board (right side in the below image).
0J2004.600.jpg

On the right logic side, the description on the pololu website says "the smaller V+ pad on the logic side of the board gives you access to monitor the motor’s power supply (it should not be used for high current)."

I was originally inputting 5V into that right-side V+ pin since I assumed that was needed to power the logic side of the board.
But now I'm not sure if I actually did something very wrong here. Am I not supposed to *input* power into the logic side V+ pin? Is that only meant for reading the motor's voltage as an output?

What is the correct interpretation of the logic-side V+ pin?
And if I'm doing this wrong and you're not supposed to input anything into the right-side V+ pin, then how do the chips on this board get powered? (since I'm assuming the big V+ input on the left side would be too much for the chips since I'm connecting a 24V power supply to drive the motor on the left side)

Thanks.
 

Tha fios agaibh

Aug 11, 2014
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Aug 11, 2014
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2,241
If you look at the trace on the back, they are physically connected together so you should be fine.

Point is, the logic side is only designed for monitoring the motor voltage and has smaller traces that cant handle high current.

In an automotive example, you could monitor the car battery voltage with a tiny wire, but that same wire would burn up if you used it to the starter motor.

Make your power connections at the larger lugs.
 

bertus

Moderator
Nov 8, 2019
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Hello,

When you look at the back, the V+ connections are all in the same plane:
pololu 36v15 driver back.jpg

Bertus
 

rasen58

Apr 30, 2021
9
Joined
Apr 30, 2021
Messages
9
Hi I actually don't understand how you were able to look at the traces on the back to determine that.

My naive view of the back made me look at it like this, and I don't see how they're connected that way.
upload_2021-5-3_21-30-51.png

I also tried following those black lines (are those the traces?) but those lines seem to go to the top 5 pins on the left side, not just the V+ left side pin.

What is the correct way to read the traces?
 

Bluejets

Oct 5, 2014
5,995
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Oct 5, 2014
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5,995
You could try a basic multimeter.
Green layer is the trace and to me it clearly connects to V+ on the right and encircles and connects to V+ on the left as previously pointed out.
As they say, if it had teeth it would jump out and bite you.
 
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