dire help needed on simple question - more power to single DC motor from ada shield!

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enerj
 
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dire help needed on simple question - more power to single DC motor from ada shield!

Post by enerj »

Ok guys, I hate for my first post to be an SOS due to severe procrastination, but i'm out of options :roll:

I have a mechanical setup that involves a geared down motor driving a sprocket that pulls a chain through a path guided by some chain guides. I thought the application would draw lower current than actual, and my Arduino Uno and Adafruit motor shield will barely budge it. When I take the arduino out of the circuit and use a regular battery and a push button, the thing flies and does great. Unfortunately my multi only measures 200 mA current, so I can't tell how much this thing is drawing. I could get the figure in the morning.

My question is, how can I get more power from the ada, with what I have. Can't do any chip stacking/replacing at this point, as it needs to be demo'd tomorrow :evil:

I read something about a guy hooking up M1 and M2 in parrallel for the motor, heck I'll do all 4 for this 1 ha. How would I do this? Split the wires from the motor and take one to M1 and one to M2, and do the same for the other? How do they match up? (no + or - on the blue screw terminals).

any help will be so very appreciated!

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adafruit_support_bill
 
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Re: dire help needed on simple question - more power to single DC motor from ada shield!

Post by adafruit_support_bill »

Can't do any chip stacking/replacing at this point, as it needs to be demo'd tomorrow :evil:
Shouldn't take more than 10-15 minutes to piggyback a chip.
When I take the arduino out of the circuit and use a regular battery and a push button, the thing flies and does great.
Are you sure it is a current limitation? There will be a ~1.2v drop through the H-bridge. With low-voltage motors this voltage drop can be enough to keep it from starting - especially in a geared system with a lot of friction.
I read something about a guy hooking up M1 and M2 in parrallel for the motor
This is possible. Just be very careful to make sure that all channels turn on at the same time and in the same direction. Best to write the code and verify the output with your multimeter before bridging the terminals together.
heck I'll do all 4 for this 1 ha.
Not advisable :!: M1/M2 are on a different PWM timer than M3/M4.

enerj
 
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Re: dire help needed on simple question - more power to single DC motor from ada shield!

Post by enerj »

I only meant the time constraint because I likely can't get another chip today. Could I remove the other one and put it on top?

Also how do I know the channels come on at the same time? Method calls one after another? I can verify the directions by doing it twice with each and marking the connector on the board. That and it'll be good?

thanks!!

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adafruit_support_bill
 
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Re: dire help needed on simple question - more power to single DC motor from ada shield!

Post by adafruit_support_bill »

Could I remove the other one and put it on top?
Yes.
Also how do I know the channels come on at the same time? Method calls one after another?
Back-to-back calls with the same speed should be good enough. But be sure to stop before reversing direction. You don't ever want to have the two bridges working against each other.
I can verify the directions by doing it twice with each and marking the connector on the board. That and it'll be good?
Should do it!

enerj
 
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Re: dire help needed on simple question - more power to single DC motor from ada shield!

Post by enerj »

big demo in 2 days - just in case i can't get this figured out could I brute force it and have M1 switch a relay directly connected to my battery and drive the motor one way, and have m2 switch a relay with the polarity switched to drive the motor the other way? I know its messy but I don't know if i want to risk hurting these chips/boards at this point.

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adafruit_support_bill
 
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Re: dire help needed on simple question - more power to single DC motor from ada shield!

Post by adafruit_support_bill »

That should work.

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