Adafruit Motor Shield External Power Supply

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kruzan
 
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Joined: Fri Feb 11, 2011 7:17 pm

Re: Adafruit Motor Shield External Power Supply

Post by kruzan »

is this right?

cut this trace:
Image

then i can put a switch between these two locations. when off no power to board (as long as EXT_PWR is not connected)
Image

could i damage the microcontroller? if the sketch is trying to move a motor with shield unpowered

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adafruit_support_bill
 
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Re: Adafruit Motor Shield External Power Supply

Post by adafruit_support_bill »

That would be the trace.

I did check one of my shields on the bench: WIth no external supply connected and the jumper off, I see a steady 4.36v on the H-Bridge side of the power jumper. When running the MotorTest sketch, I also see a few hundred mV on the motor terminals. That much is consistent with what you are reporting - But my LED doesn't light at all.

It could be that your bridge-chips are just a little leakier than normal, but it sounds like they function normally otherwise.

rlounsbu
 
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Joined: Sun Mar 06, 2011 9:13 pm

Re: Adafruit Motor Shield External Power Supply

Post by rlounsbu »

rlounsbu wrote:Clarification is needed for the schematic (mshield2). Power from the ext_pwr header pin P1 shows the signal as V+, but the power to the L293D H-bridge drivers is show as Vcc. Should the external high power V+ go to the motor drivers, not Vcc. Vcc is shown coming back on JP1 pin 3 from the Arduino regulated +5V. Instructions clearly say don't tie regualted +5V to motor drivers. Similarly, LED1 is shown powered by extr_pwr V+, not Vcc.
Any clarification you can provide would be appreciated.

kruzan
 
Posts: 55
Joined: Fri Feb 11, 2011 7:17 pm

Re: Adafruit Motor Shield External Power Supply

Post by kruzan »

Here is same issue, looks like its the driver chips

http://forums.adafruit.com/viewtopic.php?f=31&t=17525

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thomedwards
 
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Re: Adafruit Motor Shield External Power Supply

Post by thomedwards »

I've got a similar issue, and started a new thread. http://forums.adafruit.com/viewtopic.php?f=31&t=20356

Baset
 
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Joined: Mon Sep 12, 2011 7:34 am

Re: Adafruit Motor Shield External Power Supply

Post by Baset »

maybe its the same issue where some can not boot a pc if usb and external power connected to the arduino?

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