PiDA Power Draw Estimation

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PiDA Power Draw Estimation

Postby alanmcdonley » Fri Jul 31, 2015 4:46 am

With motor power, and both servo power banks set to external:


    What is the (approx) idle 5v power draw of the Pi Droid Alpha?

    What is the approximate additional 5v power draw when two external powered DC motors are driven at max (external 8.6v 0.6A/1.2A surge each)?

    What is the approximate additional 5v power when an external powered servo is driven at max (SG90 external 5v at 650ma max)?

Thank you for your efforts to educate,

Alan
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Re: PiDA Power Draw Estimation

Postby mikronauts » Fri Jul 31, 2015 7:12 am

You are most welcome - and these are great questions, don't be surprised if the answers end up in the FAQ

For now, I will supply guesses, however in a few days I'll take actual measurements.

idle power:

should be <1mA as long as no 5V sensors etc are drawing power, and the motor directions are set to 00 & disabled.

5V draw should remain very low as the motors would be externally powered. Please note, there is a roughly 1.4V drop from Vbat to voltage delivered to the motors due to the on-board diode & drop from L293D.

You can bypass the diode if needed by shorting it, but you lose the battery polarity reversal protection.

There should be no noticeable extra draw on the Pi's 5V when supplying external servo power at Vservo, note a 0.7V voltage drop due to protection diode (which can be bypassed)

alanmcdonley wrote:With motor power, and both servo power banks set to external:


    What is the (approx) idle 5v power draw of the Pi Droid Alpha?

    What is the approximate additional 5v power draw when two external powered DC motors are driven at max (external 8.6v 0.6A/1.2A surge each)?

    What is the approximate additional 5v power when an external powered servo is driven at max (SG90 external 5v at 650ma max)?

Thank you for your efforts to educate,

Alan
mikronauts
 
Posts: 119
Joined: Tue Sep 16, 2014 6:58 pm


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