Date: Wed, 19 Jan 94 17:10:08 EST
Message-Id: <9401192208.AA00801@tortuga.media.mit.edu>
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From: "Fred G. Martin" <fredm@media.mit.edu>
To: Multiple recipients of list <robot-board@oberon.com>
Subject: Re: Power Consumption of MB? 

Jordan Nicol wrote:

> I'm sure this must be a FAQ but here goes anyway...
> How much current does the MB draw when it is on but not controlling
> any motors? My best guess is that it's around 70mA. This is based on
> the following:
> 	68HC811 (single-chip mode)                  15 mA
>         2 * 293D motor driver
>            quiescent supply current (Ven low)        8 mA
>            quiescent logic supply current(Ven low)  48 mA
>                                                    -------
> 				             Total  71 mA
> 
> Is this roughly correct? With this amount of current required just to
> idle, never mind run motors, it can't take very long to drain a
> battery, can it?  

You are right on the mark, check out the Mini Board Technical
Reference, Section D.1: 

 |_____________________|_________________________|_____________________  |
 | Power              |     supply required      |  5.6-36 volts DC    |
 |                    |__________________________|_____________________|
 |                     |     current draw       | 80 mA (motors off)  |
 |                    _|________________________|_____________________|_
 |                     |   +5v output limit     |       80 mA        |
 |                    _|________________________|____________________|_
 |                     |       connector         |  screw terminals    |
 |_____________________|_________________________|_____________________|
 
Moral of the story?  Don't try to run the MB from a 9v battery, unless
you like buying a lot of them.  Want to run the MB for a while?
Remove the motor chips.

	-Fred