From: Sean Luke <sean@cs...> - 2005-03-10 22:30:34
> I think you're confusing the various power connections.
> V_BATT doesn't go to the servos. It's only used for the gumstix
> itself. The name is a bit confusing, but it existed before the
> Robostix so it's still used as the voltage that goes to the gumstix
> board itself.
> Either V_ROBOBATT or V_MOTOR (depends on how you've got things
> jumpered) can be used to drive the servos. You can have seperate
> batteries for V_MOTOR than you use for V_ROBOTBATT, or you can use the
> same battery for both.
What I'm trying to figure out is why there are THREE power inputs when
there are only two things to be powered: the gumstix and the servos. I
would have assumed that the arrangement would be to have 6V in for the
gumstix, 6V in for the servos, and an option to jumper the two together
if they're running off the same supply.
I presume V_ROBOBATT is for the gumstix and V_MOTOR is for the servo?
If so, is the third (V_BATT) supply there to allow you to plug the
gumstix into a wall? And if so, what happens if power is provided into
V_ROBOBATT and V_BATT at the same time?
> Just an aside, but servos also typically run with 4.8v to 6v, and I
> routinely take mine up to 9v.
They *do* run from 4.5 to 6V, but they very often at sub-par speeds at
lower voltages. When you're using modified servos as motors, as is
often the case for small robots, this can be a problem.
As to above 9V: given all the dire warnings I see about going above the
standard voltage of 6V, you're a braver man than I am!
From: Dave Hylands <dhylands@gm...> - 2005-03-10 23:39:12
> What I'm trying to figure out is why there are THREE power inputs when
> there are only two things to be powered: the gumstix and the servos. I
> would have assumed that the arrangement would be to have 6V in for the
> gumstix, 6V in for the servos, and an option to jumper the two together
> if they're running off the same supply.
On the robostix board, V_BATT isn't an input. The 3 inputs are:
1 - V_POWER (same type of power connector that's on all of the other
boards). This allows the gumstix/robostix to be plugged into the wall
2 - V_ROBOBATT - really the same as V_POWER, but it's a 2 pin 0.1"
header, rather than a jack like the one on the wall wart. You would
only ever use one of V_POWER or V_ROBOBATT at the same time.
3 - V_MOTOR - goes to the servos.
There is a jumper which allows V_MOTOR/V_ROBOBATT to be connected
together which results in the motors and the ATMega being powered from
the same battery (connected to either battery connector or the
> I presume V_ROBOBATT is for the gumstix and V_MOTOR is for the servo?
> If so, is the third (V_BATT) supply there to allow you to plug the
> gumstix into a wall? And if so, what happens if power is provided into
> V_ROBOBATT and V_BATT at the same time?
The gumstix board itself has an onboard voltage regualtor that
requires less than 6v. This is V_BATT (it's on the 60 pin hirose
connector). Gordon put a voltage regulator on the robostix that can
take V_ROBOBATT/V_POWER and convert from the 6-12v range down to 5v,
so the gumstix board will be happy.
On the waysmall board, the power connector for the wall wart is
V_BATT. On the latest schematic of the Robostix, the power connector
is called V_POWER.
Vancouver, BC, Canada