I’m constructing my first robot from a Boarduino (Arduino-compatible), a LVDSMC, a servo, an IR rangefinder, and a Tamiya dual gearbox with standard motors.
To properly power everything, I’m coming up with the following list of battery packs:
- 9V: to power the Boarduino
- 3V: to power the Tamiya motors
- 6V: to drive the servo
(All of these are actually NiMh or NiCad rechargeables, so the voltages vary somewhat, but you get the picture.)
Is all this really required, or is there something I can do to cut down on the battery requirements…without driving the Tamiya motors at a damage-inducingly high voltage?
You probably will need all those batteries. It’s difficult to power the servo and motors with something other than a direct battery connection, and the recommended voltages don’t overlap. However, if you don’t need much current for the Boarduino, you might be able to find a step-up converter (dc-dc converter or boost switching power supply) that could give you 9 V from your 6 V servo supply. Such a converter would be more expensive than a 9 V battery, but it could save you size.
One other option is to regulate your 9 V to 6 V if your servo doesn’t use much current. With a linear regulator, you’d be dissipating quite a bit of power, and the battery would have to be capable of delivering more current (a standard 9 V alkaline probably wouldn’t cut it).
You’ve confirmed my suspicions–thanks!
I’m chiming in on this topic a bit late, but the BoArduino really only needs regulated 5V if you bypass the on-board regulator. You could get regulated 5V from the 6V servo power supply using either a low drop-out regulator (cheap, inefficient) or a DC-DC switching regulator (expensive but efficient).
If I were building this robot, I would probably use 2 power supplies; a 3 volt supply for the Tamiya motors and a 6 volt supply for the servo and electronics (when regulated to 5 volts).
Many servos can run off “6V” in the 5-cell NiMh pack sense, which actually gives you 7 V when charged. So I’d recommend using that for your servo and electronics so that you can still have 5 V even after the battery is quite discharged (or when the servo is straining more).
The plot thickens…
Is it possible to use a single power supply, to directly power the servos and also supply regulated power to the Boarduino and electronics (5V) and motors (3V)?
(Aside: I’m now speaking hypothetically, and with an eye towards my second 'bot. The tiny little perfboard I’m using is just barely large enough for the Boarduino, motor controller, screw terminals, headers for servos and sensors, a single pushbutton, and I think I’ll be able to cram a cap in there to smooth out the sensor power rails. Fitting a regulator in would be extremely difficult.)
Yep, it’s certainly possible. I’d recommend using a switching regulator to do so. I really like the DC-DC switching regulators from Dimension Engineering (are we allowed to mention other companies on this forum?). I think they have one that will give you enough mA for the Tamiya motors.
However, as I believe someone else suggested in another thread, you might have a much easier time of things by using another motor that can handle 6V like the solarbotics motors. I have a few robots that I run off of a single 6V or 7.2V battery pack. The motors or servos run right off the battery voltage and I use a single regulator for all the electronics (or two regulators if I’m using 3.3V devices). Unless your design needs it, you might save some time, money and headaches by using other motors rather than trying to keep a 3V supply in your designs for those noisy Tamiyas.
I’m beginning to see that. I’m heading over to take a look at the RM3 motors (so I can use my second, as-yet-unassembled dual gearbox and Pololu round chassis) and some other stuff…
I find myself drawn to the Orangutan controllers for my next stab at this. In the interest of power-supply simplicity, would I be better off with the mega168, or the LV-168? (I’d like to continue using the Arduino environment for a while, and I don’t see that the mega168 is capable of that in the same way that the LV-168 is.)
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