I’m trying to build a little kit for us to use in our activities at the library. My first goal is to get a simple activity where children can build a robopet (Just a paper or cardboard character that uses the micro bit for its face) and then attach a servo motor to it to make the hand move, tail wage, something like that.
We are trying to be cost-effective. I’ve seen the servo modules add price quite quickly. I was hoping to identify something to circumvent needing that.
We were going to power the microbit v2 via a battery pack.
That seems like a nice, easy project to start them off on.
While you’re correct in that servos can get a little expensive if you want to lift heavy things, but for light stuff like papercrafts, you don’t need to spend much:
If you’re looking to move paper or cardboard then micro and sub-micro sized servos should be just fine.
The tricky bit will be powering the servo as its operating voltage is higher than the micro:bit, you have two options there:
Connect the servo via the Monk Makes Servo board James linked which has the added benefit of having multiple servos and the microbit all powered from one battery pack.
Connect one servo to a battery pack, and the micro:bit to its own battery pack, then just connect the ground and PWM wires between them.
One other thing to be aware of will be continuously rotation servos, most standard servos will move to a position when they receive a signal. A continuous rotation servo is a bit different, it will move at a given speed continuously when it receives a signal, and is more like a traditional DC motor.
Is there any way to simplify this by having the Microbit run off the same battery pack with a resistor or something in between?
Having a look at the Monk Makes, it looks like that one provides 3v power to the Microbit? It’s a bit more expensive but it might be more straightforward.
The Monk Makes Servo board has a power regulator that will convert your larger battery supply down to 3V for the micro:bit so both devices can be powered via the servo board.
You could look for a separate regulator to do this but one I’ve found is more expensive than just getting the servo board and would still require soldering to connect.
Resistors can be used in circuits to provide reference voltages using voltage dividers but it’s a very inefficient circuit design for a power supply and will mean you lose quite a bit of your battery charge as waste heat.
I think your most effective option is to use the servo board, a lower-cost alternative is two separate battery packs but does mean there is more bulk in the robopet.
