Oops... i forgot to post the final project (i always forget to update when i'm done working on stuff). The kids love the brush bots. The project was a great success. I ended up not using the remotes because they kept falling over with the placement of the brushes and i haven't had time to figure out how to add a third brush or set of back brushes to keep them up yet.
There does seem to be an issue with the recharging feature... i'm not sure if its because of the diode i am using on the charging port. I keep taking the batteries out to recharge them. They last a while (maybe an hour or so) before dying completely. The charging takes like 5 hrs per battery but the kids only play with them for a little while at a time.
I prototyped the circuit on a breadboard. Everything seems to be working as planned. When the jumper (will be a switch) is set to charge, i'm getting power in from the external power source. When its turned "on" the led lights and i'm getting a voltage out from the motor leads. The bypass switch works fine too.
Testing the battery charge is working correctly.
So i decided to make some brush bots with the kids. Instead of going the route of just hot gluing/taping everything to the board, I wanted to add a few extra features:
- Rechargeable battery - LIR2032 doesn't have great capacity (35mah) but i had 2 of them already and they could be swapped with CR2032 which has 10x the capacity
- External Charging Jack
- LED - This will suck away the batteries but it looks nice and the kids will like it.
- Power Switch - Pretty standard but this is a SPDT to allow switching the robot back into recharge mode.
- External Push Button - I wanted to give the kids a little "leash" with a push button on it so they can bypass the switch so it doesn't have to be "ON" all the time.
We're encasing them in easter egg bottoms so the kids can decorate the exterior.
The external charger will be a modified RTC module. It has a charging circuit and can be purchased for about $1.50 which is much cheaper than any LIR2032 Rechargers on the market or even to source the parts to make a circuit from scratch. I'll post info on it when i get to that point.
Additionally i'm looking to revamp this design to include an ATiny85 and an IR detector so i can remotely control 2 motors and make a steerable brush bot. I'll probably post that as a seperate project when i get there.