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Chris Adams - 2016


This is a simple little robot made from a cheap toy remote control car.

the "Thunder Tumbler"  costs about $15 new



Toy car with Realtek RX2(RX2B)chip removed
This RX2 was a surface mount chip. I drilled very small holes through the circuit board pads to attach wires.

PWM ports connected to on board H-bridge
RX2 pin 7 pad to D5
RX2 pin 6 pad to D6
RX2 pin 10 pad to D10
RX2 pin 11 pad to D11

using Arduino Pro-mini
Any Arduino can be used.  The Pro-Mini is cheap, but requires an additional USB board to program it.

micro switches on front and rear bumpers
Front bumper switches to D2
Rear bumper switches to D3

smaller drive wheels added to reduce speed
Original drive wheels were 3.75 inch diameter. New wheels are 1.75 inches.

jumper on top of pro-mini bridges A4-A5 (install to disable 15 hit limit)
I soldered a 2 pin header in provided holes on top side of Pro-Mini. (optional)

extra AA battery in series with 4 AA batteries in car connected to Vin
With 4 batteries, you can only use alkaline batteries. Rechargeable NiMHs or alkalines can be used with 5 batteries.

This robot is programmed to follow these rules

Start when front green bumper is tapped


If front bumper hits something, go BACKWARD 

If back bumper hits something, go FORWARD

After 2 hits,  spin around and go FORWARD again


If no bumper hits for 30 seconds, stop moving

Stop moving after 15 hits

Flash LED light when stopped



Arduino Code


Cost to build $12

$1.98             Used radio control car                Salvation Army thrift store

$3.99 Arduino ProMini computer       MicroCenter

$4.00 Microswitches 4 @ $1.00           Ebay

$2.00 Misc hardware

if you don't want to solder to the ProMini pins, you could use Nano breakout board with screw terminals. Be careful, labels don't match the ProMini pins.


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