The schematic shows how to connect to a PIC's outputs, just four lines are needed. OR,
Use a toy radio control to control big motors for tank-like control.
On the receiver, cut the toy car/tank motor wires off at the motors and connect those wires to the 5 volt relay coils as shown in the schematic for the PIC..
Any speed control can be connected, like a PWM. Use heavy guage wires on all relay contact lugs.
Step 1: RELAY BOARD PHOTOS
Mount relays on a perfboard and use the heaviest guage wire you can on the contacts for really big motors.
Step 2: Toy Radio Control Now Controls "monster Car"
Salvaged "Hot wheel" type outdoor rideable kiddie car motor set-up, can now be controlled with a toy radio control receiver and this relay unit.
The toy receiver and motors probibly ran on 4 penlight batteries. Now the same toy controls 12 volts to power a car big enough for you to ride.