How To Radio Control Servos Cheaply
How To Hook Up The VEX Reciever To The Interface Chip
Motors, relays and power supplies will cause radio interference; so pick a spot on your robot where the "VEX" reciever is far away from these things.
The "VEX" reciever comes with a yellow cable. Plug the cable into the "VEX" reciever, the other end of the cable plugs into a telephone handset jack. You must buy the jack. Since I will not know the colors of the wires coming out of your jack; I will referent the yellow cable wires. If you look at the yellow cable you will see 4 wires which are yellow, green, red and white. The yellow wire gets wired to + 5 volts. The green wire is the signal and it gets wired to a 1k resistor to pin 16 on the interface chip. The red wire gets wired to ground. The white wire is not used.
You need to wire a 10K ohm pull up resistor from pin 16 on the servo controller chip to the + 5 volts. You will also want to wire a 330 uf capacitor across the ground and + 5 volts.
Pin 17 is an option input pin. It must be wired high or low and NOT left floating.
Option 1: pin 17 high, then the pulse width of 1.5 ms goes to the servos when the transmitter is off and no serial command is being given.
Option 2: pin 17 low, then a high is sent to the servos 1 - 4 when the transmitter is off and no serial command is being given. This will cause the motors in the servos to lose power. This has worked in all the servos I have tested but test to see if this works with your servos. Servos 5 and 6 will keep the same pulse width. This way if the servos are used in a arm joint and the robot goes out of range, the arm will still stay in the same postion.
Pin 3 & 11 are option input pins. They must be wired high or low and NOT left floating.
Option 1: pin 3 high, pin 11 low. The transmitter joystick will give the servos a pulse from about 1 ms to 2 ms. This is the range a normal servo uses.
Option 2: pin 3 low, pin 11 high. The transmitter joystick will give the servos a pulse from about .750 ms to 2.25 ms. This is the range to use for a "VEX" servo and motor
Option 3: pin 3 high, pin 11 high. The transmitter joystick will give the servos a pulse from about .688 ms to 2.31 ms. This is the range a "TowerPro SG-5010" servo uses.
Note: When changing options, the power to the controller chip must be turn off and then on in order for the options to take affect. These setting have no affect on serial commands.