h-bridgeswitchestransistors
I am trying to connect the 47 ohm line from the 555 timer (refer to first picture) to either A1 to turn the motors forward or A2 to reverse the motors. Problem is I don't know how to, with two inputs, have 3 states. Power to A1, A2, or neither. The provided diagram I have tried works if I have 0 resistance on the io pin and doesn't work if I have any resistance but will short it.
You really should post a schematic instead of all the hand waving. However, there is one obvious flaw in your description. One side of the relay could should be connected to the collector of the transistor as you say, but the other side must be to the power supply, not ground.
When the transistor is off, the collector is effectively not connected or left floating. When the transistor is turned on, it will pull the collector low. Since that end of the coil will be low, the other end must be high for there to be voltage accross the coil so that the relay can turn on.
Here is how you should hook things up:
Don't leave off D1. It is there to catch the inductive kickback from the coil when it is suddenly shut off. Without it, the coil will generate high voltage and fry the transistor.
Double-check that you have installed the correct value of resistor in each location.
BTW, the traces that are carrying the heavy currents between the two lower connectors and the four transistors look awfully wimpy to me. In the next revision of the board, beef up (and shorten) those traces as much as possible.
Best Answer
Your 555 circuit controls pulse width suggesting it is some form of speed control. The H bridge uses 4 x NPN BJTs with the upper BJTs pair acting as emitter followers and the lower pair as switches.
If you invert the output of the 555 and apply the two signals to either side of the bridge you should be able to control both direction and speed. At the mid point (50% cycle) the forward signal exactly cancels out the reverse signal (i.e 'off'). At 10% duty cycle it goes forward 10% and reverse 90% of the time (i.e. net reverse). At 90% duty cycle it goes forward 90% and reverse 10% of the time (i.e. net forward). The high frequency of the pulse stops it hunting backwards and forwards.