Circuitry

Power	Direction	Result
0	0	Nothing
1	0	Move forward
0	1	Nothing
1	1	Move backward

Table 1: Four possible results of combination of SDST and SDDT relays on motor (0=Off, 1=On)

For the wheelchair, two circuit boards will be in use: one for the linear actuator and one for the DC motor. Each motor will need to be able to direction two motions (up and down, or left and right) and also must have an "on and off switch." To accomplish this, a circuit board created on a PCB board will be constructed. The DAQ will create two data outputs (the two lines leaving the DAQ) for each PCB board. Each circuit will have a double pole double throw (DPDT) relay and also a single pole single throw (SDST) relay to control direction and power of the motor, respectively. The SDST is a single switch that connects the circuit. If it is open, the circuit can conduct current, if it is closed, it will not. The DPDT is a double switch that controls the direction of current. As the current passes the magnet in the motor, it will turn in the direction of the flow of electricity. Figure 7 shows a simple drawing of this circuit. There are four conditions which can arise from the combination of the SDDT and DPDT, as shown in Table 1.

Figure 9: A simple sketch of a circuit that will be constructed for each motor