The DCI111 from 4QD is at the heart of the Skid Steering system that I intend to use and it works like this. The inputs of the DCI are two 10K pots which are mechanically attached to two servos on separate channels on your radio gear. When the servo is centered then its pot is also centered so that when the servo turns in either direction then the pot can rotate freely in the same direction. One pot is for speed, so when you push your stick forward the the speed pot will turn in one direction, the amount of travel will correspond with the amount of movement of the stick, the speed output will also increase in voltage the further you move the stick. When the same stick is moved in the opposite direction then the direction output is toggled and the speed output increases as the stick is moved backwards.

The other pot is for direction. Moveing the stick in one direction will cause one speed output to increase and the other decrease (and vice versa) and when there is no speed input then then the speed output is proportional to the amount of stick travel but one direction output (depending on what direction is desired) will be toggled so that one set of wheels spins in one direction and the other set spin in the other direction causing the robot to spin on the spot.

Above is a picture of the DCI111 and it’s connections. On the top 3 pin connector (LHS) a switch or a link must be fitted between +V and IGN to power up the system. The 0v (same connector) is not used as yet. On the 6 pin connector below, +V is the power supply input for the DCI111 and is derived from the speed controller. The IGN pin will go high when the IGN switch is turned on this turns the controller ON. The Direction output is either high or low depending on desired direction. The speed output is a variable voltage that increases as the desired speed increases. The other 6 pin connector is connected the same except the +V pin does not supply operating power to the DCI but the direction switching voltage for that controller. The top RHS 3 pin connectors show the connections to the 10K pots.

Above is a wiring diagram of one way that the DCI111 can be connected to two speed controllers. Please note that the voltages on the speed and direction outputs from the DCI are higher than the inputs require on my design so if you connect up like this using two of my controllers then you will require a potential divider on the output to drop it within the required levels. This is a stage that I have not done yet so there are no values here yet, it is a case of measuring the extreme output levels from the DCI then matching them to the 5v logic level on the direction and the +0.7v - +9v level require on the speed input. You will notice that all of the 0v connections on the DCI are not used, this is because all of them are linked internally and I want to minimize the possibility of ground loops.