Objective

The goal of this project was to modify an existing dishwasher so it could perform multiple cycles without having to be reloaded or constantly checked by the user. This added functionality would serve to perform a kind of accelerated life cycle on items placed inside.

To accomplish this, a board from an old dehumidifier was used. The board was chosen because it has two 8-segment displays, 7 buttons and 8 LEDs, all of which are controlled from only seven pins thanks to a shift register IC( 23 pins if the system was not multiplexed!).

Coding and Hardware

After looking at the specifications for the IC, the controller was programmed to accept the pushbutton inputs and control the LEDs. Originally, the 'wash restart' sequence is activated only after the wash is completed, the door is opened, a wash selection option is pressed and the door closed. These events were simulated outside the dishwasher controller with microswitches and the correct output sequence for the 'wash-restart' operation was programmed with the help of LEDs connected to the output pins.

The next step was to modify the existing PCB cover to correspond to the newly programmed controls. Up and down buttons next to the 8-segment display increase and decrease the number of washing cycles and the start/stop buttons start the cycle and stop 'listening' for a signal from the dishwasher.

Final Assembly

The finished controller was soldered into an empty PCB and mounted on the back of the controller. The control panel was placed outside the door.