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The client had a preliminary design of a product to be used in the medical field. This product circulates icewater through a pad that they designed to be used for post-surgery recovery. The existing design had a variable speed control, but it did not maintain a consistent temperature.
The above photo shows the final design. The board includes a small display and an membrane keypad. A Microchip PIC processor controls the system. It drives the multiplexed display and uses a pulse-width-modulation output to control the pump speed. A small temperature sensor monitors the temperature of the return water from the pad. A simplified PID algorithm us used to maintain a constant temperature.
The temperature can be set in Centigrade or Fahrenheit
Total time for the project was several months. The initial design was working in only about 2 weeks. There were changes for production and user interface.
This has been very successful for the client. He has ahd delays setting up offshore production, but now thousands are being sold. The design of the board has made it inexpensive.