First Wave Technologies hired me to build a life tester for their new product. They had a prototype of their second generation pill crusher, and wanted to run a cycle every 30 seconds until the internal software sensed a low battery level and shut off the unit. They would then put the unit on a charger and repeat the cycle again. I came up with a simple solenoid powered fixture that would press the on button every 30 seconds. I used my Arduino to send a 5V signal to the gate of an N channel mosfet for 1 second every 30 seconds. The mosfet acted like a switch, and turned on 18V to the solenoid (rated for 12 to 24v). This pulled down a lever that turned on the unit. I counted each cycle and output the number of cycles to an LCD display. The LCD display had a “backpack” on it that utilized I2C protocol, so that I didn’t need to use many digital lines on my Arduino microprocessor to accomplish the display output. They used this fixture to run 2 complete charge/run-discharge cycles per day for 30 days. Based on this, they made a few slight changes to the electronics, but concluded that their overall design was sound.
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