“I was asked to make a set of automatic hand-sanitizer dispensers (on a short-time notice, of course) for Barcamp Yangon 2020 Event. Amid Corona/COVID-19 virus outbreak events, event organizers took public health protection in consideration and planned to hand out face masks to attending audience and place hand sanitizer dispensing stations at a number of locations.
Commercial dispensers were hard to find/buy at the moment and easier alternative would be to make it DIY. With cost efficiency and local availablity of resources/parts in consideration, we (a team of contributers) prototyped and supplied some dispensers for Barcamp Yangon 2020 event.
Although a simple 555-IC timer circuit would do the job, we wanted to implement (in the future events) a function that will log how many times have it been used the dispenser throughout the event. We chose a small, simple and cheap (which you can get from Aliexpress for $2) Digispark ATtiny85 USB Dev-Board (or alternative ones) as our main controller. Logging functionality will be implemented in the future through EEPROM.
Based on the viscocity of the liquid, we used a 12V/DC 120L/H submersible pump and for that a 12V AC/DC adapter is used to provide adequate power supply. This 12V supply is fed into Digispark Board’s VIN pin and an onboard voltage regulater output a 5V power supply to be used with reflective sensor module and relay module.
The rest is much simple, we have used an infrared reflective sensor module to sense the hand placement and relay module to connect/cut the motor to 12V power supply. Don’t forget to adjust the IR module’s gain setting so that the sensor will detect the hand at a desirable distance.”