RF Proximity Sensor, Electronic Dispenser

End User/Market: Commercial Buildings

Background:

A battery operated, electronically controlled paper towel dispenser uses an RF proximity sensor to detect a person's hand near the dispenser and then disperse a pre-determined length of paper towel. Previous designer's RF proximity sensor design resulted in about a 2-month battery life.

Opportunity:

Battery life must be increased to 2 years to insure market acceptance of the dispenser.

Solution:

Measure RF proximity sensor current rather than frequency to detect a person's hand near the dispenser. Use 10-bit A/D convertor on microcontroller with oversampling and DSP algorithm to accurately measure a 0.1% change in RF proximity sensor current.

Results:

Electronic dispenser with more than 2 year battery life. US patent pending.

Technologies:

MSP430F2012, RF proximity sensor, A/D oversampling, digital signal processing.