Pull down

Open wadebob opened this issue 1 year ago • 1 comments

Such a neat project. I'm an electronics noob so probably a very simple reason for this but curious as to why you used smd resistors instead of using the built in pull down functionality on the pico?

Dec 10 '24 00:12 wadebob

The built-in pull-downs are in the range of 10k-20k. The external pull-down resistors are 1M. The higher resistance is needed to be able to measure the small capacitance of the touch pad and how it changes when you touch it. This is done by measuring the time it takes for the pin to go LOW after being set HIGH. That time is on the order of microseconds with a 1M resistor. With a 10k resistor it would be in the nanosecond range: too fast to measure

Dec 10 '24 00:12 todbot