• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

ADC0820 and drum pad

Not open for further replies.


New Member
Bit of a newb with electronics, so if this question has an obvious answer, please excuse me.

I am trying to attach an electronic drum pad to the Vin input of an ADC0820 flash ADC. I am powering it with 5v and using a 3.3v reference voltage (the voltage ref is a differential input on this IC, with a VRef- of 0V. When I attach a 10k pot to the ADC Vin input, everything works as expected.

Here's the thing that's confusing me: when I hook up a scope and read the drum pad when it's not attached to the ADC, it reads at 0 Volts when not being hit. However, when I attach it to the Vin input this level rises to 0.1 Volts and causes the ADC to read above 0. It seems the Vin pin is charged from the VRef+ pin and this is being sent back down the drum pad. I have confirmed this by connecting a pot to the VRef+ pin and turning it up and down - the charge leaving the Vin pin changes! This doesn't happen when I experiment with different ADC chips. Why is it happening here?

Thanks for the help

Not open for further replies.

Latest threads

EE World Online Articles