electric short

I opened up a remote to see how the keypad works.

I see some interlocking traces on the printed circuit

board below each button. When the button is pressed

they get shorted.

I tried to short them myself and it has the same effect

as pressing the button

I measured one set of traces they were at 3.3 v the

Second trace was at 0v

So I presumed when I short I connect the 0V to 3.even

But here is what is strange. If I take 3.3v and connect

It to the trace that is at ground it does not have the same

Effect as pressing the button. But shorting the two works

This baffles me.

Saleem

What you have, is an input to something, which has a pull-up resistor to 3.3V, and a normally-open button connected to ground.

When the button is not pressed, the input sees the 3.3V, which is a logical 1. When the button is pressed, the input is shorted to ground and the input sees a logical 0.

This is the normal method of connecting a button input to the arduino, or any microcontroller, or any device that has an input to detect a pressed button.

But here is what is strange. If I take 3.3v and connect

It to the trace that is at ground it does not have the same

Effect as pressing the button. But shorting the two works

This baffles me.

If you connect your power supply voltage to a ground trace, this will make the whole circuit meaningless.

Buttons in a remote are usually matrixed to minimise the I/O lines for the chip. When you press a button, one pin of the chip is connected to another pin of the chip. The X-row might be normally "high", while the Y-row is normally "low". http://www.circuit-projects.com/cimg/32_channel_IR_remote_controller_by_SL490.gif This example has 32 buttons and uses only 11 IC pins. Leo..