I have a Veypor VR2 dash and would like to fit external buttons on the steering wheel, I have found the schematic for hooking up the buttons here:
http://www.veypor.com/forum/viewtopic.php?t=2037&view=previous
The diagran looks simple enough but I am confused by the text, what does the line "pin 3 must be pulled to ground with a resistor, then when the button is pressed it should short it to +5v" mean ?? I understand the short it to +5V but do I need a resistor somewhere as well ?? Any electronice people here who can help out ??

Thanks,

John

Hi,

From the sound of it you need a resistor between pin 3 and pin 1 (ground). This resistor should be around 4700ohms (4K7) to 10K and this value is not too important. It's purpose is to provide a 'weak' connection between pin 3 and ground to ensure that whatever is behind pin 3 always sees a defined logic level. If pin 3 is left disconnected then it is possible that the voltage on this pin can 'float' and the circuitry could see unpredicted levels and start to do funny things.
Anyway - tedious bit over. Connect a 10K resistor between pin 1 and pin 3. 10K resistors are colour coded either brown, black orange, or brown black black red depending on the type.

HTH,
Ed.

In fact, like this:



Ed.

^^^^ wot he says - maplins will sell resistor - 17 p, you need low popwer ones - make sure they get meter out and measure it - monkeys that work there cannot read the codes and too many a time they gave me wrong one whcih is really effing annoying as I then have to go back to get the correct value.

if you are stuck, don't want to spend 17 p or don;t trust maplins staff, I can pop one in post to you.

Thats great, thanks guys, makes sense now !! I think I've a 10k resistor kicking around.

Thanks,

John