AVR Freaks

Seams like its working. Cant say for sure as everything has not been put together yet but those Qtouch Atmel chips that jgmdesign suggested work a treat. They work so consistently even behind the LCD when it is displaying digits and changing digits. I am just etching a board (taking some time because the traces are 0.1mm) then I am going to re-flow everything and put it together to see if it works.

So I got a PCB etched and populated this weekend, unfortunately the touch capability is not sensitive enough. it works if I put my hand on the LCD touching the whole screen but does not pickup just your finger. What I will do now is increase the Cs capacitor from 10nf to 33nf. By doing this the sensitivity will increase as per the Qtouch data sheet. I will try this and hopefully it works. The LCD did not falsely trigger the Qtouch circuit which is good news but it might now that I am going to make it more sensitive but I guess the only way to really know is testing it so back to step 1 for me.

I will report again when i'm done. I also noticed that my LCD was connected incorrectly so the seven segments were not displaying correctly. i will need to make another PCB now fixing this along with changing the Cs cap value.

So i got another speedometer built this weekend and unfortunately it doesn't work:( strangely though it works when i disconnect the TSOP IR receiver. So i am guessing the IR receiver creates too much noise for the Qtouch chip to actually work. It was fun doing all of this. I have refined my etching process to get finer tracks more reliably so at least that was good news.

I have another plan though, I am hoping you guys can give me your opinions though if this would work or not. I want to connects a small piece of wire to a transistor base so that when you touch the wire then a uC pin will see HIGH or LOW. I might need to connect two in a darlington pair to be sensitive enough or something.

"What you want is some ITO (indium tin oxide) film" this film is unfortunately not available to me so i cannot use it. As a last resort I guess i will need to use an actual mechanical button. But i am hoping my transistor idea will work. 

I will do this and see what happens. Thanks for the idea.

The reason why i wanted to use a transistor or thought i need to use a transistor was because i thought my finger touch will not create a high enough voltage to sufficiently turn on the port pin. Now that i actually sketched it out i see that i would actually need to use a PNP transistor to let the port pin see a high 5v when i touch the wire. but then again you need to ground the base for the PNP transistor to come on.

I believe that your method would work but i do not understand how it will work. I will def do it and see what happens. 

Here is a sketch of what i wanted to do which now does not make sense 

Ok that is great news thanks Kartman. By just using the uC pin i will also reduce the amount of parts i use which will help me layout the pcb easier. So just to clarify i must use a 10M resistor to a PORT Pin set as input floating? or to ground?

Alright i understand thanks, i will try this and report back how it went.