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Proximity/Capacitive Touch Computer Mouse

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Hi, I am a beginner and don't really know a lot of the electronic lingo as my main knowledge is mechanical so please try to answer my question in lay-man's terms.

I am trying to develop a mouse that has its clicks as a proximity/capacitive touch sensor pads. Basically, the custom designed mouse shell is going to use the same boards from a USB mouse and going to add a double sided pcb that has the touch circuit (using QT116H as the IC) on one side and the electrode/pad on the other side.

Now my question is: the use of relays and transistors. I'm going to wire my touch pads to the mouse clicks (of the original mouse board) so that a touch on the pad would register as the click. I know that I have to have something in the middle of these two boards: as I cannot just have the mouse click (original mouse board) come and connect to the output of the IC. How do I use the relay and transistor circuit to handle this problem? Or is there a better cheaper way around this problem?

Also another similar question: I have a USB Keyboard Chip (24 pads - pads (1-8) and pads (9-24) in different combinations complete a circuit and output is registered). Example: Pad 2 + Pad 24 registers the 'Windows Key' output. If I want this key to be using the same touch technology (IC) as stated above again I need to use the relay transistor to act as a median between the the output of the IC and the keyboard. I can't just take a wire from Pad 2 and Pad 24 each and connect it to the LED which is connected to the output of the IC. Doing this as you would guess just completes the keyboard circuit and a click is registered indefinitely, regardless of either you are touching the electrode/pad (of the IC).

Thanks for your help regarding this and it is greatly appreciated.


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If you do away with the switch you will need to add a click sound, since the operator depends upon that sound to know that he has performed the operation. And if you add a touch circuit and relay to replace the switch, you are just making the circuit more complicated without adding any value.

What is the purpose of going to the touch pad? You will need to design the pad so it takes noticeable pressure to activate. It can't be so sensitive that resting your finger on it will activate it.

You should be able to replace the switch contact with a transistor, but it depends upon the circuit. What is the voltage that the click switch normally switches?
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