Electronics Touch Control Panel Design : New Schematic 05-02-2005 - NEED FEEDBACK

Here's a stripboard i built for someone, the sensor is a metal 5.1/4 protection cover. It has a sensing range of about 4 cm's.
** Warning BIG pic! **

Perhaps we should do a topic on sensor design, it's very interesting stuff.

 

What size caps are you using on the sensor lines? Larger cap = more sensitivity according to the docs...

My main thing is that there's a comfortable gap between led activation and switch activation, so you can see the switch with a safe margin before it activates.

Coorz: yeah, some discussion of sensor design would be interesting

Also a brief update: I'm swamped with work and out of town this weekend, so it's looking like I'm not going to get back to this before 5/21. I will be ordering the parts before then, however, so hopefully I'll have everything and can put this together that weekend.

 

That, sir, is amazing looking technology there. Send me a model when you finish it? I'll pay you well.

And because I'm somewhat lazy, what is it for?

 

hmm, here is my design:
http://www.hellzbellz.net/screen_dumps/touchswitch.PNG

6cm diameter, circuits fit over one another back to back, jumpers on option pins BTW

10 NF (0.01uf) cap used on sensor pin (between pin 6 and 7)

bu it might have like 5mm proximity detection once you touch it with your hand through the acrylic it is stuck to. didnt have much though at all...

 

K so i'm going to do something similar... but am stugeling with the transistor choosing...
basically my scheme is just like the one from technomancer.
3 of the 4 outputs go straigth to the mobo, one however will control the lighting in my case... Now here lies the problem. I just want to turn the lights on and off, it will be +- 10 leds (maby only 9) in parrallell with one resistor of 39 Ohm (need 37,5). The voltage of each led is 4.5V at 20mA, my source Voltage will be 12 Volt of the old molex.
Now I was looking at PnP and NpN transistors and well can't make up my mind witch one to buy.
If I follow the guide on : http://www.kpsec.freeuk.com/trancirc.htm
then I should get one with following spec's : 180 mA Ic(max), 180 hfe(min), and a resistor of 2k4 Ohm between my qprox and the transistor...

more info on the transistor I'm eying: http://www.farnell.com/datasheets/2466.pdf

Does this sound right?

Any help is welcome... and if I offended anyone by posting this (don't want to be called a thread hijacker), sorry in advance...

 

The digikey part # for the Resonator has a different datasheet. its http://www.ecsxtal.com/pdf2/ZTA.PDF

 

Thanks. I've grabbed the datasheet and will edit previous posts. I'll probably also be revising the schematics as I don't think I'm going to do the lighting controller... which will allow me to use slightly larger sensors plates as it drops # of switches from 4 to 3.

 

I'd think it safe to assume the QT output is bounce-free, so you shouldn't need the complex flipflop circuit, a simpler one should do. You might want to add the pulsing components I've added to my original design to start up with the lights either on or off.

May also be simpler to run the flipflop on 5V, same as the rest, and just have the lights & mosfet on the 12V rail. Will need a logic-level mosfet, plenty around these days, but would eliminate Tr1, just need a pull-up resistor on the QT output/flipflop input connection.

You've got the MOSFET grounded both sides.

 

another note, some of the other qprox devices (i know qslide and qwheel for sure) have a "PROX" output which does what you want without having the outside rings.