While browsing a component website I came across an IC shown as a 2 Channel touch switch.
It was under a couple o quid so I added a couple to the order to have a play with.
When it arrived it as an 8pin dip device with a small sticky label on the top. I immediately pealed this off to see what the device was.
It turned out to be a 12F683 PIC.
The code was protected (as expected) so I was not able to read it to see how the device was programmed
I wired it up on the bread board to test it out, and it works exactly as shown in the specs.
I built it up on a small PCB with a couple of chrome touch sensors.
The sensors are screw in covers to fit in a countersunk screw from the local diy shop.
Because they are chrome plated it was not possible to solder them and the thread is not long enough to use a nut and connector on the back.
The touch inputs are use a 1M-ohm pull up resistor to Vdd.
I made the connection by having a couple of bent over bits of wire under the dome, and connected these to the pcb.
The switches allow the sensors to be set to either latch or momentary.
Pins 4 & 5 on the chip are connected to the switch common termnals, with pins 1 & 2 on the switch to Vdd or Gnd
The screw terminals are left to right
Vdd, Gnd, Output1, Output2
The device will work on any voltage from 2.5V to 5V.
This makes it usable with PIC, AVR, ARM or Raspberry Pi without the need for an external voltage regulator.
- Circuit Diagram
- Touch-Circuit.gif (3 KiB) Viewed 12601 times
- Breadboard Prototype
- Breadboard.jpg (103.58 KiB) Viewed 12601 times
The 4mm binding posts are connected to the regulator input and the spring termnals to the regulator output (5V).
The switch on the top of the case turns off the battery.
The blue & yellow wires at the bottom of the photo are the touch inputs.
It will actually switch by touching the insulation as well as the metal contacts.
- Touch Switch
- Touch Switch.JPG (115.15 KiB) Viewed 12601 times
