Hi, my first time, so please be gentle
I have created a touch switch, using a 555 IC. I have it timed using a variable resistor and a capacitor. All is good, except, I want to be able to be able to use the same touch plate to toggle the circuit on and off..so I can touch and leave it to time out, or touch it again to turn on /off.
I have used a 2n2222 as part of the trigger input. The collector voltage goes from 10v to 7v (measured on a basic multimeter). This is enough to trigger the circuit (Pin2 on the 555). I have tried to adjust the bias resistor on the collector (attached to 12v through a 5Mohm variable resistor) and can reduce the voltage to 8v and 5v respectively when the resistor is at 5Mohm. I tried to up the 5M to a 10M resistor, but the circuit stopped working (although I may have popped the transistor!).
Anyway, to get the logic to allow me to automate a reset (Pin 4 goes low), my solution was to use a 4011 Quad nand IC. I created a logic circuit that gave me an output that would hold the RESET Pin on the 555 HIGH unless the touch plate was touched.
Trouble is....the collector output is at best 8V reducing to 5v when the base is touched and this is not enough to trigger the NAND gate.
What I am trying to do is to take the 8v as a high (easy), but to take the 5V as a LOW (STUCK!!!)....
I thought about using a couple of resistors to reduce the voltage, but I think I need at least 5v difference (high to low)...and also worried that this solution may not be reliable.
So, what I need is some help!! Is there a way to take the 8v to 5v output and easily transform it to 8v and 0v? (enough to trigger the NAND gate).
Happy to show a picture of my circuit so far if that helps.
Any help would be appreciated.
Alex