hi guys , i've just built this circuit , with a touch sensor , so when you put your finger on the sensor the led flashes , when you press harder the led flashes faster .
Could any of you guys explain to me why ? And how this circuit actually works . Sorry if i'm being a pain , i have numerous books as i explained in my opening post , and i understand to a degree what each component does , apart from the ic , but if i could get a kickstart with an explanation i could go from there .

 

i think this would be a better view of the circuit

http://www.flickr.com/photos/74030723@N06/6673026955/

 

Look up 555 astable. It will explain it all. Do you have any initial thoughts as to what is going on? Digging for info is a great way to learn.

 

as far as i can gather at the moment bill is , R2 is lowering the current for the LED , R1 and the resistance of your finger across the touch sensor control timing and duration of LED flashes ( but i don't know why !!) C1 controls timing and duration of flashes (but again i dont know why) and the 555 sends pulses of current to the LED

 

as far as i can gather at the moment bill is , R2 is lowering the current for the LED , R1 and the resistance of your finger across the touch sensor control timing and duration of LED flashes ( but i don't know why !!) C1 controls timing and duration of flashes (but again i dont know why) and the 555 sends pulses of current to the LED

The answer is given on page 4 of the attached document in the section entitled Astable Operation. Most other questions about the 555 are also answered in this document.

The 555 is probably the most versatile IC ever built. As such, its basic operation is relatively simple, but the different ways it can be connected and used are many.

 

ok tracecom many thanks for the help

 

Radio Shack sensor kit?

 

haha right on the button thatoneguy , hope its ok is it ? the only problem is that the book doesn't explain how the circuits work in any detail

 

haha right on the button thatoneguy , hope its ok is it ? the only problem is that the book doesn't explain how the circuits work in any detail

Yeah, a kid I know has one, it looked familiar. I think they should at least try to explain what is happening in the circuits, otherwise it's not so much educational as putting circuits together.

 

yeah thats what i thought too , i've spent the rest of the day trying to figure out how it works !!

 

is the touch sensor in the circuit diagram a Force Sensistive Resistor ??

 

is the touch sensor in the circuit diagram a Force Sensistive Resistor ??

No, it's just copper pads spaced closely together, but not connected, there's sort of a picture of how it looks in the schematic posted above.