graphite has high conductivity , so i though of making a touch button out of a pencil drawn pattern on the wall.the pattern is shown below.
when not touched -resistance between ends of the pattern >200Mohm (exceeds dmm limit)
when fully pressed - resistance between ends of the pattern = 1.3 Mohm.
but Vout rises after delay or falls after delay of some 100 ms.due to high impedance
this pattern connects skin resistances in parallel
can someone suggest a better pattern ( of lower end to end resistance) ?
for faster response

 

T1 is drawn with the collector and emitter swapped.
I am surprised that there is enough current through that 1.3MΩ to turn on T1 at all. Try this circuit with a darligton at T1 position and make R2 4.7k.

 

While this seems like a cool idea, it won't work for a permanent type 'switch'. After a few times the graphite will be less and less, think eraser. The pencils with high graphite percentages are the softest, and easiest to remove. Why not use one of the conductive silver pens for your lines? https://www.adafruit.com/product/515


Chart of percentage of graphite in pencils -
Pencil Number, Graphite %-wt, Clay %-wt, Wax %-wt

9H 41% 53% 5%

8H 44% 50% 5%

7H 47% 47% 5%

6H 50% 45% 5%

5H 52% 42% 5%

4H 55% 39% 5%

3H 58% 36% 5%

2H 60% 34% 5%

H 63% 31% 5%

F 66% 28% 5%

HB 68% 26% 5%

B 71% 23% 5%

2B 74% 20% 5%

3B 76% 18% 5%

4B 79% 15% 5%

5B 82% 12% 5%

6B 84% 10% 5%

7B 87% 07% 5%

8B 90% 04% 5%

 

thanks for help. ive decided to use conductive ink

conducting paint is too expensive.
are there any other alternatives to copper foil strips or Bare conducting paint

i found this
http://www.ebay.com/bhp/copper-tape ebay