# idea for creating Touch sensitive wire strip like variable resistor

#### Vignesh0025

Jul 4, 2013
9
Hii, I want to create a touch sensitive wire strip... That is .. When i move my hand over a copper wire

#### BobK

Jan 5, 2010
7,682
Well, there is not much variation in voltage along a copper wire unless it is drawing a LOT of current, so I don't see how.

Bob

#### davenn

Moderator
Sep 5, 2009
14,240

you need to understand you need 2 wires

Dave

#### CDRIVE

##### Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
That's partially true. One leg can be commited to ground leaving only one conductor as the capacitive pickup. I think it might be prone to false triggering though.

Chris

#### Vignesh0025

Jul 4, 2013
9
I searched for capacitive touchpad but could not find able to find any actual idea to work it out?? Where can i find the details??

#### CDRIVE

##### Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
If you're looking for a simple finger bridging circuit that demonstrates where along a resistive divider your finger has bridged the circuit you can put this together. I show a 9V battery and an Ammeter but a basic Ohmmeter will work just as well. Placing your finger across any of the 4 touch points will give a different Ammeter or Ohmmeter reading.

Chris

#### Attachments

• Touch(R)sense.JPG
16 KB · Views: 246
Last edited:

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Well, there is not much variation in voltage along a copper wire...

On a technical note, this applies only if the length of the wire is short compared to the wavelength of the signal.

#### CDRIVE

##### Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
On a technical note, this applies only if the length of the wire is short compared to the wavelength of the signal.

Are you referring to SWR?

Chris

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Are you referring to SWR?

No, I'm referring to the propagation of a signal through a conductor.

If the conductor is short compared to the wavelength, you can consider the signal identical throughout the length of the wire, and the signal at both ends are the same.

If the wire is long, both ends of the wire could be at different potentials.

As toy realize, an antenna is a perfect example. However, regardless of SWR the effect still happens.

#### CDRIVE

##### Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
No, I'm referring to the propagation of a signal through a conductor.

If the conductor is short compared to the wavelength, you can consider the signal identical throughout the length of the wire, and the signal at both ends are the same.

If the wire is long, both ends of the wire could be at different potentials.

As toy realize, an antenna is a perfect example. However, regardless of SWR the effect still happens.

Yes, but this does not hold true for transmission lines properly terminated in it's characteristic impedance at both ends. In this case the only differences from input to output should be dielectric and radiation loss. Usually,the more expensive the transmission line the less one should see in either regard.

Chris

#### CDRIVE

##### Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Steve, brain fart on this end! Yes, you're absolutely correct and so was Toy. My last post I was still stuck on SWR, which is better described and stated as Reflected Power. It has little to do with Toy's theory.

Yes, that's how antennas work!

Chris

Replies
4
Views
273
Replies
4
Views
340
Replies
6
Views
905
Replies
37
Views
4K
Replies
2
Views
2K