Solid-State Button

M

Mumble

New Member

• May 31, 2006

• #1

Would this work as a solid state button?
**broken link removed**

 

audioguru

Well-Known Member

Most Helpful Member

• May 31, 2006

• #2

What do you want the circuit to do?
If the transistors survive the load's current then the circuit allows a cheap little pushbutton or toggle switch to turn on the high current load.

 

M

Mumble

New Member

• May 31, 2006

• #3

Im hoping that you touch the two electrodes at the far left with a finger, and the circuit activates.

 

audioguru

Well-Known Member

Most Helpful Member

• May 31, 2006

• #4

It won't turn on a high current if your finger is dry. It won't work if you wear gloves.

 

M

Mumble

New Member

• May 31, 2006

• #5

but perhaps a few leds or a relay?

 

justDIY

Active Member

• Jun 1, 2006

• #6

you must have removed your schematic, or it's hosted somewhere my ad-blocker has removed, as I can't see anything

good solid state buttons:

capacitive discharge - check out quantum research corp ... qprox.com

IR beam break / reflection - ir emitter + ir detector arranged such that a finger near the 'button' will reflect ir into the detector - modulate the signal such that random IR doesn't interfere.

Bi-directional LEDS - two leds working as a light source and a light detector, if both indicate a change, you could interpret it as a "button push"

 

philba

New Member

• Jun 1, 2006

• #7

you want a simple capacitive touch sensor. check the circuits listed here: http://www.discovercircuits.com/C/capacitance-sw.htm

 

Oznog

Active Member

• Jun 1, 2006

• #8

If you connect those two wires with anything low resistance, it will burn out the transistor. You need to add some resistance in series with the lower wire.

I agree this circuit is flawed in other ways as well.

 

audioguru

Well-Known Member

Most Helpful Member

• Jun 1, 2006

• #9

The simple circuit is fine. It is two cascaded emitter-followers. Short the input to the supply and if the 2nd transistor can handle the load's current then the base current of the 1st transistor will be very low.