Looking for a circuit- proximity switch ?

I am building a fiberglass car and I do not want to have any door handles. In otherwords, this will be a very smooth body. I am looking for a circuit to make a proximity swith that has 2  elements in it. When I  pass my hand over one of the plates it latches power to the second sensor and  when I pass my hand over it it causes a solenoid to open my door. One of my students made a similar device for me a few years back and it got destroyed by mice in my car..  I will be using isolation relays with 1 amp draw to operate the door solenoid at 12 v. Any ideas?I already have 2 3x4 inch metal plates fiberglassed into the body for antenna.

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Here's a circuit, if you can get the chips. You'll need to rig a 5V supply from the car for it.
Copy of QPROX touch.png
Oops wrong final circuit.
Copy of QPROX touch.png
gurobuzz (author)  steveastrouk5 years ago
easy circuit to read, but I am not sure how to step down from 12v to 5 volts other that a transformer
gt.bmp
Use a "7805" regulator - its has three pins, Input, ground, output. Input 7-35 V, 5v out.

Steve
gurobuzz (author)  steveastrouk5 years ago
Ok, I guess you did not understand my previous statement that I can read schematics but have no clue what things do .
I am able to read schematics and solder tho- better than nothing
Buy one, wire the input pin to your 12V supply, wire the ground pin to your circuit ground, and take the 5V output to the circuit. Its that simple.
You can get a cheap single chip that will work for each touch pad - the logic you need is only an "AND" - if this pad AND that pad are touched, unlock the door.

Steve
gurobuzz (author)  steveastrouk5 years ago
And that would be..... I have no clue. I don't know what chips do what- I can follow a schematic tho
Are you happy to place orders on people like Digikey ?
gurobuzz (author)  steveastrouk5 years ago
yeah but I have several electronics stores locally
See if you can get Qprox QT113 chips.

Steve
gurobuzz (author)  steveastrouk5 years ago
and just what do I do with this chip? I have no schematic- I have no proximity switch- I am looking for a kit or a schematic to follow to produce this item I asked about.
I know how to follow schematics and I know how to solder- but I have no knowledge of what chips do what when placed in a circuit
I'll draw you a suitable circuit to try out - but there's no point if you can't get the chips, and there's no point still if the buried plates don't give us enough signal to trigger stuff with......