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Looking for a circuit- proximity switch ? Answered

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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steveastrouk (author)2011-12-31

Here's a circuit, if you can get the chips. You'll need to rig a 5V supply from the car for it.

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user

Oops wrong final circuit.

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gurobuzz (author)steveastrouk2012-01-01

easy circuit to read, but I am not sure how to step down from 12v to 5 volts other that a transformer

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steveastrouk (author)gurobuzz2012-01-01

Use a "7805" regulator - its has three pins, Input, ground, output. Input 7-35 V, 5v out.

Steve

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gurobuzz (author)steveastrouk2012-01-01

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

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steveastrouk (author)gurobuzz2012-01-01

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.

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steveastrouk (author)2011-12-31

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

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gurobuzz (author)steveastrouk2011-12-31

And that would be..... I have no clue. I don't know what chips do what- I can follow a schematic tho

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steveastrouk (author)gurobuzz2011-12-31

Are you happy to place orders on people like Digikey ?

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gurobuzz (author)steveastrouk2011-12-31

yeah but I have several electronics stores locally

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steveastrouk (author)gurobuzz2011-12-31

See if you can get Qprox QT113 chips.

Steve

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gurobuzz (author)steveastrouk2011-12-31

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

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steveastrouk (author)gurobuzz2011-12-31

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......

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