22 Nov 2011 00:26 UTCTue 22 Nov 2011 - 12:26 am UTC
I am seeking a sample low voltage (5 V or below) proximity sensor switch. TTl level device (4.75V - 5.25V)
Small form factor, no bigger than 10mm in diameter. Can be capacitive or magnetic.
The device needs to sense at least a 5mm distance.
It is to be placed on a metal door, where it is desired to have no physical connection (i.e. a typical mechanical switch) to sense when it is closed. The choice of inductive proximity switch (vs capacitance) is so human hands do not send a false signal when placed over the switch. IR range detectors have been considered, but decided against as they cannot differentiate between human and door.
Such devices have been found in large quantities (must buy 960 of them at $2.50 each) so it is also desired that these devices can be purchased in small, sample size quantities.
22 Nov 2011 00:46 UTCTue 22 Nov 2011 - 12:46 am UTC
Can you give us a link to the large quantity devices you found? It would help us in searching for a source for sample size purchases.
22 Nov 2011 09:18 UTCTue 22 Nov 2011 - 9:18 am UTC
Would your needs be met by a magnetically-operated switch? It closes a circuit like a relay, so it is usable at TTL voltages.
There's no physical contact when the door is closed. A small magnet, fixed to the door, comes within a few millimeters of the switch (which is fixed to the door frame) and closes or opens the circuit according to your needs.
23 Nov 2011 01:44 UTCWed 23 Nov 2011 - 1:44 am UTC
Magnets are not an option because it is desired to have all sensing within one unit.
"Miniature Inductive Proximity Sensor" devices:
25 Nov 2011 02:27 UTCFri 25 Nov 2011 - 2:27 am UTC
Here is an example of an inductive sensor
25 Nov 2011 02:56 UTCFri 25 Nov 2011 - 2:56 am UTC
woolyisland...I'm a bit confused about what you need, as your question asks for a capacitive or magnetic switch, then seems to suggest you want an inductive switch, while your clarification says no magnets.
That said, there are plenty of sources specializing in sensors, such as ATM:
Note that they offer small-footprint inductive as well as capacitive proximity sensors.
Let us know if any of these seem to meet your needs.
5 Dec 2011 11:33 UTCMon 5 Dec 2011 - 11:33 am UTC
Thank you for the information. No luck. The challenge still remains for a small sensor (mini metal detector) to go on the door at the latch/doorknob side with a power consumption of less than 5V. The suggestions have been very much appreciated.