Have a look at QT300 (charge transfer sensor). Your transmitter is your finger, and works throu glass, plastic, almost anything non conductive. There are even arrays of sensor in a single chip. Rafael Fraga ----- Original Message ----- From: Mike Harrison To: Sent: Wednesday, March 03, 2004 7:04 AM Subject: Re: [PICLIST] [EE:] IR as a substitute for tact switch On Wed, 3 Mar 2004 01:03:37 -0600, you wrote: >I have a working PIC circuit that uses a single tact switch for all user >interaction. The user can either change mode with a "dash" (press and hold >for > approx 2 secs) or can can some value within a mode with a "dot" (press >and release quickly). LED displays provide proper feedback, btw. From a >schematic standpoint, the tact switch simply connects one I/O pin to ground >(with Port B internal pull-up active). > >I now intend to replace the tact switch with an IR remote control, and felt >the easiest way to do this is to just drop in an IR detector (I'm using a >38khz Vishay TSOP4838) and on the transmitter side use a 38khz oscillator >(555 timer) with an IR emitter LED and a pushbutton on/off switch. Usage is >expected to be the same with this -- dash or dot. > >However, when I activate the transmitter, I get a quick low-going pulse (and >the detector output returns to default high) rather than a sustained low >output. > >Is this a misconception on my part of the way the detector works? Or should I >see a steady-state change in the output? Some of these parts have a limit on the maximum carrier-on time due to the way their AGC and data slicers work. A solution would be to use a 556 to produce bursts of 38K carrier at, say, 1KHz >At a higher-level, the intention is to eliminate drilling holes in the red >semi-transparent acrylic panel covering the electronics, so I have alternate >options. Small reed switches seem like a great option, but I'm not sure what >the "transmitter" would be ... a small electromagnet? The transmitter should >fit into a small key-fob (from an old car alarm). But I have to figure out >how to easily fit this into the space of a tact switch. Or can I achieve >this with some type of hall-effect device? Why an electromagnet - you could just use a magnet. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics