Sealed Magnetic Reed Position Sensor Kit

In our research vessel, S/V Nomadness, we are installing dozens of these to monitor the position of all valves (thru-hull stopcocks, diesel fuel distribution, water processing, and sewage system). This lets the corresponding micro nodes, as well as the central hub, have accurate real-time knowledge of the status of all plumbing... not only for error-detection and usage monitoring, but also to present a web page with live configuration graphics. We also use them to monitor the positions of hatches and interior compartment doors, providing data for the security software.

These are magnetic reed switches sealed with clear adhesive-lined 3:1 dual-wall polyolefin heat-shrink to 6" wire leads, paired with a .25" diameter N45 neodymium rare-earth magnet. The combination gives an excellent detection range covering the whole length of the switch and its leads, with this magnet type being much more effective than the cheapies (or even those harvested from Sonicare toothbrushes, historically my favorite but non-scalable magnet source).

You can certainly track down all this stuff yourself, but since we are now stocking what we feel are the best components (including special clear heat-shrink that forms a glue bond when heated), we've decided to offer them as kits. Wire color is random; if you have specific requirements to maintain a color-coding scheme, please let us know in the comments with your order.

Installation is easy. The reed assemblies can be hot-glued, taped, or zip-tied in place; the magnets stick well with polyurethane Gorilla glue. On stopcocks and other valves, just find a spot to bond the magnet under the handle where it won't get in the way of your hand, and build up a sensor mounting substrate from a nearby surface with scrap material (I'm fond of hot-glued Divinycell foam for hidden valves since it doesn't mind being wet, but you can get as beautiful as you want with the ones you'll be looking at more often). At some point, I'll post a little gallery of application images in the file area or on the Nomadness website.

Electrically, the switches are open until the magnet comes within range (a half inch or so). Personally, I like to use them to ground an input pin that is otherwise pulled up through a resistor at the processor board. This keeps stray voltages out of the bilge and minimizes the potential for damage if something gets shorted.

Please allow an extra day or so for delivery; the parts are in stock, but we assemble them to order.