Source or design for a waterproof multipole magnetic reed switch - Page 1
Forum section: electronics / projects

author: e100
author_rank: Frequent Contributor
timestamp: August 11, 2013, 12:20:59 pm
content: I 'm looking for the type of switch used on dive torches with a magnet or magnets on the outside and a reed relay or relays on the inside with no mechanical connection between the two.I haven't been able to find any "off the shelf" switches on the web, so presumably most solutions are custom built into the body of the device.My particular application is for a bike light where I need to be able to switch it on/off and change the brightness by means of a rotary switch.The basic on/off function needs to be a reed relay so there is no power drain when the light is off. Once it's on then either a Hall effect or series of reeds would be needed for sensing the position.Does anyone have any photos or diagrams that could provide inspiration for a DIY solution?ThanksMike

author: Rerouter
author_rank: Super Contributor
timestamp: August 11, 2013, 12:39:50 pm
content: as far as my submersible water scooters go, (20Ah battery driving a motor) it has 2 reed switches in parallel, i believe for reliability, and based on how it mounts there is only a 1.5mm gap between the read switch and the plastic casing,on the outside of the casing there is a shallow screw in spot for the magnet shaft that in this case connects to a cable throttle, you squeeze the trigger, the magnet slackens hard to the plastic, the switches close and away she goes,there was also a one off in my batch, a variable speed one, in that case i believe it had something like a hall effect transistor in the control loop, so depending on how close or how far varied the speed, sadly it was this part that made that one very hard to repair (magnet gets bashed and is looking for a particular field strength)

author: amyk
author_rank: Super Contributor
timestamp: August 11, 2013, 12:42:22 pm
content: A bike light doesn't need to be waterproof above atmospheric pressure, so you could just use a rubber boot over a regular pushbutton, as done with regular waterproof torches. For the rotary switch, a circular seal around the shaft should be sufficient.

author: free_electron
author_rank: Super Contributor
timestamp: August 11, 2013, 01:24:08 pm
content: Get one of those melexis angular hall snsors. That little chip can give you the orientation of the mgnet in degrees. So you coul have the chip insed, magnet outside. Spin the magnet and the chip gives you a voltage that tells you the angle of the magnet above the chip. There you go .contactless potmeter...

author: BravoV
author_rank: Super Contributor
timestamp: August 11, 2013, 05:49:34 pm
content: If finally you decided to go on DIY route instead of using some off the shelf switch, an experienced fellow in this forum shared his experience using cheap material for long term water proofing in quite harsh environment like thermal cycling/sun exposure/salty environment, read the detail here ->Rufus's post

author: e100
author_rank: Frequent Contributor
timestamp: August 14, 2013, 04:47:25 am
content: I found some pics of a circular reed switch someone built for audio switching.http://i797.photobucket.com/albums/yy259/dhem7/Audio/DSC08656.jpghttp://i797.photobucket.com/albums/yy259/dhem7/Audio/DSC08667.jpgFromhttp://www.diyaudio.com/forums/analog-line-level/234967-reed-switch-audio-attenuator.htmlMike