activating reed switch

Try using finer wire.

Look under "solenoid".

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Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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You could also try a capacitor and resistor in parallel to drive a quick surge of 3 amps to activate the reed relay, and the resistor to provide just enough current to keep it activated. I have done this to operate AC relay coils using DC.

Paul

Yes they have reed relays that draw 10mA at 6 volts. Three amps means you don't have nearly enough turns and, of course, the wire you are using is a

1000 times too fat.

If you are serious about it you'll have to wind them with AWG 44 or thinner wire. Good luck finding that. Good luck winding that with 10,000 turns. Not a job for the timid.

Look for reed relays under relays. Jameco has them.

That brings up what the original poster is wanting to use this for.

I was going to say "well can't you buy coils to activate them" and then I realized standalone reed switches are mostly activated by a permanent magnet.

So there either has to be a better way, or the poster needs a different method.

Figure out a mechanical system to move the permanent magnet in close to activate the switch.

Take apart an existing relay for the coil, and use that.

Or figure out why a normal relay can't be used; there may be reasons, such as the reed switch has a more direct contact for RF use, but there really should be a good reason to do it this way rather than a "normal" relay.

At this point, I'm even willing to believe that the original poster is unaware of regular relays.

Michael

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Look under "reed relay".  Here\'s one:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=HE100-ND

JF

Why not simply get a reed relay?

To wind an efficient electromagnet is not practical. You will have to use a very thing gauge of wire, and calculate the proper number of turns and select the proper core type. Then you will have to task to properly wide the coil.

You can take an old relay apart that uses the voltage you want and use the electromagnet, but this may not be practical.

If you look on the web pages where they sell science experiment devices they have electromagnets. Most of what they sell is on the large size.

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JANA _____

I made myself a small electromagnet to activate a reed switch using a

6v supply. The problem is that I am pulling 3 amps, I do not want the electromagnet to be bigger by making more turns, I believe there are such electromagnet on the market that can activate a reed switch with current in the milliamps. anybody know such device, I looked at digikey and mouse but I did not find anything under electro magnet.

thanks

ken

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That\'s not true; the people who make reed relays do it all the time.

I'm wondering if the op isn't envisioning something like this:

reed ---====--- (||) (||) (||) +_(||)_-

Coil around a core, core at 90 degrees to the reed, with maybe a bolt or nail as the core.

Ed

Ken,

I use to work for a company that made pneumatic and hydraulic cylinders (with rods coming out of one or both ends). We used reed switches and electronic magnetic sensitive sensors to detect the rod(s) extension (see:

Since I was the only engineer there that knew one end of a battery from the other, I was in charge of designing these magnetic sensors. We used a magnet ring mounted around the piston heads of our cylinders and the end user could place the sensors wherever alone the length of the cylinder to detect the extension(s) of the rod(s) and send that signal to a PLC or whatever.

Anyway, my point here is that perhaps you could use a solenoid or similar device to move a permanent magnet back and forth to activate/deactivate the reed switch. Magnets are cheap as are most low-power solenoids. There is no need to make your own electromagnet to operate the reed switch. And 3 amps is certainly excessive when some current in the milliamp range would do the trick as described above. Look up solenoid at digikey, etc.

Hope this helps,

// Jim