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activating reed switch

L

lerameur

Jan 1, 1970
0
Hello,

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
 
P

Paul E. Schoen

Jan 1, 1970
0
Tim Wescott said:
Try using finer wire.

Look under "solenoid".
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
 
B

Bob Eld

Jan 1, 1970
0
lerameur said:
Hello,

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

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.
 
M

Michael Black

Jan 1, 1970
0
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
 
E

ehsjr

Jan 1, 1970
0
John said:
---
That's not true; the people who make reed relays do it all the time.
---




---
The core will be the switch, and the rest of it is just knowing the
sensitivity of the switch and providing a coil with the proper
resistance and number of turns to achieve that with the desired coil
voltage and current.
---

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
 
Z

Zagan

Jan 1, 1970
0
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:
http://www.fabco-air.com/products/sensors/sensors.html). 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
http://members.atlantic.net/~jcd/
http://www.writingservicesunlimited.com/
 
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