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Author Topic: changover / proximity reed switchs  (Read 1020 times)

destroyer42

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changover / proximity reed switchs
« on: November 11, 2013, 07:15:34 PM »

Hi All you electronics experts out there!
Hope some one can help?
I want to turn off the receiver and lights on a lifeboat once the crane has lifted it onto the mothership, but I'm not sure if i need a two way reed switch and magnet or a proximity switch and magnet.I want to connect it to the live from the battery 12volt 3amp hr.
So when the crane lifts the boat it livens up and stays live until it is returned to the mothership and switches off.
Any Ideas?
Destroyer42
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Stavros

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Re: changover / proximity reed switchs
« Reply #1 on: November 11, 2013, 07:39:16 PM »

Cant you wire it up like hte RTR boats.....What I mean is the prop wont work untill it is water...so if it was ire up like one of these then the reciever would be dead
 
 
Dave
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StuartL

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Re: changover / proximity reed switchs
« Reply #2 on: November 11, 2013, 07:42:09 PM »

Ok, couple of things here...

1) A reed switch will probably work if you can get the boat placed accurately.  This may be a result of guides/locator pins/magnets, etc.

2) Consider a microswitch instead, although that might introduce other complications.

All switches are available in changeover, normally-open or normally-closed configurations.  A normally-open switch is open-circuit when unactivated and closes when activated, a normally-closed switch is closed-circuit when unactivated and opens when unactivated.  A changeover switch has a pair of switches in tandem, offering both functions together.

You want your circuit to be active (i.e. the contacts closed) when there is no magnet present and to open the circuit (turning off the lights) when the magnet becomes proximal.  This means you need a normally-closed or changeover reed switch.

The next problem you will have is figuring out the current draw of your lights to make sure the switch can take it.  If you're using LEDs (small ones, rather than ultra-brights, etc) then figure on 20mA per LED.  Ultrabrights are 50-100mA per LED and high power LEDs are 300mA plus.

If you had ten 'little' LEDs and one ultra-bright you'd need about 300mA of switching capability.  This will be listed on the spec for the reed switch.

A quick search on RS reveals: http://uk.rs-online.com/web/c/?sra=oss&r=t&searchTerm=reed+switch+nc&x=0&y=0&sort-by=P_breakPrice1&sort-order=asc&pn=1

This one looks promising: http://uk.rs-online.com/web/p/reed-switches/3615150/

It's 250mA switching capability, which isn't enough for the scenario I mentioned above, but would be good enough for 10-12 little LEDs or 2-5 ultrabrights.  Higher current switching looks pretty expensive, but you can use other circuits to switch it with cheap reed switches if necessary.

Have you considered using a channel on the remote for the daughter-ship for the lights instead?

Stuart
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HawkEye

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Re: changover / proximity reed switchs
« Reply #3 on: November 11, 2013, 08:20:31 PM »


A hall effect relay may be an option if you have the room, much larger current switching than a reed switch.

http://www.circuitstoday.com/hall-effect-switch

HawkEye
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StuartL

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Re: changover / proximity reed switchs
« Reply #4 on: November 12, 2013, 10:47:25 AM »

You could also use a reed switch to switch a relay?  This would be a simpler circuit.
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HawkEye

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Re: changover / proximity reed switchs
« Reply #5 on: November 12, 2013, 12:16:16 PM »

You could also use a reed switch to switch a relay?  This would be a simpler circuit.

Ah ! yes,this is very true,I think copious amounts of Glenfiddich may have affected my train of thought  :}

HawkEye
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