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building a simple latching switch

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danrogers

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hi everyone, i need to build a latching switch, activated by a reed switch so i guess i will need to add a relay because i want to be switching 12v.

Im unsure as to what type of gate i will need to latch the switch.

any help would be greatly apprieciated :)
 
Can be done with just the relay and the reed switch. Under what conditions do you want it to "unlatch"?

Ken
 
basically one signal from the reed switch to latch, then waiting for another signal from the reed to unlatch?

thanks very much
 
Is there 12V available for the relay coil? How much current will the relay contacts be switching?

Ken
 
not entirely sure of the current, but its a small water pump. i will find out.

when you say 12v available for the relay coil what exactly do you mean?

thanks kindly
 
I assume that if you are switching 12VDC for the pump, then you have the 12VDC available to drive the coil on the switching relay. The pump current determines the minimum size of relay you will need.

What's the project...reeds as part of float switches?

Ken
 
i see, thanks. its for my dad as he does alot of biking and running and wants a portable shower to power from the car battery.

the idea i thought of was to use a reed switch and a magnet in some kind of foot operated switch arrangement which would also be waterproof i guess.

it would be easy enough to make a simple switch, i suppose i will have to drop the volatage and current quite a bit for the reed switch?

the thing im completly lost with is how to latch it open untill the switch is pressed again?

thanks
 
You're right that a reed switch will not handle the current required, even for a small 12V pump. If you reduce the voltage/current to the pump to a level that the reed can handle, the pump won't work. That's why you will need an intermediate relay. The attached schematic is a switching circuit that should do what you want, but that relay is rated at only 2 amps. If your pumps draws more current you would need a different relay and other component values.

Ken
 

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  • PushOnPushOffRelayPump.gif
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here's what I did on my buggy, one reed turns it on, the other reed turns it off. I use it to fill an auxiliary tank. The + is 12 vdc
 

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  • Pump Switch.PNG
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Here's a toggle switch that turns a relay on and off when a push button is pressed - once for on, once for off. i suppose you could replace the push button with the read switch.

**broken link removed**

I built it and works nicely :)
 
dan,

As you can see there are these and many other ways to do it. Depends on you skill level in electrical and electronic construction.

Ken
 
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