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building a simple latching switch

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danrogers

Member
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 :)
 

KMoffett

Well-Known Member
Can be done with just the relay and the reed switch. Under what conditions do you want it to "unlatch"?

Ken
 

danrogers

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

thanks very much
 

KMoffett

Well-Known Member
Is there 12V available for the relay coil? How much current will the relay contacts be switching?

Ken
 

danrogers

Member
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
 

KMoffett

Well-Known Member
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
 

danrogers

Member
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
 

KMoffett

Well-Known Member
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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kinarfi

Well-Known Member
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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homik

New Member
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.

CircuitDB | Relay Toggle Circuit

I built it and works nicely :)
 

KMoffett

Well-Known Member
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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