How much power does my relay need to turn on.

[Les Jones]

Most normal read switches are open when NOT in a magnetic field. As yours are closed when NOT in a magnetic field I think there is some electronics inside them . I would guess that the 20 K resistor is connected between the gate and MT2 (Which would trigger it.) But an normal reed switch is connected between the gate and MT1. When the reed switch was closed it would prevent the triac from triggering. In the past I have user this method to reverse the switching sense on DC with a transistor biased on with a resistor to the base and the reed switch connected between base and emitter.
I think the simplest way to do what you want is to use a normal reed switch (As used on door and window alarms.) and use it with a mosfet and resitor to reverse the switching sense. The source would be connected to the negative of your 12 volt supply. the gate would be connected to +12 volts via a high value resistor (Say 220K) The 12 volt LED would be connected between the drain and +12 volt, The reed switch would be connected between the gate and source.
There would be a small continuous drain of about 55 uA from the 12 volt supply.
You need to supply some details of the LED lamps that you plan to use.

Les.

 

[Visitor]

"Most"....yes, normally open is the most common, but normally closed reed switches are also available.

 

[Somarl]

I do believe I may have chosen the wrong reed switch for the operation. Are there any switches designed for 12v use? All the ones on places like ebay or amazon do seem to all be very similar with little description. Just to make the process more simple is all.

The LEDs used are just 12v LEDs.

**broken link removed**

 

[Visitor]

The LEDs used are just 12v LEDs.

"...just 12v LEDs...." is missing a key detail. An important consideration is the current draw of the LED strips. The listing for them isn't entirely convincing in its details, but the important part is this. The specifications are:

Power = 0.96 watt

Current = 0.08A

Number of LEDs = 15

I believe the spec is for power and current draw per LED, so the entire strip draws 0.08 × 15 =:1.2 amps.

How many strips are you using all together?


Regarding reed switches, if you follow my schematic, the reed switches are switching a tiny amount of current. Ebay's UK site has many suitable normally closed reed switches.

 

[Somarl]

"...just 12v LEDs...." is missing a key detail. An important consideration is the current draw of the LED strips. The listing for them isn't entirely convincing in its details, but the important part is this. The specifications are:

Power = 0.96 watt

Current = 0.08A

Number of LEDs = 15

I believe the spec is for power and current draw per LED, so the entire strip draws 0.08 × 15 =:1.2 amps.

That would seem to make sense. When I power one strip directly from the bench power supply it reads as pulling about 1amp so that must be right.

I would be using about 4 or 5. One for each drawer that ends up in the back, so also 4/5 switches. But basically one LED for each switch.

So I need to find a Magnetic Switch capable of pulling an amp or a little more in order for this to work simply?

I have found an alternate in case I can not get this to work. The equivalent method would be using a mortice switch - again used in cabinets for lighting - so if I could not source the correct items I could always revert to these, though again I understand they would need to be able to pass through a certain amount of current to work I believe the standard ones are enough.

The important thing I am trying to do is keep it simple. Its only a drawer that lights up when open. I dont want to be building complicated custom circuits, I'll only end up baffling my head and at the end of the day, its just an LED that turns on when a draw is open, not some heart surgery robot. So I do think you guys are right - the solution is to get the reed switch right - that's where the problem is and everything should fall into place from there.

Thanks.

 

[Visitor]

I would use the relay module, as reed switches aren't rated for a lot of current. I believe the relay is rated for 10 amps, so no problem if you want to turn on all of the strips when any switch is activated.

 

[MacIntoshCZ]

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