# Escape room: How how to switch between lamps?

I’m building an escape room and have a little puzzle here…

There is a lamp normally turned on when the people enter the room. When they solve a puzzle by putting a magnet in the correct place, I want the normal light to go off and a blacklight to come on.

I’m planning to use a normally open switch that can be closed by a magnet in the puzzle.

But I am not sure if it’s possible to switch the power from the normal light to the blacklight just with this?

Here’s a picture of my idea:

Is there something I could do in a junction box to achieve this effect? A diagram or links to parts would be really helpful.

Thanks so much! This is my first question because I’m at my wits end… also, not to worry, I’ll have someone qualified check my work once I’m done.

Sounds like you need a single pole double throw relay.

In this case it can power 1 of 2 circuits at a time:

The relay will switch up or down which will power only one circuit at a time.

Something like the following:

So the NC (normally closed) would be on and powering the regular light, then when the circuit gets 5v on it then it would flip to the NO (Normally open) side and regular turns off & black light turns on.

• Great, thanks for the link! Apr 1, 2022 at 17:42

You need what's called a single pole double throw (SPDT) relay. It's a two-way switch that is activated by a low current and (I suggest) low voltage signal applied to two other contacts. If you're using a reed switch as the magnetic sensor, you might want to consider adding a snubber circuit to prolong the life of the contact leaves. There are plenty of relays in suitable mounting brackets that make them easy to hook up and don't have a lot of exposed terminals which is a plus when you're working with line voltage (and yes, definitely have someone qualified look over the finished product).

simulate this circuit – Schematic created using CircuitLab

• Super, I’ll try this. Thanks for the advice! Apr 1, 2022 at 17:43

A 'Form C' (SPDT) reed switch, that can switch a 120V 10W LED lamp, would suffice.

Reed switch specifications:

1. Switching Power 10 W / VA Max.

2. Switching Voltage 175 V DC/AC

3. Switching Current 0.5 A Max.

4. Carry Current 0.5 A Max.