Russell's Halloween Controls

12VDC Automotive Relay

(see the WARNING at the bottom of this page!)

This is a 12VDC SPDT (Single Pole Double Throw) 40AMP Automotive Relay. It is your freind. The 40AMP (amperage rating) is the most common but I have found that for our purpose the amperage rating does not matter (e.g. 20, 30, and 40 have all worked for me). You do not need to know what SPDT means. What you do need to know is that you need a lot of these. Expensive as hell at an auto parts store, they can be found dirt cheap on EBay in bulk with enough patience.

The relay has 4 terminals of interest to us and are numbered 85, 86, 87, and 30. When 12VDC is sent to terminals 85 and 86 a connection in made between terminals 87 and 30. This connection between 87 and 30 is what I consider a trigger and use it to control all my props. More about automotive relays

Get a power supply from the junk drawer or local thrift store. Make sure it has 12VDC output. Make sure the amperage (1.2A pictured below) is 1.0 or greater. Use the power supply to test the relay. Touch the positive wire from the power supply to terminal 86 on the relay and touch the negative wire from the power supply to the relay terminal 85. The relay should click. No click? Try reversing the wires from the power supply. When you hear it click you have a trigger. Congradulations!


Halloween Props and their components are inherently dangerous and could cause severe injury or death. These instructions are being offered for entertainment purposes only. Do not attempt to actually build or use any of the mechanisms described in the instructions below unless you (1) are aware of every potential safety issue with each component, (2) wear every personal protection device ever invented, and (3) follow all Federal, State, local, and standard industry safety procedures associated with the handling and use of each individual and combined component. KEEP YOUR ARMS, LEGS, HEAD, AND BODY AWAY FROM MOVING PARTS AT ALL TIMES and don't catch yourself on fire. ENJOY!