DIY Functional Frankenstein Light Switch

Introduction: DIY Functional Frankenstein Light Switch

About: We are Mike and Lauren. We make videos on YouTube about money, travel, homesteading, and DIY.

I bought an old knife blade switch off of eBay to use as a decoration. As soon as I got it, I knew I had to make it actually work. Running full 120V power through exposed metal on the wall wouldn't be very safe, so I ordered a DC-AC relay. I used an old phone charger to provide 5V of power to run the relay. It's been in use for over 4 months now without any problems.

Step 1: Materials

  • You can get these switches on eBay for anywhere from $10-50 dollars. Just search "vintage knife blade switch." I paid $40 for mine.
  • The relay I used was a SSR-40DA Solid State Relay. It cost $4 dollars shipped.
  • Any low voltage DC power supply with work. I had an old phone charger on hand.
  • Long machine screws that fit electrical box holes.

Step 2: Make It All Fit

I wanted all of the components to fit and mount inside a regular double gang electrical box. I didn't want to modify or repair the wall. First I drew the outline of the box.

Step 3: Phone Charger Too Big

My phone charger was too big, so I took it apart. The circuit board was the perfect size.

Step 4: Find 5V Positive/Negative Leads

I used my multimeter to find the positive and negative terminals of the USB jack. This is where my 5V would be coming from. Then I soldered my wires to the board to connect to the relay.

Step 5: Wiring Diagram

This is how I wired everything up.

Step 6: Cut Down Phone Charger Case

I cut the phone charger case down to the size of the circuit board. This worked perfectly and fit right inside the box.

Step 7: Fixed a Mistake

Luckily I realized that if I centered all of the components, it would overlap the trim of the door next to the switch. So I moved everything over a few inches and glued it in place.

Step 8: Drill Mounting Holes

Using a spare box as a template, I drilled new mounting holes in the switch.

Step 9: Mount on the Wall

Mount on the wall using 4 long machine screws. I used a flash in the picture so it doesn't look very flattering. You can't really see the mounting screw heads very well in normal light. I may use some fake screw heads to cover the holes on the 4 corners.

Step 10: Final Test

I metered the current and it was only drawing 20mA at 5V. It's been in use for several months now without any problems. I was concerned a solid state relay would provide too much heat, but it seems either the switch acts as a heat sink or the relay just isn't getting hot.

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    6 Discussions


    5 years ago on Introduction

    That's an awesome looking switch. Excellent that you made it functional. So cool!


    That's pretty sweet! It's scary if you don't know that there's a relay there though! lol. I'm curious as to how many people ask if you ran 120V to your switch and are nervous to touch it. Are you able to use your body as a conductor to make the lights flicker or anything? Does shorting the switch with your fingers affect the relay at all? Thanks!


    Reply 5 years ago on Introduction

    Thanks! I would say most people are scared to touch it at first lol. And no, you're not able to complete the circuit with your fingers or anything.


    5 years ago on Introduction

    I'm Totally going to try this ! Love the Mad Scientist feel of it :D