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Description: Want to control a standard wall outlet device with your micro controller, but don’t want to mess with the high voltage wiring? This might just be the right device for you!

The PowerSwitch Tail Kit is designed to allow you to safely control an outlet device without exposing any 120VAC voltages while being able to “customize” it to meet your applications needs. You can optimize the voltage required for the control signal by selecting and installing different resistor values for R1/R2 slots on the kit PCB. With this ability to choose the control signal voltage the PowerSwitch Tail Kit is given the ability to provide an input voltage from 3VDC all the way to 26VDC. Additionally, power cables are sold separately to give you the choice of cable you wish to use with this kit.

This variation of the PowerSwitch Tail is sold as an easy-to-assemble kit and includes everything listed below with clear assembly instructions listed in the documents section.


  • 1x PowerSwitch Tail PCB
  • 1x PowerSwitch Tail Enclosure (w/ Case and PCB Screws)
  • 1x Relay (120VAC, 40A)
  • 1x Red LED (3mm)
  • 1x Metal Oxide Varistor 14mm (130V)
  • 1x Metal Oxide Varistor 7mm (130V)
  • 1x Resistor 1.0K ohm (1/4w)
  • 1x Resistor 1.5K ohm (1/4w)
  • 1x Resistor 4.7K ohm (1/4w)
  • 1x Resistor 470 ohm (1/4w)
  • 1x Resistor 1.1K ohm (1/4w)
  • 1x Resistor 3.0K ohm (1/4w)
  • 1x IC MOC3063
  • 1x 3-Position Terminal Block (5.08mm)
  • 2x Rubber Grommets


  • Customizable control signal voltage
  • 3VDC to 26VDC control signal range
  • Drive directly from microcontroller pin with as little as 3VDC @ 3mA
  • Connects directly to Arduino, Raspberry Pi, Beaglebone or other 3.3V or 5V MCU
  • 20A switching capacity; 5300vrms isolation
  • Two wire control signal; no separate DC power source required
  • No exposed ac wiring
  • LED status indicator


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Customer Comments

  • Now all we need is one that provides power for the MCU as well.

  • Will there be a 240v version of this kit? It seems only the movs and relay needs to be changed?

    • There is a 240V version I have purchased 2 and use them daily for the past year or so. They work well with an ATTiny chip driving them. See I don’t know if Sparkfun carry the 240v version of the kit.

  • Is this UL listed? I assume not…

  • The LED Silkscreen on the board has the wrong polarity. The LED is prebent to correct way but, the silkscreen is showing the polarity reversed so I had my son look up the + leg of the LED and test it with a battery and bent it to correspond to the silk screen - Epic Fail! I now have to take it apart and fix it :(

  • IgnacioV: Per your question - Haute Solutions sells a complete kit with the enclosure and also includes a power supply for the MCU and a clear cover. One power cord into the enclosure and one (20A) power socket for your 120V device - thats it. User configurable MCU mounting plate, clear cover, and has enough room to add a shield of your choice. Also available as a pre-built item with a GSM/SMS arduino based board (and SIM card) already installed:

  • There are optional terminal blocks (J1 and J2) in the kit instructions for the 120 vac supply and load side but no part numbers or other details - does Sparkfun have these terminal blocks? Note that the kit says the maximum gauge wire for the terminal blocks OR the solder pads is 14 ga. solid wire.

  • Does this kit have a higher Max currently rating than the assembled one?

    • The kit and assembled versions appear to use the same parts. However if you build the kit with a 12ga power cord it should handle 20A.

      • Okay thank you, I was just curious as the assembled one says 15A only and this one says 20A, but the wiring gauge makes sense.

Customer Reviews

4 out of 5

Based on 2 ratings:

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1 star

Great kit

Split a drop cord and wire it up. Have a Moray board controlling my de-humidifier in the basement when there’s excess solar from my roof panels.

Great tool to have on hand

I originally used the PowerSwitch Tail to control my Solidoodle 2 printer with an OctoPi.. Since upgrading from the SD2, i’ve now used it for a few random tasks including switching Christmas lights off and on. A really great tool to have around!