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Description: Your 5V system can wield great power with this big, beefy relay board. How does 10A on the NC contacts and 20A on the NO contacts at 220VAC sound? The SparkFun Beefcake Relay Control Kit contains all the parts you need to get your high-power load under control. Only minimal assembly is required!

The heart of the board is a sealed, SPDT 20A/10A Relay. The relay is controlled by 5V logic through a transistor, and an LED tells you when the relay is closed. This is a kit, so it comes as through-hole parts with assembly required, which makes for some nice soldering practice. Screw terminal connectors on either side of the board make it easy to incorporate into your project.

There are some pretty beefy traces connecting the relay to the load pins, but the 3-pin terminals are only rated for 15A max! If you plan on connecting a larger load, you’ll need to solder directly to the board. As always with high current and voltage, play it safe and use your judgment when deciding how much of a load you want to put on a board – in open airflow the PCB can handle the full 20A for a few minutes at a time, but in an enclosed area heat can build up.

Note: Please keep in mind that this board is really meant for someone with experience and good knowledge of electricity. If you’re uncomfortable soldering or dealing with high voltage, please check out the PowerSwitch Tail II. The PowerSwitch Tail II is fully enclosed, making it a lot safer.

Get Started With the Beefcake Hookup & Assembly Guide


  • Voltage Rating: 220VAC/28VDC
  • VCC requirements: 4-6V, 150mA capable
  • SPDT pins exposed (Form C)
  • 14 AWG screw terminals for relay connections.
  • 10 AWG solder lugs for relay connections.
  • Flyback diode included
  • Zener recovery diode included (decreases turn-off time)
  • Heavy 2 oz. copper on PCB


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Customer Comments

  • I would strongly recommend using this relay (same footprint) with this PCB. It gives you proper spade terminals for the high current connections. I have replaced so many of these relays in different devices because they overloaded the bottom pins on the relay.

  • Hi! What are the differences between this and the previous version?

    • What meljr says, plus better isolation between the high voltage and low voltage sides of the board and this version uses thicker traces (more copper) to increase the current carrying capability.

    • I have an earlier version. The biggest difference I see is that on the output (hi voltage) side, there are now three connections, a common with normally closed and normally open outputs. The previous version only had the common connection with a single output. This new configuration seems to be much more flexible and allows for an either/or situation with two downstream outputs you want to control. I’m going to order a few.

  • Why use this over a solid-state relay? The latter is two bucks more expensive, but needs a lot less power to drive and switches the load on zero crossings. The only thing this one has going is that it has on NC and one NO contact, but how often do you switch between two loads?

  • How can i hook this one on a board with only 3.3V ? I can get 12V, can i do that?

  • Could I use this with a 3.3V device like an ESP8266?

    • 3.3 volts on the CTRL pin is definitely enough to cause the relay to trigger. 3.3 volts on the 5V may not be enough to reliably power the coil in the relay though since it’s expecting 5 volts. I tested an older version of this product on 3.3 volts and it worked fine, but since it’s below spec, you may run into trouble. Give it a shot with 3.3 volts and if you’re having trouble, bump the voltage on the 5V pin up to 5 volts and you should be good.

  • Per product safety (UL60950-1 and UL62368-1), this product appears to meet most requirements for switching 120Vac, but not all; which is commendable and unusual for ‘maker’ vendors. You people are finally getting better at this, but SF and others should know that you and your ilk were the subject of several discussions at the IEEE Product Safety Engineering Society symposium (last month in Anaheim). The director of OSHA’s NRTL program was there and listened with interest, as this stuff has been, as of late, starting to cross from the home workshop to the work-place.

    • Can you provide some insight as to which 120Vac switching requirements are not met by this product?


      • Any response would be fraught with legal and technical liabilities. In any case, no reasonable response because intended end-use environment not defined, and installation (O/V) category not specified, and conditions of acceptability not known. But here is a minimal list to start with:

        1. reference UL60065/60950-1/62368-1 for scoped end-use requirements.
        2. reference UL796 for PCB requirements.
        3. reference UL1977 for AC mains connector requirements.
        4. reference NFPA70 (NEC) for wiring requirements.
  • If I use this relay to turn on and off a window blind motor, what protection (for the relay) do I need?

  • What is the paste brushed on the pcb at the end of assembly in the video?

    • That looks like some sort of flux removal- water, rubbing alcohol, or possibly some specialized formula. Electronics solder wire (including the one we sell and use in production) will often have a flux core to allow better wetting and flow when you solder your parts in. The residue left after soldering is often a little sticky, slightly conductive, and may eventually corrode your board. It’s a good idea to clean the board when you are done, just make sure you let the board dry completely before connecting it to power.

    • It’s just rubbing alcohol to clean flux off the board.

Customer Reviews

4.9 out of 5

Based on 7 ratings:

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1 of 1 found this helpful:

This is a pretty nice little relay board.

I have several projects where I need to be able to turn larger pieces of equipment on and off and I’ve been making my own relay controllers but these little kits put everything together in one nice package and the price it good. I haven’t had mine in service for long so I’ll re-post if I have any problems in the future, but so far so good. The LED is a nice addition. My only concern is that people could shock the crap out of themselves if this isn’t properly enclosed in a box. But then again, that’s what makes it fun right?

1 of 1 found this helpful:

Excellent kit

I purchased 3 beefcake relay kits for a water control project. Two of them were exactly as advertised, but the third was missing one 1k resistor and had an extra transistor. I used a 1k from my junk box and completed the kit. They will be operating in a humid environment so durability remains to be established. I used two soldering irons - a small one for the low voltage side and a big one for the relay pins.

Just what I needed.

Easy to solder together and assemble. Have three running off an Arduino Uno to cycle power to different sensors for testing. Works great.

wicked cool

i just now finished soldering the kit together. purpose: to switch a DC motor which is actually a fountain pump, using the Arduino. the fountain pump is for a hydroponics grow-tower, so, using the “blink” sketch with the delay set to 1-million (about 16-ish minutes) that gives the plants 16 minutes on, 16 minutes off, of hydroponic solution. it’s sitting beside me as i type this and is working perfectly! thanks guys!

Easy to assembly and cost effective

Amazing Kit

The Beefcake Relay Control Kit (Ver. 2.0) Is an amazing kit. It is easy to assemble and works wonderfully. It works great with the Arduino and the Raspberry Pi.

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