Single Relay Board


I'm trying to run an Aerobed motor for a short period of time to "make it snow" by blowing a bunch of hole punch snowflakes for a Christmas decoration. The blower motor is one of those DC car cigarette lighter type that run on 12V DC. I understand the coding portion of this, that part is pretty clear from the code sample. I'm using the Basic Stamp, Board of Education revC.

My question is on wiring up the single relay board. I've never used this component before, or any relay for that matter, and the documentation is a little unclear ( I'm not sure if the 5V is supposed to come from plugging it into Vdd, Vin, Vss or a separate 5V battery pack altogether. The same question applies to the ground wire, where does that go?

Also, I know I need to put a fuse in the load side based on the documentation, but any advice on what type of fuse I should get? Is that just a fuse for a car, would that suffice?

Here is the product page:

Any help would be much appreciated! Thank you!


  • The Board of Education and single relay module is perfect for this. Thoughts:

    The Board of Education has a 5v regulator capable of supplying 1 amp. The single relay board only needs 5v at 85mA for proper operation, so the BoE can easily support it. Vdd on the BoE is where the 5V pin of the relay module should be connected.

    The fuse on the diagram in the single relay module is to protect the load circuit, not the relay. The text below the diagram states:
    In the example in Figure 1 the relay is switching a 120 VAC load, such as a lamp or brushless fan. Notice
    the fuse in the example is 5 A, not 10 A. The fuse should be chosen according to the load, not the max
    current of the relay. You want the fuse to blow when the device draws more current than it is supposed

    If you are using the "official" Aerobed cigarette lighter adapter, then it has a 10amp fuse built in to it. The relay on the relay module can handle 10amps at 30V, so a 10amp 12volt fuse in the circuit is appropriate.
  • Thank you very much Andrew. Your answer was very helpful! I just have one more question, where should I plug the ground wire into on the BOE?
  • WBA ConsultingWBA Consulting Posts: 2,885
    edited 2016-12-16 - 18:41:39
    You're welcome! The ground wire should go to Vss. Be sure to post some pics once you get it all squared away!
  • Thanks again Andrew! You were a life saver. It's been a while since I made my own circuits (I'm an ME that dabbles in EE for fun on occasion, like this one) so I forgot those details about Vss & Vdd, etc. After an all nighter on Thursday and into the day on Friday, it came out great and the relay worked perfectly. All electronics were Parallax components. You can see the video on our company's FB page here:

    Can't thank you enough! Otherwise the user would have had to hold down our snow button with a DC battery pack hooked up which isn't nearly as good as how it functions with the relay.

    Thank you!
    Andrew P.
  • Very nice decorations, it reminds me of being a kid, and how downtown storefront windows were fixed up during the Christmas season. Animated characters and other objects, every window was a different little world, for a kid to just stand there in amazement. These days businesses are too worried about the bottom line, and that space has to be used to promote sales.

    Thanks for helping me get in the holiday spirit, great job!
  • You're welcome again! Glad I could be of some help. That's a pretty nice door decoration. My wife is a major fan of Rudolph. We made a 4" shelf that goes between our couch and the wall to hold at least 50 Christmas stuffies, most of them Rudolph. I showed her this and she liked the picture. You should add an LED under the red push button!
    Anyhow, thanks for showing the results. It does help others who may be looking to do something similar and stumble upon this thread down the road.
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