Santa Detector

by littleBits

Published on December 12, 2014

Invent a santa detector. Catch him red-mitten handed when he takes a cookie from this spring-loaded cloud-connected plate.

How it works:
A roller switch sits below a spring-loaded mechanism with a plate of cookies on top. When Santa takes a cookie from the plate, the the springs relax slightly and the roller switch releases, activating an LED and a cloudBit. When the cloudBit is activated, it triggers an IFTTT recipe to send you a text message [via IFTTT's SMS channel] to let you know that Santa has arrived.

IFTTT (If This Then That) is a service that lets you connect to different web apps through simple conditional statements.


How To Make It


Set up your cloudBit if you haven’t done so already. Instructions for setting up the cloudBit can be found here.


Connect your circuit: USB power + wire + roller switch + wire + long led + cloudBit. The roller switch should be set to "open mode" so that the circuit triggers when the roller switch in NOT pressed. We held our circuit together with littleBits adhesive shoes.

Test to make sure the circuit is working correctly. In the receive tab on Cloud Control, you should see the readout change when you press and release the roller switch.


Create an account on IFTTT.com and activate the littleBits channel.


Set up the text alert with IFTTT’s SMS channel. The recipe should read: IF my littleBits cloudBit is triggered, THEN send me a text message. 

Check out our recipe below.


Test out your IFTTT recipe. Press and release the roller switch. When the roller switch is released, you should receive a text message.


Build the spring mechanism. See the attached file for the templates we used to make the base and spring holder parts. 

We cut our parts out of 1/4" plywood using a laser cutter. If you don't have a laser cutter, you can use a hobby saw, band saw, or whatever cutting tools are available to you. Whatever material you end up using, the most important part is to drill holes so that the springs have a place to sit. You will want to make sure that the holes on both spring holder parts align and that the springs fit snugly in the holes. The holes in the template fit a 1/2" diameter spring.

Click here for a detailed look at the mechanism.


Assemble the parts. Glue one spring holder to the base. When dry, place a spring in each of the holes. Then add the second spring holder on top of the springs. It should fit snugly. 

Remove the backing from the adhesive shoes and stick your circuit down onto the base. The roller switch should sit under the top spring holder with the roller part pointing up. Secure the roller switch in place with glue dots or another double-sided adhesive.


Adjust the height of the springs. You will need to do some fine tuning here. To begin, we suggest placing your plate of cookies on the mechanism so you can see how much the springs depress when you add weight.

You will want to spring height to allow light pressure on the roller switch when the plate [and a certain number of cookies] are placed on top. When a single cookie is removed, you will want the pressure on the roller switch to release, triggering the cloudBit. Use wire cutters to cut your spring to the right height. Our springs came out to be ~1.25" tall. Keep in mind that this height will also depend on the springiness of your springs.


Now, your Santa Detector should be ready to go! On Christmas Eve, place it by the fireplace in preparation for your late night visitor. When he takes a cookie, you might just catch the jolly man in action if you move fast enough in response to the text notification.


There are many ways to frost this cookie of a project. Try this optional alternative interaction.
This circuit has a buzzer to notify you when santa takes a cookie while the cloudBit tweets "Santa just paid me a visit".
Click here to see the alternative circuit diagram.

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