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Control Snap Circuits Relay With Kano Computer

How to control a relay with the Kano Computer (Raspberry Pi)

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A simple circuit to control a Snap Circuits relay with the Kano Computer (Raspberry Pi). The Scratch program is for an intermittent fan. Intermittent fans are used for ventilation, for instance in your kitchen or bathroom, where the fan simply needs to be on a timer. You might switch the fan on and then forget to turn it off. So, you can preset, say, the bathroom fan to switch off after thirty minutes. The Scratch program switches the fan on for a few seconds, then switches it off for a few seconds, and this process repeats ten times.

Follow me on Twitter: @SteveSchuler20 and right here on Hackaday: KRA5H

This circuit is similar to my project, "Variable Speed Fan: Snap Circuits, Kano Computer" (control a variable speed fan with the Kano Computer), but instead of controlling a motor with the Kano Computer, I'm controlling the Snap Circuits relay (which in turn controls a motor). For some background on this circuit, see the following projects:

Variable Speed Fan: Snap Circuits, Kano Computer

The Diode

Snap Circuits Relay

Initially I used pin 11 (GPIO17) on the Raspberry Pi to try to switch the relay on and off, but unfortunately all I heard was a faint clicking from the relay. Pin 11 just didn't supply enough current to switch the relay on. Pin 2 is 5V and also supplies enough current to to switch the relay on. So, I used pin 11 to switch the transistor on and Pin 2 to power the relay.

I used the Snap Circuits to header pin connector that I created to connect the circuit to pin 9 (Ground) and pin 11 (GPIO17) and made a second Snap Circuits to header pin connector (my cat got a hold of one of my Snap Circuits Jumper wires and chewed through it so I was able to put it to good use after all).

To make the wire I used a header pin jumper wire, Wire Glue, the salvaged Snap Circuits jumper wire, and shrink tubing:

And connected it to pin 2 on the Raspberry Pi

Intermittent Fan Scratch Program

Project Build

The Raspberry Pi pin 9 (Ground) is connected to the NPN transistor (Q2) via the black/black jumper wire and pin 11 (GPIO17) is connected to the 1K resistor (black/red jumper wire). Pin 2 (5V) is connected to the Snap Circuits relay (S3) via the blue/red jumper wire (and the 2-snap conductors).

Where to get the Kano and Snap Circuits:

Kano Computer website: http://us.kano.me/products/kano-kit
Snaps Circuits (individual parts or whole sets): http://cs-sales.net/sncirepa.html

Teaching programming and Electronics with Snap Circuits and the Kano Computer PREVIOUS ARTICLE

  • 1 × Kano Computer/Raspberry pi
  • 3 × Custom made Snap Circuits to header pin jumper wires
  • 1 × Base Grid (11” x 7.7”) # 6SC BG
  • 1 × Diode 1N4001 # 6SC D3
  • 1 × Battery Holder (2-AA) # 6SC B1

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