This useless machine uses a Digispark to control the servo.

Before wasting your time, have a look at how it works.

If you are still interested, let me explain what I did. There are many implementations of a useless machine, some of them are pure mechanical machines which I love, most of them use two switches, some of them use a 555 timer ... and God know how many others.

The Digispark is a development board based on an Attiny85 microcontroller (http://digistump.com/products/1) it is an Arduino like hardware and software implementation. It is cheap and easy to embed in your projects. I decided to use this board instead of the more popular 2 switches, mainly because you have full control of the servo movement; you can decide the speed and the direction at will.

Parts needed.
- Digispark development board (any other Arduino will work as well using the regular servo library)
- DPDT switch, although I only use half of it
- 180 degrees servo, I’m using HiTech HS-422
- Lego structure, although any other will do
- 5v power supply

Step 1: Most Useless Lego Tower. Part 2.

Part 2. Wiring

I don't have the Digispark part for Fritzing, I'll just list the connections.

Arduino  Motor    Color
----------   -------    --------------
5V             5V        Red
Gnd         Gnd      Black
pin 3      Signal   Yellow

Arduino  Switch   Color   Connector
----------   ---------   --------   --------------
pin 0    Signal        red       mid
pin 2    SW Gnd     black   any end connector

The digispark has only one pin for ground, if you need more than one you'll have to use a regular pin (2 in this case) and set it to 0 (ground) in the setup section.

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