There are a lot of similar projects on Instructables, but I found this version on YouTube and I've decided to make a tutorial.
For this very easy project you need:
the transparent cylinder of soldering on iron (lead free)
1 servo horn (cross),
glue UHU Por (my favorite)
the very always very useful Camembert cheese box (please check my game for mini drones)
1 Arduino Uno Development Board http://www.banggood.com/Wholesale-Arduino-Compati...
1 servo (I think mine is 4.5g). http://www.banggood.com/TowerPro-SG90-Mini-Gear-Mi...
power connector for arduino http://www.banggood.com/2Pcs-9V-Battery-Buckle-Sna...
1 battery PP3 9V https://www.banggood.com/Wholesale-9Volt-Battery-C...
some pieces of Correx
some weight (100g) to be placed inside the box
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Step 1: Preparing the Cylinder
Empty the cylinder (it won't be difficult to finish the soldering wire if you are a good hobbyist :-)
Make 4 large holes on the same line of the cylinder.
Glue the servo horns at the top of it.
Step 2: Servo and Camembert Box
To keep the servo nearly straight, I cut some Correx I had available.
After I glued the servo inside the box.
You can now place the Arduino Uno Development Board inside the box, attaching the power connector and the 9V battery. Keep the Arduino Uno lifted a few millimeters from the bottom of the box, placing underneath some plastic tops (2) cut in half horizontally.
In this way you'll improve ventilation.
Don't forget also to add the weight inside the box, that will keep it in the right position, when the servo moves the cylinder, sprinkling the food for the fish inside the aquarium.
Step 3: Veryfing the Alignment of the Servo
I've attached more Correx even inside the cover of the Camembert box, to be sure the servo will work always in a nearly straight position.
Step 4: Attach the Cylinder to the Servo
If you want to be sure 100% the cylinder will stay in its own position, secure using a small screw the cylinder to the servo.
Step 5: Ventilation Holes And... Coding, of Course!
Make some ventilation holes on the cover of the Camerbet box, adding some copper foil or kitchen foil, to increase the dissipation of the heat.
In this way your Arduino will work at the optimal temperature.
Final stage is to load the code on your Arduino...
I used the examples for the timer (12 hours) and the servo, simply merging these 2 codes.