Task: To programatically control a mechanism
Difficulty: Intermediate
1 Gather all of your materials together.
2 Carefully cut along the edges of the painting.
3 Measure the width and height of your picture.
4 Draw a frame around the painting. Your measurements will help.
5 Then draw a new line 1cm inside of your frame, and cut it out.
6 You should now have a frame that covers 1cm of your painting (4cm thick).
7 With your knife, carefully cut around the eyes.
8 Hopefully your painting looks as creepy as ours!
9 Place the picture onto the box and draw around the eyes.
10 Now, using the knife, make the eye cutouts.
11 Cover your box in glue!
12 Stick the picture onto the box.
13 Measure and cut out a 10x2cm oblong.
14 Do the same on a scrap piece of paper.
15 Glue them together, so that they are one piece.
16 Place the card behind the eyes (white side down), and trace around it, so you know where it goes again.
17 Now hold the card behind the eyes of the picture, and mark where the pupils will go.
18 Remove the card and fill in the pupils – make them look scary!
19 Yellow the eyes a bit, and make them bloodshot.
20 Pierce a hole in the end of ‘eye piece’.
21 Cut out some small pieces of card, for supports.
22 Stick the supports to hold the ‘eye piece’ in place.
23 Fold a piece of card and use it as a guide rail.
24 Bend the paper clip like this, and hook it onto the eye piece.
25 Attach it to the servo, and stick the servo into place. Make sure the servo can move backwards and forwards enough, to make the eye movement work.
26 If you want, you can draw a design onto the frame, and use a the glue gun to ’emboss’ it.
27 It doesn’t have to be perfect – it will just add a bit more authenticity and character to the piece!
28 Paint over your frame – we have used gold.
29 To age the frame, mix in a bit black with your chosen colour.
30 Brush small amounts over the wet frame. It should hopefully catch onto all of the nooks and crannies.
31 When your frame is dry (you may need to flatten it), put glue on the 1cm strip we marked earlier.
32 Attach the frame onto the picture.
33 After adding a ‘caption’, we’re all ready to wire it up!
34 Connect the battery pack to the Crumble, + to + and – to -.
35 Wire up your servo. You need a + and – connect, either from the batteries or the Crumble, and an output (A,B,C or D) to the servo.
36 You’re now ready to program it!
37 Now we want to control the servo. Try the following program. Notice how we have to use a do forever loop.
38 To get the eyes moving around basically, we can use a program like this. We’ve set the servo to one angle, waited, and set it to another etc.
39 To get the smooth motion, we have utilised some variables and a loop. We set our start angle (ServoValue) and our counter which will be one. We then set the servo, wait 30ms and then decrease our servo value by 1 (counter). After this has done this 70 times, we want to increase the servo value again. By multiplying ‘Counter’ by one, when we subtract it from ‘ServoValue’, we are actually increasing it (–1 = +1). It is a neat little trick to make programs more efficient. If you wanted, you could do another loop instead.
And there you have it. Your very own creepy moving eye portrait!
