Introduction: Magnetic (goodbye Screaming) Hand

What is it?
This is a fantasy on the drawdio. The shape is made using a small laser cutter. The 555 chip is on top of the hand surface, the rest of the wiring is on the backside. You can attach the goodbye hand to a metal surface using the magnet from the small speaker at the back.

What does it do?
If you touch the thumb and one or more of the metal contacts in the fingertips then you get the characteristic draw dio sound! (The screaming means that you must not go away but remain very closely "in touch" :-) It is an anti goodbye screaming hand :-)

How does it stick?
Using the speaker at the backside, the hand stick to every metal surface!

Step 1: What Do You Need, Tools:

The soldering device, pliers, pinchers and cutters.

I used thick soldering stuff for metal in the fingertips, but you can use anything conductive fitting in the holes of the finger too.

The glue gun is used to order the wires and glue the speaker and battery holder to the back surface.

Step 2: What Do You Need, Components:

You can get the components for under 5 euro's: (The most expensive is the speaker, maybe hack a toy gadget for the speaker!)

A 555 timer chip, 0.25 euro's.
A resistor 100K - 500K, 0.10 euro's.
A capacitor 22 pF, 0.10 euro's.
A capacitor 10 muF, 0.10 euro's
A speaker, around 2 euro's.
A battery holder, 1 euro.
I used a 3V battery, for a decently soft sound. If you want a real scream, apply more voltage, the 555 can withstand until 15V (but be careful with your ears!!!)
You need some wires.

The hand could use a switch, now I have to remove the battery to keep it quiet.

Step 3: The Principle of the Drawdio

The 555 is a timer chip.
The history of it is interesting! Check it out:

Normally you would use the 555 for generating a regular tick, or a nice pure sound (which is a regular tick but fast).

The frequency of the sound is regulated using the capacitor and a combination of resistors.

But your body is also a resistor! So choosing the resistor and the capacitor in relation to the skin resistance you can use the tactile touch as the missing resistor. Pressing harder lowers the resistance of the skin and makes the pitch of the sound go up.

So this contraption using the body is called the drawdio:
Link for the official drawdio:

So far the theory...

Check it out the possibilities of the drawdio on youtube! There are lots of nice movies.

We already made a drawdio glove:
reducing the official circuit even further.

Step 4: What Do You Need: a Hand Shape.

I had the luck that a friend ( bought a laser cutter!

Then you just need this AI file of the hand:

and some material (you can use card board, perspex, cloth, whatever, only not any metal)

But you can think of a design even more funny yourself!!!

(By the way he "BEAM" on the hand is actually my name. Change this to your own name please!)

Step 5: Making It

First make sure in a sketch with a breadboard that your idea is working "electronically". The Arduino is just used for the power (4V). See the schema's for the wiring, in principal it is easy. The 555 always performs.

Fit the chip
Then fit the 555 on the front of the cardboard hand. Push it through. My cardboard was just too thick, so I had to cut out a bit of cardboard. (You can even do this with the laser cutter.)

Then you have to solder the few components to the chip.
I started connecting PIN 4 and PIN  8. Then the speaker with the 10 muF cap attached. Then the rest.
The wiring is going to the thumb from PIN 2, and to all the other fingers from PIN 7. Look at the eagle circuit from step 3. PIN 2 goes to PIN 6 (and to the thumb). PIN 3 is the output for the speaker. PIN 7 is also for the other resistor. PIN 6 goes to the body resistor. PIN 4 and PIN 8 to VCC, PIN 1 to GND.

Blobs in fingertips
I used the very thick soldering tin to make the conductive blobs in the fingers. All kinds of other possibilities here, as long as the stuff is conductive.

Testing again
Finally testing, and gluing the wires around the holes.
You can see the test on youtube, a 3 seconds video!

A Bonus!
The speaker is magnetic, so you can attach the hand to a metal surface for free!


mtoeters (author)2011-10-09

Nice combination of materials!

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