Blinky, the creature I made in my first instructable, blinked his eyes and told me he was lonely. He also reminded me of my promise to make him a friend one day, and he told me about the Instructables Monster Contest. "Now would be a convenient time..." he said softly.

"So all right, all right then! I will make you a friend!" I said. Easily said, but where to go for advice? Who to consult about the hardware to equip a monster so, that it will bond with a creature like Blinky? Well, that's easy! I consulted the absolutely brilliant Forrest M. Mims III of course! From his "Engineer's Mini-Notebook, 555 timer IC circuits", I chose two circuits that hopefully and possibly can match with Blinky's five component brain: A dark detector and a touch-sensitive switch.

Thus came to life Monster 555. Short, but not small. Severe, but righteous. And indeed a frightening monster, even among monsters.

To get to know Monster 555 really well, just looking is not enough. You also have to listen to him. He speaks a very peculiar language. See and hear the video to get to know Monster 555...

Having trouble viewing the video? Here's a link to YouTube...

I made Monster 555 from scratch, with only a vague idea to start with, in two or three days working on and off. Now that there's a blueprint (this Instructable, that is), I guess building another Monster 555 would use up about 5.55 hours of your time...

Please don't feel obliged to take this "blueprint" literally. Make your Monster the way you like, and use my Monster 555 just as a headstart.

Most pictures are commented. Hopefully, the comments make the body-text in the steps superfluous.

Known Bugs in Monster 555's blueprint:

The battery drains pretty fast (in four days! I forgot to take off the battery clip at night...). My circuit doesn't contain a switch, but it actually needs one, I guess. What would be super cool is a solar-powered Monster 555: A rechargeable 9 Volt battery, and solar cells mounted on the wings, charging the battery...
The leds turn off immediately after the wires are released. The leds are supposed to stay on for a couple of seconds after releasing the leads, however! This worked fine on the breadboard, and has also worked on the PCB, before I soldered the components for the dark-detector. I think there's a short in the circuit somewhere, but I can't find it... Or maybe I ruined the elco? I don't know, really.

Step 1: Stuff and Tools

Well, everything I needed was on the kitchen table :s

Stuff you need:
Apart from the electronics, Monster 555 is made up of very common and very practical stuff. Available in any hardware store.
The electronic parts are all commonly available. Radio Shack should have it all. Euros, shop at Conrad. Aussies (and Euros), shop at Farnell.

For the body, legs and wings:

Solid kernel copper wire. Stiff enough to hold Monster 555 upright, flexible enough to bend with pliers.
16 Amp wire connectors, 18 to 24 studs. Blinky laughs about this amount.
Transparent, colored foil.
Some tie raps
One 9 Volt battery and a battery clip

For the head:

2 bolts, nuts and washers, M3 (sorry, metric system :-))
16 Amp connectors (again!), 4 studs
Jumper wire
A breadboard to prototype the circuit (important, because you need to calibrate the light-sensor)
A circuit board (I used a thing with pre-etched stripes, which was a real pain to debug. I strongly recommend to make your own PCB)
Some LED's. Pick a color.
8 Ohm speaker.
Some LDR's (Light dependant resistors). I put two LDR's in parallel, to increase the sensitivity of the circuit)
100 kOhm potentiometer (Probably. The pot meter is needed to calibrate the LDR. Depending on the specs of your LDR, you might need a higher or lower value)
3 resistors: 100k, 27k, 1k
2 555 timer IC's
2 electrolytic capacitors: 0.1 uF and 4.7 uF
2 ceramic caps: 10nF and 47nF
1 transistor BC547(B)
Very little ducttape

Tools you need:

Soldering iron
Pliers for cutting and bending
Power drill or Dremel-like tool
Multimeter (for debugging)
Sanding paper
Small saw
Small screwdriver
Sharp knife (to cut loose the connector studs)
Glue (to fix the transparent foil to the wire of the wings)

Step 2: Monster Head

Making the head is by far the hardest part of the Monster 555 project. Because the head plays a dominant part in the appearance of Monster 555, it is wise to start with making the head anyway. The body can be easily adapted to match the looks of the head. The other way around will be a difficult if not impossible path.

Monster 555's head is just the PCB with all the parts mounted on it. If you can, etch your own PCB layout. I have never done that yet, but for my next project with more than 10 parts in a circuit, I will take the trouble of learning it. Debugging this board (finding the shorts between the leads and removing them) was a real pain!

Tips for prototyping:

Build the circuit on a breadboard first.
Calibrating the LDRs is looking for the appropriate value for the var. resistor, so that the 555 starts beeping when the LDR's are covered.
The resistance of my LDR drops to about 1kOhm in full daylight, but this is a very brand-specific spec. Check your LDRs resistance in full daylight with a multimeter. If you find a much lower value than 1 kOhm, you may need a lower value variable resistor too.
To increase the sensitivity, I used two LDR's in parallel. I tried using four LDR's, but I had a hard time finding the right resistor to make them work.
Experiment with the LDRs and the variable resistor: The circuit is a "dark-detector", that is: The speaker starts beeping when it gets dark (little light is on the LDRs). In 555-talk: Pin 4 resets the 555 (stops beeping) when a potential of 0.7 Volt or higher is set on pin 4. With a 9 Volt battery, this means that the value of the variable resistor may be at most 12 times larger than the value of the LDR's to reset the 555 and thus to stop beeping. The speaker starts to "sing" when the resistance of the LDR is around 12 times smaller than the var. resistor.
About the transistor: A BC547 can break down by peak currents on the base (middle lead) rather easily. If your LEDs light up continuously, chances are that the BC547 is bust. It is easy to check by pulling out the middle lead of the transistor: Leds should _not_ light up then, whatever you do. If LEDs do light up: replace the BC547.

Tips for making the board:

Be patient!
To give Monster 555 a face, the layout of the board is important: The speaker and the LEDs on the back, on the left and right side. The rest of the parts in front of the speaker and the LEDs.
If you use a striped PCB: Start with cutting the leads on the marked spots. Doing that after soldering the components will ruin your solders and cause shorts between the leads.
When you're done soldering: Use a camera to check for shorts between the leads. Zoom in as close as possible on the solders and take a pic in bright daylight. Zoom in on the solders on the camera's screen (see pic 6).
Solder the 555's in place first.
I mounted the connectors against the bottom of the PCB using M3 bolts and nuts. To avoid the bolts causing a short, wrap a small piece of ducttape around them.
Instead of using bolts, you can also glue the connectors against the bottom of the board. Superglue works.

Step 3: Body and Legs

Making Monster 555's body and legs is pretty straightforward. The body is actually only a "backbone" of 6 connector-studs. In the pictures, I mounted three coin cells in between the studs. Please ignore these, I had to replace the coin cells eventually with an ordinary 9 Volt battery :-s.

The neck (multi purpose)
The solid kernel wires that make Monster 555's neck serve two purposes: They support the head, and provide electricity to the circuit on the head. So one neck-lead will be connected to the plus-side of the battery, the other neck-lead will be conected to the minus-side. Make sure that the neck-leads are mounted into different connector-studs, to avoid a short.
Don't cut the neckwires too short. Now is the time to define the looks of your Monster 555. Once you decided on the height of the head, bend the neck-wires in a straight angle.

The legs
To make the legs sturdy, I twisted two solid kernel electrical wires together. Here's a great Instructable on how to do that easily. Mount the legs into the lowest pair of connector studs. Long legs? Short legs? Four legs? Three? A tail too? It's up to you.

Support for the wings
To support the wings (in the next step), mount an extra pair of connectors on Monster 555's back. I used a small tie-rap to do that.

Step 4: Wings

This is the easiest step, and a very satisfying one too. The wings are made of pieces of solid kernel electrical wire. One tip is mounted in the top stud of the backbone, the other tip goes into the extra pair of studs on the back.

Make a wing

When a wing is fixed into the connector-studs, the wire will be under tension. Therefor, you can only glue the foil onto the wire when the wing is mounted into the studs.
Remove one wing and the neck leads.
Put the Monster upside down on the table, with the foil beneath it.
Put (little!) glue on the wire, and push the wire against the foil to fixate it.
Proceed to the next wing.

If your monster falls over because of the weight of the wings, don't worry yet. Attach the head first (next step), then there are plenty of possibilities to adjust the legs, neck and wings to balance it.

Step 5: Finish Up

Mount the head and connect it.

Solder two longish jumper wires onto the PCB: One jumper wire on the minus-lead of the circuit, the other wire goes into the "touch"-hole in the circuit (see step 2).

Put the head on the neck leads now. Fixate the tips into the outer two connector-studs on the PCB. One neck-lead will act as the plus-lead from the battery, the other neck-lead will be the minus-lead to the battery.

The only thing missing now is the battery. Since my experiment with three coin-cells failed (they couldn't power the speaker...), I used a 9 Volt battery.
The battery is fixed against Monster 555's hips with two tie-raps. Connect the wires from the battery clip in the backbone, in the connector-studs of the appropriate(!) studs. See also the comments with picture 4.

That's it, you're done! When the battery is connected, your Monster 555 should come to life. If it doesn't respond to darkness in the way you hoped, adjust the pot-meter on the PCB a little.

Have fun, enjoy your new companion. Pics of your creatures are highly appreciated in the comments.