Ah, electronics. I am slightly skilled with this sort of thing, I usually tell people that I know just enough to break things. Most of the time--and this is no exception--my electronics solutions are kludges at best.
The first major electronics component of the Dalek is a voice modulator. Here's the parts list
- 3 x LM386 IC
- 3 x 220uf electrolytic capacitor
- 3 x 10uf electrolytic cap (optional)
- 2 x 10k ohm resistor
- 1 x 100k potentiometer
- 1 x 9v battery clip
- 1 x Speaker
- 1 x Microphone (I actually used the speaker from a telephone)
- 1 x 3.5mm audio jack
- 4 x 1N4048 diode
- 2 x TM018 or equivalent transformer
- Mp3 player
- 9 volt battery
As I say, this is a total kludge. I found various circuits around the web and just started soldering things together, and amazingly it worked! There are four main parts to the modulator, which actually helped me keep track of everything while I built it, since I could build each part separately and then put them all together. Incidentally, I would love to see a simple sine wave generator circuit, if you have one that you like and is easy, please let me know in the comments!
The central, most important part of this circuit is a device called a ring modulator (I found plans here
). The basic purpose of this circuit is to add two audio signals together and output them as a single sound. The Dalek voice heard on the TV show all the way back to the sixties is simply a human voice added to a 40hz sine wave. The ring modulator is an unpowered, unamplified circuit, so the other parts of the circuit are there to boost the signal.
The beauty of this circuit is that if there aren't two input sounds, it outputs nothing. Therefore, you feed one of the inputs a constant 40hz sine wave (available for download here
) through an mp3 player, and attach the other input to a microphone. When you speak into the mic it completes the input and outputs your voice modulated with that wave. I already had the diodes lying around, and I scrounged the transformers from an old telephone, but they are both available from Radio Shack if you need to buy them.
The other three parts are all amplifiers. I used a very stripped down version of the circuit that instructables user killersquirrel11
The two input amps are wired up thus, based on the pins of the LM386 (starting at the top of the IC, which is denoted with a dot, the legs are numbered 1-8 counterclockwise):
- Pin 2 connected to ground
- Pin 3 connected to 10k ohm resistor, then to input (one wire from the mic / audio jack)
- Pin 4 connected to ground, input, and output (one wire each from the battery, mic / audio jack, and modulator board)
- Pin 5 connected to + leg of 220uf cap, then to output (one of the wires to the modulator board)
- Pin 6 connected to +9v
- Pins 1 and 8 can be jumped with a 10uf cap to increase the gain if your mic or mp3 player are still too quiet, but I found I didn't need this
The output from the modulator board goes to another amp which feeds the speaker, I also put a volume control potentiometer and the battery clip here, besides those changes the circuit here is the same as the other two amps, here are specific changes:
- +9v and ground are bridged by a 100uf capacitor to clean up the sound
- Pin 3 goes to the central pin of the 100K pot instead of the static resistor
- Output from the modulator board goes to the other pins of the pot
- Looking straight at the pot from the knob side, ground goes to the left hand pin
- Outputs go to the speaker instead of the modulator board
And that's really it, except to run power wires to each of the other amps from the battery. It takes some playing about with the volume settings of the mp3 player and your output volume, but with some practice it's pretty easy.
This circuit is functional, not pretty. It has some flaws I suspect could be fixed by someone more knowledgeable about electronics than myself. It really just tears through batteries, I suspect all that amplifying is just too much for a single nine volt. Also, the signal is very dirty, but I couldn't seem to work that out--every time the sound smoothed out it started playing freakin' republican talk radio! Curse you Lars Larson!
I hope my instructions here are clear enough (and correct), but if you need a clarification or have a suggestion for where I went wrong, let me know and I'll fix the instructions.