The real TV Robot had a man inside. He had a switch in his left hand that he operated to light up the neon synchronized with the words the Robot would speak. In some early episodes you can see his left claw moving slightly when ever he operated this switch.

To do this automatically requires a circuit that has sound as an input and an output with enough power to turn on the LEDs for the light bars. This is not a trivial task: the LEDs for the Very different not neon need almost an amp (700 ma @ 12 vdc to be exact) of current and the sound signal is down in the milli volt range.

I have not been able to find a ready made circuit that can do this, at least one that I could get to work. But if the problem is cut up into two parts it looks more solvable:

Step 1: Sound detector

We have all probably seen electronic equipment that has LEDs that display relative sound volume: rows of LEDs that sequentially light up as the sound gets louder. These are commonly known as VU meters. An integrated circuit, the LM3915, to do this was first made available back in 1982. Today a kit is available, CK1005, that uses this IC and saves us the trouble of building a circuit board. They are inexpensive, around $20, and simple to build. One such kit is here: http://www.electronickits.com/kit/complete/ligh/ck1005.htm

Since this is a stereo kit there are two circuits on the board. This is actually very important as it allows two separate sound inputs: one for Robot sounds from a remote source and the other from the RoboPhone 

One advantage of using this kit is that it already has a circuit to filter and rectify sound from a speaker connection. But it does need a very minor modification. The problem is that it is not sensitive enough to turn on LED’s with low volume sounds. A very simple change: replace R2 & R5 with 6k resistors. This will make the full scale output around 6 volts instead of 10. Now most of the LEDs will come on for  quieter sounds.

Pick one LED on each side, probably one of the first to light up, and remove it. In its place connect up a wire from the cathode terminal that will lead over to...

Step 2: A Big Honkin Transistor

Humans have built untold quadrillions (more?) of transistors in the last 60 odd years. So why not use one more here? A single large transistor can be used to take the small signal from one of the LEDs in the VU meter, say from the first or second LED that lights up, and use it to turn on the large electrical load of the LED array. A suitable transistor is a PNP that I got from Allied Electronics, NTE252. About $8.

Put part 1 and 2 together:

The outputs from the LM3915 can really only handle about 10 to 20 ma. Fine for little LED’s, nowhere near enough for the 700 ma that the Luxura LED’s need. I removed one LED from the each circuit of the VU meter. In its place are wires and a resistor that leads over to the transistor. See diagram below:

The Luxaura LEDs are all connected in parallel with the positive connection wired to the “C” terminal of the transistor.

There is data around that says a resistor should be used in this connection with the transistor to limit current. This was calculated to be 180k but when I did tests the LEDs did not light up very brightly. After some trial and error a 10k resistor worked best, the brightness was excellent and nothing blew up or got hot even over extended tests. So that is really all there is to it.

Note: The Luxaura LED’s have current limiting resistors built into

them so they can operate at 12 vdc. Normal LEDs can not do

this, they need correctly sized current limiting resistors. Since the

VU meter operates from 12 vdc it is simpler to have LEDs that also

use 12vdc. Current limiting resistors must be calculated to take all

this into account.

When the first LED comes on it (remember the first ones goes to the transistor) it turns on the Big Honkin transistor that switches on power for all 14 Luxura LED’s. As an adjustment any LED could be removed and a wire connected up in its place.

For the small cost and effort required this circuit works surprisingly well. The parts cost around $30, considerably less then the $80 or so for the Tech 22 Neon music interface and transformer.

Here is a test with everything set up on the table before installation in the torso: