Jaco’s Random Writings

Hey folks! As my first act, I will post up all the pictures of my work so far. This is going to be a big one, so watch out.

This is the steel prong used to generate the signal in the pick-up.

The bobbin (or the spool, if you would like to call it that) for the magnetic wire is mostly constructed out of cardboard, paper, and some glue.

For the Winder, I realized I needed to count the revolutions in order to keep track of how many windings I had on the bobbin. I programmed it through the Arduino IDE and used the Serial monitor to keep track of the windings.

The Winder is completely constructed of LEGO Technics. The arm of the axle strikes the “touch sensor” (don’t be fooled, it’s a pushbutton), thus signalling the completion of a revolution (down with the monarchy!).

The first pick-up was made entirely hand-cranked. It took 4 hours and a lot of patience. The Gameboy helped keep me sane during this time.

I screwed up the first pick-up, so I had to make another. This time around, I added a motor to the Winder. This cut down the winding time to about 2 hours.

Once the pick-up was done, I fastened it to a perf-board with beeswax and fastened the wires to an anchored set of leads, making this pick-up much easier to hook up to a circuit.

To test the pick-up itself, I hooked it up to a guitar amp. Don’t worry, I knew what I was doing; the amp is fine. The sound was surprisingly good (considering I only have half as many windings as a guitar pick-up).

The initial circuit was based off of a circuit diagram I found for a digital guitar tuner. It didn’t work very well, nor did the testing program work too well either.

With a new testing program in the chip, I redid the circuit. This time around I based off of a transistor linear amplifier circuit.

The buttons function like this: When you press the smaller button, the chip samples the signal and stores the values. When the array is full, it lights up the LED on the far left. Press the larger button and the Array gets dumped to the computer. Once the Array is empty, the LED gets switched off. This was a fantastic idea, except that chip only had enough memory for 4/100 of a second. Yeah, this was an epic fail.

This is the circuit diagram for the linear transistor amplifier as it’s being tested in the circuit simulator. The chart on the bottom left is the output signal (what’s supposed to be read by the chip) and the chart on the bottom right is the signal being generated by the pick-up.

I ditched the test program on the chip as 4/100 is a little too small a gap to effectively sample the signal. Instead, I wired an audio jack to this and I’m now directly running this into my computer and testing it with an oscilloscope.

So this did work out too well. Part of the problem is that the transistor didn’t amplify the signal at all, much less even letting it through. I suspect that this is because I’m using a switching transistor. So, the circuit is being tested using an OP-AMP (Operational Amplifier) and a FET (Field-Effect Transistor) in separate circuits. I’ll post pictures of that later along with the results.