I’ve been messing around with linear resistor tracks recently – looking to create a new kind of controller for my PAIA 9700 analogue synth, when I came across this clip:

Initially it didn’t seem to offer anything new, but just check out the volume control – utter genius!

The guy has a neat concept website too:

http://www.maywadenki.com/english/00main_e_content.html

It’s taken most of the weekend, but I finally got the clock up on the wall. The more observant reader will spot that the driver weight is missing – so it’s not ticking yet. Also despite my best efforts with a custom jig, the pendulum balance is a little bit off – so that will probably have to be re-done.

The CNC mill is cutting a little “long” in the X axis, so I think a spot of recalibration is in order.

I’m struggling to find things to weight the pendulum with. Weight discs from a lifting kit are too heavy, and fishing weights are too light. At the moment there’s no real weight to the pendulum so it wouldn’t tick for very long.

I predict about 3-4 weeks of further tweaking and balancing to get it to keep accurate time.

The plans came from Brian Law’s Clock site – this is Clock #1 – I used some telescoping brass tube from the model shop for all the spindles – it works remarkable well…

OK, So how annoyed was I at 6:30 today when, after finishing all the final gear alignments and tweaks, I dropped the escapement gear and broke off two of the teeth?  Grrr…

Luckily I still had the toolpath saved and so I cranked up the mill and cut another one – this one fits a little too snugly and is going to need a bit of work to get it running as smoothly as the original.

I even found a place for the first gear I ever cut on the new mill – although this one is only for decoration, as if came from a completely different clock plan.

I just need to attach the weights and the pendulum to get it ticking.

Oooh… so very very close now…

I bought the $85 dust collector from Harbor Freight, and added this to my router setup. It makes a big difference to the amount of “airborne particulates” that get thrown up by this set up.

I also borrowed an adapted the technique described on the www.buildyourowncnc.com site about using bookshelf pins and driven wedges to hold the work-piece down.

If it’s good enough for building the pyramids, then it’s good enough for me…

I just downloaded Windows Live Writer – this is my first post using a Windows based editing client, so far it’s been very slick, and my blog still works after the initial hook up…

Which was nice.

I recently revisited some of my early laser harp work and thought it worth making a posting of the original beam detection circuit. This is an active low comparator circuit and the output line can be hooked directly into an Arduino.

Shine the laser/light onto the Light Dependent Resistor and turn the 100K potentiometer until the LED just comes on. Then shading the LDR should turn the LED off. All the parts are easily available from Radio Shack (Note: the power and gnd connections for the LM324 are not shown).

The circuit is in 5 parts. See attached picture.

Part 1 is the power hookup – you need to connect the 5 volts output from the Arduino (or another source) and gnd to the two lines that run along the longest edge of the breadboard.

Part 2 is the first of 2 potential divider circuits. These divide the input voltage up from part one into different levels. This first one is adjustable with the potentiometer (100K). If you connect the resistor and the potentiometer as shown, then measure the output of the divider ( the middle tab of the potentiometer) you should see a voltage change as you turn the control knob of the potentiometer.

Part 3 is the second potential divider circuit. This uses a light dependent resistor in place of the potentiometer alter the voltage. Same as before though, if you wire this up and measure the output (the line that is connected to pin 3 later in the circuit) you should see the voltage change as more or less light shines on the circuit.

Part 4 uses the op-amp integrated circuit to compare the 2 voltages from parts 2 and 3. When the voltage output of part 3 is above that from part 2 the pin 1 from the IC will go “high” and cause the LED in part 4 to light up. In addition to wiring in pins 1,2 and 3 you will need to connect the power and gnd pins to the power and gnd lines we created
in part 1.

Part 5 is the output stage – this uses a simple LED and current limiting resistor to light up when the pin goes high. You want to have this LED light up when the laser pointer is pointing at the photocell, and go off when it is not. Note the polarity of the LED, it should only go in one way round.

I used 8 of these circuits in the very first static laser harp I built:

Not too bad for the first go...

I was inspired by the recent documentary on Kit Williams to look into wooden clock making. Also, I thought it would be an excellent test of the CNC router I built over Christmas.

So after a week of learning about ramping, lead in and out, cutting paths and other engineering type stuff I finally got all the parts together to start assembling my clock.

(The basement is currently swamped with sawdust, and failed gears…)

There are lots of plans for clocks out there, but in the end I went with one of the Brian Law designs.

At the moment the post holes I cut do not line up with the gears, so I need to rework them….