Tag Archives: Lunar Clock

Cost-Reducing the Lunar Clock: IoT really is here

I have to confess that sometimes I need a push to make the right design choice.

It’s been a long time – way too long – since I worked on my Lunar Clock project. In the meantime, Sparkfun has introduced new, inexpensive microcontrollers aimed at Internet-of-Things applications. I knew one of those new microcontrollers would be perfect for the Lunar Clock, but I dragged my feet.

Continue reading Cost-Reducing the Lunar Clock: IoT really is here

Mounted the Lunar Clock opto-interrupter

In my last post about the Lunar Clock I described the opto-interrupter that will detect the slot in the lunar images disk. At that time I wasn’t sure how to mount the opto-interrupter to the strip that holds the stepper motor that turns the lunar images disk.

Recently I bought an angle bracket to mount the opto-interrupter.  Although it’s the smallest bracket I could find, it’s still pretty big, with holes that are far too large for my use.

the angle bracket holes are too large
the angle bracket holes are too large

So I used a hacksaw to cut one side of the angle bracket down to a size I could use.

hacksawing the angle bracket, using a board as a guide
hacksawing the angle bracket, using a board as a guide

Next I drilled new, smaller mounting holes the size of the short bolts I have used in the clock.

drilling the base mounting holes
drilling the base mounting holes
drilling the size hole that will connect to the opto-interrupter
drilling the size hole that will connect to the opto-interrupter

I then bolted the opto-interrupter to the bar of wood that holds the stepper motor.

Opto-interrupter fastened to the clock
Opto-interrupter fastened to the clock

In my next post, I cost-reduce the electronics by swapping the Arduino, etc. for an IoT microcontroller.

A bit of the mechanics of the lunar clock

I’ve been doing a bit of mechanical work on the lunar clock.

As a prototype to help me design the laser-cut parts, I cut out a strip of 1/8″ MDF, cut a square for the motor’s shaft and two holes for the motor mounting holes, then mounted the motor to that strip of wood.

mounted the stepper motor
mounted the stepper motor

With the motor fastened, I placed the hub on the shaft, making sure to provide a little clearance so the hub won’t rub against the wood. The hub will hold the wheel of lunar images.

Tightening the screwhub onto the motor
Tightening the screwhub onto the motor

Turning to the photo-interrupter that will detect the slot in the lunar wheel, the photo-interrupter breakout board from Sparkfun, fine product though it is, lacks mounting holes. …so I added some.

Looking at the breakout board, it seemed likely that I could add holes at the corners of the board, near the text “PWR” and “SIG”.

Sparkfun's photo-interrupter breakout board
Sparkfun’s photo-interrupter breakout board

Drilling the holes and testing the board proved it out: nothing untoward happened to the board’s circuit, other than connecting the mounting holes to the ground plane of the board.

Sparkfun board with holes drilled into it
Sparkfun board with holes drilled into it

I then soldered the parts onto the breakout board and used the holes to mount the board to a scrap of MDF, for testing.

Photo interrupter mounted to a scrap board
Photo interrupter mounted to a scrap board

Notice that the screw heads are low, to keep from interfering with the photo interrupter, and the scrap board is mounted underneath the breakout board, to keep the parts away from the lunar wheel which will pass through the photo-interrupter.

Notice that on the flip side, I had to align the nuts so they wouldn’t interfere with the pins on the back of the board.

underneath the breakout board
underneath the breakout board

My plan is to design laser-cut parts to mount the photo-interrupter and the stepper motor.  Here’s how the photo-interrupter should align with the lunar wheel.

How the photo-interrupter is supposed to be mounted
How the photo-interrupter is supposed to be mounted

I am a bit puzzled about how to mount the photo-interrupter to the board.  My current plan is to use a small right-angle bracket to fasten the parts.