With the clock face constructed, I turned my attention to seeing what I could do to get it moving.
I knew it was going to have to be wirelessly-controlled because there was no way we would be able to run a control cable from a hanging beam to the side of the stage without complications.
So I put a few ideas together. I knew that an Arduino-like controller would be simple to put together. I’d played around with building a Bareduino ( https://www.virtuabotix.com/product/bareduino-bare-minimum-16-mhz-arduino-kit/ ) and found it fun and, more importantly, inexpensive. I ended up buying the components in bulk on eBay. Now I’m hooked on getting electronics from China for a couple of dollars.
The number of add-ons that are available for the Arduino market is impressive. I knew that it was possible to get wireless transceivers so I bought some nRF24L01+ transceivers from Amazon (http://www.amazon.com/gp/product/B00E594ZX0). These have good Arduino library support. There are a couple of libraries on GitHub and I found that the maniacbug version worked for me (http://maniacbug.github.io/RF24/). Also, I found his blog entry “Getting Started with nRF24L01+” really useful, particularly the pin connections from the ATmega328PU to the transceiver itself. The blog is at http://maniacbug.wordpress.com/2011/11/02/getting-started-rf24/.
I called my project a Nerduino due to the anticipated comments from my “friends”.
Initially, I breadboarded the circuits to show that I could send and receive
The wrinkle in building the circuit is that the transceiver is *powered* using 3.3v but the ATmega32PU is 5v-powered. This meant that I needed to build a voltage regulator to drop a 5v input down to 3.3v just to power it. That adds a few more components.
A LM317T is useful for building the regulator because it is adjustable based on the resistors that are used in the circuit. More information can be found at http://www.reuk.co.uk/Using-The-LM317T-To-Regulate-Voltage.htm but the schematic required to build a 5.5v to 3.3v regulator is:
At the time I built the circuit, I didn’t have a 240 ohm resistor so I had to use a variable resistor instead but I managed to get the conversion to 3.3v
I soldered together one Nerduino with the voltage regulator and tested again
After the successful test, I soldered another Nerduino and added a control panel
I added the servo output pins to one of the Nerduinos so that it became the receiver
The servo motor was running fast and unless I added gearing to the clock hands themselves, I needed to add a speed control to the control panel and slow the motor down from there.
The circuits needed to be able to run independently of a wall power socket so I wired up a USB cable to act as a power cable from a phone charger battery that I got from work.
Once the circuitry was working, I assembled it into the clock face with the help of a friend who was there to stop me from throwing the whole thing into the trash the moment we stumbled across minor issues.
I made sure that the clock could be operated from the sound desk at the back of the theatre (i’m standing next to the camera operator).
For those interested, the Arduino sketches for the transmitter and receiver are at: