Before the snow fell we were able to fish up some wires to run lights on the North End Tower. We’ve previously run lights in the Engineering Expo Office and on a tree on the Engineering Mall but that typically turns into a mess as it is difficult to prevent people from destroying the lights or computer controlling the system when it’s exposed and when there is less snow.
We started by running new wires up into the pool/tower this fall. We ran a single feed of 120VAC which will be disconnected before refilling the pool with water and we also ran a single terminated ethernet wire up to the top of the tower. The reason for choosing ethernet is that it gives us 7 analog channels, more then enough to cover the tower in lights, and is cheap and readily available (thanks CAE!). Now having our wires up we needed to get to work on a sealed box to put the control electronics/relays into and get the lights strung up on the tower.
We initially planned on Pulse Width dimming LED holiday lights with the National Instruments CompactRIO, however that quickly was put off citing the difficulty of building the hardware, so we decided to start with simple solid state relays which will allow us to cycle the lights at up to 60 times per second (which would typically be fast enough for PWM, but not with unsynced AC current, as you’ll get random behavior).
To sort out the hardware we first started by building a test board on a proto-board.
The picture above is the PWM setup, note all of the extra hardware to syncronize the solid state relay (SSR) with the incoming AC current, this is necessary to switch in the controlled fashion to regulate to duty cycle and therefore trick the eye into seeing a dimming and brighting lights. The above board only controls a single channel, the board soldered up and shown below controls all 7 channels, you can see why we initially opted for a simple on-off control of the lights:
The next step was to create a waterproof and weatherproof box to put the control curcuit into so it can be safetly mounted to the tower. I went to Menards and picked up a PVC electrical enclosure and some bulkhead conduit wire fittings. Then it was off to HarborFreight to pick up the world’s cheapest NPT tap set to we can thread the plastic and run the bulkhead fittings.
Taps plastic very well, I’m not sure I’d run it into a piece of stainless though
The control board fits nicely into the box, after this picture stand-offs were added to get it off the bottom of the box and closer to the input/output connections.
Next up was to finish assembly of the control hardware:
And to get the software written for both the Server:
And for the Compact RIO:
The final step was to get outside and string up the 7 strings of LED holiday lights, 2 red, 2 blue, 3 white and to get the default patterns written for the server.
The final step is to write control code to allow the Kiosk to run as a control point for the lights to allow local control from Engineering Hall, and finally to get lights up in the Calipers and to PWM them so the caliper color can be controlled.