DMX Readout

Part of my lighting system design utilizes DMX as a communication protocol between my controllers and the fixtures. The system has the ability to map various data fields to any DMX channel. This is fairly easy to test with RGB fixtures but becomes difficult with more complex fixtures. I found Max Pierson’s excellent Arduino DMX receiver code. I hacked on it a bit to add a standard parallel LCD display that can display any eight sequential channels in real time. The display also shows the number of frames being transmitted per second. The whole thing wired on a perf-board and thrown into a cheap plastic case that originally held a Christmas ornament (a mistake, these cases are too fragile).

Circuit Diagrams (Arduino-based and Stand-alone ATMega168) and Arduino Code. Note that this only compiles under Arduino 0016 (let me know if you fix it for a later version!). I had only three signals left over for control after connecting the serial interface and LCD. I implemented a three button solution for setting the starting address. Up and Down buttons increment or decrement the starting address by 1 for each press. Holding the Fast button causes the channels to change rapidly while Up or Down are held. Holding Up and Down together resets the starting channel to 1.

Power Supply Voltage Display

I bought an inexpensive adjustable power supply based on the 732 regulator IC from canakit and then designed a simple digital voltage readout for it using a PIC 16F373A and 2.5 volt reference. I scrounged around and found some 0.1% resistors that summed to 28.005 k-ohms to go with a 4.000 k-ohm 0.02% resistor I had to create the input voltage divider (0-20 volts scaled down to 0-2.5 volts). The displays were bright enough that I didn't need common cathode drive transistors and could sink the current for an entire digit with on PIC IO pin. Probably took 3 hours in total. Obviously it would have been a better use of my time to have just purchased a cheap DPM on ebay but we don't always choose the most efficient route and I didn't want to wait. If you're in a bind but have a few parts laying around perhaps this circuit and program can help you out. You can easily adjust the input voltage divider or code to deal with whatever resistors you have at your disposal. Write it in C for your favorite microcontroller or an Arduino and the coding will only take a few minutes.

Event Counter

Along the same lines as the power supply voltage display I also built an event counter using a PIC 16F84A and Siemens DL2416T display. I have primarily used this event counter to count the number of packet failures I see in the digital radio that is part of the lighting control system. However it has proved helpful occasionally for other projects as well. It can count to 19999 and then indicate an overflow. The "1" is indicated by the LED turning green. An overflow is indicated by the LED turning from green to red. Another very quick and dirty project based on an immediate need. I had the display and PIC. I only used this alphanumeric display to display numbers 0 - 9 so I could tie off unused data inputs and have the PIC only output BCD information. Schematic and code if you're interested.