Poor man's moving head fixtures + Poor man's DMX512 - Page 1
Forum section: electronics / projects

author: botcrusher
author_rank: Regular Contributor
timestamp: March 04, 2016, 01:54:04 pm
content: Yup. Moving head fixtures. You can either pay 300-500 USD for a decent one, 130 for a cheap Chineese one, or, you can build your own.Most of the parts are still coming in, but the core of this (moving head) is a 2 buck arduino mini clone, a sparkfun pan/tilt bracket, 2x sparkfun submicro servos, cheap (maybe 100W...) Lights. And my favorite, an old ATX PSU.Now i *could* go and buy a dmx shield for each arduino, but what fun would that be! (also, money) So, I'm going to have one arduino uno as the host device, which is in turn a DMX slave. This single dmx device will grab all the commands for the various connected fixtures, and then spew out commands on serial using what I'm thinking of calling the Woodroffe Lighting Protocol.I'll post updates as i assemble parts and make it work!

author: ajb
author_rank: Super Contributor
timestamp: March 04, 2016, 05:40:19 pm
content: What's the purpose of translating DMX to another protocol? DMX is pretty much dead simple, so any other protocol is likely to be at least as much if not more work than just putting DMX in each unit. If the concern is the cost of the RS485 transceivers I suppose you could just use one and run 3V or 5V TTL serial from there to each of the receiving devices...

author: botcrusher
author_rank: Regular Contributor
timestamp: March 04, 2016, 06:48:04 pm
content: Well, the reasoning is that:A) Its funB) serial is included with every atmega board, so implementing it over serial reduces the complexity and cost for each unit.Plus, I'm only using DMX because I'm going to be installing these units in an auditorium already wired for DMX, If there was no dmx present, I'd be using a desktop with Python spitting out the serial commands. DMX is more to give it an option, as I'll likely patch most of the system into the ancient strand lighting console we have (complete with WYSE monochrome terminal) but I'll likely run the moving head lights on a laptop communicating directly in the protocol over serial. I'd rather not control moving head lights by using a pair of faders.

author: ajb
author_rank: Super Contributor
timestamp: March 04, 2016, 07:02:35 pm
content: Well, I can't argue with doing it for fun.But DMX is a serial protocol, and it's implemented using the exact same UART hardware you'd be using for whatever other serial protocol you'd be implementing. The only hardware difference is that DMX uses RS485 signalling to improve noise immunity and enable longer runs (which is a good idea when implementing ANY serial protocol over any significant distance). DMX also specifies how packets are delineated (break and mark-after-break signals, which are easy to detect as a framing error, which is functionality built into most UARTs, including those in the ATMegas)--if you do your own protocol you'll need to come up with some solution for packet framing yourself.And if your lighting desk doesn't have 0-10V outputs it isn't ancient

author: botcrusher
author_rank: Regular Contributor
timestamp: March 04, 2016, 07:47:49 pm
content: Yes, I'm more than anything lazy about the voltages.As for the lighting board, it *barely* come out late enough to support the dmx 1990 spec.