Four channel DMX-512 light dimmer

I happened to find this AnyTronics 4 channel dimmer thrown out as trash. It looks looks like Anytronics wall mounted dimmer 4 x 10 A that someone has adapted to become rack mounted and moved the DMX-512 address selection switches outside the device. I expected that Anytronics DP410 dimmer pack installation instructions would be about right for this, but after some testing revelealed that that was not the case.

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Next task was to look what is inside. This looks as pretty typical 4 channel analogue controller light dimmer, and resembles pretty much the design of newer models. As you can see there are some wires that go to the fuses cut out and most fuse holders missing, So there is something to be fixed before this can be used.

The basic circuitry looks pretty normal. The main board has triacs with heatsinks, control electronics, filtering component (big coils because they need to handle 10A current) and related. The board has pretty good markings what is what in there. It seems that the board is designed so that it can be used to build several different dimmer models (4 and 8 channel dimmers). On the right you can see an extra circuit board that does DMX-512 to anlogue (0-10V) conversion.

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The dimmer circuit outlook looks pretty normal. This is four channel dimmer powered from one phase 230V AC 50 Hz mains power. Because the dimmer can output 10A per channel, it will need to be powered from 40A 230V power source if you want to use all the capacity. If you don’t need to use all the power, lower amperage power feed is OK (for example 230V 16A).

The dimmer circuit looks at quick outlook as pretty normal looking analogue dimmer design. There is a low voltage side (powered with one transformer) where there is a ramp voltage generator, and a set of voltage comparators (LM324) that feed opto-isolators. The basic construction of control circuit design look somewhat similat to SchematicsForFree disco power pack and my four channel dimmer pack design. On the mains voltage side of opto-isolators there is circuitry needed to trigger the triacs (powered with the second transformer).

Here is a closer look of the DMX-512 to analogue 0-10V adapter circuit board. The board looks pretty much like homemade circuit board. The main components there 7805 regulator, RS-485 transceiver IC, microcontroller with DMX4ALL label one one IC made by Maxim. This board takes DMX-512 signal and converts it to analogue signal that goes to main dimmer board.

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I wanted to test the DMX-512 part, so I needed to fix the problems on the dimmer power wiring, and get suitable hardware + software to generate DMX-512 signals from PC. For harware interfacing I used my pwn USB-to-DMX-512 adapter I had built years ago based on popular open hardware OpenDMX USB design (based on a FT232BM chip and RD-485 transceiver). I did some testing first with  Q Light Controller software that provided easy to use basic light desk  (worked on old Windows XP PC, not with Open DMX adaper on Windows 10 due some driver issues). On the newer PC I started to use Q Light Controller Plus software that worked well.

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The end result was that I have now a working DMX-512 controlled light dimmer.

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