Doubling channels by using a couple of relays

[Jimm]

Has anyone put relays on the commons of the output of a DMX controller so that that controller can be used for multiple lights that do not have to be on at the same time?
I looked around a bit and could not find much on the subject. If the topic already exists please point me in the right direction.
Thanks,
Jim

[DynamoBen]

On a related but slightly different subject: has anyone put relays on the commons of the output of a DMX controller so that that controller can be used for multiple lights that do not have to be on at the same time?
I looked around a bit and could not find much on the subject. If the topic already exists please point me in the right direction.


As far as switched commons/neutrals it works in theory. In practice its a little odd, the biggest thing to keep in mind is the neutral needs to be sized correctly and each hot need to have a matching neutral. I'm guessing you will just run all your hots and neutrals to a junction and have a large single feed (hot and neutral) running to your power source. If that is the case switching the hot or neutral should work the same way, although this will mess up any GFI circuits you have.

BTW if you want to continue on this vein I may move this part of the thread to the electrical section.

[mrpackethead]

My five cents worth on this.. It would seems to me that the cost / effort of putting in switching relays might be higher than just creating the extra channels in the first place? How much current are we talking?

[David_AVD]

Switching the common won't with incandescents due to the back feed through the filaments on the set switched out. (massive crosstalk)

[ErnieHorning]

Hmmm... Kind of strange when a moderator moves a thread while your in the middle of reading it.
Switching the common won't with incandescents due to the back feed through the filaments on the set switched out. (massive crosstalk)

I could see if you're switching the neutral with a TRIAC but not with an actual relay with a real switch.

I may do this for 2010, not because I need to but because I can. I've read theories of delays, noise, contact failure, crosstalk and various other reasons why this won't work and I just don't see it.

[David_AVD]

It's not the switching method that's the problem. It's the feed from one energised channel going to another (not energised) channel via the (floating) common connection of the set that's switched out.

[DynamoBen]

Hmmm... Kind of strange when a moderator moves a thread while your in the middle of reading it.


Sorry.

[David_AVD]

If there's any doubt about what I'm saying, I can draw out an example. Being boxing day I'm just too lazy at present! :p

[djulien]

I am not using DMX, just regular Renard, but I make extensive use of relays to "bank select" channels that do not need to be on at the same time. Last year, I used 112 physical channels that were equivalent to about 200 channels through the use of bank selects, so it can cut dwn on the number of SSRs considerably. For example, I have several SSR7s where 2 of the channels drive a 1-of-4 decoder via a pair of DPDT relays; combined with the remaining 5 channels, this gives 4x5 = 20 channels.

I have some details in this write-up (page 9):

http://doityourselfchristmas.com/forums/dynamics/showentry.php?e=32&catid=17

EDIT: I used 10A relays from All Electronics, http://www.allelectronics.com, and they were about $1 - $2 each, so in my particular case, it was cheaper to do that than to build a bunch more SSRs.

don

[Jimm]

Don,
Thank you, this is similar to what I was thinking about doing next year and was not sure if it had been tried.
Jim