Blast from the past...

[sleah]

Don't 'spose anyone knows if you can use a DMX splitter to split the old Martin RS485 protocol as used with old Roboscans etc, with appropriate 2/3 pin swap?

I've discovered Martin made a 'Martin RS485 Optosplitter' (there's on on t'bay at the moment) but wonder if it is just a DMX splitter with the pins swapped?

Edited October 10, 2023 by sleah

[KevinE]

I've just had a look at a few commercial DMX splitters/isolator diagrams  and they all seem to be simple rs485 receiver > TTL > rs485 transmitter with each transmitter hooked to an opto and supplied with their own dc-dc converter, so in theory these should work, after all they're not analysing or buffering or manipulating the data in any way. I suppose there will always be the exception where some clever clogs designer has used a microcontroller to improve something or other.

[sleah]

I'm going to give it a try and see. I've put an offer in anyway for the ebay one, nice to add to my authentic vintage Martin collection. I'm also fortunate enough to have the coveted Martin DMX > 485 converter 😁

[Don Allen]

Circuit for Martin RS485 Optosplitter and pdf manual. It states they work with either polarity pin 2 and pin3.

Circuit.pdf RS485SplitterManual.pdf

[sunray]

6 hours ago, sleah said:

Don't 'spose anyone knows if you can use a DMX splitter to split the old Martin RS485 protocol as used with old Roboscans etc, with appropriate 2/3 pin swap?

I've discovered Martin made a 'Martin RS485 Optosplitter' (there's on on t'bay at the moment) but wonder if it is just a DMX splitter with the pins swapped?

It has polarity reversal switches on all 5 ports. The thing is if all switches are set the same the pin2 in is connected to pin2 out (via the electronics) so it quite happily works with pin 2 hot or cold and faithfully relays that to the outputs. One only needs to use the switches if there is a mixture of devices with different polarities.

Basically older Martin kit used pin 2 hot (Like audio) but when they made later fittigs Martin/DMX compatible they obviously became pin 2 cold.

Edited October 10, 2023 by sunray
Oh dear, I started writing this hours ago. since I've been Granddads taxi, prepared food, been on the phone for ages booking a holiday for 4 couples.

[sunray]

4 hours ago, Don Allen said:

Circuit for Martin RS485 Optosplitter and pdf manual. It states they work with either polarity pin 2 and pin3.

Circuit.pdf 102.3 kB · 2 downloads RS485SplitterManual.pdf 152.96 kB · 3 downloads

Oh... The version I knew (came out of nightclub work in 1996) had a singe multi-wound transformer and no 5 pin XLR's

[sunray]

I'm getting a bit confused, the picture in the manual is, I believe, a unit with no switches. Therefore I think the 2 pdf's are for 2 different units. I don't remember the unit pictured as being by Martin. 

At the time we used several Splitters, one was even universal audio/data ands another used pheonix connectors.

 

I've tried to look at the eBay listing to jog my memory but not found it, hope you have already purchased it.

I must bow out as I struggle to differentiate between units used by different install companies. 25 years ago.

EDIT: £70 Edinburgh? Yes that's what I remember but I think that version doesn't have polarity switches.

Edited October 10, 2023 by sunray
To update

[sleah]

11 hours ago, sunray said:

EDIT: £70 Edinburgh? Yes that's what I remember but I think that version doesn't have polarity switches.

That's the one! Yes, I've already bagged it 😁

For the benefit of anyone interested, it just has one 3 pin input and one 3 pin thru with four 3 pin outs. No obvious polarity switching.  No 5 pin, which makes sense as it was built mainly for the old Martin RS485 (but claims DMX compatibility) which I think was only implemented with 3 pin connectors, with the obligatory 2/3 swap.

Edited October 11, 2023 by sleah

[sunray]

1 hour ago, sleah said:

That's the one! Yes, I've already bagged it 😁

Oh good

1 hour ago, sleah said:

For the benefit of anyone interested, it just has one 3 pin input and one 3 pin thru with four 3 pin outs. No obvious polarity switching.  No 5 pin, which makes sense as it was built mainly for the old Martin RS485 (but claims DMX compatibility) which I think was only implemented with 3 pin connectors, with the obligatory 2/3 swap.

 

Bear in mind the PAT is out of date😁

 

I wouldn't swear to it but I think Don's circuit diagram is for a later version in a 1U rack mount unit in the style of the 2510 controllers... But I'm very happy to be put right.

Edited October 11, 2023 by sunray

[sleah]

2 hours ago, sunray said:

Bear in mind the PAT is out of date😁

Eagle-eye Sunray 😁

Good job I'm a fully one-day-course-in-a-church-hall qualified PAT Monkey, with my own Martindale tester 😆

I'll be opening it up partly for curiosity and also the description said one channel may be dodgy. I'll post a piccy when I get it.

[Don Allen]

The electrolytic capacitors are mounted very close to the transformers for each circuit and dry out, if you have a faulty circuit, probably due to no +5V supply,  replace all of the electrolytic capacitors with high temperature ones.

[sunray]

On 10/11/2023 at 1:18 PM, sleah said:

Eagle-eye Sunray 😁

Good job I'm a fully one-day-course-in-a-church-hall qualified PAT Monkey, with my own Martindale tester 😆

I'll be opening it up partly for curiosity and also the description said one channel may be dodgy. I'll post a piccy when I get it.

How did you get on with this?

[sleah]

17 hours ago, sunray said:

How did you get on with this?

I've not had chance to try it! The rig I had in mind when I got it turned out I didn't need it... however there will be other times when it'll be put to use. I'll update when I get chance to test it out.

[partyanimallighting]

I had one of these for years up to a few months ago and it worked fine across regular DMX. The only issue I could recall would be loss of signal if the encapsulated transformers burnt out on that particular output.