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Strand MRL protocol / scroller help

Tom Baldwin

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I've just acquired some 15" scrollers, which I'm told are Strand units driven exclusively by the MRL protocol.


I'd like to use these for the (am-dram) shows that I do, and so want to build a protocol converter. I know Stageline make a converter, but at €1000, it's not really affordable for am-dram, and I also fancy the challenge of building the converter myself.


At present, I have very little information on the MRL protocol, and wonder if any BR members can provide further information?


I did have a question lodged with Strand UK about this, but after recent events I don't expect a reply. (My sympathies to those who appear to have been left high & dry by the closure).


So far I know that MRL is:

- a digital protocol running on RS485

- a command based protocol (cf. state-based DMX), i.e. Fixture 3, Colour 2 in 3s: GO

- also used for PALS and Pirouettes

- derived from an interdesk link protocol used on Galaxy desks

- pan and tilt attributes are 10 bit resolution

- colour & iris attributes are 100 step resolution


Some specific things I'm trying to find out (although I'll settle for a complete specification if anyone has one ;-)

- what baud rate (80pin PLCC microcontroller with built in UART, and an 11MHz crystal - which gives odd baud rates using the usual dividers. The microcontroller p/n is obscured by the choke glued to the top)

- maximum number of unique fixture addresses

- 8 or 9 bits?

- start & stop bits?

- format of the command word(s). Are they instantaneous cues per fixture, as above, which a fixture starts to execute immediately on receipt or a list of "standbys" followed by a single common "go"

- is there only one fixture type (i.e. one with all attributes, where the scroller ignores all others). This could be determined by the operating practice for PALS with scroller - if the main PALS unit is set to the same address as its scroller, that would confirm the theory.

- what does MRL stand for*


Any hints or fragments of information would be gratefully received.


If all else fails, I'll be looking for a Galaxy to which I could attach a scope (and subsequently a data analyser)!


Finally, if anyone could identify the scroller model, I'd be interested to know. As far as I can see, they aren't Colour Calls, but there is no model information on them (The text "COLOUR SCROLLER © R.F. 1987 FOR LIGHT WORKS LTD" is silk-screened onto the PCB). The scrolls are driven by a pair of DC motors, with an slotted opto-encoder on one scroll. The opto encoder PCB does mention Strand Lighting.


Thumbnailed, clickable pictures below:
















* Gareth, I found your post to RATS challenging people to explain it - unfortunately, you never told RATS the answer!

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Finally, if anyone could identify the scroller model, I'd be interested to know. As far as I can see, they aren't Colour Calls, but there is no model information on them


I can't actually help, but as I thought the only scrollers Strand ever made were the Colour Calls, I'm surprised to see another!

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Tony, there were Strand scrollers pre-ColorCall - they were part of the PALS range.


Regarding the protocol, perhaps the best person to try to talk to would be a chap called Peter Willis, who now works for Howard Eaton Lighting. Also, BR member Kazeja is a veteran (I hope he doesn't mind me calling him that!) of the Strand service department, and as such might be able to help. Ordinarily, I'd also strongly recommend talking to John Wright in the service department at Strand, but I think the chances of you being able to get hold of him at the moment are pretty slim :angry:.


Incidentally, to answer Tom's last question ... the story I was told, by a very reliable source who was one of the very first users of Strand's first-ever moving lights, is that MRL is an acronym for Mohammedan Religious Leader. By all accounts, the early Strand moving heads on Starlight Express were affectionately(!) known as the "Ayatollah lights", due to their tendency to all face in one direction and bow up and down at random intervals ............ I'm sure that's not the strictly correct definition of what MRL actually means, but I suppose it's quite plausible, and I like it! :)

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These scrollers are associated with the Strand PALS (programmable automated luminaire system). There were 2 types various sizes made.


Independent and dependent. Independent ones are can be thought of as the modern scroller. Had own address switch.


Dependent. These lived on the front of cantatas and cadenzas etc and were addressed via the lanterns address number.


You didn't have to have a Galaxy to drive them as there was a PC interface with its own control panel available as an alternative.


Will have a look through my archives and see what else I can find.

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Thank you Gareth & Andy.


From your description, Andy, mine would appear to be independent, since they have three rotary switches to (presumably) set their address.


Gareth, I'll follow up with Peter.


I've also discovered that a company called Light Works originally developed the fixtures - they appear to still be trading (although they do seem to have shifted market segment somewhat) - and see if they can help.


Keep the hints coming!






UPDATE: Must learn to count. It's a 68 pin part, and the "choke" is not actually a continuous piece of wire.

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Hi Tom


Had to dig deeper into archives than I thought and I only had a little spade.


According to the diags I have, the big square 64 pin bug with a curly whirly stuck on top is a N8097-90 with an 11 meg xtal.

Your assumption of the command based protocol is fairly accurate and I'll send you protocol details separately once I've scanned them in.




PS. Found an extra 4 pins on the processor on another diag. Sorry, yes you were correct. 68 pins it is. Must try harder.

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Quick update.


Many thanks to Kazeja for sending me the protocol.

I've now got the scroller under PC control using an RS232 - RS485 converter, and am starting to work on the PIC firmware for an embedded DMX - MRL converter.

Will keep everyone posted.



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