# My $85/free 5 min EASY projector dowser



## GageStryker (Feb 23, 2010)

I have a production coming up in March that I need a pair of DMX controlled projector dowsers for. So I check City Theatrical and find... $550 a pair??? So I come back to trusty Control Booth, and see some DIY posts about how to make your own. I'm intrigued, but I don't really have that much electronics background or a huge amount of free time to make my own solution. Besides, I need somthing a little bit beefier: For A Christie RoadRunner projector.

What I DID have, however, were some old ChromaQ color scrollers that had long since ripped through a few gel strings, irritated tech, and generally fallen into disrepair. They did have what I needed, however - a DMX to motor interface, and an active servo motor to turn something. I needed a flag, however - a 7.25" gel frame, actually. 5 drill holes to line up holes with the pegs on the ChromaQ gel spindle, and... voila!

I realized that you could do this just fine even with a rental scroller (as long as you don't mind reloading the gel yourself). All I did was pop the four screws out of the bottom and take the guts out.

My next step is to take a table saw to the housing and chop the top off to make a case for these guts (although they're surprisingly resilient even uncased). 

You'll need a 24V PSU to run these, but other then that, I see no real problems. It turns out the other scroller reel even acts as a safety stop so your flag doesn't go flying around.

Old / broken ChromaQ scroller w/o scrolls generally go for about $83 around these parts, with $2 worth of gel frame. I'll be putting cinefoil in this one, although you could put ND or something similar if you wanted to just cut the output down. 

Only problem I can think of is that I'd better make SURE the DMX values supplied don't go past that first turn of the scroll, or I'll be working the motor against itself. That and the way the ChromaQ's home means I might not get consistent values reset to reset for the flag position, but I should be able to tweak if needed.

It looks like painting that flying frame black is going to take more time then getting the dowser to work


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## GreyWyvern (Feb 23, 2010)

Well, that is one way to do it! Kudos on the creativity.


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## Lotos (Feb 23, 2010)

Well, yes, that will work 

I should warn anyone that want to try this, however, to not use current edition Chroma Q's for this.

The old ones, of the issue used in this example, contain three DIAL SELECTORS for DMX address... These scrollers power on, and maintain position of the 'scroll reel' (in this case, a 7-1/2" frame) according to the current DMX value.

The newer scrollers, with Dip Switches or LED Screens and buttons, attempt to 'auto sense' the length when powered on and thus first and last position of a gel string... This would basically cause the frame in this example to whip around and possibly cause some damage to the motor, the other scroll reel pin, or who knows what else.


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## Wood4321 (Feb 23, 2010)

I have also had good luck just using a scroller as a dowser, using mylar as a frame, and ND frames to "Dim" the video.
That is very easy, and shouldn't damage the scroller, no matter the type.
Joshua Wood


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## GageStryker (Feb 23, 2010)

Well, if that was the case, I'd just rent two scrollers with a dowser string from my local rental company. (and yes, they DO have some...)

*doh*

Ah, well. Now I have two dowsers in my inventory and two Chroma Q's out of the "to fix... ish" pile. 

Tweaked the design a bit as well - added a bolt / foam / gaff combo as a bumper to prevent the excessive travel of the frame and get more reliable homing to the blocked position, and did a little case mod with a bandsaw.

So all I saved was rental of two scrollers for two weeks.

But I got an excuse to use the bandsaw! I think I'm still on the upside of this one


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## avkid (Feb 23, 2010)

You might want to close the back of the case and look into a better method of attachment.
Otherwise it looks good, field engineering at it's best.


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