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Discussion Starter #1
Over the next couple months I plan to ditch the Servo Controller I am using (SSC-32 from Lynxmotion) and migrate to a DMX system.

If you don't know my project, I'm the guy who built "Sindy Skinless and the Decomposers".

I am brand new to DMX and have no experience in it, so I wanted to toss this out there and see what knowledge I can gain from those of you who are way ahead of me in this area.

First off, I am moving this way because in my application, I am using about 45 servos and need my controller to be a fair distance away from the servos. I have fought with finding the perfect balance between long servo extensions and signal loss resulting in jittery servos and other problems. Also, all that wiring is hard to deal with and there are a lot of things that can go wrong and a lot of difficulty troubleshooting it all.

As I understand it, with DMX, I can have the computer pretty much as far away as I want from the props without fear of signal loss. Each character will have to have its own servo controller which is a bit more pricey, but there will be no long extensions to deal with. I can have a single XLR cable running from my computer to the first character, then each successive character can be daisy-chained off the the previous one up to256 times. I only need 4 times. In addition to the single XLR cable per character, I will also need to feed power for the servos and power for the DMX servo controller board to each character. I can d this either by sending DC voltage out there or sending a simple AC line out anbd using a separate power supply mounted in each character. If the DMX Servo controller board operates on 6VDC just like my servos, and I have a 6VDC power supply with enough amperage at the output (I have a 6VDC 100 amp supply, so I think I'm good there), I would only need that single DC power line to go out to each character and use it for everything. Please correct any assumptions I am making that are not correct.

I will be using VSA software from Brookshire Software which already supports DMX, so no problem there.

OK, so now for my questions:

1. What DMX Board would you suggest I use? I need 12 servo outputs (minimum per board). I don't NEED relay outputs, but I'll take them if they are there. I need to be able to feed one of the servos 12VDC instead of 6VDC, but I assume I can use a separate power supply and send the 12VDC direct to the servo which needs it (a Linear Actuator actually) and just connect the ground from that power supply to the ground of my 6VDC power supply to keep them all happy the same as I do for the SSC-32. That way the signal wire still uses the same ground as a reference even though the voltage is different. I also need to be able to control 2 tri-color LEDs with the controller board. These are common anode LEDs and I have to be able to dim any color I want, fade between colors and mix colors. I am using a board I made myself for that now, but want to incorporate that function into the DMX board. So back to the question, which board would you suggest given those requirements? I am only aware of 2. The BoC from Skulltronix and the Medusa Board from OhmMyGadgets.com, although it looks like the Medusa may not have enough servo channels for what I need, and I really don't want to buy twice as many boards, but if I am given some good arguments in favor of the Medusa, I might be persuaded. If there are others that I am unaware of, please fill me in.

2. Next, I need to know what else I need. There's a bunch of EnTec products, DMX adapters for the computer,, the cables themselves, I am kind of lost here. I need a list of exactly what I need to buy and what my choices are for everything starting from what plugs into my computer (I assume some sort of USB adapter) to whatever I need at the other end after daisy-chaining through 4 DMX boards. I seem to recall needing some kind of terminator. (without the accent) I need to know if I can use standard microphone cable, or if I have to use special 3 wire cable with the same connectors as mic cable , but priced at 3 times the cost for DMX. I don't know what kind of adaptersI need at the DMX board end that accepts the XLR plug and connects to the board, etc.

Thank you for tolerating all these questions from a complete newbie in this area. I hope some of you can steer me in the right direction and help me make up my shopping list.

Bob
 

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Hi Bob, really like your work.
I wonder if you might get a better response posting in the tutorials wanted section ?
Good luck, looking forward to seeing the results of your project.
 

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I would highly recommend the Medusa board, They are well built and easy to hook up. most servo controllers you will find are going to be 8 channel because DMX is usually address in 8 bit packets. The Medusa board not only gives you 8 servos but 8 LED channels and 8 relay channels.

The only things you would really need, is a DMX interface, I would say go with an enttec pro, it offers isolation and a little more processing power for complex shows.
---usb cable---enttec pro DMx interface----- DMX cable----control board-----control board-----control board.--------- DMX terminator. (easy to make or buy on ebay)

Ive always used microphone cables for my runs, some people say its good some say bad, Ive never had a problem using mic cable. unless you data runs over a few hundred feet.

I can help answer any questions you might have, hope this helps as a starting port.
 

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Discussion Starter #4
Thanks for the reply! That doesn't sound too bad. The question is Medusa vs. BoC. They are both around $90.00

Unless I am mistaken, the BoC has 16 Servo outputs. It has only 2 Tri-Color LED outputs, but I only need 2. Actually, I really only need one in most cases because I can parallel my two eyes off the same output as I would never have one eye doing something different than the other eye. The BoC does not seem to have any DMX Relay outputs, but does power down the servos automatically after a per-determined amount of inactivity. That is really all I need the built in relays to do.

Does anyone know what the servo resolution is on the Medusa board? It can be either 8 or 16 bit on the BoC.

So, the main issue I have with the Medusa is that I have 4 characters and each one will need it's own servo controller board in this configuration. None of my characters have fewer than 12 servos in them which need controlling. So my cost doubles if I go with the Medusa because I would need two boards for each character, as opposed to a single BoC for each character. Is there a reason why I should still want the Medusa for my purposes over the BoC?

Some other questions:

1. Are all DMX Terminators the same? Is it universal, so if I buy anything that's labeled as a DMX Terminator regardless of make or model, it will work with any DMX control board?

2. I do not see an XLR jack on either the BoC or Medusa board, so I assume T would need some sort of an adapter that I plug my Mic cable into that then connects to the board, and the same adapter for the output that then goes to the next board and so on adding to the list of parts needed as follows:

---usb cable---enttec pro DMx interface-----DMX cable----DMX Cable adapter----control board----DMX Cable adapter----- DMX cable----DMX Cable adapter----control board----DMX Cable adapter-----DMX cable----DMX Cable adapter-----control board----DMX Cable adapter------- DMX terminator.

It appears that a DMX Terminator also requires an adapter and can not directly connect to the control board.

Thanks!
 

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It took me a minute to actually remember you can buy the BOC on skulltronixs. That may be the better choice for your setup, Ive never worked with one of the BOC so i cant really speak to its use. it looks like it would be a good fit.
for connecting them in to the dmx network, I usually just buy a 3-5 foot mic cable cut it in half and connect it to the screw terminals, that way you have DMX in and DMX out. then you can use a standard cable to connect each character together. this would also give you the connector for a DMX terminator.
the terminators should be universal some of them have leds to show the the signal at the end of the chain. (a tester of sorts) when i start i made 5 or 6 terminators just to have on hand. they are pretty much 2 resistor soldered to the connector, helps to eliminate bounce back signals.
http://www.webbspinner.com/DMXtester.html
 

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Discussion Starter #6
OK, I'm getting there. I will opt for cutting mic cables instead of buying interfaces for $30.00 a pop.

So from my computer, I will need one of these: EntTec Open DMX USB

But they only make that in 5 pin, so I will also need one of these: 3 pin Female to 5 pin Male Adapter

Then my mic cable, followed by a cut cord into the BoC, etc. etc. with a terminator at the end, or just a resistor across the right pins if I want.

Does anyone know what voltage the BoC requires to run? I have not found it's operating voltage anywhere in the info on the website.

Thanks again for all the useful info. I'm sure once I buy these, I will have many more questions.
 

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Please take my advice... Buy DMX cables....

They are data cables and interference and resistance may be an issue especially in long runs....

Be careful buying them on eBay too... Be sure the description says it is a DMX cable... Many pop up when you search but the description says mic/DMX cable in the fine print.... Run away!

Terminators are the same... They basically are just a 120 ohm resistor...

The Enttec Pro should give you no trouble...

I have Medusa DMX and love it... I am building my first servo based prop this season (maybe two if I can) so I have no experience with the servo resolution....

I recommend you contact Brian Hook via the website and talk to him... He has been more than helpful to me...
 

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Discussion Starter #8
I already have an abundance of mic cables, and don't expect to have to run any more than 20 or 30 feet total. That said, I appreciate your warning on the cables, and will buy them if my mic cables give me any trouble.

I would love to use the Medusa board and support a member here who is not part of a large company, but I'm afraid it simply does not have the number of servo outputs I need and my budget will not really cover buying twice as many cards.

Thank you again. I am learning and appreciate all wisdom which is sent my way.
 

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The BOC has terminators you put the spliced DMX cables into and screw them tight.....Your definitely going to want the DMX terminator plug at the end of your DMX chain....I had weird stuff happening until I put one on mine......I also used a combination of mic cables and DMX cables without any issues but be aware, mic cables aren't shielded and electrical interference can cause issues just like not having the terminator.....If you plug in the terminator and things are still buggy than switch out those cables like you said....Since your show is a musical show, you may want to add DMX lighting to dramatically enhance it....I used the chauvet colorsplash jr's throughout my haunt and it added a lot.....Not sure if you've seen my video but here is 3 VSA routines in my haunt using 2 videos, and at least 5 colorsplashes ......Good Luck.....Ted

http://www.youtube.com/watch?v=lg3tHE2Om3U
 

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Bob, if I might suggest the DMX dongle from holidaycoro.com. They are less expensive than the entec open but function like the entec pro and do all the signal repeating On board. This places less of a processing load on your cpu. I have used one to drive 30 servos as well as all my dmx controlled led lights. No problems at all. By the way, love your work. You inspired me to build my first animatronics. Keith
 

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Discussion Starter #11
Great to know! I will look into that. Were you using the BoC as your DMX Control board and VSA as your software?

Also thank you for your kind words about my work. I am glad you enjoyed it and that it inspired you in some way.
 

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Bob
I have been a fan of yours for years, great work and you also got me into 3 axis skulls.
A few years ago i switch over to the medusa dmx board and would highly recommend it, while it would cost you more I believe it will
give you room to expand you show. Brian support is second to none and he supports this site. First year i used his board I had issues, he called
me from CA on his way to work to help me out. Last October I shorted out all sorts of electronics, Brian was right there helping me trouble shoot
my problems and repaired my board for shipping cost. You just can't put a price on that kind of support.

Rich
 

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Discussion Starter #14
@Sparky0028 Thanks for the compliments. I appreciate your support of Brian and the Medusa Board. It seems to be the favorite here. Perhaps Brian might be persuaded to create a new version with more servo outputs or maybe even a smaller expansion board with only 8 more servo outputs for people like me.

I will talk to him about this and see what I can do about expanding my budget to purchase more of his boards. I do like to support people on these boards who have worked hard and contributed a lot. I am being swayed. In the end, it may simply come down to what I can afford, but I will do what I can.
 

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Discussion Starter #15
I am moving into DMX finally. I just ordered the boards and necessary accessories.

A HUGE apology to Brian who makes the Medusa boards. I really wanted to support your work and go with those boards, but because I needed more outputs than your boards provide, my budget simply didn't allow me to buy twice as many boards and I went with the BoC boards.

I will update this thread as I migrate from one system to the other and also give details on how I will convert all my existing routines to work with the new settings for the DMX boards.

Thank you for all the advice and information in this thread.
 

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Looks like I'm 3 days too late to the thread - haha...

Glad to hear you're moving to DMX. Hopefully it'll simplify your wiring and make things more robust. No apology necessary; I understand your decision, given the number of servos you need to support. The Medusa is more geared toward controlling an entire display (albeit a smaller display). Let me know if you end up needing control of any relays or higher powered LED lighting. Good luck with the changeover!

- Hook
 

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Discussion Starter #17
Once I get all this working and all my routines converted over to DMX servo settings, I may consider adding some LED Scene lighting to the whole thing.

I would be very interested in your opinions/suggestions for that sort of thing.

For right now, my boards still haven't come in.

Bob
 

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Discussion Starter #19
Thank you! I broke down yesterday and decided to order real DMX Cables. Most of the ones I need are real short 3 to 5 feet, so they weren't so bad. Got a 25 foot one for $13.00. That should be far enough away for me. I hope to be able to start and play with this next week once everything arrives. I will post questions and progress here.
 
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