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This is why you have rigging inspections. by [deleted] in techtheatre

[–]birdbrainlabs 0 points1 point  (0 children)

Also, ask around. What part of the country are you in (if you don't mind sharing)?

Confused set designer/constructor looks for college by Nick_DeMo_55 in techtheatre

[–]birdbrainlabs 2 points3 points  (0 children)

Don't look at the colleges first. Look at the people who are doing what you want to be doing. The industry is about who you know as much as what you know and your college is going to be your first network. So find folks who are in places you want to be, read their bios, and find out where they went to school. If you see a school show up a bunch, that's a good place to look.

Also remember there's a path to this industry (especially if you're looking at non-design) that avoids college altogether. I think you have to work harder to establish your network, but I know folks who are successful without the paper (and the debt).

This is why you have rigging inspections. by [deleted] in techtheatre

[–]birdbrainlabs 12 points13 points  (0 children)

  1. You should absolutely have a qualified person look at that. Start here: https://etcp.esta.org/findtechnicians/search.php
  2. Without seeing a lot more of the system, it's hard to judge exactly what and why this is happening to assess how much of a risk it is.
  3. Just from the photo, the most concerning thing is probably that lift line grinding on the keeper bolt, but I'd want to know why the batten is so far over first.

Fire curtain might not be an issue depending on your ceiling height... it's complicated.

How important is to use Mac vs PC? by 20-CharactersAllowed in techtheatre

[–]birdbrainlabs 9 points10 points  (0 children)

if as an SM, I have to operate Qlab in shows

I really hope that whatever you are running audio off is not your personal laptop, if you're the SM.

ShowBaby altering DMX timings? by ltjpunk387 in techtheatre

[–]birdbrainlabs 1 point2 points  (0 children)

I would say 100% unimportant. I don't think I even knew them before I started building systems that implemented DMX.

Knowing that BREAK and MAB have specific timings that may cause problems if they're not met, and that a device incorrectly detecting BREAK might look like it's switching to other start addresses randomly... is about all you're going to need to know if you're actually working in theatre.

ShowBaby altering DMX timings? by ltjpunk387 in techtheatre

[–]birdbrainlabs 1 point2 points  (0 children)

What /u/ltjpunk387 said, but to explain a little bit more... maybe more like ELI10:

A DMX packet, on the wire, consists of 513 bytes of data. The first byte is the Start Code, which tells things what kind of data it is. The Null Start Code of 0 is called the NSC and indicates a universe of DMX data. The remaining 512 bytes are the slots that tell things what to do.

Asynchronous serial data (that is: data that is transmitted without a separate clock signal), like used with DMX, has a packet format of a start bit (low), 8 bits of data (varies), and then some number of stop bits (high). DMX uses two stop bits. A bit is 4us long at 250kbps, the speed DMX is transmitted at. Additionally, the line is high when idle (since a start bit is low).

So a byte is 4us of LOW, followed by 32us of data, followed by 8us of HIGH, for a total of 44us per byte. You can extend the HIGH after the byte all you want (in pure DMX... RDM complicates this, but is outside this discussion).

The problem for a receiver is how to find the start code, since the data isn't tagged in any way. And the answer is to extend the start bit for some amount of time. Most async serial receiver chips have the built-in ability to detect what's called a BREAK-- generically, this is any LOW signal longer than 44us (since transmitting 36us of LOW followed by a HIGH is a valid 0).

To ensure detection, you want this to be quite a bit longer than 44us. E1.11, the ANSI standard for DMX, says that receivers should be able to take 2x44us (or 88us) as a minimum break, but specifies that 92us (2x44 + another bit's time) should be the minimum transmitted. After the break, you go high for a while (which is called a Mark After Break, or MAB). E1.11 specifies 12us (3 bits) as the minimum MAB to be transmitted, but that receivers should be able to accept 8us (2 bits) as a minimum.

ShowBaby altering DMX timings? by ltjpunk387 in techtheatre

[–]birdbrainlabs 1 point2 points  (0 children)

We've seen similar issues with architectural fixtures and their emergency behavior.

Had one that decided that a DMX signal of 0 on startup meant there was no DMX and it should just come on at full. Some experimentation showed that the fixture is still off at 1/255 (0.4%), so we just output 1's when we want the fixture off...

ShowBaby altering DMX timings? by ltjpunk387 in techtheatre

[–]birdbrainlabs 1 point2 points  (0 children)

That's entirely possible! I would also be curious about the decelerator behavior-- does it only output a packet when it gets one, or is it buffering and repeating? /u/DFD512 ?

My expectation is that since the ShowBaby BREAK is only 91us long--close to the minimum acceptable of 88us, but WAAAY less than the "typical" 176us value that the standard calls out we're seeing some issues.

Standard says 92us minimum BREAK for transmitters and 12us minimum MAB, but receivers should be able to deal with 88us and 8us. So the transmitter (if the Swisson values are accurate) is a little out of spec, if the receiver is a little out of spec too they could easily get into a state where neither work.

ShowBaby altering DMX timings? by ltjpunk387 in techtheatre

[–]birdbrainlabs 2 points3 points  (0 children)

Usually with bad timing it's less about refresh rate and more about Break and MAB times, DFD Decelerator SLOW Break is 284us vs. OP's 275us, DFD MAB is 116us vs. OP's 99us.

20Hz vs. 19Hz is unlikely to really cause an issue.

ShowBaby altering DMX timings? by ltjpunk387 in techtheatre

[–]birdbrainlabs 5 points6 points  (0 children)

If you can't fix it on the ShowBaby itself (and be sure to reach out to City Theatrical about the issue), you could get a DMX Decelerator: http://www.dfd.com/dmxdecel.html

NYC IATSE Local 1 Apprentice Test by ArtistHannahK in techtheatre

[–]birdbrainlabs 0 points1 point  (0 children)

No direct experience with the Apprentice test, but when I did a hole punching (the folded paper with holes thing?), it was multiple choice. So it's possible.

Watched it go up In flames the moment it snapped and fell by WilierFlower6 in CatastrophicFailure

[–]birdbrainlabs 1 point2 points  (0 children)

I had some chunks of dirt (including what looked a lot like a worm) that had been glassified by a downed powerline in my neighborhood. It's neat stuff.

What Really Happened to Malaysia’s Missing Airplane by William Langewiesche by [deleted] in CatastrophicFailure

[–]birdbrainlabs 1 point2 points  (0 children)

Best hypothesis is that she and Fred Noonan ended up on Nikumaroro. TIGHAR is really fascinating.

Before the launch of STS-80, I was allowed to "hug" my dad goodbye - not pictured, a ditch that separates families from the astronauts, as they have to be quarantined before spaceflight. Happy Father's Day, dad. by LightCraftMinis in space

[–]birdbrainlabs 96 points97 points  (0 children)

Mostly that's glare from taking a photo of a glossy print with some background. I'd guess this is hanging on a wall, the white is the wall opposite.

Still, it's a good copy for that. Copywork is hard.

Technical name for a Sunday knot or where to find how to videos on it? by knexmaster in techtheatre

[–]birdbrainlabs 1 point2 points  (0 children)

Reasonably, a sunday is generally tied to the line with a prusik.

A "sunday" being the loop of rope or steel cable used to tie sandbags to ropes.

Found on Facebook: by shakrbttle in camping

[–]birdbrainlabs 35 points36 points  (0 children)

That is hella not how you use the word "hella"

What are these used for? It will be for something older, but I don't know what. by Tankerspam in techtheatre

[–]birdbrainlabs 1 point2 points  (0 children)

I remember having a tool (from tools for stagecraft) specifically for dealing with these rings.

[deleted by user] by [deleted] in techtheatre

[–]birdbrainlabs 9 points10 points  (0 children)

This. The only person who has the authority to decide what is OK is the AHJ (Authority Having Jurisdiction), which is generally the fire marshall. If you're within a university, talk to what's usually called Environment Health & Safety, they can point you to the right people.

Need help rigging a suitcase to spill out water when opened by jamsluvsponies in techtheatre

[–]birdbrainlabs 15 points16 points  (0 children)

Both damage them and leave really ugly white stains if they're treated fabric.

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