DMX Drop Box

[CharlieH]

Hello All

For my AS Drama moderation we want something to be dropped from the grid. I know you can hire a device to do this, but I would like to build one as a) I believe it would be good for me, and b) I think it would be useful to have in future.

 

My thoughts are to go for a wooden box, maybe 0.5m square, with a hinged bottom. The unhinged edge of the bottom would be secured with an electromagnet, controlled via a DMX relay, so it can be controlled form the desk. It would also have a second hatch on the side, so the load can be inserted with the bottom hatch shut, and the bottom hatch would have a latch for securing in transit.

 

I plan to get a 12v Transformer mounted inside the box, and running it to this relay (after replacing the 3pin in with a 5pin in), which would in turn be run to a magnet (either the type used for securing doors, or something more like this).

 

So firstly can anyone see anything wrong with this plan?

 

But my main question is I would like to make it well, with as many 'features' as possible, so it can be used in the future. One of these would be a DMX out. I know I can't take a simply y-split of the DMX signal, so I was thinking of using one of these to do it properly.....would this work, and does anybody know of an easier/cheaper way of doing this?

 

Finally, can anybody think of any more features that would make it more usable in the real world? Can you see a neater/easier way of doing this?

 

Many thanks for your help, and I wish you a Happy New Year!

Charlie

 

EDIT: I can't seem to link to the relay, but if you search VM138 - DMX Controlled Relay Module in the search on the website linked then it should come up

Moderation: Link fixed

[smalljoshua]

For the DMX out, you can go DMX In ----- Receiver Chip ----- DMX Out so both cables are connected to the terminal block on the Relay.

 

The link for your relay is duff BTW.

 

I'd go for a solenoid instead of an electromagnet. That way you'd not drop your contents if someone cut power and you'd not need to always have power going to the unit.

 

Is there any reason you can't just leave the top of the unit open?

 

Josh

[charl.ie]

What happens when you forget to terminate the chain / you get a dodgy piece of DMX kit on the chain / you get some other sort of data corruption in your DMX stream and you drop a load of stuff at the wrong moment? At best it'll be a massive inconvenience, at worst a massive safety hazard. What stuff will you be dropping? Under what conditions will the relay allow the trap to open. Will the box drop its content when it loses power?

 

I believe y-splits are okay when one side of them is very short (i.e. the side going into your box of tricks).

[paulears]

keeping in mind the the technical complexity required to get top marks is extremely low (as in being moderated by somebody who may know nothing at all about electronics) - It strikes me that the box, a mains or 12V operated solenoid, length of cable and a push button could do exactly the same. Why would you want the drop box operated from the lighting desk? Much better to have it operated by the person who'd call the cue? A nice simple, project that has a purpose, and if it works, the same chance of grades. A collection of stand alone circuits daisy chained together - especially utilising something with a two pin mains connection - could make for something not too reliable?

 

The plans will look good, the operation more reliable and the grade probably the same if not better. Adding DMX just complicates it when it's not necessary. A nice big button - and my favourites are nudge buttons from fruit machines, that light up - are the most impressive! Especially to a drama specialist who believes anything electric is magic!

[CharlieH]

Thanks for the responses.

This isn't directly for my grade - I am making it for the performance, but I don't believe it is part of my course....I wasn't expecting to get marked on it.

 

The responses on losing power are very valid - a solenoid and physical catch may work better, I will look into it.

 

The reason I wanted it DMX was because for this performance I am the only technician, so am running lighting (getting marked on) and sound (not getting marked on) already. I haven't got enough hands to operate 3 switches simultaneously, and don't want to get into the realms of MSC. I could get someone else to help, but that requires finding someone, comms etc which is also a lot of effort. If I was to do it on a standalone switch I would connect the switch via XLR so I can extend it easily and run it down a multi if needed....would the voltage drop for this be too large?

[Jivemaster]

Again a caution that DMX can be glitchy especially when you use cheap devices on the line. a half metre cube will hold a LOT of mess which will be disastrous if dumped off cue by a DMX glitch, maybe even dangerous. A good big switch with a safety system seems a MUCH better idea.

[paulears]

charlie - you are overcomplicating something so simple. Remember KISS. A bit of string is hard to beat. Show control for a drop box is just daft! It's a school show - nobody will remotely be that accurate.

 

3 switches at the same time isn't a problem - surely? even if you have left hand fully stretched out left to lights and right hand extended to a sound fader, you still have two feet, a head, two knees and two elbow that can prod a single, one-off button. We used to do lighting with bits of wood to shove more than one fader - or even bits of wood with prongs to only shover certain ones. an LX prod, sound fader/pause button and a drop box isn't going to stretch you - and even if you linked it to the lights, if it misfired, then it would be a lighting MISTAKE which you are being graded on. Big button and stamp on it!

 

I've spent my life making things simpler - not more complicated!

[themadhippy]

why bother making something complicated when a swing top bin a pin hinge pin and a bit of string works rather well.if you want to get complicated replace the pin with a solenoid

[CharlieH]

Okay then, so the overwhelming opinion is not DMX. String doesn't appeal as nobody will be backstage to pull it, so looks like solenoids and a big switch is the way forward.

Thanks for the advice!

[david.elsbury]

My experience with drop boxes at uni this year is that the string, apart from being unsightly draping over the grid, is terribly prone to making the cue go much earlier than planned, if you so much as brush the string before it's due.

 

Is this the case with other people or did we just not get the setup right?

 

On my "to do" project list is to make a set of drop boxes with the solenoids from central locking systems in cars. Cheap, very available in NZ (not much else is...) and easy.

 

David

[paulears]

Never had that problem - pin stuck in a hinge with some nylon window type cord works well, and only ever goes early if the actuator causes it - and of so, give him a kick. The weight of the lid, and length of the pin has never made false drops a problem for me.

[CharlieH]

Okay, so how about my original deign with one of these in place of the electromagnet/DMX chip? The cable wired into an XLR plug, and a large switch on the other end, wired into an XLR socket. This can then be extended as far as needed with XLR leads, making it easily expandable too.

If you were to take a guess (I imagine there is some formula for calculating this) how long could I extend the switch before the voltage drop being too high?

Thanks for your help - I appreciate the advice & telling me to go standalone in place of DMX!Charlie

[pritch]

I think something that expensive probably comes under the heading of "overkill"

 

http://www.ebay.co.uk/itm/Solenoids-PUSH-and-PULL-37mm-x-26mm-x-20mm-12v-24-vdc-/160693233386?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item256a1026ea#ht_826wt_1160

 

That might be a bit more apt.

[themadhippy]

If you were to take a guess (I imagine there is some formula for calculating this) how long could I extend the switch before the voltage drop being too high?

yep,its called ohms law,if you think of it as a series circuit of 2 resistors 1 resistor is your load and the other resistor is the cable

[Smallsy]

I made a lovely drop box system using one of milinsts DMX relay units (www.milinst.co.uk). Using 8x 12v solenoids (I used Car Lock Solenoids in the end which turned out to be quite cheap) I made 8 simple drop buckets:

 

Putting a simple hinge on the bottom of a bucket, the solenoid held it up in a horizontal postion. When power was applied the solenoid was pulled and the bucket would drop to a vertical position dropping its contents.

 

While DMX is an elaborate thing for drop boxes:

1. you need an operator if you were to put them on a rope and pin on the ends,

2. Running lines to 8 boxes in a fixed grid can be difficult and tiresome with a set in the way.

3. The drops had to be exactly on cue to music and lighting. All of these boxes were controlled by the lighting desk meaning worked brilliantly.

 

Feel free to PM me if you want any help. It's a cool project.