I want to make a set of twinkling white LED ‘stars’ for use in (amateur)theatrical backdrops - the problem with using christmas lighting for this is that it s very conspicuously ‘strung’ - no matter how you arrange it, it is hard to disguise the close regular spacing of the lamps along the wire.
The other problem is controlling the twinkling (or needing to) - unless you run them on a large number of circuits, it is hard to achieve an effect that doesn’t give away the wiring layout.
Enter my idea…
I plan to make the individual stars as small potted circuits with their own ‘twinkle’ circuitry (probably nothing more than a 555 timer and a few other components, including a small potentiometer to control the interval between ‘winks’ - they will remain illumited, and briefly ‘wink’ out every so often) - this way, they can all be powered by a single circuit.
What I want to do is to be able to run a circuit of (something like) speaker wire, then clip the stars to it wherever I want them - I need the kind of connectors that cut through the insulation and make their connection in a single operation (without severing the wire), but I don’t even know what they are called.
I can picture the kind of thing, I’ve seen then before…but i’d avoid them at all costs. It’s guaranteeing that something will come loose, or just start to connect intermittently, at the crucial moment. Better to invest a couple of hours with wire strippers and connection blocks, for the sake of your later sanity
3M makes a line tapping connector called IDC-popular for things like adding a trailer light hookup to an existing vehicle harness.
They range from 22-10AWG size. No special tool needed.
A similar connector is used for outdoor low voltage lighting-each fixture taps the main 2 wire buried run. Intermatic makes most of them in the US.
I’ve no clue where to get them on your side of the pond, but you can see them (3M) by visiting www.alliedelec.com and checking mfr. stock numbers 617-4507, 4505, 4515, and 4758.
You may want to also check out something called a Twinkling Light Sculpture String. They contain “twinkling bulbs” to create a “random twinkling effect.” Here’s one link; I’m sure a google search will turn up more:
I don’t know if you are thinking this, but reusing this (unclipping these connectors and moving the lights) is a risky idea.
They leave behind holes in the insulation where the bare wire can be exposed. Much of the time the insulation will tend to expand back up to fill in the hole (mostly), but you still have the possibility of electrical shock, especially if the wire is moved (like by an actor brushing against it in a crowded backstage).
So to be safe, plan on buying extra wire (it’s the cheapest part of this, anyway) and using new wire when you redo this for next years production.
I’ve used these connectors in the past for my car stereo. They’re utterly crap - sometimes severing the wire, sometimes slipping off, sometimes just not working at all. I’d recommend using more wire.
To use the Scotchlocks, youll have to split the wire first (if the paris are connected together or vulcanized), obvioulsy. Secondly, you cant re-use them or move them once they are crimped in place. Well, you can remove them but they are not designed to be undone and removing them pretty much wrecks them.
Tools;
Razor knife-- to split the wires if you have one pair of wires vulcanized together like speaker cable, I assume.
Thanks for that, but I’ve found that twinkling Christmas lights tend to be way too decoratively twinkly for the purpose - I need lights that remain illuminated for, say, ten seconds, then ‘wink out’ very briefly, then remain illuminated for ten seconds again. I plan to make the illumination and wink interval tunable so that they will be out of phase from the moment they are turned on.
may not be a problem as it is often quite easy to split (locally, at the junction point) a two-conductor cable into two separated insulated conductors, or I could just run a pair of single conductors.
I know you’re sold on your current solution, but have you considered leaving the bulbs on an always-on string and doing the twinkle manually with smokes or strips of fabric being blown by a fan? I’m always inclined to go with a mechanical rather than electrical solution because of reliability.
If you taped a thin strip of ribbon dangling on the front of the black backdrop, near where the star pokes through, then it’s possible that the air currents of actors onstage (if there are enough of them moving on a small enough stage) would move the ribbon around, creating a twinkle effect.
I’m aware that this idea in its current incarnation is unlikely to work as well as you want it to, but perhaps it’ll give you a jumping-off point for a reliably chaotic star-twinkle backdrop.
For reliability, you’d be better off stripping the power distribution wires wherever you want to tap in for a light cluster and solder the connections. Scothlocks won’t survive much contact with actors or stagehands.
On re-read - you’re planning to make how many little modules of 555 timers, pots and white LEDs? Yikes… I’d be looking at mechanical solutions as well.
Something that just came to mind - how about using one or more fiber-optic decorations (xmas tree, etc) and modify the rotating wheel that lets light into the fibers?
I’m planning to make a hundred or so modules - sounds like a lot of hassle…
…but… I want the system to be as flexible as possible - in the last production, we wove a 'net out of white Christmas lights, but it wasn’t easy to disguise the fact that the lights were at very short, regular intervals on a bunch of cables and there was no way to make any single lamp twinkle independently.
I can get 555 timers for a few pence each and I won’t need to make any PCBs - I can solder the few components directly together, then pot the whole thing with silicone in a short length of clear vinyl tubing.
Fibre optics are a possibility, but they are going to end up more expensive and (I think) less realistically twinkly.
The stars will be suspended behind a semitransparent scrim curtain, so there’s no problem with interference from humans.
What I’m not sure about is whether the duty cycle of a 555 can be extended to ten or more seconds - they are more commonly used for much higher frequencies.
Does anyone have any experience of using 555s at frequencies of fractions of a Hz?
>> Does anyone have any experience of using 555s at frequencies of fractions of a Hz?
Yup. You can do it but you will need high value resistors and, therefore, capacitors with very low leakage. I used to use tantalum for this reason.
>> I won’t need to make any PCBs - I can solder the few components directly together, then pot the whole thing with silicone in a short length of clear vinyl tubing
I do this sometimes. Messy and shoddy and unreliable. If it’s worth doing, it’s worth doing right. You will also need decoupling capacitors. and you will have some voltage drop in the wires so better feed one wire at each end so all the lights get the same voltage. In other words if you have the schematic looking like a ladder running from left to right then you want to feed the top wire from the right and the bottom wire from the left