Driving a 2KW movie light with a basic stamp

henrytj

I'm working on my other project, but have a new one in mind.

I helped out on a indie movie 2 years ago. To simulate lighting, one of the crew had to click a bright light, like a 2KW movie light on and off at the switch. It didn't work very well as the light flashed on and off and sound peopel could hear the loud clicking of the manual light switch.

So, now thinking, I'm certain that tere is a device that a basic stamp could control that would turn on and off, and vary power outputs inbetween, the light coming from a high capacity movie light. Besides a lightening effect, others could be programmed in, such as the flicker of a fire, a movie theater projector, etc. I'm certain that there are very expensive movie industry solutions for this. But maybe I could put something usable together with a basic stamp.

I geuss what I'm asking about would be a stamp controlable POT that could handle the 2KW of power (maybe even more if more than one light is involved).

Just asking. (really getting iin to this now.)

Henry

PropNut1960

A Solid State Relay would do it.

Mike Green

Controlling the light levels is a bit more complicated than simply turning a light on and off. The brightness is non-linear with regard to voltage and current and the color temperature varies with the light level. Most movie lights also use halogen bulbs which have a much shortened lifespan when run at less than full brightness. As PropNut1960 noted, a SSR (solid state relay) would work very nicely for on and off.

At 120VAC, a 2KW load takes about 20A, more when turned on cold. A SSR rated for this is not cheap and needs a heatsink as well, possibly a cooling fan too. The combination might cost $50 to $100 in small quantities.

JonnyMac could probably give you some practical suggestions and realistic costs.

henrytj

I figure that the lightning effect light would be blue gelled.

Lightning has a distinct look. Just turning a light on and off quickly might not be good enough. There is often an iregular brightning with followup lower brightness flashes as discharges trigger other lesse discharges, etc.

I have seen people talk about using a photo flash unit, and saw that this was tried on a set once, but it don't look right. And sometimes the photo flash is so fast, it isn't always captured, as it may happen entirely between frames.

In one case for a big-budget movie they went through hundreds of old photo style flash bulbs. But the special features commentary, the director stated how difficult it was to find those things. Pyrotechnics might be a posibilite, but I want to avoid that route.

If used for a closeup, maybe several high intensity LED's might be able to be controlled in a pattern.

Duane Degn

If you do want to try a SSR, they're not as expensive as Mike is remembering. I've used one like this for several years to control the temperature of our kitchen oven.

There was a recent Kickstarter for a very bright LED, one of the example uses mentioned was to simulate lightning. SparkFun mentioned this light a while back.

Moskog

ebay is your friend:

http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1311.R0.TR11.TRC1&_nkw=solid+state+relay+40a&_sacat=0&_from=R40

henrytj

Thanks for the SSR info and ebay links. Once I have a little bit of money I'm going to get one of the 4 channel SSRs. (Under $10, wow.)

My Basic Stamp controller box is just about done. Looking forward to test it out once I have access to the resources.

Thanks,
Henry

henrytj

I usually get outbid on ebay. I'm down to gas money at the moment. Is there a direct source for the two 4 and 8 channel SSRs, than look best? Here are the links. The library is closing in 15 minutes

here are the two links

http://www.ebay.com/itm/5V-Four-4-Channel-Relay-Module-optocoupler-PIC-AVR-DSP-ARM-Arduino-8051-/310574401892?_trksid=p2045573.m2102&_trkparms=aid%3D555001%26algo%3DPW.CURRENT%26ao%3D1%26asc%3D14909%26meid%3D6824055570220810373%26pid%3D100034%26prg%3D1117%26rk%3D2%26sd%3D180946984104%26

and

http://www.ebay.com/itm/Eight-8-Channel-5V-Relay-Module-Expansion-Board-Arduino-PIC-AVR-ARM-MCU-DSP-/330902782576?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D14952%26meid%3D6824065804050335336%26pid%3D100005%26prg%3D1118%26rk%3D4%26sd%3D310574401892%26


Thanks

Duane Degn

I don't have a better source for you but I just want to make sure you know you need to use an AC SSR for AC loads and a DC SSR for DC loads. Make sure you get the right kind for your project.

PropNut1960

Henry,
The 2 ebay links you posted are mechanical relays which are not capable of the AC loads you specified.

henrytj

Duane Degn wrote: »

I don't have a better source for you but I just want to make sure you know you need to use an AC SSR for AC loads and a DC SSR for DC loads. Make sure you get the right kind for your project.

This what happens when I have only intermittent access to the Internet. I thought I saw specifications for both DC and AC voltages and currents. And didn't see that these were mechanical relays rather than solid-state. Again, had only a few minutes to look them over before my Internet access cut off.

THanks for the heads up. Guess this will involve more research that I had first hoped.

henrytj

Actually, I'm going to limit my project to having (4) outlets capable of being able to drive a 1KW (max) light each. So, thought the 250VAC 10A specification could handle that. That way the microcontroller could opperate a bank of 4 lights, up to 1KW each max. Then by turning them on and off, was hopping to simulate a lightning flash, or even a faulty flourescent light flickering. But also concerned that tungsten filiment, or quartz bulbs, might have too long of "strike up" delay, and "glow decay." But if there is not critical acting in the scene, the time can be compressed and sped up in post video production for that shot. An alternative, and faster responding light source, might be high lum LEDs. Have to reseach those too.

Doing this on literally a shoe string budget. (Like most projects I get myself into.)

Henry

PropNut1960

Actually, I'm going to limit my project to having (4) outlets capable of being able to drive a 1KW (max) light each.

You would probably be OK with these then. Just keep in mind that you'll need to insure the relay board is well isolated to protect anyone from the 120VAC which can be dangerous.