Inherited prop lighting problem... Need someone with electronics knowledge input...


Active Member
I'm currently lighting a production of "Disaster." One thing needed is a light up slot machine for when a character wins, triggering an earthquake... They had attempted to put led strips and also "fairy lights" behind the upper logo, with no success, as the painter painted the plexiglass front very heavily. I got handed the task yesterday.

My solution is to use LED TV backlight strips cut into 9v segments(3 LEDs). (6) of these in parallel, driven by a 4a buck converter. This will be driven by a small lead acid battery, with a switch to connect/disconnect power and a tap off just before the buck converter to power some LED strips on the outside of the machine.

I've got it wired up and working on my bench, with a current limiting power supply, it draws ~1/2 amp). The tech director is picking up battery this week, and I'll get it installed next Saturday.

My only real concern is if I need to put in a resistor to current limit the LED's. I don't think so, as the buck converter should be enough regulation. Adding a resistor will also additionally load the battery more, and the TD's hoping to get the 3 shows without recharging the battery. Personally I'd rather charge it every night, although access into the piece involves removing the entire back, so I understand his concern. I may prehaps put a battery charger inside the piece all the time, with a small hole to access the power cord. The show's only running for 3 days, so simple/easy is the goal.

I've got enough to figure out on this show, as I've only run 99% conventional fixture rigs controlled via Expression in the past, and this is an EOS System controlling 99% LED fixtures including several moving heads.....likely being over-utilized, as the guy that designed the system miscounted and didn't order Lekos for an entire position, hence what we thought was going to be a 4 sets of 4 fixtures for cover the downstage+2 systems of 4 upstage), replicating what was there, turned into 2 systems of 3 downstage, + 2 system of 4 upstage. Another issue is that the previous fixtures were all 30 and 40 degree's. these new fixtures, FOH, are primarily 19deg, with some 26deg. I'm trying to now mess with the lights positions too much, as my knowledge if this equipment is limited, and the way the installer set everythign up makes moving fixtures around a real pain. The FOH positions also only had ~30 addresses open on universe 1, and no one seems to know if universe 2 is wired FOH, or is just over stage. To give an idea on the confusion, I asked for the patch file, and was told that they were "working on it."
Even not knowing the board, I found it when I got hands on within a couple minutes.

Mac Hosehead

Well-Known Member
Here are my thoughts:
If you match the voltage being suppied by the power supply on the bench then I would expect the circuit to draw the same current. I would expect adding a resister to reduce the total current and brightness. I would not expect a resister to reduce the charge life. I think the opposite would occur.

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