Hi,
Here's a description of how to use the 108" automatic screen offered by Lumenlab- without the use of a step-up transformer.
Disclaimer/Warning:
I was asked by Kellie to post this- and I am by no means an expert on the subject of automatic screens, electronics, or the general non-burning down of houses. Anything described here is done at your own risk, and while if done correctly- is safe- I can not, nor can lumenlab, account for your ability to do basic wiring.
This involves mains-level AC. It has the potential to be lethal. Bad wiring also has the potential to burn down the house. If you do not feel comfortable handling this- do not attempt the mod/project described here.
Background:
Ok, now that that is all out of the way.... I was sitting over at my friend Scott's apartment the other week, and over the course of some drinks we cracked open a broken 108" automatic screen to do some troubleshooting.
A riddle inside of a mystery wrapped in a fortune cookie:
First off, the "remote" is next to useless, I suggest putting it away in a box. There were a couple hours of staring at the electronics within the remote, trying to figure out what exactly was going on. And, the short answer is "not much". As far as I can gather, it does nothing but ensure that the wrong voltage is powering the motor. To call it 'over-engineering' is besides the point, the thing is can be replaced by a simple switch.
The Motor:
The motor, for those who have not cracked it open, runs natively at 110v AC. This happens to be the same as north american house mains-voltage. In other words, you do not need a step-up transformer for it to operate. There is some interesting wiring going on inside the motor, what would normally be the safety-ground (the round pin on the standard 3 conductor connection) is connected to one of the motor "hot" connections, both "grounds", that is, the outs on the motor are connected to the neutral (the smaller of the two flat conductors), and the other hot is connected to "line".
Theory:
How this operates is that 110v AC is switched to one of the two inputs on the motor, this determines the direction of motor spin. Once the motor winds far enough in that direction- a switch is flipped inside of the housing that disconnects power from the corresponding input. All of this prevents the screen from over-winding.
Bypass:
First, you need a fairly beefy soldering iron. Second you need a single-pole double-throw switch with center "off". This switch needs to have the minimum rating of 110VAC 2 Amps. You will need a multimeter to check your work. You'll also have to devise a way of housing this switch (and I would advise against metal housing for the sake of simplicity and safety), the more industrious of you could surely devise a way to wire a wall-switch to an outlet- but since I'm not certain about the implications of this and your local electrical/building code- I'll leave that in your hands. You'll also need a way of connecting a standard IEC power cord between the motor and your switch- either by splicing this box in the middle of a cord, or by including an IEC inlet, and IEC outlet.
Here it is... wire the center terminal of your switch to the hot conductor of your inlet or cable splice. Wire the outlet so that the neutral will bypass the switch altogether, and is connected with the neutral wire on the inlet. Now, wire the ground on the outlet to one of the two remaining terminals and the hot wire on the outlet to the other. What is happening here is that the switch is selecting which input on the motor receives power. Pretty simple. A variation of this arrangement can be done with a DPDT switch, which may be better- as there is a varistor within the motor assembly which presumably functions as some sort of over-voltage protection which would require the electrical connection of all conductors in order to work. But I really do not believe that it is necessary. Also, the motor has no safety ground. This is fine- as safety grounds are included almost exclusively as a way to prevent electrocution in the event of a lightning strike- as well as to help protect against a massive shorting between mains power and a metallic case. If you are so unlucky as to be touching the enclosure for the screen- when it is hit by lightning, then you'll still be protected since the neutral side of mains power is always grounded eventually. If you are using a metal case for your switch enclosure, you should wire the safety-ground on the inlet side to the metal of the case. But this is not required for non-metallic cases (since there is little to no chance of a short), and can simply be left floating. I specified the use of a switch with "center-off" as another safety issue. It isn't absolutely needed, but I figure that it's best to be on the safe side.
Ok, Sorry if this was overly confusing, it's one of those things which is incredibly simple to visualize- if you already know what's happening.. I'll come back here for the next while to answer questions that you may have. And if there's sufficient demand- maybe a diagram or two. Also, I purposely left out instructions on how to do soldering/wiring. If that isn't something you've already had a bit of experience with, again, you shouldn't take this on.
Robin


