The torsion spring, not the operator (or motor), does the heavy lifting. Aesthetics aside, the big changes in today's 300-pound steel doors are in insulation. Tighter perimeter seals and sandwiched polyurethane panels get some doors' U-factors, which measure resistance to heat flow and air infiltration, down as low as 0.2. A door under 0.3 qualifies for a 2010 tax credit of up to $1500.1. Motor & Gears: The motor is typically about a 1/2-hp, 6-amp machine hooked to a 120-volt outlet—that's all it takes to overcome the inertia of a stopped door. The machine also slows a door in transit, preventing it from crashing to the garage floor.2. Drive Guide: This track (aka the T-rail) guides and shields the chain, screw or belt as it moves the door open and closed. It connects the operator to the trolley, which in turn is connected to the door.3. Height Adjustment: Operator settings determine the distance the door travels. The machine kicks in to arrest the door's motion or to make adjustments if a door isn't opening or closing completely.

The force of the door's motion can also be adjusted so the door stops moving if grabbed.4. Inverter & Battery: To allow smaller, more efficient motors, most garage-door operators use DC current. An inverter switches household AC power to DC, which is also used to charge a battery backup system that kicks in when the power is out.garage door openers albuquerqueIn the past, suburban burglars sometimes gained access to garages by using radio scanners to eavesdrop on a code transmission between a remote control and a garage door. cabinet doors canada unfinishedDoors in the 1960s were easy targets—they used only one code. garage door centre sunderlandIn the 1970s and '80s, code grabbers pilfered one of 256 codes that the remotes cycled through. reclaimed wood doors virginia

"Since the mid-1990s, we've had rolling codes with billions of combinations," door-operator manufacturer Chamberlain's Paul Accardo says. "The remote sends a code to the receiver; it opens the door and creates a new code for the next time the door opens. Someone could still capture that code, but it won't be used again." bifold door hardware suppliersAmong the quietest (and costliest) drive options, the belt's Kevlar polymer body is molded into nubby teeth on one side. screen door repair fort collinsThese rotate through a gear on the operator top to pull the trolley.The cheapest and oldest technology, the bike-chain-style chain sits slightly slack when the door is open—at least 1/2 inch above the bottom of the T-rail. The chain makes a racket, but maybe that's a good thing when your teenagers are sneaking out.

A continuous threaded shaft connects the operator to the trolley, and its arm reaches for the door. Its threads require biannual lubrication with silicone, and it wears out the trolley more quickly than the other options. But the screw is the Goldilocks drive—median price and noise level.When the main plastic gear stripped, I had to replace my garage door opener. I thought that it might be fun to "salvage" the electric eye sensors forI was also interested to see how they worked, since there are only two wire connections on the opener and yet the devices use them for both power and signals. The opener was a Chamberlin 1/2 HP dating from 1994. Yours may or may not The electric eye has two small boxes -- one which sends (infrared) light, and the other which receives it. The opener is able to tell when the light beam is blocked. Each of the two boxes has a pair of wires, one white and one white with a black stripe. Those wires go in parallel to two connectors on the opener.

With the devices hooked up, an oscilloscope was used to see what was goingWith the light blocked between the transmitter and receiver, the white/black wire is 6VDC above the white wire. When not blocked, a periodic signal is observed, where the white/black wire is 6V above the white wire for about 5.5 ms, then falls close to 0V for about 0.5 ms. This suggests that the opener is supplying 6V through a resistor -- the receiver is "pulling" the voltage to (near) 0V briefly and periodically. One cannot expect it to pull too hard, so a resistor must be present. The devices were removed from the opener. With a DC voltmeter across the terminals on the opener, the voltage was measured while resistors with gradually decreasing values were put across theSince the small boxes both have lit LED's when operating, the internal equivalent resistance can't much more than about 1k for a 6V source, so that was the starting value for the external resistors.

in voltage (though less than by 1/2) was noted for a couple hundred ohmsThat means that the Thevenin equivalent resistance is less than about a couple hundred ohms. A 6V power supply was wired through a 150 ohm resistor to the two boxes. Plus to the white/black wire, 0V (gnd) to the white wire. was observed to be virtually identical to what was observed from the opener, except the maximum was closer to 5V rather than 6V. that a smaller resistor is expected or that the circuit is not linear (hence, Thevenin's theorem is not applicable). But it works, anyway. To make a completed electric eye for use without the opener, a small circuit board was used which included a 6V regulator (7806) and a 555 (low-power) wired as aThe circuitry for the latter can be found on the 555 data sheet, and is easily found with an internet search. It has been copied and recopied by many. Referring to that diagram, I used a 2N3906 PNP transistor, and a 0.1 uF capacitor and a 75k resistor