Safety pressure swith for doors

[brother]

Just curios as to how do those pressure safety switches work for these roll up doors. Any links or info would be appreciated.

 

[mdshunk]

You mean the one that check for a broken belt and dumps the power to the clutch, or the door edge bumper thing?

 

[brother]

You mean the one that check for a broken belt and dumps the power to the clutch, or the door edge bumper thing?

I think the 'door edge bumper thing' . Basically its just a cord like thing on the end of the door so when its comming down if someone is under it and the door hits them it will immediately stop and go up.

 

[mdshunk]

I'm only real familiar with the rubber ones that Overhead Door uses, and they're pretty primitive. The bumper edge is hollow inside, and is airtight. The tube goes up to a pressure switch. When the pressure switch gets a "jolt" from the air in the edge getting compressed, it makes an electrical contact to send the door back up. Much like the bell from the hose you drive over at a service station. These sorta stink in harsh environments, because if they get snagged or ripped, they'll "leak" and not work when you need them. The other one looks similar but is all electric. The rubber bumper has two metal strips running the full length, and they touch when the rubber gets compressed. These can get pretty shredded up and still work fine.

 

[quogueelectric]

Rollup doors is my favorite pastime to watch people who dont know what they are doing to screw up. I will help anyone set the limits all you have to do is ask. I have seen more jerks rip the entire rollup off the wall because it went all the way down past the limits and started rolling up backwards onto the spindle. It should be an x game event. rollup door geniuses. They usually get really screwed up because there is usually a few people who dont know what they are doing have thier hand in the pot before they call a pro.

 

[mdshunk]

Just thought I should add that a few of these all electrical edge sensors, mostly on rolling gates, are 4-wire. They monitor themselves, sorta like 4-wire smokes for a fire alarm.

 

[iwire]

Marc's description matches what I have seen as well. Just a air switch at one end of the door with a long air tube.

I saw my first 'four wire' edge just last fall at a new Lowe's, the two large roll ups at the front and back had the four wire trip edges and the construction guys could not get it to work. :roll:

I got sent there to get them working, they needed a diode as well so they could not be easily bypassed when the cord breaks.

BTW, once the door gets very close to the ground the safety edge is disabled by a second down limit switch so that the door will not bounce back up when the door hits the ground and so that you can not open the door from the outside by squishing the air tube.