Regular switching and switch loops

Hi Anonymous.
An emergency shut-off loop will almost always be set up so that the circuit is closed during normal operation, with a press of the emergency off button breaking, or opening the circuit. It's set up that way so that if a wire in the emergency circuit breaks, or gets disconnected, the system will shut down, rather than allow operation where the emergency off won't work.

Functionally speaking, if you only have two wires to the switch/button, then which way you connect them won't matter, since the switch will complete the circuit regardless of which way you flow the current. From a Code and consistency standpoint, one of the wires will be ground, and one of them will be hot. Most switches have leads indicating ground and hot on them, and you should be consistent with that. If nothing else, if someone else is later servicing or replacing the switch, also not knowing which wire is which, then they have less risk of mistaking a hot wire for a ground and getting zapped.

Depending on the setup, and whether it's AC or DC on the loop, you should be able to use either a voltmeter or an electricians hot-wire-detector to tell which lead is the hot lead.

Hope this helps, and good luck!
D

There are several ways a gate will open. You need to check each of them but the most common issue we find when repairing gates is the exiting vehicle detection device is opening the gate.

There are two main types. The best type will be a loop embedded in the driveway. These normally open the gate by driving over them. A sensor in the operator sends an electrical wave through the loop. A vehicle affects this wave and the sensor detects it, flips a switch and opens the gate.

If the installer used standard PVC wire, and the driveway cracks to let water sit on the wires, they could change the wave occasionally and open the gate. Water can take days to soak through and remain around for days. So while you do not have rain or sprinklers going the day the gate opens, it could still be the cause.

The sensor inside the operator could also be going out. Usually, they have lights showing when they are active. If you have one, and the detection light is on, turn off the machine, disconnect and reconnect the sensor and see if the detection light comes back on.

Next check the loop wires. Physically, look at the wires wherever you can. Check the driveway for exposed wires. If you find them, call a pro to replace them. Once this is done, you need an ohmmeter. Plunge a screwdriver deep in the ground. Set the dial on the ohmmeter to measure how much resistance there is between one wire in the loop and the screwdriver in the ground. Make sure you are not touching the leads or wires with both hands since you will be measuring your bodies resistance and not the short between the ground and the wires you are looking for.

If you find anything but an open circuit, there is a problem with the loop wires and you will need to replace them. If you have a completely open circuit, then change the detector. Ideally, you have another detector for the safety loops and can switch them to see if the problem moves to the safety loops. If it does, replace the detector.

The second type of exit device is called an exit wand or exit probe.

These are overly sensitive and don't last as long as the loop detector. Your dogs collar can set it off as can a bicycle or even a workers steel-toed boots. Add to this, the propensity to fail, and if you have one of these, you have likely found the problem.

The fix for these is to pull the probe up, look for nicks or cuts in the wire and fix them, dig a deeper trench, cover the wire with PVC pipe to prevent more cuts and finally bury the wand itself at least six inches deep. By the way, if the probe cable runs next to other electrical lines, they can make the probe react too. I have heard this can be prevented by using copper pipe instead of PVC pipe.

Other causes could be a remote in someones purse or pocket going off as it bumps around, a switch used to open the gate shorting out, a call box getting signals and in general anything used to open the gate breaking down or being set off inadvertently.

Rarely, and I mean very rarely, a control board, the big circuit board controlling the gate motor itself, will go out and cause this sort of problem. Out of everything, this is the least likely.

Good luck.

Turn off the power to the receptacle that will be replaced by switching off the circuit breaker in the fuse box. Check that the battery is good in a circuit tester. If not, replace the battery. Place the tester's two ends in one set of the receptacle's slots, then the other set. The light on the tester should not come on. If it does, the correct circuit breaker has not been switched off.

2

Take off the receptacle's face plate by first removing its screw. Detach the two screw securing the receptacle to the box and pull out the receptacle. Loosen the receptacle's terminal screws and pull away all wires from the back of the receptacle. Take out the receptacle (if working properly, it can be reused). If the ends of the wires are chewed up after removing them from the existing receptacle, cut them off with wire cutters. Strip off 1/2 an inch of insulation from the ends, using wire strippers. Bend them into loops with the pliers.

3

Bend the copper ends of all wires into a loop, using a pliers. Connect the white wires to the silver terminal and tighten the screw to the wires. Connect the black wires to the gold terminal and tighten the screw to the wires. Connect the bare ground wires to the ground terminal and tighten the screw to the wires.

4

Push all cables into the back of the box, followed by the receptacle. Attach the receptacle to the box with the two screws. Hold the new faceplate in position and install the screw. Turn on the power at the circuit breaker.

HOPE THIS HELPS YOU...Jim...Please leave a comment

This is a relatively common problem in the Dimension 4600c. The small, fan-less heatsink for the Northbridge chip (a memory/video-to-cpu communications chip) is held down by a spring, which is anchored by two small wire loops soldered to the motherboard at locations marked "HS2". The spring completes an electrical circuit between the two wire loops. The spring puts a substantial force on the minscule bit of solder holding the loops to the motherboard, and was a poor design.

If a loop breaks off, the circuit is broken, which tells the BIOS that the heatsink fell off. To fix this, you need to 1) secure the heatsink to the chip, and 2) reconnect the circuit between the two "HS2" locations on the motherboard. I have sucessfully used this solution. This solution will not necessarly stand up to a lot of abuse if the Dimension's enclosure is frequently opened and closed to replace other components such as RAM and hard disks.

0) unplug the computer.

1a) Recover the heatsink, spring, and loose wire loop. Discard the spring. Get:
- a fresh tube of thermal paste from Radio Shack or other electronics supply store,
- some epoxy,
- a round toothpick,
- about six inches of insulated 14 to 20 gauge solid copper wire,
- electrical solder, flux, and a soldering iron,
- and a box of cotton swabs.

1b) Using pure alcohol and lots of cotton swabs, clean *all* of the existing thermal paste off of the Northbridge chip and the bottom of the heatsink. When both are dry, apply a dab of paste to the center of the Northbridge chip. Use a round toothpick like a kitchen roller to spread the paste evenly across the small raised center square of the chip.

1c) Apply small daps of mixed epoxy just outside of the four corners of the raised center of the Northbridge chip. Place the heatsink onto the Northbridge chip, centering and squaring it as best you can. Press firmly to make good contact with the thermal paste. Allow epoxy to dry.

2a) Firmly seat one or both detached wire loops into their mounting holes at the "HS2" locations. While pressing down on the loop, apply a small dab of epoxy to one end of the loop to secure it to the motherboard. Allow epoxy to dry.

2b) Strip the ends of the copper wire, and bend the wire so that it can reach around (rather than over) the heatsink to the two wire loops. Solder the ends of the wire to each loop. Knowing how to solder is an exercise left to the reader. "Use head main ting": don't drip solder onto the motherboard.

You can now plug in the computer and restart. The BIOS and/or OS may have saved the error state and return a different message about the heatsink issue. You may need to reboot a couple of times to allow the BIOS to notice that the "HS2" circuit is (hopefully) now complete. When you've sucessfully booted the machine, shut it down and gently close the Dimension's enclosure.