Gate remote opener fails


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Old 09-23-16, 10:07 AM
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Gate remote opener fails

We have an intercom to the gate with a door opening button.
It is a two wire system, and the long run, about 50m uses old phone wire (so quite the in)
So the camera and microphone all works ok but when we press the gate Open button it only works for fraction of a second and then Phut, the phone is no more. It comes back a second later, and if the person at the gate is quick they manage to open it, but for visitors we actually have to run to the gate to let them in.

So, my theory is that the solenoid takes too much power, the power supply can't supply and thus everything fails (so get a higher power psu). BUT surely with the long run of thin cable (ie high resistance) it should take less power?

It's a dc system, and it's in France

Does anyone here know about these things?

Thanks
 
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Old 09-23-16, 10:26 AM
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Welcome to the forums.

Yes... we know all about systems like that. The first thing you need is a test meter.
A meter that can measure AC and DC voltages. Without that... we'd just be guessing.

Your power supply may be failing. With a longer run of smaller wire you'd want a higher voltage supply for the distance to have less effect when loaded heavily.

Your solenoid could also be failing.
 
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Old 09-23-16, 10:51 AM
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Thanks for the quick reply

I can try to do some measurements but it all happens a bit quickly. What to measure? It's a DC system. The solenoid has been replaced so it's not that.

Steve
 
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Old 09-23-16, 11:58 AM
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Sounds like a power issue to me as well. If the system had been operating properly, the first question is "What changed just before the problem appeared". New solenoid and then the problem? If not, reterminate your power connections; they can corrode (particularly those not in a climate controlled area) and cause a high resistance connection.

You said old phone wire. I know it's in France, but telephony is pretty much the same world wide. I hope it's not 22 gauge station wire. Hopefully it's solid copper drop wire (pole to the premise) which is 18.5 gauge here. If it has never worked for you, I suggest you download Installation manuals for the unit. Not knowing things like require voltage and current is a lot like shooting in the dark.
 
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Old 09-23-16, 12:04 PM
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Oh yes it's thin wires*. The voltage drop might be enough to stop the solenoid from working, and that I could understand, but that's not what's happening. And no it never worked reliably, it's just I've decided to do something about it. (Oh this isn't the first interphone either, the old one got zapped during a storm)

* I think probably each wire1/0.6mm = 23 awg = 70ohms/km = appx 3.5ohms for our 50m run. But the actual cable is a 2 pair cable where each pair is twisted together to make one fatter wire so 1.8ohms
 

Last edited by shimself; 09-23-16 at 12:20 PM. Reason: wire facts
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Old 09-23-16, 03:20 PM
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The wire gauge is a problem. A solenoid draws relatively high current (the "inrush current") so the voltage drop over the long run of small gauge wire is probably dumping your voltage just below the functional level. For what you are doing, the smallest gauge I would use is 18ga, possibly even 16ga.
 
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Old 09-23-16, 03:45 PM
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Two #23 wires in parallel is roughly equivalent to #19.

You need to check the circuit as both ends. You need to see what it is at the origination end.... where it comes from..... and what you end up with at the solenoid.
 
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Old 09-24-16, 01:10 AM
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I agree that would be good to do, but it would be a real pain to do. AND it doesn't explain the phone crashing
 
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Old 09-24-16, 02:11 AM
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If it's a common power source for the assembly, then naturally, the whole thing would shut down on voltage drop.
 
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Old 09-24-16, 02:48 AM
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um, why? The cable adds resistance so the current draw would be less (wouldn't it?)
 
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Old 09-24-16, 03:36 AM
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The cable resistance increases current draw. Think of it like Nichrome wire. It heats up turning current to heat. The power supply only has X watts available.

If this is 2-pair cable (4 wires) as suggested by Pete try using two of the wires for each conductor.
 
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Old 09-24-16, 01:23 PM
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erm Power consumed is Vsquared / R V-volts R-resistance
V is whatever it is (12V in this case) and doesn't change. As resistance increases power consumed reduces. Surely?

I am using the all wires as you say
 
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Old 09-24-16, 01:36 PM
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As resistance increases there is less power to be consumed.

For example....
Your door release solenoid requires 12v at 1A to open. As the current increases thru the wiring the amount of available voltage decreases. As measured open circuit you would see the full 12v. When the solenoid was connected to the wiring.... the voltage would drop to a level below what the device needed to operate.
 
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Old 09-25-16, 02:27 AM
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Well yes. BUT why does the phone crash?
 
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Old 09-25-16, 08:03 AM
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Is not the phone mechanism sharing a power source with the solenoid?
 
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Old 09-25-16, 08:27 AM
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Yes it is sharing the power supply
 
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Old 09-25-16, 08:29 AM
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Since it never worked reliably, it could be equipment at either end or the wire in between. My money is definitely on the wire. The easiest thing to do is locate and reterminate all the connections, looking for a solid wire that is broken but still held in place by the insulation. Remember, I said easiest, not easy.

Next, lay some wire on top of the ground between the gate and the house, then terminate it to see if it is the wire. From long experience, I wouldn't use less than 18 gauge wire and recommend 16 gauge (I'm lazy and hate doing things over ). If the wire is buried, double-or-nothing it isn't rated for wet locations (water will penetrate the cable jacket/conductor insulation and eventually create a high-resistance short). Any cable you install must be rated for wet locations and if it isn't in pipe of some type, it must be rated for direct burial (as I said, I'm lazy and trenching or repulling wire is hard work ).

Why would someone install wire that is too small? Because:
  1. They could not or would not read the installation instructions
  2. They didn't know any better
  3. They didn't care

I spent many years reinstalling things after the original installer said "Can't see it from my house!". There are a few occasions when even the manufacturer's instructions and recommendations aren't sufficient, but that is usually when someone tries to exceed the capabilities of the equipment.
 
 

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