Help with mag lock ?

leeobrien · Sep 20, 2014

Hello, I was hoping somebody might be able to help with a problem I've been having with a pair of mag locks.
I have attached a diagram of what it is I am hoping to do.
All the parts are new as replacements and i have followed the manufacturers wiring diagram however it is a diagram for 1 lock. I was hoping that I might be able to control 2 locks, but the problem is that when I reinstate power nothing happens. If I disconnect 1 of the mag locks then it works. So my question is do I have the locks connected correctly or is there another wiring config. that I'm missing, or is the opinion that it cant be done this way, or should I try to control it by inserting a contactor and allowing the keypad to control this.
Im afraid don't have a great deal of experience with this type of lock, so any tips would be much appreciated. Cheers.
******EDIT..JUST NOTICED ON THE DRAWING THE NEGATIVE IS NOT SHOWN THIS GOES FROM THE - (NEGATIVE) TERMINAL ON THE PSU TO THE - (NEGATIVE) TERMINAL ON THE KEYPAD, SORRY COULDN'T EDIT THE PICTURE AFTER POSTING*****

[ElectriciansForums.net] Help with mag lock ?

cliffed · Sep 20, 2014

Loading concerns mAybe,add another psu for add on mag lock,then switch through relay

Paul651975 · Sep 20, 2014

First thoughts would be that psu isn't big enough as it works with one mag but not two. Secondly would switch mags through a relay as easier to change a relay than keypad when the contact fails. Also would have the break glass in series with the mags not the keypad.

leeobrien · Sep 21, 2014

Many thanks For the info, I shall try to find a bigger psu, fit a relay, and cross my fingers.... Cheers

shanky887614 · Sep 21, 2014

ah and put a buzzer in the breakglass, makes its easier to find out if its been used

sarky spark · Sep 21, 2014

Not the sort of stuff I work with but out of curiosity what is the purpose of the varistor?

shanky887614 · Sep 21, 2014

sarky spark said:
Not the sort of stuff I work with but out of curiosity what is the purpose of the varistor?

we normally just use a resistor, it is so you can tell if the cable has been cut.

its more for secure doors tbh

Barry White · Sep 21, 2014

sarky spark said:
Not the sort of stuff I work with but out of curiosity what is the purpose of the varistor?

think its transient voltages produced by the coil in the maglock they can be quite high and it supresses them (the varister breaks down at a given voltage/current and effectively shorts the transient voltage) it will work without it but can damage sensitive electronics used in control circuits

shanky887614 · Sep 21, 2014

mykey said:
think its transient voltages produced by the coil in the maglock they can be quite high and it supresses them (the varister breaks down at a given voltage/current and effectively shorts the transient voltage) it will work without it but can damage sensitive electronics used in control circuits

it shouldnt damage it because its only a switch.

same as a contactor coil wont get damaged if it switches a load.

we normally run the supply trough the bgu for the maglock so when its pushed it breaks the circuit

if all it does is send a signal to open the door then thats not a very good emergency breakglass

Barry White · Sep 21, 2014

forgot to add it also reduces arcing on relays, contactors or switches

davesparks · Sep 22, 2014

Look at the diagram again shanky, the break glass is going to cut the positive feed to the keypad and so disable the whole lot and permanently hold the door shut even if the push button is pressed!

And how can you say that it is just a switch? Do you know the internal wiring of the keypad and know for sure it is a relay and not a solid state switch? And even then if the relay is not suitably rated the surge from the mag locks could burn it out.
It is good practice to fit a diode across a DC relay coil to prevent damage from the spike caused by the field collapse and the variation will be doing much the same job here.

tazz · Sep 22, 2014

If you look at the diagram you can see the mag has a constant positive keeping it energised.
The psu should feed the keypad, and then power the mag via the break glass for safety...Normal mags draw aprox 480mA each, and a keypad 250mA. So a 12v, 1.5A or 2A power supply will work fine. If you follow my diagram, you can see how the keypad o/c the negative supply to the mag, via the operational relay, for safety, if the break glass is activated, it also cut the negative supply to the mag.....hope this helps.