I have a number of these electromagnetic locks from eBay. On some doors I have multiple 600lbs ones. In all of them, I use a Meanwell DIN 12V supply, an “automotive fuse block”, then the magnets. I switch the 120V to the power supply, as this keeps all the complexities of switching potentially “high” current.
A word of caution, the main drawback, could cost you or your loved one their life. Really you need to have a big “PUSH TO EXIT” style button that interrupts the magnet. Having a door you gotta putz around in an app with to open when the house is on fire is a nightmare scenario.
I am new to forums so I can only link 1 product, and that is going to be the push to exit butotn. Push to exit
I use 20 AWG wire.
One “280KG 600Lbs Holding Force” draws 0.45A @12VDC. I have each unit fused at 2A. Your mileage may vary, these aren’t exactly brand names. I’d expect OP’s proposed units to draw less current…
They are warm to the touch, but I could hold them all day and not be injured. I’ve tried running them at higher voltages, they get quite a bit warmer at 24V (don’t recall the current).
Um and chickenfeed is bad right? we’re not feeding the chickens in this scenario? (
Actually somewhat honest question - as I’m not sure I understand electronics enough to fully understand what you’re saying there.
Are you saying there will be too much resistance/power lost by using that size cabling (AWG20 = 0.8mm = fairly thin cable)?
Or is it more of an indication of wasted power?
Did some googling, and looks like 12vdc over 50m of 0.8mm cable would be ~1.7-2volts… which seems like a lot … would you combat this by starting with a higher voltage? say 14V? or that’s not really an option?
Think the ‘push to exit’ button needs to be hard wired? Or having a wireless button/switch through HA would be suitable? I guess it depends on where the fire starts… hrm, definitely things to consider, thanks everyone.
Think of it that way: A normal Hairdryer has wire with a high resistance. You put 1000W of electrical energy in there and the wire becomes so hot, that you can dry your hair with the air fanned trough it. In this scenario, you are “loosing” 1000W in the wire. @nickrout calculated a “loss” of energy in the wire of 0.3W which is not even going to warm up the wire, so no problem.
Well the “Push to exit” button is the emergency scenario, if some part of the automation (sw or hw) fails. If you wire it in HA, it becomes part of the automation, thus it becomes part of the problem, not the solution.
With hardwireing it, you are creating a safety circuit that makes sure that the doors are openable in any (?) given scenario and are not locking someone in.
You want it hard wired, and if at all possible illuminated. Imagine finding and operating a small wireless remote while taking in lungfuls of thick dark burning couch smoke.
This is not legal advice, your jurisdiction likely has regulations pertaining to this. In the US this is generally phrased like “All exit doors must be easily opened from the interior without the use of special knowledge”. A big lit up “PUSH TO EXIT” button can be argued is NOT special knowledge.
If you are worried about the voltage drop, most GOOD industrial 12V supplies allow you to adjust the voltage up a little bit, so that you can get 12V at your load (magnets). The Meanwell DIN supply I use allows you to adjust up to 14VDC, you can see the little screw pot on the front “ADJ”.
How far away would the power supply be? Do you know what type of wire you would use? Given this we could estimate voltage drop. This must be factored into the circuit design but likely won’t be a big issue.
Are you in 120V land or 240V?
Thinking it would maybe be 20m or so to the magnets, not sure what size writing would be at this point.
240v here in NZ.
With those DIN modules, can you run several locks (in parallel) off the same source, nothing that the one you liked was 10A, which would be enough for several. Or is that a bit of a no no?
Thinking of I have to have an exit button next to the door, that might be a good place for the Transformers and Shelly’s etc? Just the heat/ventilation issue at that point I guess?
I run multiple locks off of the same 12V supply, it is fine to do so. I run 2 per supply, because I switch the input to the supply to operate the locks. A 10A supply you could probably run 15, of them. Having lots of capacity headroom is fine.
At 20M, 20AWG (not sure what nz uses) would be a fine conductor to use with 1A of current. Won’t hurt to go larger conductor (other than your wallet), but it won’t enhance safety.
The problem putting it in the wall is you’ll need to be able to access the equipment. That is going to end up being a fairly large junction box that’ll be pretty ugly. You do not want to bury anything in the wall without access. Drawing 0.5A from a 10A supply it wont generate much heat.
Ok so I’m now thinking of:
1x 240v -> 12v 10A DC DIN module (in switchboard)
1x Shelly RGBW2 (in switchboard next to Driver) - Looks like this can control 4x12v channels independently, even if I won’t use the dimming function
4x 180kg Magnetic locks (2 sliders, 2 normal doors)
4x ‘Push to exit’ type button - connected in series wih magnets
lots x tiny wire (0.5-0.8mm?) - for feeding chickens
Having been through the Chch earthquakes, there were weeks without power and we had to leave our house. I would have been gutted to leave them unlocked. However even a power cut in the middle of the day for a couple of hours would leave you vulnerable.
So I think you need a backup system like a UPS, and you need other backup locks for when you have to be away for a while or there is a disaster.
We’ll still have the standard locks they’ll install with the door, this is more for additional peace of mind to auto lock everything at the end of the day.
Did suggest to wife we could remove all the standard locks, bit not keen…
Any reason you wouldn’t just use an electric strike designed for a sliding door? Doesn’t require power all the time and is always fail safe as all you do is use the existing unlock (key, lever) if the strike fails.
I worked in a building with a magnetic lock for years. It’s an odd thing for sure. We’d get bad storms that would blow through over the weekend, knock out power, and blow the door open. Eventually maintenance started manually locking the door at night. And yeah, a push to exit button is a must. Make sure it is hardwired and easy to find in the dark.