12v AC/DC supply for door intercom/access system

18 Apr 2007
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United Kingdom
I have a door intercom system and door access system that I plan to use on the same door.
The door intercom system is basically one intercom outside the door and a handset inside the door. The handset has a lock release button to operate the electronic lock on the door. This system runs on 12v AC
The door access system is a keyfob unit outside the door that is designed to operate the same electronic lock as above using a keyfob or keycode. This system needs 12v DC.
Can I use one 12v DC supply to operate both the intercom and access system? i.e will the intercom kit (& electronic door latch) operate ok on 12v DC rather than AC?
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Quick answer is NO

The door lock coil is designed to work on AC. It is a coil with inductance and therefore has a higher impedance ( resistance ) to AC than it does for DC Running it on 12 volt DC would mean a higher current and possibly overheating of the coil.
Would the intercom system itself be able to support DC? If it did, presumably if I replaced the door latch with a DC version this might work?
depends on the intercom.

if it were me (and it isnt) i would have one supply for each, which is what they are designed to run on, that way you only have to install it, not fiddle with it
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The only problem then is I would need to have two separate door latches on the door operated by AC/DC voltages. They would also need to operate at the same time to open the door. Unless there is a door latch which supports 12v AC/DC ?
why not use a relay on one to operate the door release on the other?

please don't tell me this is for your front door?
This is for an office door. The idea being that the intercom will be used for visitors with the door latch operated by staff using the handset inside the office.
The door access fob system will be used by staff to open the same door latch to open the door using their designated keyfobs. The problem I have is that the door has one (AC) latch which ideally I want to operate using both the intercom and access fob system.
Worse case is to use separate AC/DC power supplies for each but change the latch to DC so it can be used with the fob system. The intercom would just then be used as an intercom and not be able to open the door remotely.
what does the door release hold onto?

most of the time they hold onto standard yale type lock, if so perhaps if they all had a key?

or why not get the fob output to operate a relay as i suggested?
first you need to do is my line of work
you will need a couple things
1. 24 Vdc transformer
2. AC DC converter 24V - 12V
3. if i were you ,i would use a remote for both ,easier to change a battery,and put a relay to the alarm, i have a schematic for for this .
4. BEA MC 25 ( can order at local electricians supply store)
5. 18 ft. 18 gauge insulated wire(need 2 different colors or use 2 colors
electrical tape.
6. 2- 24VDC RELAYS
7. A CONTROL TRANSMITTER your job is find out what kind you need for your app. if you cant find something just mail me and well figure something out it depends also on compatibility of your receivers on this system where might also need a separate relay for those as well .
mail me
thinking about too many things, sorry
you will 2- 12vdc relays and 12 v dc transformer and transmitter ,12v AC DC
converter (5.00) very cheap
you may need to wire in receivers for both units and but can be done,without much issue and the door coil will be fine they can have long term issues but you will get 2- 5 yrs from any product because preventive maintenance is required on all electronics but the issue is moot because you need it and it seems easier this way
careymark24, you over complicate things, and considering that pls1 (the OP) asked over 1 year ago i dont think it matters, please read the date before you post a reply.

For what its worth pls1 has not posted for the last 5 months

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