Relays

[cliff123]

This should go into the Security section but i notice it is restricted, but can anyone explain how on a access control system the following works

(REX) inputs are designed to operate a relative relay output when
selected.
The request to exit function is activated when a zero volts signal is
momentarily presented to the REX connection. This in turn
activates, the relative relay output for a timed period.​

It seems that a Relay is activated by zero volts​

Regards​

Cliff​

 

[Darkwood]

i can only assume the brains behind the access control is some kind of plc that has be programmed to energise relay if 0volts present at mentioned input, how these operate is varied aqccording to the manufacturer and model

 

[pmac10]

it is using an NPN tranistor to energise a relay. if your unfamiliar with basic electronics imagine a relay with say 24v connectted to A1 while A2 is open circuit, whatever your input is, turnns on the transistor and this in turn connects A2 to 0volts and so current flows in the coil energising your relay, hope this helps.

 

[cliff123]

Many thanks for that as you say i have very little knowledge of electronics, would you be able to reccomend a good book to get me started.

 

[pmac10]

anything by john c morris, analogue electronics, digital electronics, applied electronics, preferably in that order. hes easy to understand and his example circuits actually work if you have the facilities to build them. as youre a spark youre definitely not a beginner.

 

[cliff123]

I am actually a locksmith who does access control, but i am a Part P domestic Installer and have the 17th addition 2382 , but I would like to know more about how the access control systems actually work as their are so many different manufacturers. and fault finding is a big part of my business.

I have ordered the first book as you sugested

Do you know how I can gain access to the Security section of the Forum

many thanks for your sound advice

Cliff

 

[pmac10]

im an industrial maintenance engineer and fault diagnosis is my bread and butter (and stops me getting sacked). i have very limited knowledge of access systems but a system is a system no matter what application, ie input, process,output. each manufacturer should supply you with the relevant technical manual and description of operation. if you know in theory how electrical, electronic and mechanical systems work, and without trying to teach you to suck eggs, you will be able to look at a system and say, "whats is happening??", what is not happening that is supposesd to happen?? and finally, what component is supposed to make that happen???. by know you should be testing the functionality of your first suspect part, if its ok trace back etc,
again i dont know your circumstances so i dont mean to sound patronising, but i have diagnosed faults on our companys access control systems using the above thought process, manufacturer's description of operation,and a wiring or pcb diagram.
hope this helps and john c morris will be better able to fill you in on npn and pnp transisitors.

 

[Paul P]

For some reason most intruder alarm and access control systems switch the negitive for stuff to operate(latch relases,bells. etc). It is simple electrical theary they just break the neg insted of the pos. Lets face it we only switch the like for safty reasons not functional. 12v is not going to be a safty issue.

 

[Gerry24]

I am actually a locksmith who does access control, but i am a Part P domestic Installer and have the 17th addition 2382 , but I would like to know more about how the access control systems actually work as their are so many different manufacturers. and fault finding is a big part of my business.

I have ordered the first book as you sugested

Do you know how I can gain access to the Security section of the Forum

many thanks for your sound advice

Cliff

Hi Mate,

I am also a locksmith who does a bit of access control stuff. I did a 3 day training course with these guys Tavcom Training - the UK's leading security systems training company when I first started doing access control stuff and it helped me get my head round some of the electronic stuff. They do BTEC accredited courses and they do a 3 day foundation access control course and a 3 day advanced access control course. If you've been doing access control for a while you might think the advanced course is better for you. BTW these courses are not in any way similar to the many Micky Mouse locksmith courses that have been set up over the last few years, which I am sure you have read/heard about in the lockmith industry. Tavcom is a proper training organisation with properly accredited courses.

In answer to your original question. I haven't come accross that particular form of words before. Try giving Advanced Access a call on 01604 647555 as I have found their technical guys to be very helpful in the past.

And when you find out how to get onto the Aceess Control/Security Systems section of the forum let me know too.

 

[pmac10]

For some reason most intruder alarm and access control systems switch the negitive for stuff to operate(latch relases,bells. etc). It is simple electrical theary they just break the neg insted of the pos. Lets face it we only switch the like for safty reasons not functional. 12v is not going to be a safty issue.

is that like breaking a circuit instead of breaking the circuit??? its current sinking and current sourcing electronic devices.

 

[Paul P]

is that like breaking a circuit instead of breaking the circuit??? its current sinking and current sourcing electronic devices.

Sorry I dont understand.

 

[pmac10]

didnt think you would, your speculating about things you dont understand, im just advising a forum user.