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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #1  
Old 09-06-2009, 06:35 AM
johntee johntee is offline
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Default wiring Relays, in an RFID door access system

Hi Folks. I’m hoping someone can provide me some direction in my (stalled) project.
I think I’ve bought all the parts I need, but I’ve managed to completely confuse myself when it comes to a couple of the wires…

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Access Control Unit: I have an RFID Access control unit (where you swipe an Radio-Frequency ID tag near the reader to gain access into the building). Once it verifies that it's a valid tag, I want to trigger 2 things -- (1) buzz the electric door strike for a few seconds to unlock the door, and (2) turn on the lights in the room for a period of about 10 minutes.

It's an off-brand access control unit (but it had most of the features I was looking for at a good price), and it seems to be made by KAWA, model #MG236C. The unit and its built-in Lock Relay output are 12VDC. It’s already programmed to buzz the strike for approx 5 seconds.

The manufacturer told me to “connect the 12V +ve and Ground from power supply to the +12V and GND terminal respectively. Then if you have NO type strike, connect to the NO and DGND terminal.”

------------
Door Strike:
The door strike is 16-24VAC. I have a doorbell transformer that can put out that voltage.

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Relay to feed Door Strike:
I bought from factorymation.com this relay:
782XBXM4L-12D Magnecraft Electromechanical Relay, "Ice-Cube" Style, 16A DPDT, 12VDC Coil Specs
And the socket for it:
70-782D-1 Magnecraft Relay Socket, 8-pin Cube Style, 2 Pole, 16A, 300V, IP 20 (Finger-safe) Specs

FactoryMation told me: “The 782XBXM4L-12D relay requires a 12VDC signal between terminals 13 & 14 (referred to as the coil) to energize.
When energized the normally open set of contacts between terminals 9 & 5 will close. You will use this open set of contacts to switch the voltage required by your load.”

------------
Time-Delay Relay to feed regular 120VAC lighting circuit:
I bought: 822TD10H-UNI Magnecraft 10 Function Programmable Time Delay Relay, 15A DPDT, Universal Coil Voltage 12 - 240 VAC/VDC Specs

FactoryMation told me: “You will need to connect a separate power supply to the 822TD10H-UNI for control power. This power supply voltage( 12~240V AC/DC) needs to be connected to terminals A1 & A2.
When energized the normally open set of contacts between terminals 15 & 18 will close. You will use this open set of contacts to switch the voltage required by your load.
The timing signal needs to be a dry contact (no external voltage) between terminals S & A1.”

After a follow-up question by me, he said: “In order for the timer to work, the voltage that is applied to terminal A1 needs to be connected to terminal S, typically through some type of external switch.”

Then after a further question by me he said: “Yes, A1 & A2 are used to power the timer.
You CANNOT use an external voltage to control the timer. The S input must be connected to the A1 input (through a switch or a relay contact) to start the timing sequence.”

This time-delay is where things really got confusing for me… I figured that the time-delay relay needed a separate power source even after the 5-second signal had stopped (that makes sense, so it can keep counting down). But he’s saying now that it has to be the SAME power as the Signal? That part I just don’t understand. (In his first answer, he even said “you will need to connect a separate power supply…for control power.”)

Here’s my drawing of the various components, with my attempt at the wiring.
If anyone could give me the correct wires to connect, I would be so appreciative!!

Does polarity matter on 13 and 14? Did I get the polarity right on all the other wires?

Do the 9&5 pair and 15&18 pair care which terminal of the pair is the input and which is the output? Or is there a protocol for that?

(I decided to buy Double-Pole relays so that I could eventually expand the controlled functions, once I started to realize how cool relays are! But right now I’m just looking to control one function for each of the relays -- feed the door strike from one, and turn the lights on for 10 minutes with the time-delay relay.)

Thanks in advance for helping me get this project back down off the shelf!
John
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  #2  
Old 09-06-2009, 10:01 AM
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williamj williamj is offline
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johntee

The way your sketch shows the S and A1 connections, tells me that they are recieving signal voltage from the access control unit. If S and A1 are to be "dry contact (no external voltage) then this is incorrect.

"A1 & A2 are used to power the timer. You CANNOT use an external voltage to control the timer. The S input must be connected to the A1 input (through a switch or a relay contact) to start the timing sequence.”

Try connecting S and A1 to 12 and 8 on the 782XBXM4L-12D Magnecraft Electromechanical Relay.

Not only do I hope this helps I hope it works.

williamj
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  #3  
Old 09-06-2009, 06:46 PM
johntee johntee is offline
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Wow, you guys are good! (And fast!)

In your diagram, Alberto, I had a few questions --

On the Access Control Unit:
So I shouldn't use the DGND terminal as the manufacturer said? Just bypass the Access Control Unit entirely for the Relay's neutral?

Time-Delay Relay:
This is where I'm still confused. Isn't A1 positive, and S is also positive in your diagram? If I'm interpreting the symbol on the relay's wiring diagram right, it seems to show A1 and S as potentially connecting...

That's the part I really don't understand -- how the constant power and the signal power interact in the relay, and the warnings about no external voltage and the need for a "dry contact" (I just don't know what that actually means.)

Below is your diagram with my markings, to help it be more legible to me.
Thanks!
John
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  #4  
Old 09-06-2009, 09:26 PM
johntee johntee is offline
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Hi Alberto.
Was I interpreting the symbol on the Time-Delay relay's wiring diagram right? Are A1 and S potentially connecting to each other?


Here's some info on the Access Control Unit:
Pic of unit

Specs

Pamphlet Page2-4

Pamphlet Page5-7
Thank you!
John
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  #5  
Old 09-07-2009, 12:36 AM
johntee johntee is offline
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OK, so A1 and S never connect to one another, even when the Signal comes from the Access Control Unit... So it makes sense to you, with A1 and S both being positive? (I don't want to blow out the Time-Delay Relay; it was pretty expensive.)

I like that you added in those protective features (diode and fuse). A couple questions about them --
What parts of the system is the Diode actually protecting? Is the Access Control unit protected if the diode is located on just the one leg of the wire that feeds #13? (i.e., couldn't a spike from the 782XBX relay travel right back to the N.O. terminal?)

What kind/size of diode is it? (I couldn't find any Google results on "1N4UU4".)
What kind/size would the fuse be? (Note, it's only a 120VAC circuit, not 240V as you originally had in the diagram, and it will be run in 12/2 wire (20-Amp circuit breaker).)

What's the appropriate gauge of wire to use for all these 12V runs?

Thank you!!
John
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  #6  
Old 09-07-2009, 08:56 AM
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williamj williamj is offline
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Alberto,

Just or my edification, wouldn't putting A1 to S through the second set of contacts(8,12), in the 782XBX relay, eliminate the need for an additional componet (the diode)?

williamj
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  #7  
Old 09-24-2009, 03:32 PM
johntee johntee is offline
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Default A set-back...

Hi Alberto... I began wiring all the various components last night, and I started with just the 12VDC transformer connected to the Access Control Unit.
I had first tested with a multimeter the 2 black cords that come out of the 12VDC transformer (since the wires weren't marked as to positive or negative); when I got a Positive voltage reading (rather than a Negative one of the same amount), I marked the cord connected to the Red probe as Negative, and the other as Positive.

These wires got connected to the GND (Red wire) and +12V (Black wire) terminals of the Access Control Unit. When I plugged in the transformer, the Unit made a soft clicking sound after a second (almost like it was activating itself in some way), but after about 3-4-5 seconds, it made a sizzle and a puff of white smoke came out...

Did I get a bad unit, or did I reverse the wires? The red probe is on the multimeter's VQ port and the black probe is on the COM port, and now I'm starting to second-guess myself... Did I just fry the control unit?

Thank you!
John
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  #8  
Old 10-05-2009, 02:05 PM
johntee johntee is offline
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Hi Alberto. Could you check your private messages for a question from me?
Thanks!
John
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  #9  
Old 02-13-2010, 06:17 AM
johntee johntee is offline
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Quote:
Originally Posted by Alberto View Post
williamj, the diode is there as a clamping diode in parallel with the relay's coil to prevent damage to the devices connected to the +12 Volts rail, by suppressing the voltage spikes caused when the inductive load is turned OFF. (Known also as Flywheeling Diode)

Removing the Flywheeling Diode (cost of the diode is negligible compared with the cost of the other units) is not recommandable, unless you remove the inductive load (the relay)

Alberto
Hi guys, and especially Alberto... I'm finally getting to wire up this circuit, and using the multimeter I found that the N.O. terminal on the Access Control Unit is actually a Negative. (In Alberto's schematic, it was assumed as Positive.) I've altered the schematic, and utilized the 2nd set of contacts in the 782XBX relay to feed a burst of Positive over to the S terminal on the Timer Relay (since the older schematic would actually have been sending Negative to terminal S).

Could you take a look at it and see if I've covered everything? Also, does the clamping Diode need to be reversed in its directionality now? (Since 13 and 14 switched polarities in the revised diagram.)
It seems like the Diode is not in a position to protect the Timer Relay now. Do I need to add another Diode down there? If so, where and in what direction should it allow flow?

Thanks all, as always!!
John

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  #10  
Old 03-03-2010, 08:36 PM
tattooekaos tattooekaos is offline
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hello John

I am a total newbie when it comes to electronics and building circuits and things, but I am going to be starting a similar project very soon. I live in an apartment building, so I am unable to modify the door jamb to allow for the electronic striker, so I am working on building a device the will kick on a linear actuator that will drive gears to turn the deadbolt from the inside. I also want to be able to have it turn on my main living room light when it unlocks the door.

I am at a loss so far at understanding a lot of the stuff involving relays and switching, building the box and a the actuator and gears is much more my style, but I am a big tech geek and always love to learn things. I believe I have purchased the same kawa rfid controller keypad that you have. I am hoping that you can give me some advice and some help, bc I am often carrying a lot of stuff when I come home and being able to just wave the fob and push the door open with my light already on would be amazing!

I hope your project has gone well, and any advice or help you can give would be greatly appreciated!
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