Close a circuit for a second to control a buzzer, to be powered & controlled via landline telephone

Thread Starter

Moses123

Joined Jan 10, 2019
10
Hi all, I'm new here so sorry if I act like a newbie.

I have a security gate that is opened via a computer software, it's a complex system that only allows entry for members to the area at certain times of the day, it allows you to self-pay your membership on that computer etc.

So the software developer showed me that when I signal a specific Port with a -5V current for a second the computer gets notified, & it sends a signal to unlock the door. It can also be done via closing a circuit (closing the output of that Port with the input)

So I want to install a telephone line, that when it gets a call, it should close the circuit for a second, then right away release the circuit.
(In case of emergency, the managers should be able to open the door remotely with a phone call to a specific number)

Basically I'm looking for relay that gets powered when the telephone is supposed to ring, bit the relay should only close once & reopen after a second, or remain closed till the phone finishes sending ring pulses.

I researched for a telephone powered relay, but only found relays that close & open with every ringi. If it closes the circuit with every ringr then the computer will get a few signals to open the door, whilst I only want it to open once.

So please if anyone knows of a relay that does the above mentioned, please reply.

Thanks in advance
 

Ramussons

Joined May 3, 2013
797
Why not trip the ring when the relay closes the first time using an auxiliary contact? There will be no more "rings" till the phone is called another time.
 

Thread Starter

Moses123

Joined Jan 10, 2019
10
Why not trip the ring when the relay closes the first time using an auxiliary contact? There will be no more "rings" till the phone is called another time.
Thanks for replying

can you please elaborate? or tell me specifically which device to use? (best would be if the device can be powered from the phone line, not requiring external power)

I checked this, but this gets activated every ring, so they have this that you can make for that they relay should close for 6 seconds, hence making it 1 long contact, but this requires external power, & it makes the cotact for a minute, & I would prefer to have it only for a second.

Also thinking of this, but i gotta figure out if the ringer is isolated , & does not have any contact with the 12v power(its probably isolated but i goota make sure) (as more then 5v can burn the computers motherboard


Thanks in advance
 
Last edited:

tranzz4md

Joined Apr 10, 2015
310
Well, it does take time for the gate to open. I'd think that an ordinary dry contact relay would do the job. Sure the "ring" will generate multiple momentary contact closures, but it will stop before the gate is even open, and the software SHOULD handle multiple requests in fast sequence as a single opening.

My recollection is that ring voltage is 90V, pulsed DC. It should be easy to find a relay that will work on that.

You could also use that device which gives a long pulse, connected to an on-delay relay. Using an N/C contact, you could get a pulse as long as your delay setting.
 

Thread Starter

Moses123

Joined Jan 10, 2019
10
Thanks for replying.
Well, it does take time for the gate to open. I'd think that an ordinary dry contact relay would do the job. Sure the "ring" will generate multiple momentary contact closures, but it will stop before the gate is even open, and the software SHOULD handle multiple requests in fast sequence as a single opening.
Computer opens door almost instantly, so this will send multiple requests to open the door.
My recollection is that ring voltage is 90V, pulsed DC. It should be easy to find a relay that will work on that.
Can you please link to a cheap one that will work.
it could also use that device which gives a long pulse, connected to an on-delay relay. Using an N/C contact, you could get a pulse as long as your delay setting.
Can you please elaborate?

Thanks in advance
 

sghioto

Joined Dec 31, 2017
1,038
Here's one possible solution. The circuit should operate the relay when the first ring comes through then seize the phone line at the same time. This will stop the ring signal at which point the relay will drop out quickly.
The component values for R and C are starting points using the recommended relay available from Mouser # 655-7-1462039-5, most likely will need tweaking. I don't have a land line at my house so can't verify operation.
SG
EEE telephone ring operated relay.PNG
 
Last edited by a moderator:

Thread Starter

Moses123

Joined Jan 10, 2019
10
Here's one possible solution. The circuit should operate the relay when the first ring comes through then seize the phone line at the same time. This will stop the ring signal at which point the relay will drop out quickly.
The component values for R and C are starting points using the recommended relay available from Mouser # 655-7-1462039-5, most likely will need tweaking. I don't have a land line at my house so can't verify operation.
SG
View attachment 167732
Seems like your on to something, but i'm a real newbie in this, so I don't get exactly what you mean
 

sghioto

Joined Dec 31, 2017
1,038
Seems like your on to something, but i'm a real newbie in this, so I don't get exactly what you mean
Like I said without a telephone line I cannot confirm the values of the components shown.The schematic is a starting point with the specified relay listed. I guess will depend on your skill level to assemble the circuit.
SG
 

Thread Starter

Moses123

Joined Jan 10, 2019
10
What I am trying to get to is why not do this wireless ? What is max distance
control point to gate ?

Regards, Dana.
i would like to be able to call in a phone number from anywhere in the world & it should signal the computer to open the gate
 

danadak

Joined Mar 10, 2018
3,682
Then this is a classic phone line interface where an intelligent
part answer the ring, takes line off hook, and decodes touch
tone to discriminate crank calls from legit call.

Ramsey Electronics made a kit, TT7, that would do this. They went out
of biz 2 years ago, but you might be able to find one on web. Key component
was MC145436 tone decoder. Here are the kit instructions -

http://www.repeater-builder.com/ramsey/pdfs/tt7-touch-tone-decoder.pdf

Here is a manual with additional info. A closeup shot of PCB, maybe you
could deduce a schematic from it.

http://na5b.turkkonferans.org/TA2DC/RAMSEY ELECTRONIC/TT7 Touch-Tone Decoder.pdf

Alternative is to use a UP to detect ring and decode tone(s).

Here is another possibility - http://www.cermetek.com/catalog/telephone-line-interface/datasheet/xe0068dtrevc.pdf

https://www.futurlec.com/Mini_MT8870.shtml


Regards, Dana.
 

djsfantasi

Joined Apr 11, 2010
5,829
i would like to be able to call in a phone number from anywhere in the world & it should signal the computer to open the gate
Ok, someone had to ask. And I’m sure you have a very good answer.

Why not a cell phone? You can ghost a signal from the vibrating motor, which can be used to trigger the gate. In some circles, this seems to be a popular solution. Although researching it might bring a law enforcement agent to your door.

So far, this solution satisfies your requirements. Remote control of the gate, accessible from anywhere in the world.
 

Thread Starter

Moses123

Joined Jan 10, 2019
10
Ok, someone had to ask. And I’m sure you have a very good answer.

Why not a cell phone? You can ghost a signal from the vibrating motor, which can be used to trigger the gate. In some circles, this seems to be a popular solution. Although researching it might bring a law enforcement agent to your door.

So far, this solution satisfies your requirements. Remote control of the gate, accessible from anywhere in the world.
cellphpne requires a plan... PSTN i get free from obi
 

djsfantasi

Joined Apr 11, 2010
5,829
cellphpne requires a plan... PSTN i get free from obi
A cheap throwaway phone doesn’t require a plan. You prepay for x number of minutes of usage. In your application, I don’t see a ton of usage and a prepaid plan for a few minutes likely will last you a long time.
 

MisterBill2

Joined Jan 23, 2018
4,472
What you need tor docoding a signal on a phone line to unlock the door is a DTMF decoder. I purchased 3 of them last year on line for less than $10, including shipping. The only problem is that they come with NO information at all, such as what the signal voltage must be, both minimum and maximum voltages. The output is 4-bits binary. So you use an and gate to detect when the chosen digit arrives and trigger the door unlock driver..The big challenge is determining the required signal voltage, and how to get that from the phone line while avoiding that 16Hz 100 volt ringing signal.
 

Ramussons

Joined May 3, 2013
797
Thanks for replying

can you please elaborate? or tell me specifically which device to use? (best would be if the device can be powered from the phone line, not requiring external power)

I checked this, but this gets activated every ring, so they have this that you can make for that they relay should close for 6 seconds, hence making it 1 long contact, but this requires external power, & it makes the cotact for a minute, & I would prefer to have it only for a second.

Also thinking of this, but i gotta figure out if the ringer is isolated , & does not have any contact with the 12v power(its probably isolated but i goota make sure) (as more then 5v can burn the computers motherboard


Thanks in advance
Use 2 of these (https://www.vikingelectronics.com/product_docs/DOD/406.pdf) in parallel.

Use terminals 6 and 7 of First to trigger your system
Connect 6 and 7 of the second to the telephone Lines.

When the Ist Ring is received, both the relays operate, 1 triggers your system, the second extends a loop to the exchange to trip further rings.
 

MisterBill2

Joined Jan 23, 2018
4,472
You really need more than just a ring signal to unlock the door, at least in the USA you do. We get huge amounts of calls from marketers and mostly scammers, 5 to 10 calls every day. So the door would be frequently unlocked, not a good condition. Adding a single DTMF tone, or multiple DTMF tones, would assure that all unlock commands were only from one who knows the code. perhaps the arduino can detect DTMF tones??
 

djsfantasi

Joined Apr 11, 2010
5,829
You really need more than just a ring signal to unlock the door, at least in the USA you do. We get huge amounts of calls from marketers and mostly scammers, 5 to 10 calls every day. So the door would be frequently unlocked, not a good condition. Adding a single DTMF tone, or multiple DTMF tones, would assure that all unlock commands were only from one who knows the code. perhaps the arduino can detect DTMF tones??
There are DTMF shields for the Arduino. Here’s one, for example.
https://www.dfrobot.com/product-1150.html?gclid=EAIaIQobChMInJmYua_v3wIVA4_ICh34BAuKEAQYASABEgJqDPD_BwE
 
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