# Door buzzer low voltage signal, need longer signal. Would like input on what type of circuit needed.

#### robertcoyne

Joined May 7, 2019
2
Hello. First time poster, hope I'm in the right place.

What I have:
A secured entry door for guests.
A push-button switch behind the front desk to signal the door to unlock
A low-voltage signal.
Obviously it only sends the unlock signal when the button is pressed.

What I want:
The unlock signal to remain on for 3 seconds after the button behind the desk is pushed and released.
This way the receptionist does not have to hold the button down the entire time.

In my mind this seems very simple. I'm hoping someone here can lead me in the right direction.
Do I need a relay? Something more complex?

Thank you!

Mechanically inclined but a circuit rookie,
Robert

#### RPLaJeunesse

Joined Jul 29, 2018
214
Instead of a pushbutton switch you could use a slow-release dashpot that actuates a microswitch. Something like this: https://www.ebay.com/itm/Airpot-2K1...-A2-Switch-and-Mounting-Bracket/351909043315?

To do it electronically would take a timer with relay output, and a power supply for the timer. Or us an industrial timer module that provides an "off delay". Finding something that works with your supply voltage might be problematic.

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#### Bernard

Joined Aug 7, 2008
5,788
Measure V across the switch, then measure the current, give us the results. Just a guess that there is a relay in the circuit so that lock current does not flow thru PB SW?
Is V supply AC or DC ? A big IF there is a relay & reasonably high impedance & a V common is available, then might just add a high value capacitor across relay coil.

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#### Wolframore

Joined Jan 21, 2019
2,549
Monostable 555 with 3 sec pulse.

#### SamR

Joined Mar 19, 2019
4,294
He already has all the wiring and devices in place. I used to do that with 120VAC octal base delay relays. Not sure if it is available for low voltage. What is the circuit voltage???

#### Wolframore

Joined Jan 21, 2019
2,549
He said low voltage signal, but good question

#### SamR

Joined Mar 19, 2019
4,294
For less than $30USD you can buy an OFF-Delay timer relay to match 5-24VAC. When the door button is pushed and released it holds the circuit on for the set time and then goes off and de-energizes. Just mount it under the desk near the button and use the existing circuit to insert it into. Thread Starter #### robertcoyne Joined May 7, 2019 2 Instead of a pushbutton switch you could use a slow-release dashpot that actuates a microswitch. Something like this: https://www.ebay.com/itm/Airpot-2K1...-A2-Switch-and-Mounting-Bracket/351909043315? To do it electronically would take a timer with relay output, and a power supply for the timer. Or us an industrial timer module that provides an "off delay". Finding something that works with your supply voltage might be problematic. Thank you for the suggestion. I'll run those switches by my boss and see what he thinks (meaning, does he want to spend$30 on something he doesn't necessarily "need")

Measure V across the switch, then measure the current, give us the results. Just a guess that there is a relay in the circuit so that lock current does not flow thru PB SW?
Is V supply AC or DC ? A big IF there is a relay & reasonably high impedance & a V common is available, then might just add a high value capacitor across relay coil.
Haven't had the time to measure anything yet. I'll get back. Thank you for the response.

He already has all the wiring and devices in place. I used to do that with 120VAC octal base delay relays. Not sure if it is available for low voltage. What is the circuit voltage???
As above, I'll have to get back with the voltage. It's been hectic since I posted, but appreciate the input!