Need a relay 12v activated to connect 120v and stay on after 12v goes off

Thread Starter

larryjbjr

Joined Jul 8, 2023
4
Ok, so I'm a newbie here just trying to solve a problem and looking for some help. Not an electrician, though I can do my own basic home/auto wiring no problem. I'm actually more of an IT person....

Anyways, I have a setup I'm trying to do for our small business fueling station. I want the drivers to be able swipe an RFID card to turn on the fuel pump for about 10 minutes while they fuel up, then turn off. Mostly to stop honest thieves, not necessarily Ft Knox tough.

I purchased an RFID keypad and 12v power supply like people use to unlock a door. But, the power supply only has a max time of 15 seconds. So I purchased a timed relay, but when I went to set it up it dawned on me that once the 12v power turns off then the timed relay turns off too. Duhhh... kind of a facepalm moment....

Anyways, the more I thought about it the more I realized that I have no idea how to send 12v to activate a timed relay but keep the relay active after the 12v goes away.

Is there such a relay that can do what I need without breaking the bank?

Here are the items I already purchased. Any way to make these work, or do I need to start over from scratch? I do have a small budget for this system of $500 or less.

https://www.amazon.com/dp/B0BXL5QV1R?psc=1&ref_=cm_sw_r_cp_ud_ct_AV6VV1WR87K2W7WY8KNA

https://www.amazon.com/dp/B00V55INJE?psc=1&ref_=cm_sw_r_cp_ud_ct_AV6VV1WR87K2W7WY8KNA

https://www.amazon.com/dp/B07CGB9XRD?psc=1&ref=ppx_yo2ov_dt_b_product_details
 

geekoftheweek

Joined Oct 6, 2013
1,223
Would it work to wire your relay into the NC connection of your power supply and set the timer to less than one second? Every time your keypad is triggered it would cause the power supply to break the relay power and cause it to reset.

I know it's not ideal and would cause the relay to always be powered and timed out, but in my mind it would work other than if you loose power or for whatever reason the relay resets it will provide power for a short time.
 

Tonyr1084

Joined Sep 24, 2015
7,905
If you want a relay to provide 12V for 10 minutes then you need a power source that will provide that for the period of time desired. At first I thought of a latching relay, but those need to be de-latched after the time period has expired, which means sending another 12V signal.

What voltage are you wanting to keep powered for 10 minutes? If it's 12 volts then you need a constant 12 volt source. If you want to control that power source (i.e. keep it on for 10 minutes at a time) then you need a timer to control the 12V source.

The system I can imagine is an RFID reader that activates a timer that powers the keypad for a set period of time. But that requires a constant 12V source. When the time period expires the system has to go into sleep mode, otherwise there's no power to reactivate it the next time someone wants to access the keypad. I'm sure others here will have other ideas as well.
 

Thread Starter

larryjbjr

Joined Jul 8, 2023
4
Would it work to wire your relay into the NC connection of your power supply and set the timer to less than one second? Every time your keypad is triggered it would cause the power supply to break the relay power and cause it to reset.

I know it's not ideal and would cause the relay to always be powered and timed out, but in my mind it would work other than if you loose power or for whatever reason the relay resets it will provide power for a short time.
I'm thinking this one through, but I believe you are right. Let me try it.
 

Thread Starter

larryjbjr

Joined Jul 8, 2023
4

Thread Starter

larryjbjr

Joined Jul 8, 2023
4
Would it work to wire your relay into the NC connection of your power supply and set the timer to less than one second? Every time your keypad is triggered it would cause the power supply to break the relay power and cause it to reset.

I know it's not ideal and would cause the relay to always be powered and timed out, but in my mind it would work other than if you loose power or for whatever reason the relay resets it will provide power for a short time.
This worked beautifully on the bench. I am sure it will do what I need.

Thanks again to all.
 

Colevig

Joined Feb 1, 2024
6
Could you break down how i would wire this timed relay to provide power to the fuel pump? If i purchase this relay and adapter and a similar keyed access panel I’m assuming the ground and neutral wire would go direct to the pump and then the hot wire would go to into the com and then would go from the NO to the hot wire on the pump completing the circuit? Other than a box to mount everything in would i need anything else? Sorry i understand 115v wiring but not so much with these switches. I did a similar project using a pair of timers to a relay running a linear actuator for a door to open and close.
 

sghioto

Joined Dec 31, 2017
5,392
Could you break down how i would wire this timed relay to provide power to the fuel pump?
The 115 vac wiring you described for the relay and pump are correct. The relay module requires a 12 volt supply which I'm also assuming will power the keyed access depending on which product you have in mind. Knowing the exact access panel switch will help also.
Wiring would be like this:
1706843901997.png
 
Last edited:

Colevig

Joined Feb 1, 2024
6
Thank you, these are what i was planning to use unless you have a suggestion for the 12vdc power supply that can be direct wired into 115vac. IMG_7283.png
 

Colevig

Joined Feb 1, 2024
6
I would Just need to run the com wire to the relay from the switch correct? No need for the nc, no, open, d0 or d1 wires?
 

Tonyr1084

Joined Sep 24, 2015
7,905
Sounds like a hijacked older thread. Better off starting a thread of your own and start out by describing the goal and the approach you're thinking of taking. It's been almost a year since this thread was active, and it seems like you're taking it in a new direction.

If it has not yet been said; Welcome to AAC.
 

sghioto

Joined Dec 31, 2017
5,392
I would Just need to run the com wire to the relay from the switch correct? No need for the nc, no, open, d0 or d1 wires?
Not sure which wires you are speaking of. Are these wires coming from the Card Reader as I have no info on the wiring without the manual.
 

Tonyr1084

Joined Sep 24, 2015
7,905
Exactly what are your requirements? Do you need a relay to hold a setting for a period of time or are you just using a relay that is controlled by 12V(AC or DC) and the contacts are connected to control 115VAC?
 
Top