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I've been thinking about setting up a timer relays for my cameras as a way to leave them running when the car is left in a parking lot while precluding forgetting them on overnight and draining my car battery. After a lot of research and learning about relays, I figured out that the best way to accomplish this is with an off delay relay which can connect devices to battery power when energized by ignition power, and wait a set period of time before turning off battery power.
After a lot more research I discovered that there are digital relays referred to simply as "timers" that do this but also allow adjustment with buttons. The one unit I could find that could possibly hold up to the temperatures in a vehicle was the Panasonic LT4H-DC24VS which is rated for 55 Celsius (131 Fahrenheit) and it happens that it seems to be the easiest to control as it has a rocker button for each digit. It also has several modes of operation unlike a simple off delay relay. The 24V means it can handle up to 24V DC, and they also make AC versions. The S refers to screw terminals, as opposed to other versions made to fit into special relay sockets. http://www.newark.com/panasonic-electric-works/lt4h-dc24vs/timer-multifunction-12-24vdc/dp/67C7777
The next thing I learned was that the LT4H isn't like a typical automotive relay, it is triggered using a simple switch. So if you were to try to trigger it using the car ignition power, it could be damaged.
I figured that would be a simple obstacle to surmount but it turns out relays are more complicated than I thought. They require diodes and resistors to protect the control circuit because upon switching off the physical motion generates a current in the coil which goes backwards and can be very high voltage! Additionally, automotive relays are bulky and require sockets. I found one relay that is compact, cheap, has built in rectifier diodes to protect the vehicle, and has simple screw terminals--- a model railroad relay made by Azatrax https://www.azatrax.com/track-power-relay.html
The Azatrax relay is energized by the ignition power tapped from the fuse box, which acts as a "start" switch to control the LT4H. The LT4H has tiny dip switches that let you choose between several modes of operation. The one I selected connects the "common" and "normally open" terminals as soon as the relay's "start" switch is triggered. Common is getting power from the a constant power fuse tap. When the Azatrax relay loses power, that opens the "start" switch and the LT4H starts counting down.
Everything is housed in a cubby compartment built in to the fusebox door on my VW Golf. The wires are all gathered with a European terminal block and connected to the fuse box and output wires with a JST SM connector.
It works great and is easy to adjust. If I need to turn everything off immediately, I just press the "reset" button on the LT4H
After a lot more research I discovered that there are digital relays referred to simply as "timers" that do this but also allow adjustment with buttons. The one unit I could find that could possibly hold up to the temperatures in a vehicle was the Panasonic LT4H-DC24VS which is rated for 55 Celsius (131 Fahrenheit) and it happens that it seems to be the easiest to control as it has a rocker button for each digit. It also has several modes of operation unlike a simple off delay relay. The 24V means it can handle up to 24V DC, and they also make AC versions. The S refers to screw terminals, as opposed to other versions made to fit into special relay sockets. http://www.newark.com/panasonic-electric-works/lt4h-dc24vs/timer-multifunction-12-24vdc/dp/67C7777
The next thing I learned was that the LT4H isn't like a typical automotive relay, it is triggered using a simple switch. So if you were to try to trigger it using the car ignition power, it could be damaged.
I figured that would be a simple obstacle to surmount but it turns out relays are more complicated than I thought. They require diodes and resistors to protect the control circuit because upon switching off the physical motion generates a current in the coil which goes backwards and can be very high voltage! Additionally, automotive relays are bulky and require sockets. I found one relay that is compact, cheap, has built in rectifier diodes to protect the vehicle, and has simple screw terminals--- a model railroad relay made by Azatrax https://www.azatrax.com/track-power-relay.html
The Azatrax relay is energized by the ignition power tapped from the fuse box, which acts as a "start" switch to control the LT4H. The LT4H has tiny dip switches that let you choose between several modes of operation. The one I selected connects the "common" and "normally open" terminals as soon as the relay's "start" switch is triggered. Common is getting power from the a constant power fuse tap. When the Azatrax relay loses power, that opens the "start" switch and the LT4H starts counting down.
Everything is housed in a cubby compartment built in to the fusebox door on my VW Golf. The wires are all gathered with a European terminal block and connected to the fuse box and output wires with a JST SM connector.
It works great and is easy to adjust. If I need to turn everything off immediately, I just press the "reset" button on the LT4H