Electrical power question (two power wires for one camera)

[dirtymoney]

In my vehicle's particular electrical setup I have both an DC electrical outlet that turns on when the vehicle is started and another that is always on.

I would like to have the ability to have the camera turn on when my vehicle starts.... AND be able to turn it on when I want to when the vehicle is off. Specifically so I can easily record any interactions with the police after I have been pulled over for a speeding/traffic violation and I have to turn my car off.

How would I best go about this? Would two power wires to the camera cause any kinds of damage or problems? I figure I could wire in a toggle switch between the the camera and the "always on" electrical outlet and flip it when I turn off my vehicle. Would there be any damage if it was accidentally flipped on when the camera was being powered by the "on when vehicle is running" power outlet?

 

[albertson]

Need to keep the two power sources separated from each other.
Use a Single Pole, Double Throw toggle switch. On-On settings.
Something like this http://www.waytekwire.com/item/44202/TOGGLE-SWITCH-BLACK-NYLON-20A/
You can find it in typical auto parts stores. Check the amperage rating is enough for your camera.
The ignition source goes to one side. The battery power to the opposite side of toggle switch. The common center terminal goes to your dash cam to connect deliver power to the cam. During the switch motion, the cam may shut down and restart, due to the temporary loss of power. Depends on the camera.

 

[abarth]

yup the switch idea will definitely work. I had a switch mounted for my 0801 connected to the always hot wire so I could have a pseudo-parking mode. the problem was that there were a couple times I forgot to switch it off when I was leaving the car for an extended amount of time. I'm just glad I carried a portable battery pack in my hatch to jump start my car in those events. might just be easier to buy one of those battery discharge prevention devices if your DashCam doesn't have true parking mode.

 

[kuoh]

You can add a cheap relay and resistor for less than $5 to power the camera so it will automatically shutdown when the voltage gets too low, sort of a poor man's Power Magic. A variable resistor would allow you to fine tune the cutoff voltage, but would cost a couple of bucks more.

KuoH

the problem was that there were a couple times I forgot to switch it off when I was leaving the car for an extended amount of time.

 

[abarth]

that's a really great idea. I would definitely like to see the schematics for that setup. my Lukas 7200 up front has true parking mode but would be interested in that setup since my mini 0801 is now my rear camera.

 

[kuoh]

Here's a simple circuit I just drew up, there may be other more efficient layouts. If you just use the bottom relay, then the coil is always drawing current when the switch is engaged, but there are ones that can draw less than 100mA, which would be ok in most cars for a couple of days. If you chose to use both relays, then remove the resistor, switch and 12V for the bottom relay and wire the N.O. directly to the coil input as well as the output of the upper relay, as indicated by the dashed line. The advantage of this setup is when the voltage cutoff is reached, both relays disengage and no longer draw any current. If you chose your relay and resistor values carefully, or use a variable resistor, you should be able to adjust the cutoff voltage to anything you want. It's not going to be extremely precise, but it will at least keep the battery from draining to 0V. I can't give exact resistor values, as it is dependent on coil characteristics of the relay you choose. A simple LED can also be added to remind the user to hit the kill switch.

You can reduce this to a single relay if you're willing to use a couple of diodes, but some dashcams may not like the voltage drop that setup imposes. You can also use simple voltage comparator ICs and get more precise control, but that would increase build complexity and cost to the point where buying an existing product might be more appealing for most people.

KuoH

 

[xPosTech]

I think a diode across each winding of the relays would possibly save the camera's (and any other nearby electronic circuits) from the back EMF pulse the coils would generate when the relays are turned off. The magnetic field collapsing through the winding is what generates it - just like the ignition coils firing the spark plugs on your engine.

Ted