A DC Powerd Lamp
A lot of people have lanterns, Flashlights, and candles for lighting when a power outage occurs. I’ve started building my lamps into my radio power supply so that they’re independent of power mains. In essence, my shack works the same way whether the power is out or not. In this article, I’ll go through my solution and touch on the drawbacks that I was trying to avoid.
The first drawback was battery power lost in converting DC to AC. I could just run a normal lamp plugged into an inverter that is attached to my LiFePO battery bank. This wastes power that is lost in the conversion from DC coming out of the batteries to AC going into the lamp. In order to avoid this loss, I want to keep the entire system on DC power.
The second drawback is the form factor. I want normal lighting without figuring out where to place the lantern or how to hold the flashlight correctly. Lamps are nice because they’re positioned for optimal lighting and can stay there.
To address both of these concerns, I found some 12 volt DC-powered light bulbs. I can put them in the lamp and run the lamp on my battery. I could accomplish this with a simple lamp plug to power poles converter, which would run totally on DC, but would also let me use the lamp with AC power and an AC bulb. However, this raises more concerns.
The third concern is that an AC bulb should not be plugged into DC and a DC bulb should never be plugged into AC. While it is unlikely that I would make this mistake, someone else in my household that doesn’t understand how this system works might make this mistake.
To add a bit of Poka-yoke (mistake proofing) to my solution, I cut off the plug. This ensures that the lamp will never be plugged into AC again. I put power poles on the wire coming out of the lamp. It is important to get the polarity right when wiring this up. When the light manufacturers make the light, they don’t have a standard for which wire goes to the lightbulb case and which goes to the lightbulb tip. You can find this out by using a multimeter to test the continuity between each of the wires and the center connector in the socket. Whichever wire goes to the center connector, that’s your red power pole, the other is your black power pole. If neither of them connects to it, you most likely have the lamp switch in the off position.
The fourth concern is that lamps are not as simple as they used to be. When selecting a lamp be sure to pick one that is just a lamp. If you select one with a USB charger or AC outlet built-in, your conversion from AC to DC would also be sending DC to these circuits, which could have undesirable outcomes ranging from higher current draw to fire. Be sure to select a simple lamp that doesn’t have other features that rely on the AC input. I chose a desk lamp so that I’d always have lighting for my radio desk.
All that’s left to do is to plug it into a battery supply. Obviously, that supply has to have power poles coming out of it in order to plug into it. I have my batteries going into a power pole distribution box, into which I plug in my lamps. I’ll have another blog entry detailing the battery box that I’ve constructed to make the light portable enough to be moved around the house.