DIY Emergency Lighting System


When the power goes out at home, what do you do? Most of us probably scramble around the house looking for a flashlight. [Gigawatts] wanted a better solution, so he built an emergency lighting system based off a standard household UPS. A while back he had constructed a relay-switched outlet box to help periodically restart his cable modem which would get hung up a little too often for his liking. Since changing Internet providers, he no longer needed the switched outlet box, and was looking for a way to reuse it.

He hooked up the outlet box into the “battery powered” side of the UPS, and inserted a light bub into the normally closed half of the switch box. A 5v power supply was hooked into the “surge protection only” side of the UPS and is used to keep the relay switched. This causes the half of the switch box that is normally closed to remain open, and the light switched off. When power is lost, the 5v supply no longer switches the relay, and the light is turned on – powered by the UPS battery.

This is quite a useful hack if you happen to have a spare UPS sitting around – it sure beats scrambling around searching for a flashlight in the dark!

28 thoughts on “DIY Emergency Lighting System

  1. LED would last longer, and this is what a ups does , switches to battery power when power is lost, so you could just plug a lamp into the ups and call it a day.

    Im not trying to be a jerk but where is the project in plugging an outlet box , into an outlet ?
    COulda just bypassed the homemade outlet and plugged the light into the ups….

  2. bah, must be too early for my brain to work.

    The point of this is that the light only goes on when power goes off. what i suggested would have the light on 24 7 . but the first point stands, led bulb would be a better choice.

  3. addidis – the whole point it to have an emergency light automatically turn on when the power fails. the power still flows through all the outlets on a UPS when AC power is flowing. The switching outlet is needed to turn on the light when AC power is removed, and since the battery side will not know when that happens, plugging into power that will drop out is needed to tell the switched box to turn on.

    without the switching box, you just have a light plugged in to a power supply that won’t go out when the power does. but you either have to already have it on, or fumble for it in the dark.

    GREAT idea… it just needs to be miniaturized.

    2 or 3 1w LED’s and a cell phone charger for 5v instead of the brick should help with efficiency and size.

  4. @Addidis

    I agree that this project could have been done differently. I disagree with your hypothesis. Plugging the lamp in to the UPS would have left it always on, since that port provides power as long as it is on, not just when the power goes out. The DC adapter is there to set the interrupt switch so that it is open during power and closed at loss.

    All that said, picked up a commercial version of one of these a W-mart for 5 bucks.

  5. Power out? I walk to the garage and fire up the generator, I’m too cheap to pay for auto switchover.

    Build this monstrosity? nahh, I have several emergency lighting modules that are cheap and readily available.

  6. i wonder if he has ever though about tapping the back of the auto switching relay inside the ups and using a 12 volt dc RV bulb (they use the same base)or a 12 volt marine florescent bulb. It would last longer then going thorough the inverter

  7. I plugged my phone charger in the wall, and that junt hacked the AC into something like 5V1A. building your own UPS, wiring it to one of those no-touch electricity testing pens or something, and a relay or something to power it on when power is off, that would be a hack. isn’t this.. basically.. using the UPS as originally intended?
    That said, old ‘not a hack’ cliche is old. I realize that HaD is running out of legitimate hacks, because hackers are growing lazy because the price of caffeine has inflated, but there are some great hackomplishments in the making, deep down in the lab, Dexter’s lab.

  8. @fartface

    the point was for him to reuse something that he wasn’t using anymore.

    please read the posts before making dumb opinion based comments.

    there wouldn’t be a hack a day site if everyone went out and bought was already “readily available.”

  9. Yeah, I mainly built this out of boredom and as a joke. I do have a LED fixture I could use if I were to actually implement this, but I had that red CFL lying around and wanted to use it for something. I haven’t had a power outage yet in the year I’ve lived at this apartment, but this would be much more handy back at home where power outages are much more common.

    I do agree that UPS’s should have a socket built-in that switches on only when on battery power. That could be very useful for triggering something to happen in the event of a power outage.

  10. cute.. but my UPS screams like hell when you lose power and keeps beeping at you as if you didn’t know the lights went out. might be a good idea also to kill the buzzer in the UPS as well.

  11. Is there a COTS device that “does this?” Nope. This takes an already built UPS, and CFL with some reused components to make a difference of several types.

    Primary difference being- It keeps a lot of stuff in use as opposed to recycled or landfilled. That’s a 100X multiplier on many Hacks for reuse cred alone.

    But, there’s a deeper aspect. This is adding utility to all the places we have a UPS sitting there not able to use all it’s potential.

    Having a few watts of CFL, 3- 5 watt range or so are sold as “Candelabra” replacements.. that just comes on in every room we’ve got a UPS may save people from nasty falls or worse.

    If raw efficiency is set aside to just get this done? The effect of CFL’s that dim down near EOL might be exploited for places where it’s not a life safety backup light, but an additional comfort to kids etc use.

    Calling this sort of Hack an “Emergency” system sadly opens up liability if it fails.

    Calling it a “comfort” light for, oh the pet that’s afraid of the dark? Makes us a hero when it prevents bad things.

    EXCELLENT applied Hacking and a good presentation overall.

  12. This would have been nice in the LAN room at my old job. The power would go out occasionally and we would scramble in the dark to shut everything down nicely before the UPS’s would go down.

  13. I love this hack’s concept. It’s a tad bit overkill but nothing wrong with that. But certainly not cheaper than COTS solutions unless all of the components and your time are free.

    “Is there a COTS device that “does this?” Nope.”

    There is. Lead acid battery plus incandescent bulb for $25 bucks or so at a local hardware store. I would rather they be LEDs of course but this exact same thing is already available. It is called emergency lighting and it is widespread and common in commercial buildings.

  14. Quoting myself:

    Is there a COTS device that “does this?” Nope. This takes an already built UPS, and CFL with some reused components to make a difference of several types. Leads on to-

    Semantic clarification- “does this” has a defined meaning. It’s not just a boxed backup light.

    The Hack enabling device-that outlet box with power fail relay – plugs into the surge only and battery backed outlets of an unmodified UPS to provide a power fail turns on outlet “module” configuration. Beautiful design elegance in a Carlon box.

    In concept- this “could” potentially be made as an UL/CSA covered COTS item to be sold clamshelled @ big box computer stores etc. Two male plugs coded differently to denote where to plug them- and one or more standard outlets.

    There’s a gadget for transfer switching RV power that essentially works in a similar but not totally so mode.

    With it’s topology being that you plug the 30 or 50 A “shore power” cord of the RV into a matching socket in the cord storage bay. Relay/s handle select of genset or inverter or when unplugged from the socket- shore power- if it’s live to pull in the relay coil. NOT identical by far. But serves to define that a boxed emergency light is not this Hack. At all. This Hack’s flash of genius lives in using existing UPS units and a CFL or other bulb- plug in lamp “no modifications needed” to just work as needed.

    Lead Acid+ car headlight’s indeed “another Hack” but not in phase with Gigawatt’s application of an already built “by him” module in a really useful mode.

    No cutting into that UPS or bodging up lamp cords that risk fires. Build the module safe- and the rest stays safe.

  15. Well yea for location where emergency lighting isrequired, purchasing & maintaining commercial available product to CYA is a good idea. I have a small simple inexpensive unit from Walmart lugged into the recep next to the front door. On the night stand I have a 4.98 LED”camp lantern”. After an outage left me in the dark while using the computer I have another lantern on the desk as well. The on in the bedroom I have used nightly as a durability test, and it has lasted over 2 years now, YMMV.

    Nothing wrong with this hack, even if the intent is to rely on it in the event of a power outage. IMO

  16. @alan
    Fartface didn’t make a dumb comment. He simply stated in his situation there’s no point. Was it worth posting? No, not really.
    Was it opinion based? Yes, but then what’s the point of a comment section if you can’t voice your opinion?
    Next time don’t jump to conclusions about other people’s posts.

  17. Quite impressive, the red glow CFL really does fit in with the “emergency lighting”. It can be quite useful to have a light like that.

    Using the idea of a relay hooked up to the non powered site you could wire up your own serial port for the UPS (if it doesn’t have one) so you know when the power goes out.

    Also people, it doesn’t matter if there is commercial equivalents it’s called a hack for a reason. You’re taking something you have and finding a use for it. And that $17 light posted above only has a 90 min battery life. This probably could go for closer to 24hrs.

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