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Turning LED strip lights into loadshedding bulb


jharber

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Hi all

Today I noticed that the LED strip lights in my kitchen run off a little 12v wall wart with a standard DC connector. That gave me the idea of hooking up a little DC UPS to them.

However, all the DC UPSs I have and everything I can find online is meant to be always-on, for wifi and such. I want something that behaves like one of those load shedding bulbs—that always responds to the same on/off switch, regardless of whether it's running off mains or battery.

Does something like that exist? Anyone running something like it?

Thanks

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@jharber This cost me R2K to build this prototype, and yes, my kitchen is a terrible prototype ;) ... my next project after solar.

* Alarm power box - SHERLO TRONICS ( https://www.sherlotronics.co.za/power-supply-12vdc-3-2a/ )
* lead acid battery (took from my alarm)
* Couple of LED downlights from Gelmar ( https://www.gelmar.co.za/led-downlight-round.html )

I keep it permanently on but you can wire in a relay into the unit for when the power goes off. I used a buck converter to regulate the voltage (don't know if it is actually needed). Survives 4 hours without fail.

I'm going to build a second one with the relay switch for emergency lighting. This was originally built for my router but it did not work, so I tried it for lights and magic.

image.thumb.png.5b00e87311f4ba7644ec8843f0c63306.png

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Agree with @cbrunsdon. I have installed lots of 12V strip lights for friends and family.

My approach has been:

  1. 12V Remote dimmer switch: https://4x4direct.co.za/dimmers/6015-remote-controlled-dimmer-for-led-strip-12-24-volt.html
  2. A COB warm white strip light: https://www.ledz.co.za/product/led-cob-strip-light
  3. A 45 degree profile for mounting: https://www.ledz.co.za/product/flat-bed-45-degree-surface-mounted-profile
  4. 6.4A Alarm Power Supply: https://www.securityking.co.za/products/sherlo-battery-backup-power-supply-6-4amp?variant=35044907253913&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&utm_campaign=gs-2020-06-08&utm_source=google&utm_medium=smart_campaign
  5. 20Ah Lithium Battery: https://www.makro.co.za/home-garden/lighting/home-automation/smart-electrical/securi-prod-lithium-iron-phosphate-battery-12-8v-20ah/p/c77cb036-8458-4192-92ec-97ff26553ac3?gclid=CjwKCAjwov6hBhBsEiwAvrvN6HhtJvmx3v6fDaHRwpYA_7uqP24bwgMBFo0UcVOw3kPV2hvcuz9JuRoC43QQAvD_BwE
  6. 2mm Speaker Wire

 

You need to bridge the outputs as each output can only handle 1A. I use 1mm wire of the same length with a cable joiner to do this. You also need to cut the speaker on the alarm power supply - so that you don't have an alarm sounding for 4h of load shedding. For added protection, I have added a DC fuse in case their is a short in the system. I use the 2mm speaker wire to help reduce voltage drop. I have been able to run 20m of cable with minimal voltage drop.

Effectively you can run about 70W of LED lighting. That translates to about 7m of lighting. I like to run 2m lengths - so that gives you (bright) lighting for 3 rooms. The remotes can be mounted on the wall next to the light - and they are barely visible. These remotes aren't the cheapest but have a unique code to prevent interference from other remotes in the house. They also have a dimming function.

I like the 20Ah lithium battery as they can run for a long time. Running 6m of lighting continuously you can get about 3 hours of light without overly discharging the battery. Even this comes under pressure with Stage 6/7 load shedding.

An alternative is to run the lighting directly from the battery. You can then link a charger to the battery. The charger will charge the battery when the voltage drops. A simpler approach but doesn't give much in terms of low voltage, shorting, etc protection. The advantage of the power supply is that it automatically switches between grid and battery - and doesn't just use the battery.

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On 2023/04/17 at 8:10 PM, jharber said:

However, all the DC UPSs I have and everything I can find online is meant to be always-on, for wifi and such. I want something that behaves like one of those load shedding bulbs—that always responds to the same on/off switch, regardless of whether it's running off mains or battery.

DC miniUPS boxes have lithium battery management system that is always on.  However, the output of these devices can be turned on/off with a switch on their front panel.  The UPS has an internal boost converter to step up the Lithium battery voltage to a well regulated 12VDC.  This boost inverter will have a certain quiescent current when on.  So it is better to turn it off when your lights are off.  I always turn off my router over night with UPS switch.  My guess is that you intent using a "proper" light switch?  There would be no problem having the UPS on 24/7 and just placing an ordinary on/off switch in series.

I do not quite know why you want to use strip lights for L/S and not ordinary  MR16 12V LEDs.

Here is the problem:
Strip lights are normally cut to length and thus do not have a voltage control chip. They use simple voltage dropping resistors.  These lights thus require a precise 12V.  Under voltage will result in dimmed lights.  Overvoltage will burn out the LEDS.

MR16 LEDs always have an internal SMPS and can run from AC and DC.  They should be more than happy with any DC voltage between 10... 16V.  This means that you can use a lead acid battery with a corresponding charger.  Doesn't matter how much your battery is discharged or charged, the fluctuating battery voltage will have no effect.  You could also use a lithium battery but lithium chargers are expensive and hard to come by. 

With a little bit of DIY, the cheapest way would be to get a suitable 230AC 12VDC power supply, modify an internal resistor, to take the output voltage to about 13.8V (these supplies are adjustable, but the voltage is always shy of the 13.8V), then add a small high wattage, series resistor (a 5W 0.33 or 0.47 ohm might do it) and use this as a trickle charger on a suitable dimensioned SLA battery.  Ideally you want the PSU to have a settable current limit, but such PSUs are as scares as hens teeth.  So this is why one would place this small resistor on the output.  It is a crude way of voltage/current regulation that fit lead acids characteristics reasonably well.

 

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