Instructables

What is the best way to power an LED strip?

I am looking into purchasing some LED strips for a project, but I don't know how to power the LED strip.  For example: This LED Strip needs 24 VDC, but what would be the best way to supply this?  Would I use an outlet?  Are there batteries for this type of thing?

Thanks for your help.


Picture of What is the best way to power an LED strip?
pbates1234 years ago
 Powering your led strip can be done several ways.  As seen above you can use a plug in power supply or you can use solar cells. If you desire the strip to be mobile you can use batteries. 

Three 9 volt transistor batteries wired in series (the positive leg of one battery tied to the negative lead of the next)  will work and will allow a couple of hours of operation.   Only one very simple modification is required for this to work.

Three series 9 volt batteries equal 27 volts. (9*3=27) So to limit the current to 80 milliamps required by the strip you have chosen we need to use up the extra voltage so to speak. Three volts is the difference between 24 volts @ .08 amps that the strip needs to operate and the 27 volts the three batteries can supply.

To do this a little basic Ohms Law will give us the answers we need.

First the strip requires 24 volts @ .08 amps (80 milliamps same thing) we have 27 volts so 27 - 24 = 3 Volts. We can then determine what the resistance we need to keep the extra voltage from harming our strip. Using the formula  E=I * R (E = Volts, I = Current in amps, R = Resistance) and rearranging the formula to solve for R (resistance ) R = E / I   (3 / .08 = 37.5).
We have determined that we need a 37.5 ohm resistor in series with the circuit. Resistors come in standard sizes unless we pay extra for precision so a ~40 ohm resistor will work fine. 

Second the resistor in a series circuit will need to dissipate the same current as the board does so we need to make sure that the heat generated by that current does not burn up the resistor. Power in watts can be determined by the formula P = I * E  (P in watts = I in amps * E in volts)

So using the 3 volts and the current in the circuit .08 amps the result is:
.08 * 3 = .24 watts  Again resistors come in standard wattages so select a resistor that is a quarter watt or larger. .5 Watt resistors are a good size to work with so I suggest you use a Carbon Composition 39 Ohm 1/2 watt with a tolerance of 10%.  

Here is one source www.tubedepot.com/r-30bj500.html they cost about 25 cents. Radio Shack probably has a resistor that will work as well and many electronic hobby stores are good sources.

Good luck with your project.

I drew a circuit to help out a little see the attached.











downsize.JPG
jwatts82 years ago
All you need is a 24v driver however you need to work out what wattage the LED strip is pulling and make sure the driver outputs enough watts. You can choose from a range of different size drivers from 
Instyle LED Drivers

30w-led-driver.jpg30w-led-driver-plastic.jpg
obardinua2 years ago
You have two options:
1,choose LED Power Supply 110-220V AC to 24V DC
2,choose Waterproof LED Power Supply AC 110V/220V to DC 24V

and you can buy good Flexible LED Strip from www.ledstripworld.co.uk.
LED Power Supply 110-220V AC to 12V DC.jpgWaterproof LED Transformer AC110V.jpg
ethan75572 years ago
to power your dc24 led strips, as guys said, you just only need any transformers which can transformer to 24vdc.
BTW, how many amp the transformer you need to be depends on the power consumptions of the strips, so first calculate the power consumption, and then determine the LED transformer model.
tsmith673 years ago
Hi I have a lot of these 12 volt strips and I use 12 V DC plug packs supplied with the LEDS and more recently I use 12 v LED drivers available from ebay for Australian $2 they work fine BUT!! after a few weeks the LED strips start to loose brightness and eventually FAIL. I don't know why is it because the LEDS are cheap chinese product??
if anyone can ansswer I would be grateful.
Cheers
hledstore3 years ago
you need to choose a proper power supply to work with led strip. Too much can cause your transformer to overload and potentially damage your light strip. When you choose power supply for the led strips, you'd better add 20%+ tolerance. For instance, the power consumption of the led tape is 24 watt, a 24*(1+20%)=29W power supply will be advisable, which can ensure the led strip run at normal brightness
robert.d3 years ago
Hi Usually, these led strip lights are work at 12v dc, so you need a constant voltage led transformer, as well as right power consumption. Besides, you'd better connect more than 5m led strips in parellel way, but not in series so that your led strip can have best performance.
usLEDsupply4 years ago
some laptop and old printer power supplies are 19-24v or if you aren't running more then a few feet you can use a doorbell or furnace transformer as they are typically 24v AC and if you don't like the slight flicker you can add a full wave bridge rectifier after the transformer but before the lights

or you could always just buy a 24v transformer like this
http://www.usledsupply.com/shop/24v-power-supply.html
chrismorley4 years ago
most of LED strips are powered by DC 12V, you can check with sellers. Just make sure the power meet the LED strips requirement, batteries or power adapter is Ok. you can check ledstripworld for information.

LED Transformer-LED adapter.jpg
burzum234 years ago
i got 2 LED strips on my bike suplyed by 3 12v batery called A23 and i wanted simple  and it works realy good
Drache4 years ago
http://www.newark.com/triad-magnetics/wdu24-500/ext-plug-in-power-supply-24v-12w/dp/96M9188?in_merch=Popular%20External%20Plug%20In%20Adapters&MER=PPSO_N_P_ExternalPlugInAdapters_None
i use these all the time for projects with leds usually in the 12Vdc side with a http://www.newark.com/optek/ovq12s30w7/30-led-light-strip/dp/19P2486?in_merch=Popular%20Products&in_merch=Popular%20Products&MER=PPSO_N_C_EverywhereElse_None
Re-design4 years ago
You can probably find a 24 volt dc wall wart.  Just make sure that it has enough capacity (amps or parts of an amp) and is not overloaded.
Thats what I did but mine were 12vdc.
frollard4 years ago
When it comes to powering leds (like the one you linked) that already have current limiting resistors built in, you just need to match the voltage.

Otherwise, if you DIY your leds strips you need a current limit somewhere - be it a resistor, or current limited supply.

As others say you just need 24 volts.  A wall wart, or switch mode power supply would work.  There are lots, but 24v is rather uncommon.  You'd probably only run 24v if you are running a LOT of them, since each only ends up drawing 80ma (about 2 watts each).

If you plan on running a significant number of them, and want a cheap power supply - consider strands that are 12 volt - as the supplies will be far more common, and you can DIY one out of a computer power supply (instructions here on ibles)
mathews4 years ago
To provide the 24v, you could easily use a mains to DC adapter.

You could use this as a single power supply, and run anything else with a regulator to step down the voltage.