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I wanted a lightweight and portable led floodlight with a dimmer. Here is how I did this mini project.

Step 1: The Case.

Using an old solar lamp case, I went about to make my floodlight.

Step 2: The Leds.

Each array of 3528 smd leds is wired in parallel. There are no resistors here. Here is how I wired up those LEDs:

https://www.instructables.com/id/Battery-Powered-LE...

Those led strips and arrays with current limiting resistors use 4 times more power than constant current driven leds! Think about that fact. The resistors waste precious power. If you check on Amazon.com for 12/24v rated leds for cars then those are constant current driven. They actually have a supply voltage span is 9v to 30v. Look for these ratings to get a truly energy efficient led lamp!

Step 3: The Led Drivers.

I have a micro puck driver per led. Each is wired in buck mode to allow powering from a Lithium 9v battery which is really 7.2v. This allows for a very efficient design and maximum battery life.

Always remember that leds are constant current devices. Once driven in this manner the entire lighting system will be extremely efficient. Stay away from those cheap strips and arrays that have those stupid smd resistors. The second pic shows an example of a popular led strip with smd resistors. I curse the manufacturers of these low cost inefficient led lighting system. They should be all hanged.

Step 4: Wiring It Together.

I soldered the leds to the drivers and prepared for preliminary testing.

Step 5: Initial Testing.

I used a pwm controller to dim the leds. This controller is placed between the battery and the led drivers. Here is everything hooked up to make sure the pwm dimmer is working as it should.

The potentiometer to vary the pwm output I had installed in the case via a hole I had drilled.

Step 6: The Power Switch.

I cut a hole in the cast iron case and slipped in a power switch. This is wired to the 9v battery clip and the pwm controller. Even when the pwm is at its lowest output there is a 4ma Parasitic drain hence the need for an on off switch.

These pwm controllers are very easy to wire. There are 2 terminals each for dc power in and pwm out.

Step 7: Assembly.

I velcro stuck the battery and pwm controller into the cast iron case. I used duct tape to stick the leds to the glass front and then clear silicone adhesive to permanently keep the leds on the glass.

Step 8: Completion!

Here is the completed portable led floodlight! At full output I get approximately 300 lumens with a battery span of 2.5 hours. Lightweight, convenient and durable!
<p>Yes, there is a variable amount of energy wasted in the resistor, but it depends on many factors. Anyway, a Led ribbon won't never waste fourth time energy than the current driven systems, it can be 1/4 <strong>max</strong>. (25%)</p><p>Regarding constant current drivers they loose energy as well, but far less I admit. </p><p>I know there are controlers that go to zero, I personnaly made one, with one of those, there's no leaking current so you wouldn't need the added switch to go to black. </p>
<p>nah man. resistor driven leds waste a lot of energy. </p>
3hrs out of a 9v battery is pretty good. Led's are pretty amazing things. I have plans to make something similar, but hoping to be able to solar charge and charge through car if needed.....One day!
Just don't use the led strips or led arrays with the smd resistors. They are power wasters. The best ones are the 12/24v rated since they use constant current drivers to give best efficiency.

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