Here is how I made a dimmable led lamp with some smd leds from an automotive lamp and a constant voltage, constant current buck converter.
All the type 3528 smd leds are wired in parallel. There are 48 smd LEDs in this lamp. In parallel operation they are powered at 3.01v and driven at 1amp. This is how I paralleled the smd LEDs:
As per the manufacturer's data sheet the efficacy of my lamp is approximately 100Lumens/watt. This is very good and quite exciting to achieve!
Read on for how I made this happen.
Step 1: Cv Cc Converter.
This buck converter can give a fixed voltage and a fixed current. The maximum efficiency is 96% as per the manufacturer's published data. Perfect for driving LEDs. The other type of cv cc converter is the boost converter for led arrays wired in series. I personally prefer LEDs parallel since they are the most reliable (compared to one or more LEDs failing in a serial array). With parallel LEDs, a higher voltage battery will easily drive the lower voltage LED via the cv cc converter.
I however want it to be able to adjust the current from 1amp to 0. The first step is the remove the potentiometer for the cc side. I used a precision flatblade screwdriver and unsoldered.
Step 2: Adding an External Potentiometer.
I shorted the output terminals with my multimeter and turned the external pot to get maximum current. The original potentiometer I turned to get 1amp maximum.
I set the Cv value at 3.01v. I used my Handy bench power supply set at 6.7v.
Step 3: Adding a Battery Level Gauge.
This low cost battery level meter has two internal potentiometers. One sets the high or full value. The other sets the low or empty value. On a full reading all bars light right up the final bar which is blue. So cool!
Step 4: Putting It All Together.
Closing up the lamp. I stuck the Cv Cc converter inside the enclosure and sealed the lid. I stuck the battery level gauge with double sided tape on the outside near the brightness adjustment pot. The system is powered by a Lithium 9v battery (which is actually 7.2 fully charged).
A toggle switch is used to turn on power to the Cv Cc converter.
Step 5: Testing!
Step 6: Making It a Little Better.
I used a piece of windscreen sun shield to make a reflective backing and also to hide the internals. Now my nifty lamp looks great!
I added an internal charger for the battery!