Emergency lamps are one of the most important household essentials, mainly because we use it on various applications. You can use it during blackouts, while camping, doing videoshoots, doing photography and other stuff... Over the years, we've bought a lot of Lead-Acid Emergency lamps. From incandescent, to CFLs, to LEDs.
My main application for these lamps is for handywork and videography. None of which we had was powerful enough to light up the subject on a three - point lighting setup. Hot shoe video-lights are a bit pricey. As an enthusiast I decided to make a cheaper version. Cheaper but better! Better in all ways!
Behold a DIY LED lamp with 9x 3watt LEDS, powered by four Lithium-Ion batteries and controlled by a dimmer circuit. It lasts for around 4 hours to 4 days (depending on the dimmer's setting).
I'll be posting a video follow-up next week, similar to my FM Transmitter Project Video.
Step 1: Parts & Tools
- 3W White LED (9x)
- TIP35c NPN Transistor
- 7805 Voltage Regulator
- 1.5k 1/4w Resistor
- 10k Trimmer Resistor
- 220uF Capacitor
- 100nF Capacitor (2x)
- Plastic Standoffs (4x)
- On/ Off Switch
- 18650 Lithium-Ion Batteries (4x)
- Rectangular Plastic Container
- Solderless Prototyping Board
- Perfboard (Breadboard)
- Leatherman (Multitool)
- Digital Multi-meter
- Bench Supply
- Soldering Iron
- Cutting Board
- Hotglue Gun
Step 2: Screw the Standoffs
Screw the plastic standoffs to your PCB.
Step 3: Position the LEDs
Use a little amount of superglue to temporarily position the LEDs.
Step 4: Solder the LEDs
Now solder your LEDs to the PCB. This should hold the LEDs in place.
Step 5: Test It
Supply a 9v power supply to the LED array. Regarding the heat, the LEDs get very hot at 9v (max brightness). At 6-7 volts the LEDs barely dissipates heat, the PCB absorbs the very little heat given off. Bottom line, never use this setup at its max, only tune it at half the brightness. BTW, half is still bright, brighter than your average videolight.
Step 6: Prototyping the Variable Regulator/ Dimmer (Part 1)
We need to control the brightness of the LEDs with a dimmer circuit. There are two ideal circuits to use: the PWM buck converter and the Linear voltage regulator. The buck converter is more power efficient compared to the linear regulator although when you shoot videos using a light source controlled by a PWM buck converter, the videoclips tends to tear.
Here's the schematic diagram of the circuit: the 7805 regulator is used as a voltage reference for the high current transistor while the trimmer capacitor is used to control the voltage of the transistor's base.
Step 7: Prototyping the Variable Regulator/ Dimmer (Part 2)
Time to test it! Try to supply voltages from 10v to 30v. The regulator should give a constant voltage output. Try to rotate the trimmer the voultage should change from 4v - 9.5v.
Step 8: Solder the Dimmer to the PCB
Once you get the dimmer circuit to work, you can now install it to the same PCB where you soldered the LEDs.
Step 9: Add a Switch
Now, drill a hole, hotglue a push button toggle switch then solder it to the dimmer circuit.
Step 10: Assemble the Lithium Battery Pack
Recently I found a store that sells lithium 18650 Lithium-Ion batteries for $2 each. Each cell rated at 3.7v (2000mAh). I soldered four of them in series to build a 14.8v (2000mAh) battery pack. Be sure to solder them fast, otherwise things could go wrong once you heat them up too long.
Step 11: Solder the Battery Pack to the PCB
Now, solder the battery pack to the dimmer circuit.
Step 12: You're Done!
Enjoy your dimmable LED lamp! :D
Step 13: Give It a Try! :D
Step 14: Maintaining and Charging Your Batteries
Lithium batteries need special chargers, also known as balancing chargers since they are very sensitive to overvoltaging.
Step 15: Final Thoughts and Observations.
The PCB acts as a heatsink upgrading to a fiberglass PCB would improve heat conductivity and heat resistance. Adding a fan would probably solve the problem. The lamp get too hot at full power, would only last for 10 minutes without a fan. Although it could run as long as it could at half the power.
Step 16: Mistakes to Be Corrected on My Next Attempt
*Use a high-efficiency buck converter.
*Add a large heatsink
*Add a fan
*Add an ATiny85 MCU (as a digital controller)
*Add a tiny LCD panel.
*Gel diffusers maybe?