Build the Ultimate LED Lamp (Li-ion)

Intro: Build the Ultimate LED Lamp (Li-ion)

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.

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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!

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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).

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I'll be posting a video follow-up next week, similar to my FM Transmitter Project Video.

STEP 1: Parts & Tools

Discrete:

- 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

MISC:

- 18650 Lithium-Ion Batteries (4x)

- Rectangular Plastic Container

- Solderless Prototyping Board

- Perfboard (Breadboard)

Tools:

- 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.

*Use Lithium-Polymer

*Add a large heatsink

*Add a fan

*Add an ATiny85 MCU (as a digital controller)

*Add a tiny LCD panel.

*Gel diffusers maybe?

Comments

[sreeci]

I have 3 issues to discuss. Kindly verify, comment and explain.

1) Star LEDs produce tremendous amout of heat.

They can self destruct if left without heat dissipation.

There was no mention of heat sink.

2) Soldering Li-Ion batteries on to its body!

Liquid Lithium becomes unstable when hot, unless cooled. (Li-Ion batteries with Tabs are available)

3) Where did you buy Li-Ion battery 18650 for $2 ?

Let us know the location.

Thank you for your publication and thank you in advance for the response.

[kaljhan1015]

Trust me. You can get 18650 for $1.5

[mohda136]

Hi,

Just wanna ask, why did you think using Li-ion battery is a mistake? What is the advantage of using Li-Polymer battery for this project?

Thank you.

[MuhannadMaklad]

sorry, but what is the use of the transistor ?

[Yonatan24]

I believe it was used for the dimmer module

[Yonatan24]

In step #12, Pictures 2&3 don't have the same LED's in the middle, Is there a reason for that?

[Yonatan24]

Hi,

I was wondering where you bought the screw standoffs

Thanks in advance :)

[crickleymal]

A good first attempt. As you and others have said, a heatsink is really needed. Also you can buy cheaply some great little lenses to fit over the leds to focus the light a bit more.

Neat dimmer circuit though.

[gsantony]

where to connect the heatsink in this circuit

[JinkyDrew1]

stick a old cpu cooler on there... will cool miles better than anything else will

[Electrospark]

An LED heatsink is a piece of aluminum that you place the LED on to dissipate the heat like the LED chip set heatsink on the picture. for even more heat protection, you could place all the LED's on LED heatsinks and then place them all on a big heatsink that has fins but that would be a bit overdoing it.

Hope this helps.

[gsantony]

thanks a lot then one more question ....in this circuit did not mention battery specification ...can you help me

[Electrospark]

I think the circuit uses about 500mA (Milli-Amp) so if you use 500mAh (Milli-Amp hours) batteries it will last for about an hour, If you use 1000mAh batteries it will last for about 2 hours and so on.

That means that if you have a circuit that draws 1000mA, and you use a 1000mAh the battery will only be able to run for an hour since it's maximum capacity is 1000mA for an hour.

Now, if you have a circuit that draws 500mA and you use a 1000mAh battery it will run for two hours since after an hour the battery would only have used the half of it's charge.

That means that the more mAh a battery has, the longer it will last.

And the lower the amp draw of your circuit is, the longer it will run.

Here some example of the run time you will get from the LED light depending on what batteries you use.

Under 500mAh= batteries overheating and draining very quickly.

-500mAh=1 Hour

-1000mAh=2 Hours

-1500mAh=3 Hours

-2000mAh=4 Hours

-2500mAh=5 Hours

Note that this is just for a circuit that draws 500mA like the LED lamp and that the run time will be different depending on the amp draw of your circuit.

there is also the batteries chemistry but that's another story...

If you want to know some info about that, Just let me know.

I hope all that info will help you.

[gsantony]

thanks for these details already i know these things what i need to know is voltage of the battery like 1.5v or 3.3v or 6v or 9v ...... can u tell me list of components with specification clearly and exactly for this circuit because i am going to try this circuit alone

i need like this

3W White LED -9 nos

- TIP35c NPN Transistor-1no

- 7805 Voltage Regulator-1no

- 1.5k 1/4w Resistor -1no

- 10k Trimmer Resistor-1no

- 220uF Capacitor-1no

- 100nF Capacitor -2nos

- Plastic Standoffs (4x)

- On/ Off Switch

-battery (voltage? mAh)

expected these alone......

[Electrospark]

Huh, They are 3.7V not 2.4V. He just updated his instructable and said they were 3.7V.

Sorry about that.

[gsantony]

No problem.......may i use this 9 number of 3W led, directly into 9v DC supply

????because i dont want battery .....

[Electrospark]

You can, but you'll have to connect them in set of three in series connected in parallel.

I recommend using a 12V power source with a voltage regulator at your input to have a steady 9.6V output for best results.

You may also want to connect a current limiting resistor on each set of three and attach the chip set LED heat sinks to a big heat sink to have a longer lifetime.

[Electrospark]

Ah, I see what you want to know, he used four Li-ion batteries of 2.4V and a capacity of 2000mAh in series to obtain 9.6V at the output.

Sorry for the misunderstanding, if you ever have any question about electronic circuits, feel free to contact me! :-)

[karlpinturr]

Unless I'm missing something, 18650's are (as ASCAS states later, when soldering them) rated at 3.7 volts, giving a pack voltage of 14.8.

[Electrospark]

He updated his instructable and said the voltage of them was 3.7V.

I thought they were 2.4V because of the picture of the multimeter on the picture on step 7.

Look's like i was wrong...