1W Power LED Flasher

This is a common LED flasher utilizing 1W power LED and 18650 Lithium-ion battery.

As I'm supposedly moving to the rural area within several months from now, this kind of daily necessities shall be a must-have gadget.

Considering portability, all parts are housed in Tapa-ware like a plastic box as shown in the picture above.

It's the first time for me to use the 1 Watt power LED in a DIY project.

For making the power LED lighting circuits, finding some useful information from the Internet was difficult.

Commonly I can find the circuits using a simple current limiting resistor or some exotic LED driver ICs.

As power LED types are so diverse, I can't sure that the specific schematics from the Internet can support the LED I had purchased.

Somehow, I figured out a simple circuit that can drive my 1 Watt power LED finally.

Let's look at the circuit in more detail.

Overall LED flasher circuit consists of the following five major components.

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-     1 Watt power LED module

-     18650 lithium-ion battery 2900mAh (Samsung SDI)

-     TP4056 based lithium-ion battery charger break-out

-     LM339 based battery capacity monitoring circuit

-     Plastic box and acrylic board for flasher circuit enclosure

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Among the circuit components above, the most important part is the power LED driving portion of the flasher circuit as it produces the light I need.

For powering 1 Watt LED, Samsung 18650 battery is used.

And the TP4056 lithium-ion charger module supplies electricity when the 18650 battery is discharged by using the flasher.

The LM339 based battery monitoring circuit shows the remaining energy level of 18650 while using the flasher.

I found the circuit in the following instructable.

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https://www.instructables.com/Li-Ion-battery-level-indicator/#discuss

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As details are described in the instructable above, I made the battery capacity monitoring circuit by myself as depicted in the schematics drawing above.

Then let's look at each portion of the flasher circuits in the steps below.

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<Circuit modification part1>

Originally the 1Watt LED is directly connected to the Battery(+/-) pins of TP4056.

But TP4056 supports additional OUT(+/-) pins and the IC can prevent battery over-discharging with the OUT pins.

When the battery voltage drop under 2.9V, TP4056 turns off the power supply from OUT(+/-) pins to protect the 18650 battery.

As this is a quite useful feature and it can support the longevity of a 18650 battery, I modified the original schematic to the new one. (You can see the changed circuit in the pink-colored part in the new schematics above)

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<Circuit modification Part2>

Some mistakes are included in the original schematics.

As mentioned right above, utilizing the TP4056 OUT(+/-) pin is recommended for the 1W LED wiring.

The other part is using the 20K VR for correctly setting the 18650 battery level.

Please refer to the rightmost schematics for the correct circuit wiring. (Blue shaded parts are correct parts utilization)

When any 18650 battery is fully charged, the output voltage becomes 4.2V.

With the fully charged 18650 battery, you can correctly set the voltage level with 20K VR. 

Rotating a small screw of 20K VR to turn on all 5 LEDs. (When the leftmost Green LED is just turned on, you need to stop rotating the screw of 20K VR)

Then each LED indicates the following voltage level of a 18650 battery.

• Green (Rightmost) LED: battery voltage is bigger than 4.1V
• Green LED: voltage is bigger than 3.8V
• Yellow LED: >3.6V
• Yellow LED: >3.4V
• Red LED: >2.2V 

I bought this power LED module from the offline store that makes LED signboards and home LED lighting fixtures.

They stocked these Chinese LED modules for possible use but can't find any specific usage for several years.

They don't know the manufacture of the LED and the technical specification of the module.

Therefore, I need to find the electrical feature of the LED module by myself.

Because the nominal voltage of the Samsung 18650 battery is 3.6V and the common operation voltage of 1 Watt LED is 3.3V, I wired LED directly to 18650 battery without a current limiting resistor.

Usually, a 1 Watt LED can stand 300mA~350mA current with a small heat sink without any damaging effect.

With a direct connection between LED and battery, I measured current flow with the ampere meter as shown in the picture above.

When the 18650 battery is fully charged (so 3.6V output voltage), about 250mA flows to the power LED.

Even the power LED is operating at its maximum rate (so 250mA current is flowing), the LED does not produce much heat.

Therefore, the power LED is attached to a small heat sink that usually mounts TO-220 type transistors.

When energy is drawn from the 18650 battery while flasher operation, (hence output voltage is reduced from 3.6V) less current (200mA ~ 100mA) is flowing to the power LED. (therefore less heat is produced)

As all electrical parameters are within the power LED operation limit, the direct connection between LED and battery is quite OK.

As I mentioned above, I found this circuit in another instructable.

Because I'm using Samsung 18650 battery, I modified it slightly by replacing the original 4.7K fixed resistor with a 5K VR as shown in the wiring diagram above.

By adjusting the 5K VR, I can fix the 18650 battery voltage indication levels as follows.

(Please refer <Circuit modification Part2> in the Step 1 above)

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-     Battery fully charged (100%, and 3.6V output voltage) turn on rightmost green LED (max)

-     When energy drawn from 18650 is used (About 60% remained, 3.3V output voltage) middle yellow LED is turned on (medium)

-     When more energy is drawn, (Less than 30% capacity remained, less than 3V output voltage) red LED is turned on

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This monitoring circuit consumes about 30mA by measuring with an ampere meter.

Although this circuit uses valuable battery energy, still the capacity level indication is very useful.

When the red LED is turned on, then I will know that the 18650 battery needs recharging.

When a battery capacity level is lower (less than 30%), recharging is necessary with this break-out module.

As this module is quite popular for any 18650 battery using DIY projects, a detailed explanation will not be necessary.

When the power switch of the flasher is turned off, the TP4056 charging module is only connected with the battery.

Therefore, the power switch needs to be turned off while battery charging.

As the input voltage of TP4056 is typically 5V, a common smartphone charger can be utilized for charging the 18650 battery.

While charging is progressing, the red LED of the TP4056 board is turned on.

When charging is completed, the green LED of the TP4056 board is turned on.

To support portability, all components of the flasher circuit should be housed inside the enclosure.

For the circuit board mounting, I bought a rectangular plastic box.

The bottom side of the box is covered with a black acrylic board.

To show the capacity level of LEDs, a transparent acrylic board is used at the positions of the LEDs.

All circuit boards are mounted and fixed inside the plastic box with bolts, nuts, and PCB supporters.

As the capacity of the 18650 battery is 2900mAh, the flasher can operate for roughly 14.5 hours when assuming an average 200mA is used by the 1 Watt power LED. 

When the capacity level falls less than 50%, the brightness of the power LED is slightly dimmed.

But still, its brightness is adequate enough to shine the road ahead.

Thank you for reading....