The principle of operation is quite simple. According to the LED datasheet, at 300mA, the LED delivers about 400 lumens – 57x more light than the original bulb! This keeps the heatsink to a cool 60C in the open and 70C when in the flashlight’s case – and I can easily get over 3 hours of constantly bright light. No point in having a powerful flashlight if it goes dark in an hour! In the end I decided to keep to the 300mA load the original bulb draws. Also the battery pack stores only 1AH of energy when new. The low pass filter is needed to even out the square wave electrical flow to a relatively flat voltage the ATtiny85 ADC can use reliably measure the voltage differential across the sense resistor and accurately gauge the current.Īlthough the LED can easily handle up to 1A, the heat sink is not nearly large enough to keep the LED temps less than 80C in the enclosed space.
#Led flashlight driver circuit schematic code
For better accuracy, I set the code to use the internal 1.1v reference in the ATtiny85 (Also available on the Arduino UNO), and passed the signal through a 2 stage RC low pass filter. The input measures the voltage across the 1/2 ohm sense resistor. The ATtiny85 is running an Arduino compatible core, and mostly relies on the PID library to calculate the proper PWM value to drive the FET. So I redesigned the circuit, this time using an ATtiny85 as the power controller. Great hand warmer in winter, but quite uncomfortable in summer. I quickly gave up on the idea once I realized the incredible heat the FET and power resistors will need to dissipate inside the case.
#Led flashlight driver circuit schematic driver
Like I said, we live in the future.Since the LED cannot handle the 18v (20v when fresh from the charger) power from the battery, I considered using my analog LED driver circuit. As well, candlepowerforums is the place to be on the internet for hard-core flashlight geeks.Īnd finally, if you're not happy with the pre-programmed modes in your flashlight, there is even open-source firmware available that allows you to customize and burn your own driver. If you're interested in reading a little more about flashlight tweaking and tinkering, head over to the flashlight wiki and check out the DIY P60 page. With the driver replaced and the flashlight reassembled, it was time to test. Once that was done, it was easy to press the new driver into place and solder it to the pill. The only challenging part of entire exercise was unsoldering the old driver from the brass pill. All that was required was to thread the wires through the holes and carefully solder them into place (making sure to get the polarity correct!). It was easy to heat up the solder joins on the top and pull the old wires loose.Īfter the old driver was removed, the new one was installed very easily. These connections are usually blocked by the plastic isolation disc, which prevents short circuits from the aluminized reflector. On the top of the drop-in, you can see the actual LED with the black and red wires from the driver soldered into place. That last mode though – the seizure-inducing blinking mode – was a deal breaker. The low, medium, and high modes are nice, though the switch is a little too sensitive and prone to switching modes by accident. by quickly tapping the switch, the light cycles between low, medium, high, and (ultra-annoying) blinking mode. The only thing about it that I don't/didn't like was the fact that it was a multi-mode light – i.e.
The light uses lithium cells (18650s) that I harvested from an old laptop battery pack, so it lasts forever, and it puts out a startling amount of light. You see, I have an LED flashlight that I'm generally quite fond of. This one might be a little bit OCD, GeekDads, but the technical details are at least a little bit interesting, so bear with me. Yes, you read that right: we live so far in the future that even our flashlights contain computers. A modern LED flashlight, on the other hand, includes a little circuit board that consists of a current regulator and a microcontroller. Now, an old-school incandescent flashlight consists of a bulb, battery, switch, and some wire, so there's not much there to tweak or tinker. That last mode though - the seizure-inducing blinking mode - was a deal breaker. The low, medium, and high modes are nice, though the light is a little too sensitive and prone to switching modes by accident. The only thing about it that I don't/didn't like was the fact that it was a multi-mode light - i.e.