Driver: Difference between revisions
add picture of FET driver
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===FET Driver=== | ===FET Driver=== | ||
This driver uses a field effect transistor (FET or MOSFET) in combination with a microprocessor to control current to the LED. The FET is basically a switch with very low resistance (lower than running the full current through the microprocessor) and can be turned on and off by the microprocessor using PWM. Without PWM, it is basically like running the light on direct drive so there is no protection of the LED. Some FET drivers add a linear regulator 7135 so the need for PWM on lower modes is reduced. This multichannel approach lets the driver limit the current to 350mA (instead of unlimited through the FET) and use PWM as needed to work from there. Also the 350mA channel gives more uniform low levels whereas the levels from the FET vary with battery strength. | [[File:A17l-fet+1.jpg|thumb|300px|A17L FET+1 driver uses FET for high modes and 7135 for lower modes]]This driver uses a field effect transistor (FET or MOSFET) in combination with a microprocessor to control current to the LED. The FET is basically a switch with very low resistance (lower than running the full current through the microprocessor) and can be turned on and off by the microprocessor using PWM. Without PWM, it is basically like running the light on direct drive so there is no protection of the LED. Some FET drivers add a linear regulator 7135 so the need for PWM on lower modes is reduced. This multichannel approach lets the driver limit the current to 350mA (instead of unlimited through the FET) and use PWM as needed to work from there. Also the 350mA channel gives more uniform low levels whereas the levels from the FET vary with battery strength. | ||
===Boost Circuit=== | ===Boost Circuit=== | ||