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PaxInstruments / t400-electronics

Electronics for the Pax Instruments T400 temperature datalogger
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LCD backlight resistor #108

Closed charlespax closed 9 years ago

charlespax commented 9 years ago

I made a mistake in calculating the LCD backlight resistor value. The backlight resistor value=(VLED-3.1V)/60mA, where VLED is the supply voltage for LED backlight.

I think we should change the resistor to a value that achieves the highest brightness while not exceeding the maximum current the ATmega32U4 can drain on the connected pin.

From the manufacturer engineer, "If the power supply for LED is 3.3V, R19 of your main board can be 3.3 ohm to 5.1 ohm. Of course you can use a larger resistor in order to reduce the power consumption with lower LED brightness."

screen shot 2014-12-23 at 12 06 00

Oh well, what's an order of magnitude among friends?

charlespax commented 9 years ago

The backlight levels can be manipulated in software if we implement https://github.com/PaxInstruments/t400-electronics/issues/109

charlespax commented 9 years ago

Implemented. Closing issue. screen shot 2015-01-26 at 07 08 02