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Power Consumption Improvements

A project log for Arduino MPPT Solar Charge Controller

The charge controller consists of a buck converter that is controlled by an Arduino via a half-bridge driver.

tobiasTobias 05/22/2016 at 02:093 Comments

LCD Backlight Analysis:

Current/Powerblue LCDtransflective (sunlight readable) LCD
backlight on

82.4mA 644mW

251.6mA 1950.4mW

backlight off

53.2mA 416.2mW

53.2mA 416.2mW

The LCD backlight turns out to be a real power hogger. 1950 milliWatts? Whoa!! Maybe I should read the datasheet more often..

240-280mA! I thought I had a short circuit, but apparently, this LCD uses that much current for the backlight. From now on, the backlight will be off in my circuit (cut pin 15 to the display), but I added a switch, just in case.

Discussions

David H Haffner Sr wrote 05/22/2016 at 22:48 point

NO problem Tobias

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Tobias wrote 05/22/2016 at 22:45 point

Hi David, I am using Sam Knight's PWM library
https://code.google.com/archive/p/arduino-pwm-frequency-library/downloads 
Just uploaded it to my repository, just in case

https://github.com/atmelino/Arduino/tree/master/libraries/PWM
very easy to use:

pwmWrite(PWM_OUT, pulseWidth);

Fortunately, the transflective LCD is easy to read in sunlight without a backlight. I added a button to briefly turn the backlight on if necessary, but I figure most of the time you don't need a backlight at all. Thanks for the suggestion though.

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David H Haffner Sr wrote 05/22/2016 at 09:30 point

Hey Tobias, man, that's is a big energy hog. Since you are using an Arduino, how are you controlling the PWM duty cycle? Usually you can design a dimmer for the LCD backlight and have the switching frequency set to about 200 Hz and maybe control the duty cycle at 25 to 50 % duty cycle to shave some of that current down.

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