The LM3914 voltage monitor is also straight forward. As told I use only 6 of the 10 led outputs. A voltage divider on the input (R1-R2) decreases the 7-12V input to about 1.96-3.36V (x0.28). The P1-R4 combination sets the high reference voltage (12/12 of 3.36V, level for 12V readout) and P2-R5 sets the low reference voltage (7/12 of 3.36V, level for 7V readout).
Calibration is very easy: Set trimpot P2 on the fan regulator to obtain an output voltage going from about 7 to 12V for a complete turn of potmeter P1. For minimum speed setting of the fan regulator, set trimpot P2 on the voltage monitor to lit only the lowest led. Then, for maximum speed setting of the fan regulator, set trimpot P1 on the voltage monitor to lit all 6 leds. Test all positions of potmeter P1 of the fanregualtor again and finetune if needed.
Read More http://www.turbokeu.com/myprojects/fanregvoltmon.htm
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This entry was posted on Monday, July 30th, 2007 at 8:58 am and is filed under Lighting, meter.
