Bar mode increases current consumption on the LM3914. When all leds are lit, the LM3914 consumes 10 times more current than when it is in dot mode. This means the individual led current will have to stay low to prevent the LM3914 from burning.
Its maximum power dissipation should be kept under 1.365W and assuming the battery supply voltage will never go above 14.4V, the maximum current admissible is I = P/V = 1.365/14.4 = 94.8mA. With all 10 leds lit, their individual currents cannot be greater than 9.4mA. So a current of 2.6mA per led is small enough to keep the IC cool. The current is set by R3 = 4K7. The current per led is approximately 10 times the current flowing in this resistor, IR3 = 1.25 / 4700 = 266uA.
The input stage: To be able to read the supply voltage from which the circuit is also powered, a 1:2 voltage divider was placed at the input pin 5. This voltage divider consists of two 10KΩ resistors and the LM3914 will read voltages that range from 5V to 6.75V, when the battery voltage swings from 10V to 13.5V. These are the values that will be used to calibrate the LM3914.
Bar mode increases current consumption on the LM3914. When all leds are lit, the LM3914 consumes 10 times more current than when it is in dot mode. This means the individual led current will have to stay low to prevent the LM3914 from burning.
Its maximum power dissipation should be kept under 1.365W and assuming the battery supply voltage will never go above 14.4V, the maximum current admissible is I = P/V = 1.365/14.4 = 94.8mA. With all 10 leds lit, their individual currents cannot be greater than 9.4mA. So a current of 2.6mA per led is small enough to keep the IC cool. The current is set by R3 = 4K7. The current per led is approximately 10 times the current flowing in this resistor, IR3 = 1.25 / 4700 = 266uA.
The input stage: To be able to read the supply voltage from which the circuit is also powered, a 1:2 voltage divider was placed at the input pin 5. This voltage divider consists of two 10KΩ resistors and the LM3914 will read voltages that range from 5V to 6.75V, when the battery voltage swings from 10V to 13.5V. These are the values that will be used to calibrate the LM3914.
การแปล กรุณารอสักครู่..
