Watch RC CHARGE and the rate of change ON LM3914 VOLT METER

RCNET
RC NETWORK CHARGE/DISCHARGE

 

 

 

 

 

 

 

An easy way to see the charging/discharging of a capacitor through a resistor is to select a value for T,  in the equation T = R*C.                         The above values work out to be 10 seconds as 100000R x .0001uF = 10.  Wire a resistor and a capacitor on the breadboard as shown above, and connect a wire from where they meet to the input of the Lm3914, (high input impedance so will not load the RC network) the power is just connecting to 0v and 5 volts on ledlabs, allowing the 5v to connect when you want the timing to start.                                                   A rising voltage is seen on the lm3914 as the capacitor charges and after 10 seconds (1T) it has reached 63 percent of 5v, which may lay around just over half way on the lm3914 (3.15v) as this scale is 0v-3.6v., after the first time constant, a rate of change can be noticed on the leds output of the lm3914 with respect to time, this is, it is taking longer for the  remaining leds to light, ie the growth of amplitude or voltage is not getting much higher within the same time frames(remember (5T) is beyond the 3.6v scale of the lm3914, so the capacitor goes on charging.  Disconnecting the 5v rail shows the decay of the capacitor through the leds on the lm3914.