While working with TTL and similar digital circuits, it is often found necessary to evaluate the voltage and logic levels at a number of places. Though digital multimeters can do the job, but at places where quick trouble shooting and testing is involved, the use of these becomes rather too cumbersome. This is the very purpose behind presenting this 5 volt bargraph voltage meter which gives a clear ten step display that easily interpretable because it is clearly colour coded.
The circuit uses a type LM3914 integrated circuit which comprises about everything in this circuit. The LM3914 has a built in reference and a precise I0 step voltage divider. R1 and r2 set the LED currents and the reference to the desired level.
The chip is wired in the 'bar' mode. As the voltage at the test probe increases from zero to five, the LEDs light up in a successive sequence from D1 to D10 ; and the display colour changes from yellow, to green,to orange, to red, in that order.
The circuit uses a type LM3914 integrated circuit which comprises about everything in this circuit. The LM3914 has a built in reference and a precise I0 step voltage divider. R1 and r2 set the LED currents and the reference to the desired level.
The chip is wired in the 'bar' mode. As the voltage at the test probe increases from zero to five, the LEDs light up in a successive sequence from D1 to D10 ; and the display colour changes from yellow, to green,to orange, to red, in that order.
The circuit of bargraph meter
