Im building digital tachometer to display spindle speed on my hobby CNC machine.
Im using optical censor to pick up the RPM signal. Signal from the optical sensor connected to LM2917. Im reading output from the LM2917 using digital voltmeter built on ICL7107 to display the output voltage. When Im increasing the spindle RPM the voltage increases and when Im decreasing spindle RPM voltage decreases.
But here is the problem:
The output voltage increases only to 3.6V. Then it stays on 3.6V, does not get any higher.
The supply to LM2917 is 6V
Please help. What am I doing wrong?
Im using optical censor to pick up the RPM signal. Signal from the optical sensor connected to LM2917. Im reading output from the LM2917 using digital voltmeter built on ICL7107 to display the output voltage. When Im increasing the spindle RPM the voltage increases and when Im decreasing spindle RPM voltage decreases.
But here is the problem:
The output voltage increases only to 3.6V. Then it stays on 3.6V, does not get any higher.
The supply to LM2917 is 6V
Please help. What am I doing wrong?