LED voltage monitor

ED voltage monitor A stable power supply is absolutely essential for the correct operation of computers and TTL circuits. A voltage fluctuation of 10% is certainly not tolerable, therefore it is prudent to keep a regular check on used, the LM 3914, is very similar to the one used as an "audio level meter" elsewhere in this issue (the LM 3915). There is a slight difference between the two however: The LM 3915 has a logarithmic scale whereas the LM 3914 has a linear scale. The latter device contains a row of 10 identical 1 k&"1 Di Vcc 5V .110% 25on The power supply for the circuit can be taken from the voltage to be monitored as the current require- ment is only 20 mA. Diode 011 is included to protect the circuit against reverse input polarity. To calibrate the circuit it must be connected to an adjustable regulated power supply. The input volt- age is then adjusted until a reading of 5,41 V is obtained on a digital voltmeter. Potentiometer P1 can now be adjusted so that D9 and D10 ...