This is a simple device designed to control supply voltage +5 V Monitor provides information signals TTL level, accompanied by the LED display, indicating that stress or deviated from the nominal value, or vice versa, is in a “box”.
The basis of the device is a low-current window comparator IC LTC1042 company Linear Technology . The reference voltage is 2.5 V ± 0.005 V for the middle “window” created by zener D1 and fed to pin 2 comparator. The width of this “window” equal to 20% (± 10%) of the reference voltage established at pin 5 chip divider R4, R5.
The controlled voltage is divided by two resistors R2 and R6, and fed to pin 3 of the chip. Voltage at the terminals 2 and 3 are compared with the established view of the deviation (10%, output 5). The green LED D2 is illuminated when the voltage is within the desired range. If the voltage is out of range, red LED D3.
In conclusion, the resistors R2, R4, R5 and R6 must be highly accurate. Linear Technology recommends the admission of 0.25%.