This indicates like LM3914 in dot-mode. It is a drawing i made made to troubleshoot a gadget, around two decades ago. Strangely it had a echo of a design i had made into a 7107 dpm years before that. Now i am scanning all my drawing and notes, useful or not. Clean or with errors. Many Errors = 1 Blunder. Some projects i made have been expensive Blunders. So see them with a skeptic eye, fix them, try them. Thats all for now.
This Circuit helps in the monitoring of mains supply voltage. It does not use a isolation step down transformer. This has to be constructed only by skilled people with knowledge of safety requirements.
C1 0.47uF can be brought down to 0.22uF for low LED currents, use high efficiency ultra bright LEDs.C1 should be 440V AC or 630V DC plastic axial yellow, polyester, polycarbonate, polypropylene, metalized film.
R3-R6-R9-R14-R18 resistor divider determines the LED turn on or threshold switch points, 10M for hysteresis.
The Measured Value and The Setpoint are two inputs to a Control System. The Measured Value is the Amplified input of a Transducer or Sensor for some Parameter that needs to be controlled. It could be Pressure or Temperature...etc.
The Setpoint is the User Defined Input using a Potentiometer, Thumbwheel, EPROM or Flash Value. This is the value at which the process has to be maintained for that parameter.
This is a Test arrangement for Leakage Testing of Diodes on Reverse Bias. The leakage current indicates the ability of the diode to withstand higher voltages. An AutoTransformer or Variac can be used to vary the test voltage. Even Plastic capacitors can be tested for leakage this way. High Resistance Indicator - del50004
Safety Precautions - Use a Isolation 1:1 transformer for safety. This circuit has to be enclosed in a insulated cabinet. A Jig or Acrylic Safety Plate with clamp can be used to connect the diode. The voltage is only applied as long as a Mains two way push switch is pressed. This adds to the safety.
This circuit is derived from an application note of L296, It is a Power Switching Regulator from ST. The advantage of using a switching regulator is that there is not much Heat Dissipation in this circuit. Switching Battery Charger with L296 - del20031
If you had to build the same with a series regulator, it would be very big due to external transistor and a huge heat sink. This circuit takes a small place on PCB, efficiency is high so power is saved and reliability of product improves, lastly the thermal gradients within the cabinet is avoided so that any form of drift or component specs variation can be avoided.