The proposed Accurate 7-Stage Op Amp Controlled Mains Voltage Stabilizer Circuit concept is rather very simple. It uses discrete op amps wired up as comparators to sense the voltage levels.
As can be seen in the diagram, each op amp's inverting inputs are provided with sequentially incrementing voltage reference levels through a series of presets which drops a certain amount of voltage across itself.
Each op amp compares this voltage with the common sample mains AC voltage level supplied to the op amps non inverting inputs.
As long as this sample voltage is below the refrence level the respective op amps keep their outputs low and the subsequent transistor relay stages remain inactive, however in case the voltage levels tends to shift from its normal range, the relevant relays trigger and toggle the transformer taps so that the output is appropriately equalized and corrected.
For example if the input AC voltage tends to fall, the upper relays may get triggered connecting the relevant higher voltage taps with the output and vice versa in case the voltage shoots upwards.
Here the op amp output inter-connections makes sure that only one optocoupler and therefore only one relay gets activated at a time.
P1---P8 = 10 K Preset,
A1---A8 = IC 324 (2 Nos)
R1---R8 = 1 K,
All diodes = 1N4007,
All relays = 12 volts, 400 Ohms, SPDT,
Opto Couplers are all = MCT2E or equivalent,
Transformer = Pink Tap is normal voltage tap, the upper taps are in the decrementing order of 25 Volts, while the lower taps are in the incremental order of 25 volts.
Full circuit diagram of the proposed Accurate 7-Stage Op Amp Controlled Mains Voltage Stabilizer.