Hello Friends
I own a Voltage Stabilizer which consists of 1 Transformer, 2 Relays, PCb with 4 transistors (Probably as a voltage detector)

The Transformer consists of four terminals let's assume a,b,c,d. Other end of the transformer has two terminals where 18 Volts is available which is feeding to the pcb and relay circuit.

1. When the input voltage is 220V Relay1 becomes active and the output
is available through the Relay1 (NO) and Relay 2 (NC) contacts.The Transformer becomes out of circuit.

2.When the Input voltage drops to 170V both Relays remains off and the
required output is available between terminals a and d

3. When the Input voltage is 250V both relays are on and the output is available at terminals a and c


I would like to convert the same to be more reliable and efficient by using the same transformer and add on AMTEL Microcontroller (4kb flash memory), Triacs etc. I have the following questions:-

1. What IC is to be used to detect the voltage ?
2. How to get rid of the relays ?
3. How to connect the Triacs directly to the transformer to change the tappings to obtain the required voltage i.e. 220V ?
4. Is MCU AT89C51 with 4KB flash memory good enough for this project?

Can any body help me out?


Thanks

Yogesh