hi

i've been trying to use a ac motor with power ratings of 5 amps 235 v and 350w and i have connected a fan to it.i also have a heater with range 0-1000'C with ratings of 220v and 5 amps. am using a spilit range controller to control temperature inside a furnace using the above devices. the output i get is 4-20 ma from the controller. this i've converted to 1-5v.am using 2 clippers to divide the output voltage into 1-3v and 3 to 5v.i am not sure bout using IC741 to split the voltage cos it saturates and does not give me proper output....

now i have been searchin the net for a proper drive circuit for driving the motor and the heater.. i thought of using a triac and do phase control to control voltage for the motor. i don no how to control the temperature but i guess an scr driver can be of some use.
i am from india so getting 220v is not a difficulty.....previosly i had a dc motor to do the same for some reason my professor here asked me to drop the idea of using dc motor.

i am basically an instrumentation student and am little weak in electrical.pls help me with the following questions:
1) is using a clipper wise to divide the controller output voltage into 1-3v and 3-5v?
2) somebody pls help me with the drive circuit for the heater and the blower.
3) is using a driver to control the voltage the best method or using an amplifier the best method???

thanks in advance

 

To control the heating unit, which I guess is a high resistance wire, you can use a TRIAC with controlled firing angle with AC voltage or use DC voltage and PWM. To control the speed of an AC motor you will need an inverter or you can use a DC motor and use PWM.

 

ok i'll do that.... and is splitting the voltage into 1-3v and 3-5v using 2 clipper circuits the best method????? i mean i have split the voltage into two.... but am not sure if i can have a more efficient way of doin it.

 

Why do you want to split the voltage? Can you post a diagram.

 

i have attached the circuit. for 1-5v signal am using a function gen. since the output from my controller is only 1 to 5v i dont mind wen the signal going beyond the limit either way cos in the practical situation this is not gonna happen. ya can also see the output voltage in the oscilloscope.

i wanna split the voltage since am bringing in split range control for controlling the temp inside the furnace