TD7294 with ac vibrator

[anoopsharma007]

hii all
i m working on a project in which i have to control vibrations with dc signals(PWM) instead of 50Hz ac. i m using an ac vibrator. i m using TDA7294 amplifier to drive ac vibrator and at input i m applying 50hz pwm. problem is that i want 50V maximum output for vibrator...
my doubts are
1. is TDA7294 is right choice.
2. is it necessary to supply +ve and -ve output like ac.(Bcoz pwm is only +ve).
3. i have conected a pot at feedback to control output.is it ok??

 

[mister_rf]

Still missing important details of this project. What are the required power parameters for the AC vibrator?
Why not use a power MOSFET transistor controlled by the PWM signal?

 

[anoopsharma007]

i am operating that vibrator on 50V ac with 3A current..
i can not control vibrations using PWM. i want to control it with voltage change i.e. by providing variable output voltage(50V 50Hz or 30V 50 Hz etc.). thats why i m using audio amplifier.

 

[Faisal Al otari]

hii all
i m working on a project in which i have to control vibrations with dc signals(PWM) instead of 50Hz ac. i m using an ac vibrator. i m using TDA7294 amplifier to drive ac vibrator and at input i m applying 50hz pwm. problem is that i want 50V maximum output for vibrator...
my doubts are
1. is TDA7294 is right choice.
2. is it necessary to supply +ve and -ve output like ac.(Bcoz pwm is only +ve).
3. i have conected a pot at feedback to control output.is it ok??

you should add full rectifier bridge (4 diodes) to reference feedback signal to control by full singnal phase +V phase and -V phase, of course when you use just one diode to rectifier the reference feedback that mean you will control by just one phase of the full signal but the next phase will be very high or very low and the circuit will be very rough.

 

[tuffyhills79]

I completely agree with Faisal Al otari.

 

[anoopsharma007]

View attachment pic.bmp

this is my circuit..now please make corrections .. this circuit is working but i m not getting proper vibrations as i was getting with ac....

 

[Faisal Al otari]

View attachment 74696

this is my circuit..now please make corrections .. this circuit is working but i m not getting proper vibrations as i was getting with ac....

Of course, you can't get proper vibrations like the AC!! cause the AC is pure sine wave while PWM is just square wave modifying.

 

[anoopsharma007]

now what i hav done..i am using a xr2206 function generator . i have generated 50hz sien wave..and fedding to tda7294 and now vibration is good but not exactly like AC..the reason i think is that the sine wave that i am generating is not touching ground(2V min and max 6V). i have tried many circuits to attain offset to ground but not successful...
so now please tell me what i do...i dont want to use any -Ve supply...

 

[Insider2009]

if you can be more specific about what you actually require to do maybe then we can help you,
uptil now the whole thing is confusing
how can you get 50 Volt AC out of an Audio amplifier I fail to understand

AC vibrators are different in structure from DC vibrators
they need a change in flow direction of the current to demagnetize
then the Mechanics is also adjusted in the same way
you should check the vibrator mechanism if its suitable for this kind of circuitry or not

- - - Updated - - -

if you can be more specific about what you actually require to do maybe then we can help you,
uptil now the whole thing is confusing
how can you get 50 Volt AC out of an Audio amplifier I fail to understand

AC vibrators are different in structure from DC vibrators
they need a change in flow direction of the current to demagnetize
then the Mechanics is also adjusted in the same way
you should check the vibrator mechanism if its suitable for this kind of circuitry or not