L298 Driver

So, I was using the L298 to control motor speed. I used PIN 9 on my arduino to vary speed using a PWM signal. At full duty cycle 255 I read ~12V on the O/P side.

Then I connected the same 'PWM input pin' of the L298 board to my 3.3V pin on the arduino. This time, instead of varying the voltage proportionately, the L298 still output full voltage.

I'm new to this, does the L298 work purely on switching signal alone ?, I ask this since I wanted to control motor speed using a digital POT in the input side of the L298. I'm doing this to avoid any form of switching and to get a maximum analog type voltage output. If it only uses PWM switching, is there a way around this?, to vary voltage other than using a PWM signal ?

does the L298 work purely on switching signal alone ?

Correct. The L298 outputs are either on or off.

This is much more energy-efficient than "analog control", that is, effectively using a variable resistance in series with the motor.

vikramnayak:
I ask this since I wanted to control motor speed using a digital POT in the input side of the L298. I’m doing this to avoid any form of switching and to get a maximum analog type voltage output. If it only uses PWM switching, is there a way around this?, to vary voltage other than using a PWM signal ?

The L298 won’t respond to analogue input. Instead, if you’re planning to incorporate an Arduino, you can read a pot on an Arduino analogue input pin with ‘analogRead()’, scale the 0-1023 result to 0-255 using ‘map(val, 0,1023,0,255)’, (or simply by dividing by 4), then output a 0% to 100% PWM signal from an Arduino PWM pin using ‘analogWrite()’.

I don't suppose you'll tell us what you're trying to do?

How will this output be used?

BTW, measuring the voltage output from a L298 won't always give a good idea of what's going on. I think the L298 may need to be under load to work well. I've read of people thinking their h-bridge didn't work because they measured the output without a load.