WHY ARE YIU USING TIP120s with an L293 ???
If you are going to use the L293 , DON'T use the TIP120 !
Use one or the other not both. Post your schematic that shows how you have the TIP120 connected.
You should NOT need transistors if you are using the L293 because it has internal transistors..
Your circuit design is flawed. Remove the TIP120 transistors .
POST YOUR SCHEMATIC
ALSO, post your code.
See, when I connect my digital pin 3 to the ENABLE pin of this chip I can do this:
analogWrite(3,50);
analogWrite(3,100);
analogWrite(3,150);
..
Changing the PWM I can make the motor spin faster and faster. So there is no "absolute HIGH". What I am asking it this: why when I do analogWrite(3,255) the chip outputs the 12 v? Where, in the datasheet of this chip, is written that passing 5V to the ENABLE pin it will output all the source power? Cause if I pass 3V to the ENABLE pin the chip will not output the 12V!
This question seems to indicate that you do not understand how PWM works. The motor voltage will always be the full source voltage . The motor speed changes due to the duty cycle changes, not due to any change in the motor voltage. If you output a dutycycle of 3% (analogwrite(pin,1)
, the motor voltage will still be 12V, but for a period of 1/255 of the 490 hz switching speed . (2 mS period)
analogWrite()
If this is your code :
analogWrite(3,50);
analogWrite(3,100);
analogWrite(3,150);
Then no wonder you have a problem. Is it really possible you don't realize that a motor cannot change speed instantaneously ? It has mass. It requires time to accelerate to the commanded rpm.
Post your entire code so we can see what you actually doing. The above code makes no sense because you don't have any delays in between the speed changes. You would be better off using a potentiometer
and using the MAP function to set the speed based on the pot position.
Look at this example.
or this one.
When I apply 5V to the ENABLE PIN of the L293 D it gives me the full 12 V at the motor.
Really ?
Is there any thing else ?
Is there any other possibility between NO voltage and FULL voltage ?
What's odd about this question is that it indicates a complete lack of understanding of both TTL logic parameters and this chip in particular. Input voltage level ranges are specified for the various logic families. An arduino or L293 using 5V TTL level , is going to consistent with 5V logic input voltage level parameters. A 3.3V logic circuit is going to have different input levels. Before attempting to use an arduino or L293, it would be prudent to start with the basics:
LOGIC LEVELS
Where, in the datasheet of this chip, is written that passing 5V to the ENABLE pin it will output all the source power?
See Function Table at the bottom of Page-2 of the datasheet
What does that say ? (OUTPUT Y H (or L)
When you look at the schematic above the Function Table, is there any doubt what "H" could mean ?
IMO, this post should have started with the introduction:
"I have no electronics ,motor control , uController or logic circuitry experience and would like to use the L293 with an arduino. What do I need to know to do this ?
This would have saved us some time.
