I simply cannot find the answer for this. I've looked at circuit schematics and read stuff about these topics separately, but still cannot grasp if I can use a low-level crude hand made H-Bridge (no factory product) using 4 transistors which are controlled by only one PWM output pin from a Leonardo.
I'm skipping the common emmiter vs collector, high input impedances, and all the other refined issues for the moment, it is simply a logical issue. In my mind, one single output pin with pwm from the arduino simply is not enough to control 2 pairs of transistors for I risk a short circuit between a high and low side pair.
If I think about it using 2 digital output pwm enabled pins from arduino, then it seems reasonable. Maybe it is a matter of not being able to integrate the possibilities that the combination of software and hardware of the arduino allow for.
Could someone point me to a schematic or two, please, to enlighten me? Maybe some explanation is also needed, because I don't see how to control the motor for opposite directions with only 1 pwm pin in the refered conditions.
It seems very complicated for my level. Trying to simplify this issue I'll ask simply if using 2 pwm pins, one for each low side transistor, is ok.
In this option it is simply a matter of writing code where each pwm pin value is assigned via some digitalWrite statement, yes? Does someone know of an example of this code which does not utilize premade market available bridges but pure crude transistors?
Two are for the PWM outputs. Only one is active at a time. They connect to the low side transistors and control the speed.
The other two outputs connect to the high side transistors, they control the direction.
The direction control pins are complementary, if one is High the other is Low
You need to make sure that transistors on the same side of the bridge are never active at the same time.
With the addition of a few logic gates, you would need only two pins, speed and direction.
It gets more complicated with a home made H bridge if the high side of the H Bridge is at a higher voltage than the Arduino. What are the voltages in your design ?
+1
Beginners often forget that you can't use N-channel fets high-side (source follower) without boosting the gate voltage 5-10volt higher than the H-bridge supply.
Leo..
If I still need to incorporate logic gates I have to forget this and resort to a premade bridge, which on top of everything else also deals with powering, switching, protection and so on.
My challenge now is the choosing of different parts, battery, charger, bridge. I use a 12V motor from printer and a 3,3 v.
This is a basic schematic for a complementary bipolar H bridge, sorry without component values or numbers. Rload is whatever you want to drive, say a motor. Control signals at CW and CCW, only one must be HIGH at a time. They could be 3.3 or 5V logic signals. The two transistors connecting the bases of the output pairs effectively do the logic level translation so VDC can be higher than logic levels - they can be general purpose small signal types such as 2N2222. For an inductive load you would also need flyback diodes at the usual places. For higher currents the output drivers could be complementary Darlingtons. You don't need any additional logic but will need to control the pins driving the two sides to avoid both sides being on at the same time in your code. Not sure this is possible using the standard PWM functionality of Arduino. So 2 pins needed for drive.
