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I'm looking for a solution to control the direction of a powerful DC Motor. I came up with the idea to use a H-Bridge. Since the motor uses up to 3.2A the amount of possible H-Bridges is quite limited. The supply voltage on my quad is 3.7V. Since my outputs are limited I want to control the position using only one Digital Output. Which does work in one direction if set to 0 and other direction if set to 1. The PWM output should control the velocity. Is that even possible?

I found this one but I have absoultely no clue if this one can be controlled only with 2 inputs per motor (1 PWM , 1Digital Output).

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3 Answers 3

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enter image description here

Above is a section from the data sheet. As you can see, the bridge needs all four data lines (IN1L, IN1H, IN2L & IN2H) connected to control it properly.

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  • \$\begingroup\$ So it doesn't work as I want. Is my request even realizable? \$\endgroup\$
    – Slaxx
    Mar 16, 2015 at 15:39
  • \$\begingroup\$ I don't think it's realizable from texas instruments. I took a look and although they do have several that are compatible with your IO requirements they either never had the current capability or they couldn't work down around the 3v mark. I'm sure there must be one around though! \$\endgroup\$
    – Andy aka
    Mar 16, 2015 at 15:45
  • \$\begingroup\$ crutschow told me i could use it with 2 and gates and an inverter. @Andy aka why do you think that won't work? \$\endgroup\$
    – Slaxx
    Mar 17, 2015 at 10:31
  • \$\begingroup\$ Of course it will work but let me remind you that you said "I only have 1PWM and 1 Digital Output per Motor". I presumed you could not add any further chips due to mass/space limitations. \$\endgroup\$
    – Andy aka
    Mar 17, 2015 at 10:44
  • \$\begingroup\$ Oh ok. No I just dont have more outputs on my Micro ;) \$\endgroup\$
    – Slaxx
    Mar 17, 2015 at 14:31
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As far as i understood your question, You can control velocity as well as direction with complementary PWM generated from any type of microcontroller. Since, recently i am working on a tracked robot, I designed H-bridge that uses two PWM (complementary with dead band) to completely operate the motor. If you are doing the same, I can provide you with more details.

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  • \$\begingroup\$ I only have 1PWM and 1 Digital Output per Motor... \$\endgroup\$
    – Slaxx
    Mar 17, 2015 at 10:29
  • \$\begingroup\$ You should better use IR2109. This IC makes a complementary pair of the original PWM given to it. and then feed the complementary PWMs to the switches as described in Theory. The same operation can also be achieved with some microcontrollers but using IR2109 is pretty simple. \$\endgroup\$ Mar 18, 2015 at 15:33
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With one inverting gate, you can control H-bridge as you described. (The built-in editor is missing a motor-symbol, so substituted it with a lamp-symbol.)

When DIR is 1, motor turns one direction, when it's 0 the motor turns other direction. PWM controlled current source would work as a driver to control the speed.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Something like this for the current source: electronicshub.org/… \$\endgroup\$
    – Zokol
    Mar 16, 2015 at 17:33
  • \$\begingroup\$ That won't work as you have drawn it. It's full of holes such as how does the output of the NOT gate rise above about 1V when the base of Q6 (that I'm presuming is meant to be NPN) is dragging it down to ground. What about the volt drop across Q1 and Q2 when either are activated (and I'm presuming they were also mean to be NPN). What about the PWM signal - it will need converting from a logic level value with low current to something much sturdier. Please don't reply with "clearly base resistors were meant to be presumed" - accuracy is the order of the day on circuits not hand-waving. \$\endgroup\$
    – Andy aka
    Mar 16, 2015 at 18:15

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