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I'm new to electronics. I'm trying to build something that will involve controlling the direction of rotation of a DC motor. A lot of online resources seem to recommend using an Arduino motor shield. But why shouldn't I just use some combination of an H-circuit (to control the direction of rotation) and a MOSFET (to switch power to the motor on and off)?

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    You can use the H-circuit (and even use it to switch the power on and off), nothing wrong with that, but you have the potential for more errors that way which is probably why the recommendations are to use a pre-built solution – user2813274 Jun 26 '17 at 20:38
  • I was just about to edit to my question to also ask if an H-bridge by itself would be enough. I just drew a little circuit diagram that made me think it would be. Thanks for your response. – lostinthecloud Jun 26 '17 at 20:42
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    Using a shield is more convenient since it should just work. Especially for beginners it is frustrating if things do not work as expected and debugging that takes some experience (which you don't have). You can always build your own MOSFET based circuit for that if you like at a later stage when you have more experience. – Bimpelrekkie Jun 26 '17 at 21:03
  • @Bimpelrekkie I hear what you're saying, but I don't see how using an H-bridge would be difficult (unless the H-bridge was malfunctioning somehow). Maybe I just don't know enough. Thanks for the warning. – lostinthecloud Jun 26 '17 at 21:18
  • Isn't the Arduino "motor shield" one or more H-bridges with drivers? In other words, your two choices are essentially identical. What do you see as the difference? – Dave Tweed Jun 26 '17 at 21:29
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The major benefit to using a shield vs building the same circuit yourself is convenience. Assuming that your circuit is identical to the circuit on the shield then they should both work in an identical manner (barring any minor variations due to the quality of solder joints or circuit paths). The nice thing about the shield is it is almost plug and play. It has the same footprint as the Arduino and you don't have to design and assemble the circuit on a perf board. Generally, you will end up with fewer wire leads running around making for a cleaner assembly and easier prototyping.

  • Thank you for your response. I appreciate your points about convenience and fewer wire leads. – lostinthecloud Jun 27 '17 at 17:58
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A Arduino motor shield is just a H-bridge (plus some other bits), but it's a H-bridge that works.

Drawing a H-bridge and a MOSFET is easy. Building one that works is much harder. Online resources recommend the shield because trying to walk someone through the development of a functional equivalent is complex.

  • Sure, but the fair comparison is to an H-bridge IC on a shield, and the same IC on a smaller generic or custom board. – Chris Stratton Jun 27 '17 at 3:06
  • Thank you @ChrisStratton for your comment that helps to clarify Heath's posted answer. I am very new to electronics and statements such as "an Arduino motor shield is just an H-bridge" have the potential to confuse me. – lostinthecloud Jun 27 '17 at 18:06
  • Heath's point is that building an H-bridge out of four discrete FETs (or less preferably bipolar transistors) is a lot harder to get right than using a bridge IC. Generally one would only do it when trying to handle very high currents, or perhaps in a few cases of extremely high production volume if that looked cheapest. – Chris Stratton Jun 28 '17 at 0:03

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