Adafruit Motor Shield

I've understand the main purpose for using a motor shield (powering motors without frying your Arduino) but I've also seen a few videos recently about using MOSFETS and pwm to power different motors. Why bother with a motor shield, libraries, etc. if simpler components can do the same thing? What does the motor shield offer that simpler components driven by any Arduino cannot accomplish?

I've been considering the Adafruit motor shield 2.3. I was discussing with a friend that wasn't savvy with Arduino when she asked me why even bother with the shield. I couldn't give a decent answer since I don't have enough electronic/programming experience. I've basically been getting by how-to's on Youtube and this forum.

  1. It is a single shield to plug into your Arduino without having to wire up discrete components.

  2. It comes with a library.

  3. The Adafruit shield in particular allows many shields to be stacked and addressed individually.

  4. It is cheaper for the manufacturer to buy components in bulk so the final cost is less than you can buy the parts for.

MorganS:

  1. It is a single shield to plug into your Arduino without having to wire up discrete components.

  2. It comes with a library.

  3. The Adafruit shield in particular allows many shields to be stacked and addressed individually.

  4. It is cheaper for the manufacturer to buy components in bulk so the final cost is less than you can buy the parts for.

  1. I understand the value in plug-n-play with the UNO or MEGA. If you are driving that shield with and UNO or MEGA, then using that form factor for prototyping would be beneficial. However, in trying to minimize the space requirement, I'd rather go the route of using discrete components (if I had the electronic/programing know-how).

  2. The only point I would argue here is if I were using an Arduino in any form with 3 Mosfets, I wouldn't have to use any library. I do think it's pretty cool that the Adafruit people wrote a solid library base for their shield though!

  3. Very handy if I had space and needed to control various motors in this fashion. Maybe this is where the value tipping point exists. I would assume that it would be easier to use multiple shields than extraneous components. I dunno....I still missing a ton of experience in this area.

  4. This surprises me. The Adafruit Motor Shield "kit" is just the shield itself, priced at 19.99 (no motors included). If I'm just powering 3 motors for example, I would need 3 Mosfets (I think). Are mosfets typicall expensive? My thought was that I could buy a smaller Arduino (Micro), 3 Mosfets and a proper power supply and that should cover it. Where is the price savings?

A MOSFET using PWM can drive a motor in only one direction. A typical motor shield has a H-bridge ( or 2) that allows one to drive the motor(s) forward and reverse.

groundFungus:
A MOSFET using PWM can drive a motor in only one direction. A typical motor shield has a H-bridge ( or 2) that allows one to drive the motor(s) forward and reverse.

Ah…therein lies the value. I’m assuming that you could piece together a simpler H-bridge but I’m assuming that would add to complexity of the “simpler driving circuit”. Pros and cons with both.

Thanks for answering!

You didn't say size was a requirement in your first post. You didn't specify how many motors, how big they are or if they need forwards and reverse. Without important details like that, it's impossible to suggest anything better than "buy the shield".

There's a lot of support components on the shield that you haven't factored into your cost+difficulty analysis. You need to connect to the Arduino with pins or headers. You need connectors for the motors and the high-current input power. You need decoupling capacitors and bulk capacitors. You need protection components in case you plug it in backwards. You need freewheel diodes for inductive kickback. You need pulldown resistors so nothing weird happens while the Arduino is being programmed. Finally you need a PCB to carry all those components.

In general though, if you need something smaller than the shield then you should build something smaller than the shield. Do you need help selecting components for your (unspecified) motors?

I didn't mean for my response to come off as negative criticism. I apologize if that's how it was interpreted. I am truly just trying to understand everything around this shield.

I assumed that there was other stuff going on within the shield but I only intended to attempt to simplify the materials required. My limited experience is definitely shining through here.

Ultimately I'm going to use the shield. At this point, I have no reason not to. I thought that just driving (2) separate 12V motors, I could simply run them with PWM and mosfets. I guess not.

I would only be running them on one direction anyway but it sounds like the stuff other than the H-Bridge would still be required.

Thanks for the help!