2 power supplies for my project - not good practice?

Using Arduino Project Guidance
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Hello,

I should've posted here before I started this project (it's completed now), but I have a 'best practice' type of question.

I thought I remember reading somewhere that when you're working with motors/servos, you should keep the power separate from the Arduino. However, now, I think I'm not remembering that correctly - it might have been different circumstances.

Anyway, so my completed project has 2 power supplies - in the photo you can see that I have a 9V and a 12V. The 9V powers the 'Arduino' part - the ATMega328, piezo, RTC, etc.
The 12V powers the motor driver board / motors. (I'm using 2 motors, both 12V DC 5RPM 'High Torque Gear Box Motor Speed Reduction Toy Hobby' motors from eBay. They don't run at the same time - I have one run for a few seconds, turn off, then the other one runs for a few seconds)

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Ok, soooo my question is - I'm thinking this isn't best practice, is it? There must be another way I could have done this (safely) with a single power supply, isn't there? I mean, I don't remember ever buying any consumer electronics with 2 power supplies.

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I mean, I don't remember ever buying any consumer electronics with 2 power supplies.

You've never bought a desktop or laptop computer?

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The 9V could have been a 5V wallwart instead, then the onboard 5V regulator would not have been needed.

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I must be missing something here...desktops have 1 power supply...?? And laptops do too, unless you count the battery...

Unless you're referring to ones with redundant power supplies :wink:

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Ok, I get the thing about the 9V / 5V regulator, but that's for the Arduino and supporting components (piezo, RTC, etc.), but the motors / motor driver still need a 12V power source...

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Your typical desktop power supply has 3.3, 5 and ± 12 Volt supplies.

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Oohh, I see, yes. But there's only 1 physical power supply, and only 1 power cord you have to plug in.

But my project has 2 separate wall warts you have to plug in for power.

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But my project has 2 separate wall warts you have to plug in for power.

Not very user friendly or convenient. From an engineering point of view there's nothing wrong with that. But, from a marketing point of view it's a Mickey Mouse design.

There's nothing wrong with 2 (or more) completely separate internal power supplies if you have one external power plug.

But, in production it would be more expensive than one multi-voltage supply (maybe not the case for a one-off DIY project) and it takes more space and requires a bigger enclosure.

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Haha, well, it was just for 1 - it's for my own project...no intentions of selling it, but yeah, that's what I thought - goofy for a 'real-life' device.

There's nothing wrong with 2 (or more) completely separate internal power supplies if you have one external power plug.

So I could've just used the single 12V external power supply, and split it out into a 5V with the voltage regulator, and kept the 12V as is for the motor driver / motors? Is that actually as simple as it sounds?

I've never heard of a multi-voltage supply - so there's wall-warts that can output more than 1 voltage somehow? I'll have to look around for something like that for possible future projects.

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so there's wall-warts that can output more than 1 voltage somehow? I'll have to look around for something like that for possible future projects.

There are lots of power bricks that offer separate 12V and 5V outputs, among other possibilities. Check the thrift shops or computer recycling depots in your area for cheap ones.

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Ok, thanks for the tip, that seems like it would at least be better than what I have now (2 separate wall warts)

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