mean_well

I see a lot of folks in the MAD Discord seemingly overwhelmed by the idea of running their own power connectors. The idea of running power using anything other than factory power connectors or factory USB cables and chargers feels unsafe to them.

Inevitably I see some of these same folks start amassing the cheapest power strips / USB chargers they can find, and posting something that looks like this:

These folks feel safe because they're using all off-the-shelf components so they don't leave their comfort zone... but the reality is the more power strips you have, and the more wall chargers you use, the more AC high voltage points of failure you're creating. By comparison, you can safely run 50 ATVs off of one DC power supply with ONE high voltage wall plug.

There are almost no legitimate circumstances in which you could convince me that it makes more sense to run USB or factory power cables to these things if you run more than five devices. Yet almost no one does it.

I decided to type of a very basic informative post on these power supplies, with the hopes that it'll empower some people with the knowledge needed to assemble these systems. It's really very simple, and really very safe. That said, a few disclaimers: I am not going to call this a "how to." Electricity can be dangerous, and if you didn't already know that then you wouldn't be reading this. Also, I live in the states and am basing everything herein on our electrical grid and my hobbyist's understanding of electronics.

This writeup is going to assume that you know very little about electricity. I'm going to go over some very basic stuff, and I'm probably going to do a really bad job explaining some it.

AC vs DC. Alternating current vs direct current. The current coming out of your wall socket is AC. The current most small electronics use is direct current. Imagine if I punch you in the face, and with the same fist extended I continue to turn my body in circles and I keep punching the same side of your face with the same fist every time my body spins around. This is is DC -- direct current. My fist is spinning around going along a circular patch, and every time it crosses your face on that path you get hit on the same side of your face with the same side of my fist. Now imagine I punch you in the face, but instead of spinning around in circles along a path I swing my fist back the way it came and hit the other side of your face with the back of my hand. Then I do it over and over again, back and forth. My fist is still moving along roughly the same path it did before, but instead of turning in a loop and completing that path, I move my fist back and forth on the path and hit you with it over and over again. This AC - alternating current. Instead of delivering power to your face by going in a looped path, my first is delivering power to your face by alternating back and forth on that same path.

This is why small electronics (DC) have a positive and negative (ground) -- to complete a looped circuit to deliver power. A grounded wall socket will three prongs, and one of this is also ground, but it doesn't work the same way as the ground in a DC circuit, and in fact, AC wall plugs can operate just fine without the ground -- that's why you'll often see older plugs with just two prongs. In an AC plug the ground is an added safety feature. The other two prongs are your hot / common... and these are the two wires the current will alternate between to deliver power.

So our power supply will take an alternating current from the wall, and give us a direct current to work with for our ATVs. This is the same thing the "wall wart" power supply that ships with the device does, just on a smaller scale.

Now that we have this basic understanding let's take a look at our power supply.