If you work with electronics on a semi-regular basis, one of the things you really need is a bench power supply. They are practical, not overly expensive and once you buy one, you’ll be using it for many years to come. Personally, I only have two power supplies. However, I regularly look for a better one, so maybe I can help people figure out what to look for…
My power supplies
Yihua 305D
This is a very basic analog switching power supply. 0-5A, 0-30 volts, max 150W, there are a thousand like it on Amazon, including a newer version of the same thing.
It has the functions you need in a lab power supply:
- voltage readout
- current readout
- voltage limit knob(s)
- current limit knob(s)
The current limiter is important, because it can work sort of like a fuse and save your electronics from burning up if you do something wrong. It also lets you use the power supply as a battery charger without having to worry about overheating the batteries.
However, there are a couple of reasons why this isn’t my everyday power supply:
- the analog knobs are easy to change accidentally, or drift slightly over time.
- there is no button for disabling the output while adjusting the current or voltage
- 5A is not enough to power a lightsaber blade
Gophert CPS-3220
At the time, most lab power supplies would only supply up to 3A, and finding one that could power a blade was tricky. However, after much looking, I found something similar to this on ebay.
This one has digital controls (although not very good ones) and it can produce up to 20A of current, which is enough to power a blade for testing. It’s also nice and stackable. The biggest drawback is that the power output is on the back for some reason. Not a big deal since I rarely unplug it.
So this is is basically what I use most of the time, and most of the time it’s set for about 4 volts, similar to what a fully charged lithium-ion battery would produce. However, I still dream of a better one…
What to look for
Ok, so lets talk about some of the features available in a power supply that you may or may not want. However, don’t expect this section to be super-helpful, because most people don’t need most of these features…
Good controls
This is obviously a matter of taste, but I don’t want too many buttons, yet I want it to be quick and easy to operate. Some power supply makers clearly think that more buttons is better, I don’t.
Digital controls
Unfortunately, digital controls tends to be a little more awkward to use than analog controls. However, I like that they don’t drift, and changing the accidentally is usually not something that can happen.
High-precision readout
Some power supplies are better and more precise than others. This takes many forms. Some cheap ones will be off by several percent when you measure the voltage with a multimeter. For hobby purposes, this usually doesn’t matter much, just check the output with a multimeter if you need precision. DO NOT trust what the manufacturers say. The power supply might have a 4-digit readout, but still be off by several percent…
Low ripple / fast load response
Precision comes in several forms. One of those is ripple, which is how much the voltage will wiggle up and down during operation. Ripple can become much worse if you hook up something that turns on/off quickly, like a PWM-controlled LED. A quality power supply has a bunch of capacitors that keep the voltage steady, but again, for most hobby use almost any power supply will be good enough. However, there are cases when this matters, like if you’re trying to run a high-powered PWM-controlled LED and an audio circuit at the same time.
Multiple outputs
Some power supplies have multiple outputs. However, buying one that has three outputs seems to be more expensive than buying three individual power supplies, so I’m not sure why anybody would want that. Maybe to save space? It should be noted however that having multiple power supplies (or one that can generate multiple outputs) can sometimes be very handy, it’s just not a common occurrence.
Programmable
Some power supplies are “programmable”, but it’s not always clear what that means. In some cases it just means that there are some memory buttons to save/restore previous settings. Sometimes it means that there is a serial port or USB port that lets you access the readouts and change settings from a computer. Not something I’ve ever felt a need for though.
Linear
Some people swear by linear power supplies. Linear power supplies use an old-fashioned transformer design and linear components. Linear power supplies tends to be larger, heavier and less efficient, but in return they tend to have lower ripple and better load response. Nowadays you pay a lot extra for a linear power supply (unless you find one on craigslist or something) but I doubt any of us would actually notice the difference.
Moar Powah!
My current power supply can produce 20 amperes. However, I do have one LED that draws up to 36A, and I have dreamt up some designs that draw even more. It would be cool to have a power supply that could power these things. However, be warned, above 30A, things start melting, catching on fire or just plain explode if something goes wrong… More power isn’t always better.
Brand names
Unfortunately, this is a space where branding comes at a HIGH premium. Most lab equipment brands make power supplies as well, but these start at a few hundred dollars and go up from there. Some of these branded ones are excellently engineered masterpieces, and some are just re-branded version of something much cheaper. Unfortunately there is usually no easy way to tell which is which.
Ok, that was unhelpful, now what?
Go to Amazon, find something that provides at least 10A and have reasonable controls. Check the reviews, check how many it sells per month. If they both seem reasonable, try it. Maybe drop a post here about how it worked out.
Here is a link to one such possibility:
https://www.amazon.com/dp/B0C1SHSPPJ
