The second most important piece of equipment you can have as an experimenter is a good, bench style, power supply. And here, there are many surplus choices available from places like Ebay. However, I would stay away from the bargain store brands, and get a name brand that you might find in a lab. The good ones are almost indestructible, and will serve you for many years. I am partial to Power Designs (Above). The one that I have has been with me for over 30 years, with never a failure.
You will end up using this supply for all kinds of things, not only to power your projects, but to test parts, motors, relays, lamps, etc, you remove from surplus equipment. It can serve as a battery charger, and as a battery eliminator for repairing battery powered items.
Make sure whatever supply you get is an Analog Supply, NOT switching (as in a pc). Switching supplies have load requirements (Not good for experimenting), and will introduce noise into your projects, especially audio. They are also prone to "Melt Down", and not as tolerant of overloading. Often switching power supplies also offer less line isolation - A big no-no.
While you will most likely acquire many power supplies over time. I suggest that you start with one good, single output supply. In addition to that, if you do a lot of breadboarding with analog components, next would be a Tri-Output with Tracking. Finally, if you do much car electronics or audio, invest in a good 12 volt analog, regulated power supply of at least 10 amps. There are many more specialty needs. Aircraft use 28v at high current. If you like to work on large robots, you may need a High Current variable supply (15-20 amp). Telephone equipment frequently works at 48v, etc. But, this will get you started.
I have found that a single output 0 to 50 volt range at 1.5 amps to be the most useful. This will cover most of what you will be playing with, from 5 volt logic to 28v Airplane parts, to 48v Telco equipment. I have a second supply that provides 5 volts at 5 amps, and two adjustable outputs of 0-32v at 1 amp. This is handy for use with a project board, etc. If you do a lot of (Or any) Car audio, etc, work, a good hefty 12v (At least 10a) supply is VERY Useful. You will acquire more, but these are a good start!
Meters are important, and the more the merrier. It should have a Volt Meter (Analog or digital), and an Analog Amp Meter for each output. With a changing load, a digital Amp Meter can become useless. My primary supplies have built in Analog meters. I also have a separate digital panel type volt meter, permanently hooked up and dedicated to the supply, and mounted to the bench under it.
Absolutely. The most important feature is adjustable Current limiting. This will save your project, and the supply, if things go wrong. This also allows you to use it as a constant current source for, say, battery charging, and experimenting with things like peltier devices. Make sure the supply can run at current limit continuously. Most good ones can.
I very much prefer 5-way binding posts. I find something very handy also is taking the cord from one of those Radio Shack universal power adapters (The ones with the interchangeable tips), cut the cord off the wall wart, and attach the cord permanently to the power supply output. Since the tips are interchangeable, I always have the proper power plug for whatever I happen to be working on. Make sure the polarity matches up to the legends on the tip adapter plugs!
On a multi-output supply, there should be an option (switch) to allow one supply to track the other. You adjust both together with one knob. Very handy, and it will keep you from melting down that Op-Amp. Make sure you can disable this feature when necessary.
A good, healthy three wire power cord, with the ground lead well connected to a metal case. Can't stress this enough. And, I like to have a permanently attached cord in this case, not a plug in, which can become intermittent. You want your bench supply to be a rock!
|This is my main and most used power supply. It is a Power Designs model 5015T. It outputs 0-50 volts at 1.5 amps. I have used this supply for over 30 years with no problems. I use it to power just about everything, to charge oddball batteries, and to check out surplus treasures. I love this power supply!! It only has one meter, switchable between volts & amps. As mentioned elsewhere, I have a Separate digital panel meter permanently connected to this and mounted under it on the bench. I normally leave the analog meter on current. It has a completely adjustable current limit with a front panel knob. I keep two long leads with alligator clips attached to it, as well as my aforementioned Power adapter cable. Other than occasionally wishing for more current capacity, this supply simply fills my needs.|
|This supply is also a Power Designs. A model TP325. It has three outputs. One is separate and supplies 0-6 volts at 5 amps. The other two have a common return and supply Plus and Minus 0-32volts at 1 amp. It has a meter for each output selectable between Volts or Amps. Note the tracking switch in the center that allows the two 32v supplies to be adjusted together. The current limiting is screwdriver adjustable (frown), but at least on the front panel. It also has adjustable Overvoltage shutdown. I normally use this with a Pre-made 5 conductor cable with banana plugs, to connect to a Protoboard. I acquired this about 20 years ago, and even though It fell off a moving truck once (and has a huge dent in one side), it keeps on working fine.|
|This is a shot of the left of my big Protoboard design station. Up in the upper left is a built in power supply that provides one 2-10 volt output at 2 amps, and two 5-30 volt outputs at .2 amps (Unfortunately not tracking). The meters are for current and voltage, and can be switched to any one of the supplies. Since this is built in, I can power my latest masterpiece without the need of wires or cables.|
|Finally, I wanted to mention AC Supplies. I do not have a real good adjustable AC supply. This is my AC Variac, which is very useful for testing old equipment. One of these is definitely a good addition to any shop, especially for repair work. Normally if I need some type of AC I will jury rig something. But, Although I will cover the subject thoroughly elsewhere I do want to point out that this is a Variac, or Autotransformer. It is connected directly to the AC Line, and offers NO isolation. Be very careful using these, they are NOT isolated!|
There are many more power supply options, and as I said you will most likely aquifer a few more. I just wanted to give some idea of where to start, and what is needed for a good setup. All of these are available surplus, and I have had incredible luck with Power Designs. I also have a number of single output supplies which are handy, but not real necessary. And 12 volt supplies likewise, are readily available, used or new. Check out an Amateur radio supply, or a CB shop. MCM Electronics has a lot of good values on these, but be careful of the quality! A note also, if you want to experiment with tubes, you will need a Variable High Voltage supply. I know B&K makes a good one I have used before. Again, check out Ebay. And that's all there is to that!