EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Ranger14 on April 16, 2017, 09:13:38 pm
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I started working on a some what but my first electronics work bench. It's a small work area and it's all I have..So how many power supplies do you realistic use/recommend for a basic electronic workbench?? Also looking for some suggestions as my main power supply died and needs repaired but I managed to get elenco ps that got busted up during shipping.. I can't decide to rebuild the elnco or build my own from a lm317 or lm338 setup??
Thanks
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The first one is the most useful, by far. I find that 0-15V adjustable, 0-2 amp with CV and CC capability covers 95% of my needs. Your needs might be different...depends on the nature of your work. I have a second 0-30V 5A one, but it doesn't get that much use for what I do.
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I would at least have two, or one with two channels. With CC/CV. I recommend the LM723 and the L200 or you build that with a op amp and a shunt plus a transistor that steals the base current of the power transistors.
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There are two universal rules of electronics. (1) You can never have too many multimeters. (2) You can never have too many power supplies.
By far the most useful power supply for general use, and by extension the most useful for a first acquisition, is a triple output supply that offers something like -20V-0, 0-20V and 0-6V simultaneously. Ideally these will be three floating supplies but a common variant is one where all three outputs are referenced to the same ground. The +/-20V supplies don't need much current, 250mA to 500mA is quite adequate. For the 0-6V rail 1A to 2A is about right.
It's no accident that every bench PSU manufacturer will have at least one PSU that fits this specification in their product range.
Ideally it'll be a linear, as opposed to switch mode, supply as at some point you'll need the low noise of a linear supply to avoid flooding some circuit with HF noise. You need at least a variable current limit on each rail to stop you blowing too many components up when you make the inevitable beginner mistakes. A constant current, as opposed to current limiting, current control mode is desirable as this allows you to extend the utility of the PSU to some measurement uses and safe battery charging.
It's worth springing the cash (if you can) to buy a good, high quality power supply. Then when you're scratching your head over something that doesn't work right you won't find yourself in the situation where you're asking "Is it my circuit, or the PSU that's causing this?". Some good bargains can be had on second hand supplies from the likes of HP, TTi, and Farnell (not an exhaustive list) if you're prepared to exercise a bit of patience on eBay and the like. I picked up an older HP triple rail supply for £60 on eBay a few months back.
Avoid the cheap supplies that appear under a dozen different manufacturer's names yet all look identical apart from the badge, most of these are of poor quality, some are actively dangerous.
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Hello,
first of all, be aware of the side effects of Chinese power supplies:
https://www.youtube.com/watch?v=wSGCqyvzlgs (https://www.youtube.com/watch?v=wSGCqyvzlgs)
I use my HP 6624A as my goto power supply. Neatly hidden under the desk, and dirt cheap. Just keep any analog scopes FAR away from it as their display goes bonkers due to the big ass transformer.
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For breadboard: http://www.ebay.com/itm/MB102-Breadboard-Power-Supply-Module-3-3V-5V-for-Arduino-Bread-Board-/231648100681?hash=item35ef4d8149:g:oloAAOSwjVVVx7U5 (http://www.ebay.com/itm/MB102-Breadboard-Power-Supply-Module-3-3V-5V-for-Arduino-Bread-Board-/231648100681?hash=item35ef4d8149:g:oloAAOSwjVVVx7U5)
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Cheapest way is to modify an ATX computer power supply by adding a power resistor. Gives 3 5 12 and -12 at a lot of amps (except the negative 12 has less then 1 amp).
Draw back is not seeing how much current the circuit is pulling.
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its good to have at least one power supply that has multiple isolated outputs which can be connected together to form a bipolar supply..great for opamp circuits and simulating multiple battery powered things, should have independent or tracking mode switch...then also have a big supply 0-30V, 3AMP, etc.. for powering most stuff
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I would second the advice to get one decent dual or triple output bench supply to begin with. You can always get more later if you need them. I tend to use salvaged "wall wart" type power supplies when I need additional voltages and I have a 12V hot swap server PSU that can deliver 57 Amps for when I need serious current.
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For prototyping and pcb checking I use two of those cheap Chinese psus and love them. You can find a couple of threads discussing their merits and issues here in eevblog
For more serious testing and measurements I use the device's purpose-built psu
If you need to verify building blocks, designs and whatnot, you will need a more serious psu though
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If you don't mind buying used keep an eye out on ebay for a Tektronix CPS250. I bought one a couple of years ago and it has been far more useful than I expected. For a beginner, it pretty much covers all the bases.
https://www.eevblog.com/forum/testgear/list-your-test-equipment-score-here!/msg634356/#msg634356 (https://www.eevblog.com/forum/testgear/list-your-test-equipment-score-here!/msg634356/#msg634356)
http://www.ebay.com/sch/i.html?&_nkw=tektronix+cps250 (http://www.ebay.com/sch/i.html?&_nkw=tektronix+cps250)
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Important is the type of power supply, best to get one with constant current/voltage with all the protection built in. Digitally set is nice as well at least with an output switch but not as important as current limiting.
An example of a double or triple power supply (with individual isolated outputs):
Channel 1: Project 1
Channel 2: Project 2
Channel 3: Project 2 logic
Keep small power supplies (e.g. usb type) handy to move projects off your bench supply to free it up or run logic or low voltage circuits.
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Cheapest way is to modify an ATX computer power supply by adding a power resistor. Gives 3 5 12 and -12 at a lot of amps (except the negative 12 has less then 1 amp).
Draw back is not seeing how much current the circuit is pulling.
That's pretty much what I did. Mine is very crude as it's before I found out about Digikey so the terminals are literally copper ends of 14awg house wiring sticking out from the grill. It is solid enough that it does not really move and it lets me put crocodile clips on them.
Something where you can adjust voltage and current limit is of course nice to have, but for a beginner like me it's a quick and dirty way of having access to a couple voltage rails like 5 and 12 volts, which is mostly what you'll find yourself using. There's a 3.3v rail too that can come in handy.
The high current output is also nice for playing around with magnetics or power electronics.
Something that can do low voltage in small increments is of course very nice too if you're playing with transistors. I want to look at building one myself at some point. I could buy one, but I feel if I build one it will make a fun project and I can learn in the process.
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If your considering making a cheap power supply with about as little work as possible, you could use a DP30V or DP50V (or whatever the latest is model is) Constant Voltage Current Step-down Programmable Power Supply as a front end and attach or mod some cheap supply as the source.
As I can get ATX supplies for free I can throw one of these together for the cost of the $25 DP30V, not tried it though.
Also using a ATX supply you could possibly connect between the +12 and -12 rails to give you a 24V source which would be 23V max, as mentioned above not sure on current draw though best start a thread if you go down that path.
Otherwise 12V output of the ATX supply is limited to 11V usable according to the instructions (DP30V says it's a step down converter). There is probably plenty of ways to cobble together a decent input source to run them with a flexible voltage so do some research.
www.ebay.com/itm/172335530729 (http://www.ebay.com/itm/172335530729)
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It depends on what you want to build. If you want to play with op-amp, 3 channel is a minimum. Something like 2x 0-30V, and 1 x 5V. You can hook up to 2 30V to get 0-60V or -30V-30V and use the 5V to drive the logic circuitry.
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5V to drive the logic circuitry.
Wouldn't you need an additional 3.3V supply -besides 5V- for logic to be complete nowadays?
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5V to drive the logic circuitry.
Wouldn't you need an additional 3.3V supply -besides 5V- for logic to be complete nowadays?
When you realize you need 5V it's assumed that you can work out how to drain enough electrons to get down to 3.3V.
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When you realize you need 5V it's assumed that you can work out how to drain enough electrons to get down to 3.3V.
Of course, just add another low-drop regulator
But it would be convenient if the powersupply offers both 5V and 3.3V.
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If you want lots of channels at some point you have to justify buying another power supply :D.
On my main supply the third channel has variable 1.5 to 6V @ 5A handy for all sorts.
Current limiting in mA resolution is useful to me as well for testing LED brightness.
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When you realize you need 5V it's assumed that you can work out how to drain enough electrons to get down to 3.3V.
Of course, just add another low-drop regulator
But it would be convenient if the powersupply offers both 5V and 3.3V.
Actually, I meant a 0-5V channel. My mistake. Sorry.
One thing I forgot to mention, is to have an over-current and over-voltage protection on your PSU. Everyone makes a mistake once in a while... ;)
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How about a home brew power supply that you can control with VB or VBA from a computer? It would also be nice to get data back from the PS (I.e., I draw or current voltage).
I do that now with an Agilent PS but a home brew version would be so cool. I have no idea how to do an interface.
Wouldn't that be a cool group project?
Sent from my iPhone using Tapatalk
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Well, I just set up my bench, and I ended up with 4 dual power supplies. It was a spur of the moment thing on Ebay, and I got all caught up on acquiring equipment. It started as two Instek GPC-3020 dual power supplies that i paid just 45 bucks apiece for shipped. I figured that a couple of old analog dual PSU's would do fine while I learn. Well, money was burning a hole in my pocket and I saw the prices for the Instek GPD-3303S PSU's at $130 apiece shipped and I bought two of them. Decided to buy them while they were affordable.
At first I figured that I could sell the 3020's on Craigslist to get rid of them. But after setting up the bench, I found that they could play a really good role by replacing the wall transformers for some of the test equipment. Now I have several cables made up with connectors to plug into various electronics and banana plugs at the other ends. The two digital 3303S units are for all other uses. And I don't have to worry about plugging in the wrong wall wart like I did to my transistor tester (The cheap Chinese one) and blowing out a cap and transistor in the process. All I do now is plug in the tool to the PSU, set the power, and turn it on. Always have good clean power to things. (I put a label on each tool that states the voltage and current requirements and leave the cable in it permanently.
So I found that there is something to what the more experienced folk say in a tongue-in-cheek manner: "You never have too many power supplies." You can find uses for as many as you have, apparently. Just dream big.
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It's not very power efficient however using a bench supply to run everything.
After you have your bench location setup the next thing is some accessible power points that you can use on the fly, there is some good examples in the benchlab post.
I prefer switched outlets as I can just turn off what I'm not using, they seem to be less popular in the USA I've noticed though.
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Sounds like a good way to fry something by giving it the wrong voltage too.
I plug all my wall warts and such into a big power strip under the bench and just switch it off when I'm done. Rarely a reason to leave any power on the bench when I'm not around.
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Three things I'd recommend in a beginner bench supply:
- Ability to set a current limit down in the 10-100 mA range so you don't needlessly blow up miswired prototypes
- Ability to see current and voltage simultaneously (this eliminates some old HP supplies that I otherwise love)
- Linear regulated -- no need to deal with the issues a cheap swicher may have on your measurements