Questions for the electronics geeks.


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    Lately I have been really getting in to little electronics projects. Various little Arduino projects, building circuits, etc. All very elementary stuff so far, but now I think I want to sink more money and time in to it. But, unknown waters are fraught with peril...and bullshit marketing speak.

    Soon I see the need for a bench power supply. I looked around and there are a few options on eBay. I don't think I need anything too advanced. I am not going to be working on anything high dollar or requiring really precise voltages. Of course, since most of the time I will be working with 3.3v, 5v and 12v, could I just use an ATX power supply? A nifty little project would be to move the guts to a new box, add a few digital volt meters and banana plugs and I should have a suitable power supply?

    Alternatively, I could pick up something like:

    The price is right, and I don't think I would really need more than one voltage at a time. Of course, other options are welcomed.

    Next, does anyone have a good recommendation for a good but reasonably priced digital multimeter? I don't want to buy a POS, but I don't think I need to spend $500 to get something suitable for small circuits projects.

    Also, any recommendations for a reasonably priced soldering station?

    I have a wide variety of tools, but as I am not the only person on this forum that is getting in to such projects (I believe @mott555 is also?), what would you recommend that a beginner might overlook?



  • I'm guessing that a PC power supply would probably be way too powerful for your uses -- especially for prototyping. I mean, 300W going through an accidental short circuit will start a fire really quickly. Odds are the power supply will shut the current off, but a fuse or breaker will break down eventually, and then you have to go inside the power supply to fix it.

    The one you picked out looks pretty good.

    Everybody likes Fluke multimeters. You really don't need a great one -- component tolerances are so high you really just want an order-of-magnitude estimate of things like voltage. (And you want your circuit designs to be robust...) Get something on ebay.

    Everybody likes Weller irons. A 40W one with a station should be fine. And get a third hand for it.


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    @Polygeekery said:

    what would you recommend that a beginner might overlook?

    @Captain said:

    I mean, 300W going through an accidental short circuit will start a fire really quickly.

    Sooooo....one of these also?

    ;)



  • I saw this on /r/diy just the other day:

    imgur album

    The onebox was messed up so I linked the album instead... Looks exactly like the ATX setup you described.



  • @Captain said:

    I'm guessing that a PC power supply would probably be way too powerful for your uses

    Also, switching power supplies don't always behave nicely if they don't have a load connected. PC power supplies expect to always have a load, at least on the motherboard connections. A bench supply is designed to be sometimes connected, sometimes not.


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    @HardwareGeek said:

    A bench supply is designed to be sometimes connected, sometimes not.

    Fair enough. If no one has anything bad to say about the one I linked earlier, I will order it later this week. I can't order it now, as it will sit on the porch until we get done with vacation.



  • First off -- the key features a lab supply provides are variable voltage(s) and a fully floating output; these are much more critical when working with analog circuits than digital though. The 3.3 and 5V rails from an ATX supply, or even a decent 5V switching wall-wart capable of a couple amps, are more than sufficient for digital circuit design when paired with a way to hook them up to your breadboard; of course, having both available to you never hurts.

    @Captain said:

    I'm guessing that a PC power supply would probably be way too powerful for your uses -- especially for prototyping. I mean, 300W going through an accidental short circuit will start a fire really quickly. Odds are the power supply will shut the current off, but a fuse or breaker will break down eventually, and then you have to go inside the power supply to fix it.

    Switching power supplies that you see today (especially ones with any quality at all behind their name), as well as just about all lab supplies, limit current by controlling how the internal switch is turned on and off -- if you attempt to pull too much current from them, they'll simply turn the internal switch off save for short bursts to either sustain their maximum rated current at the output voltage, or even drop the voltage considerably as well in order to keep power dissipation down. The latter behavior is called "foldback", and is useful in a bench supply to keep loads from frying due to accidents, although it has some caveats when driving loads that aren't ohmic (linear).

    @Polygeekery said:

    Next, does anyone have a good recommendation for a good but reasonably priced digital multimeter? I don't want to buy a POS, but I don't think I need to spend $500 to get something suitable for small circuits projects.

    Meters are relatively hard, because most cheap ones look OK for electronics usage, but then you go to use it on mains electricity and BOOM it catches alight in your hand because a powerline surge happened at precisely the wrong time. I have a Fluke myself (77 III) and am mostly happy with it, but Captain's advice:

    @Captain said:

    Everybody likes Fluke multimeters. You really don't need a great one -- component tolerances are so high you really just want an order-of-magnitude estimate of things like voltage. (And you want your circuit designs to be robust...) Get something on ebay.

    isn't complete -- Agilent/Keyspan and Gossen Metrawatt also make very solid multimeters, and you might be able to pick up a decent one from the Amprobe/Wavetek line as well.

    As to soldering stations...
    @Captain said:

    Everybody likes Weller irons. A 40W one with a station should be fine. And get a third hand for it.

    He's roughly right regarding the power level, but Hakko made some fine soldering equipment as well, and many of the Hakko knockoffs (Aoyue is the name you hear the most about) get a reasonable rep online as well. I somehow get away with my Xytronic station though, for how little I use it...

    Also, seconded regarding a fire extinguisher, especially as soon as you graduate to having to handle mains electricity.

    @HardwareGeek said:

    Also, switching power supplies don't always behave nicely if they don't have a load connected. PC power supplies expect to always have a load, at least on the motherboard connections. A bench supply is designed to be sometimes connected, sometimes not.

    Most reputable PC supplies are designed nowadays to have respectable low-load/no-load behavior because of how little load a sleeping PC puts on them. In any case, you can always use a small-ish (10W) power resistor in the right place to provide a dummy load for the power supply.



  • I don't have any advice to offer, I'm just a tinkerer who's usually in over his head. I have a $15 multimeter from RadioShack that does all the basics, and a similar cheap unregulated 45W soldering iron. And all my Raspberry Pi projects have been DOA due to poor documentation :smile:.


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    @mott555 said:

    And all my Raspberry Pi projects have been DOA due to poor documentation .

    Also, the Linux hardware. It is just not stable. ;)



  • @Polygeekery said:

    Also, the Linux hardware. It is just not stable.

    I'm sure those damn motor controller ICs would Just Work™ if I could signal them via Windows hardware instead!



  • @Polygeekery said:

    Soon I see the need for a bench power supply.

    How about making this one of your projects?

    @Polygeekery said:

    Next, does anyone have a good recommendation for a good but reasonably priced digital multimeter?

    Look into a digital storage oscilloscope. SparkFun has a kit for 80 bucks and Amazon is loaded with them.


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    Or, even better, a Mac Classic and write your software with HyperCard or FlippyCard or whatever the hell it is.



  • A PC power supply will not work -- it requires certain loads on certain power lines before it will operate. I like getting a variable power supply (0 to 15 volts should be enough) but if you want 30 volts, the one you have linked is good. Also check out http://www.allelectronics.com/ and http://www.electronicsurplus.com/ for some good deals (I've used both over the years).



  • A PC power supply conversion can work, for some uses. It's a fun project, but might not give you everything you need for your eventual needs. Main limitation is that it won't deliver high amp output. So you get 12, 5, and 3.3 volt outputs, but only for fairly low loads.

    I did one a few years ago. I don't remember what site I used for instructions, but here's something that looks similar: http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply



  • Fluke is a Seattle area company, so buy their products.


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    @blakeyrat said:

    Fluke is a Seattle area company, so buy their products.

    Do they smell like pot and Patchouli?


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    @Jaime said:

    Look into a digital storage oscilloscope.

    I was wondering about that, how much would I use an oscilloscope? Is it something I should pick up? I have always thought that oscilloscopes were amazingly cool, even though I really don't know what they are used for. I know what they do, I just don't know how that is applied to projects such as what I am doing or how often I might use one.



  • @Polygeekery said:

    Do they smell like pot and Patchouli?

    Patchouli's fireball attacks are really annoying. Honestly, you can beat most people just by pressing C with her.

    Most likely, only @aliceif will get it.



  • Seattle area. They're actually in Everett.

    So... crackhouses.


  • SockDev

    @Magus said:

    Patchouli's fireball attacks are really annoying.

    meh. they're annoying, but there are counters.



  • I was wondering about that, how much would I use an oscilloscope?

    If you need one, you'll know it. They're useful for measuring things like noise in amplifiers.


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    @Captain said:

    If you need one, you'll know it.

    Fair enough.



  • @Captain said:

    > I was wondering about that, how much would I use an oscilloscope?

    If you need one, you'll know it. They're useful for measuring things like noise in amplifiers.

    Also, depending on what you're tinkering with, you'll need one to tell things like how square your square waves are and what % they're operating at (e.g. with 555 timers). If you're looking into signal filters, it's also helpful to see at what frequency fall-off occurs.

    Note: I've not played with the stuff since college, so don't hold it against me if my terminology is off.

    As an aside, I've heard this is a great book for tinkerers: How to Diagnose and Fix Anything Electronic


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    @rad131304 said:

    As an aside, I've heard this is a great book for tinkerers:

    Added to my wish list to order when I get back home.


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    For those of us who do end up needing an oscilloscope, what would everyone recommend? That is a piece of kit that you can really drop some money on. I usually try to discern a sweet spot of price vs performance for things that I purchase, but I am currently so far out of my element that I have no idea what that sweet spot is. There are little Chinese made ones that you hook to a laptop for $40 that I am pretty sure will be utter rubbish, and there are multi-thousands scopes that I am pretty sure are way past anything that a hobbyist might ever need.

    When I am out of my element, I will admit it. So, absolutely feel free to talk to me as though you would a 5 year old. I will not take offense. But, I thrive outside of my element so I am eager to learn.


  • Discourse touched me in a no-no place

    @blakeyrat said:

    So... crackhouses.

    What does a crack house smell like?


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    @FrostCat said:

    What does a crack house smell like?

    www.edibleanus.com



  • @Jaime said:

    Look into a digital storage oscilloscope. SparkFun has a kit for 80 bucks and Amazon is loaded with them.

    No, get a REAL DSO -- my recommendation is the Rigol DS1054Z series, as the price/performance point you get with that (4ch, 50MHz analog BW, 1GSa/s shared across all 4 channels, with an intensity-graded display and all the basics down pat, as well as upgrade options for things like advanced triggering, all for $400) is amazing, and you want physical knobs and buttons on your oscilloscope -- PC-based interfaces don't come close.

    @Jaime said:

    How about making this one of your projects?

    BYOBS isn't a nice project -- bench power supplies either require somewhat-hard-to-find heavy iron if you are using a linear approach, or all sorts of tricky design work if you're building a SMPS (especially an offline SMPS, for which having a fire extinguisher on hand is highly recommended, among other safety devices!).

    @CHUDbert said:

    A PC power supply will not work -- it requires certain loads on certain power lines before it will operate. I like getting a variable power supply (0 to 15 volts should be enough) but if you want 30 volts, the one you have linked is good. Also check out http://www.allelectronics.com/ and http://www.electronicsurplus.com/ for some good deals (I've used both over the years).

    It depends on which PC supply you have -- many cheaper/older ones require a resistor dummy load on a rail to start up properly, while well-made modern ones handle no-load conditions just fine.

    @blakeyrat said:

    Fluke is a Seattle area company, so buy their products.

    Haha, yes -- I was just saying that they aren't the only name in town ;) They do make good kit though, and back it up quite well (I have used their warranty service once, and it went without a hitch).

    @Polygeekery said:

    Do they smell like pot and Patchouli?

    Not at all -- it's more like they don't emit crispy-fried-electronics odors the first time a surge hits 'em.

    @Polygeekery said:

    I was wondering about that, how much would I use an oscilloscope? Is it something I should pick up? I have always thought that oscilloscopes were amazingly cool, even though I really don't know what they are used for. I know what they do, I just don't know how that is applied to projects such as what I am doing or how often I might use one.

    A decent digital storage oscilloscope is basically the ultimate embedded debugging tool -- a 'scope shows you what your signals actually are doing in real-time, which is insight you cannot gain from any other instrument.

    @Polygeekery said:

    For those of us who do end up needing an oscilloscope, what would everyone recommend? That is a piece of kit that you can really drop some money on. I usually try to discern a sweet spot of price vs performance for things that I purchase, but I am currently so far out of my element that I have no idea what that sweet spot is. There are little Chinese made ones that you hook to a laptop for $40 that I am pretty sure will be utter rubbish, and there are multi-thousands scopes that I am pretty sure are way past anything that a hobbyist might ever need.

    When I am out of my element, I will admit it. So, absolutely feel free to talk to me as though you would a 5 year old. I will not take offense. But, I thrive outside of my element so I am eager to learn.


    See my recommendation above. I have one myself. (Rigol, btw, is what you get when Agilent and Tek start giving the Chinese hints on how to build test gear... ;))



  • @CHUDbert said:

    A PC power supply will not work

    Rubbish. A PC power supply is just fine for many projects. I use them quite a lot, especially for high-current 5V projects as they are the cheapest way to get >10A at 5VDC.
    Simply connect a maintained switch between the appropriate pins to turn it on and off.

    The key thing bench PSUs give you is current limiting. It is very useful to be able to set a max. current and know that it'll shut down if you do something silly, rather than blow a fuse, chip or track.



  • If you are mostly doing Arduino type stuff, then a logic analyser is more useful than a 'scope.

    In that type of situation you want to compare timing between multiple digital signals far more often than looking at the actual levels or high-frequency analog signals on one or two.



  • @Polygeekery said:

    There are little Chinese made ones that you hook to a laptop for $40 that I am pretty sure will be utter rubbish

    As long as you're just doing stuff with Arduino-grade clock speeds and below, even utter rubbish will probably be quite adequate.

    In general, dropping very small amounts of money on cheap and shitty tools is a really good way to make you appreciate what's good about the ones you do actually need to spend 50 times as much on.



  • @tarunik said:

    a 'scope shows you what your signals actually are doing in real-time

    Well, yeah - it shows you what your signals do in real-time as long as they have scope probes attached to them :-)

    You will learn to love your x10 attenuating probe and your almost-too-short grounding clip leads.



  • @lightsoff said:

    The key thing bench PSUs give you is current limiting

    and you can also get that from an ATX PSU, for bench use, by running your PSU wires through a little block of fuse holders. Old-school 3AG fuses are cheap and available in a wide range of capacities and fusing speeds.

    An ATX PSU will give you quite tremendous amounts of reasonably well-regulated current for the price you pay for it; economies of manufacturing scale are definitely your friend. And if you get a nice one from Corsair, you can abuse the hell out of it and not have it blow up.



  • @lightsoff said:

    If you are mostly doing Arduino type stuff, then a logic analyser is more useful than a 'scope.

    Nice thing about logic analyzers is the sheer number of inputs. Modern digital storage scopes can capture single-shot sample runs like an analyzer can, but analyzers let you set up conditions for starting, stopping or centering a capture and the more inputs you have, the easier it becomes to define the conditions you're interested in.



  • @lightsoff said:

    If you are mostly doing Arduino type stuff, then a logic analyser is more useful than a 'scope.

    In that type of situation you want to compare timing between multiple digital signals far more often than looking at the actual levels or high-frequency analog signals on one or two.

    Actually, a logic analyzer is only really useful if you have wide parallel busses -- most of the things you're dealing with in embedded work involve two to four digital signals at a time.



  • @lightsoff said:

    If you are mostly doing Arduino type stuff, then a logic analyser is more useful than a 'scope.

    That's why we specified a digital storage oscilloscope rather than a traditional one. With a DSO, you can see things like chip-to-chip communications happening and check if you have all the timings and levels correct. The output is very easy to compare to the timing diagrams that are in datasheets.



  • The problem is that while you can dash through them, she can keep launching more, and they begin directly on her, so you can't come out of the day with melee without perfect timing, whereas all she needs to do is melee you.

    Even that wouldn't be a problem if the attack wasn't omnidirectional and homing!


  • SockDev

    it's tricky i'll grant you, but it's doable and i've seen worse ones.

    at least that attack doesn't give her invincibility frames while the animation is playing.



  • It's about the worst in the game, barring komachi's aerial scythe attack, which hits around 270-degrees



  • I'd say that a logic analyser is less useful than a scope if you're forced to pick. When things go pear shaped on the analogue side of things a proper high-speed scope is invaluable to catch the gremlin that the logic analyser will show as a square, clean signal.

    I've tended to use a scope for timing issues as you can look for signal integrity issues at the same time and 4 traces at once is generally enough. If you're doing a lot of really high-speed work and plesiochronous signals across a bus might be an issue then maybe.

    Decent storage facilities on a scope are a must though, very powerful for looking at things like jitter.



  • There are decent cheap scopes for under $100 now. I haven't bought one though because most of them don't handle high voltage, and if I got one it'd be for working on guitar amps which have ~400V signals.



  • @mott555 said:

    There are decent cheap scopes for under $100 now. I haven't bought one though because most of them don't handle high voltage, and if I got one it'd be for working on guitar amps which have ~400V signals.

    Well, even my Rigol is near or over the upper limit of its voltage range with 400V signals -- I'd invest in a 100:1 high-voltage-rated probe at that point.



  • However, decent 2-channel scopes are cheap and plentiful, while 4-channel are expensive.

    4 to 8-channel PC-based logic analysers are cheap, if you go Chinese clone they are dirt cheap.

    If you do get a scope, you want a separate trigger input - being able to wiggle a spare pin to start the capture is invaluable!



  • @lightsoff said:

    However, decent 2-channel scopes are cheap and plentiful, while 4-channel are expensive.

    Did you not see my recommendation for 'scopes?


  • Discourse touched me in a no-no place

    ATX power supplies can be repurposed quite easily.

    Short green to black and bam, it'll turn on.

    It's probably prudent to put a small power resistor on each voltage rail you'll be using to act as a load.
    I'd do that, plus put in a couple automotive-type blade fuses for each rail to connect your load and prevent you from sending the whole thing nuclear.

    I'm actually looking for a good scope for auto shop use. Could probably get away with a cheap chinese USB setup, but then I'd really need a laptop that isn't useless for the shop. Of course, I really need a laptop that isn't useless anyway......



  • I hadn't, but the point stands anyway. That's the cheapest I've ever seen a 4-channel scope by quite a long way.

    However, a reasonable 8 channel logic analyser is half the price, with basic analog signal support.

    I use these guys:
    www.saleae.com

    There are clones of their older 8 channel unit for under $50. I wouldn't get the clones, but still.

    • The scope is better for the higher frequencies of course.


  • @Weng said:

    It's probably prudent to put a small power resistor on each voltage rail you'll be using to act as a load.I'd do that, plus put in a couple automotive-type blade fuses for each rail to connect your load and prevent you from sending the whole thing nuclear.

    You really can't do that to a decent-make ATX supply anyway -- they'll simply trip out on overcurrent instead. I'd still use the power resistor (although you only need one -- all the rails save for the +5VSB are on the same power transformer mainly for cost reasons, unless you're talking about a very high-end supply), though.

    @Weng said:

    I'm actually looking for a good scope for auto shop use. Could probably get away with a cheap chinese USB setup, but then I'd really need a laptop that isn't useless for the shop. Of course, I really need a laptop that isn't useless anyway......

    Yeah -- the Rigol's probably still a bit cumbersome for your environment.

    @lightsoff said:

    with basic analog signal support.

    How good is that "basic analog signal support", pray tell?



  • Basic analog is 10MS/s, 0-5V range, 10bits.
    So 1MHz bandwidth.

    The "pro" is 50MS/s, +/-10V, 12 bits.
    So 5MHz bandwidth.

    The digital performance is 100 and 500 MS/s respectively.

    I'd happily use the basic analog one for audio work, but nothing higher frequency.

    I'm sure there are better ones out there, but these are pretty awesome for the price.



  • I'd still rather have a scope from a signal integrity standpoint -- a 5MHz analog B/W isn't going to be enough to catch those pesky pesky glitches...


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    Update: For now, with just small little breadboard projects, I picked up a power supply made for the purpose.

    Nifty little power supply and so far it seems to work perfectly. I will order a larger power supply when the need comes up. I like this little piece of kit. It makes the breadboard setup a little bit neater and so far the voltages are rock solid and accurate.

    Speaking of rock solid and accurate, I measured that with my new multimeter:

    So far, I really like it. It has a good feel, it has enough features without being "gadgety". The tip-up bail is very solid and supportive and the price was right. I also picked up a nice set of test leads to go with it:

    I especially like the clip on leads. Very handy for checking measurements hands-free.

    I also picked up a soldering iron:

    Seems to do the job. No complaints. It is not a Hakko or JBC, but it gets the job done.

    I also picked up a few Arduino Nanos and a Mega, just to have. I really like the Nanos for working on a breadboard, as I can socket them straight in to the breadboard. It cuts down on one set of jumper leads. Sort of.

    Hmmmm, I think that is all for now.


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