Advice needed for cheap and good equipment for lab! - Page 1
Forum section: electronics / testgear

author: honeycomb0
author_rank: Newbie
timestamp: June 22, 2016, 10:33:58 am
content: Hey guys,I am setting up school's lab. To explain, the plan is to introduce kids to electronics through arduino projects, simple robotics, simple schematic and PCB design and ofcourse some soldering. Obviously, main criteria isreliability, and unfortunately, forlowest pricepossible. I know how "oxymoronique" it may sound for rreal pro's, however it is what it is - we have very limited budget, but looking for best option, and reliability of a tool is my keyword in describing what we are after. Main list looks like this:1. Multimeters, for buying around 8 units, what are the best options?2. Soldering stations - Hakko, is it reliable for its price?3. Oscilloscope, 4 units. My choice right now is Rigol DS1054Z, it seems good fit, but maybe someone couldconvinceme to spend few bucks more to squeeze more functionality that I didn't think of.4. Power supply. I am struggling to find anything better than Korad KA3005D, maybe someone will give me an alternative, just to explore the options.Thank you.P.s. any suggestion on "must have" equipment is welcomed!

author: nowlan
author_rank: Frequent Contributor
timestamp: June 22, 2016, 10:45:30 am
content: Not sure what your budget, or location.1. el cheap would be fine for school kids. harbor freight and the like.2. hakko is respected here. Some of the sponsers may be able to a better price.4. usb phone chargers with breadboard regulators. Get them to build Linear 317 kits?There are some other generic chinese lab power supplies around.edit: think i might be aiming a little too low. Thought you were doing some after school program.Dont forget snips, pliers, solder, kits and such. f-gen

author: Ice-Tea
author_rank: Super Contributor
timestamp: June 22, 2016, 11:06:14 am
content: If you want the kids to set the power supply themselves both in terms of voltage and max current I suggest you get something that has a discrete dial and display for Current and Amps.You may think they know the difference between A and V but they don't. Not really. You'll spend half a year explaining them that in a dozen different ways. Halfway, you'll think they've got it due to your awesome explanations. Nearing the end of the year, you'll understand they were pretending and, really, they have no clue at all. You'll get all desperate and you'll be praying for liberation which will come in the form of the end of the schoolyear.Uhm, anyway, just my 0.02$

author: nctnico
author_rank: Super Contributor
timestamp: June 22, 2016, 11:17:36 am
content: Quote from: honeycomb0 on June 22, 2016, 10:33:58 amMay I suggest looking at the GW Instek GDS1000B series or GDS2000E series? The first is cheaper the second is more expensive (if you hack the DS1050Z to full options) but both have far less bugs and more actually useful features compared to the Rigol DS1000Z series. Having a scope with bugs in an educational setting is the worst thing you can do because it will just raise more questions.OTOH in an educational setting you may want scopes with as little features as possible to avoid errors due to operator error. A low end Tektronix DSO might do the trick.

author: Fungus
author_rank: Super Contributor
timestamp: June 22, 2016, 12:06:06 pm
content: Quote from: nctnico on June 22, 2016, 11:17:36 amNo. For Arduino work you really need serial decoders. Instek doesn't do those.Quote from: nctnico on June 22, 2016, 11:17:36 amYou mean 'five less' bugs - bugs that people around here took six months to even discover.(to original poster: Yes, this threadisabout to degenerate into childish name-calling and oscilloscope fanboi infighting, just watch...)

author: pascal_sweden
author_rank: Super Contributor
timestamp: June 22, 2016, 12:07:31 pm
content: I just want to point out that there is nothing wrong with Rigol.As a matter of a fact, there are some Technical Universities in Belgium, my home country, that use Rigol scopes for their labs.

author: nctnico
author_rank: Super Contributor
timestamp: June 22, 2016, 12:16:16 pm
content: Quote from: Fungus on June 22, 2016, 12:06:06 pmThe GDS2000E has decoding and does this way better than the Rigol. But then again it depends entirely on the level of the students whether they need a really advanced scope (and decoding). Sometimes less is better hence the suggestion to look at Tektronix' educational offerings as well.And maybe a bug will never be discovered but I still wouldn't want to put a known buggy/quirky piece of equipment in the hands of a student. In an educational setting you really need instruments which work in a reliable and predictable way. There is nothing worse than having to do a project with crap equipment. Either because the teachers are just babysitting or the teacher who does has technical knowledge gets swamped with questions about how to interpret the readings because they don't make sense instead of helping the students along.

author: Fungus
author_rank: Super Contributor
timestamp: June 22, 2016, 12:41:28 pm
content: Quote from: honeycomb0 on June 22, 2016, 10:33:58 amI've got a cheapo Sparkfun multimeter that I use alotfor some reason:https://www.sparkfun.com/products/12966$15 is a bargain for that meter. It works very well and I'd have no problem using it for education. It's not autoranging but, hey, that's educational in itself.Another option would be to get some Fluke 101s for general use. They're$42 eachand basically indestructible. They don't measure amps but you mostly don't need that. Volts, Ohms and continuity is 99% of what multimeters are used for and the 101 does that very well.For measuring current you could have a fancy meter that trusted people borrow on request. This arrangement will save you a lot of trouble replacing blown fuses.Whatever you do: Don't hand out something that uses $12 fuses for general use. They'll ruin you.Quote from: nowlan on June 22, 2016, 10:45:30 amIt depends on what you mean by 'harbour freight'. The really cheap ones don't have a continuity tester, they zero input protection, no internal fuses. I wouldn't recommend them really.Quote from: honeycomb0 on June 22, 2016, 10:33:58 amHakko is a very good brand.The 'digital' Hakkos allow you to lock the temperature to a reasonable value. This will stop people burning up the expensive soldering tips and small components by cranking up the temperature. Which they will.Quote from: honeycomb0 on June 22, 2016, 10:33:58 amDS1054Z is a very good choice for Arduino work. There's nicer 'scopes for a bit more money but they mostly have two channels instead of four. You really need four for Arduino work.Ignore the DS1054Z-deniers that will no doubt appear within a couple of posts. You won't be disappointed by the DS1054Z.Quote from: honeycomb0 on June 22, 2016, 10:33:58 amEdit: eBay power supply removed.Quote from: honeycomb0 on June 22, 2016, 10:33:58 amMagnifying glasses - for inspecting solder work.

author: nctnico
author_rank: Super Contributor
timestamp: June 22, 2016, 12:46:04 pm
content: I would strongly advice against those cheap Ebay switching power supplies (I own 2 of them). They aren't electrically safe out of the box. Secondly they emit lots of switching noise because they are not properly designed. Due to the noise they are useless for powering analog circuits if you want to take meaningfull measurements. Thirdly they have a significant amount of leakage current from mains to ground so you basically have to connect the minus to ground in order not to fry your circuits.When it comes to DMMs it might be an idea to get mains powered bench DMMs so you don't have to change the batteries all the time. The VC8145 from Vici is around US $170 and offers good value for money. Also a bench DMM can be bolted onto the desk which reduces the chance of theft.

author: Fungus
author_rank: Super Contributor
timestamp: June 22, 2016, 01:06:22 pm
content: Quote from: nctnico on June 22, 2016, 12:46:04 pmOk, I'll withdraw that. I've seen some good reports on them but apparently there's also a lot of identical-looking clones which are crap. You don't know what you're going to get.(unless somebody can recommend a particular seller...)

author: Fungus
author_rank: Super Contributor
timestamp: June 22, 2016, 01:29:03 pm
content: Quote from: nctnico on June 22, 2016, 12:16:16 pmYou talk like every single reading on a DS1054Z is a struggle and is probably wrong.Therealityis that these bugs are mostly so obscure that nobody even found them until many months after the 'scope was released. They only happen under very specific circumstances and combinations of inputs, if at all. Many people can't reproduce them even with detailed instructions because they need a specific combination of bootloader and firmware to appear. Rigol even had to swap a 'scope with a forum member because they couldn't reproduce a reported bug in their labs. If one of his students can find a bug without researching them on this forum then they probably deserve a prize.Therealityis that the DS1054Z is a perfectly capable tool and has much better build quality than the GW-Instek. Build quality is important in educational settings.

author: billfernandez
author_rank: Regular Contributor
timestamp: June 22, 2016, 02:38:39 pm
content: Depending upon your circumstances, you might want to look for something like the Knight Mini Lab:http://knightedu.com/index.php/component/k2/613This has power supplies (short circuit protected), basic pulse and function generators, some basic multi-use components such as pots, switches and lights, and a breadboard area. I've found mine to be very useful for quick experiments.I see the current price of the Knight Mini Lab seems rather high ($600), but maybe someone else sells something similar at a more affordable price.

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 22, 2016, 03:55:58 pm
content: One quote that always applies "cheap and cheery dont go together".The rigol has value but compared to siglent or even GW there is a performance difference in the noise on the inputs, this is why some buy expensive agilent or other simlar scopes even though their specification may not seem impressive. USB on an oscilloscope will let you do a lot of things if hooked up to a PC. If you only measure digital signals than input noise doesnt matter.for soldering station, there are many chinese clones. If you watch EEVBlog's tutorial about setting up a lab he recommends a soldering station so focus on getting a decent one. Doesnt have to be hakko as there are a few brands (or even OEM rebrands) that are good. Honestly i suggest staying away from cloned chineses soldering stations as they pose a hazard to your hands. So Hakko and a few other brands are actually reliable, you will find other brands and some OEM rebrands of good brands like the circuit specialists something you can consider. Just make sure it is an adjustable soldering station as i've had 2 of those plug based soldering irons and they dont quite fit the generic holders properly.For the oscilloscope this is very important so your budget should be considered here most. Since this is a school lab there are 2 types of scopes, standalone (like the rigol, siglent, GW for the low price) and PC based ones like picoscope that dont have their own display, only inputs and a usb port where everything is controlled by PC. Some of these usb reliant do the job themselves like pico scope and just send the output to PC while some will have the PC do the processing which gives the benefit of as much memory depth you like as long as your PC is fast enough. It is recommended that you get one at least 5x the maximum frequency you will measure but you must also becareful with the specifications as low priced scopes may have impressive specs/price compared to expensive ones but when you change things, zoom in and out you will start seeing its capabilities change/lessen so take this into account.DMMs you can get many. Its good to have one with true RMS capability at least but if you're going to expect kids to be using them you may want to go with cheap ones that you can replace easily as kids may blow them up often. You could also get the good old analog ones that require calibration as something to show and teach too.For the bench PSU since this is a school, if you need multiple PSUs you only need single output ones unless you expect more than 1 seperate project being powered at the same time. With dual output ones people could share. Choose based on the specs you think the maximum would be so if you think 30V to be the absolute maximum the lab will be working with than get one at that voltage. You dont need one with DMM monitoring capabilities, just your simple basic heavy PSUs. Make sure to stock up on the fuses they use as you can expect them to be blown up.So for your school dont skimp on the oscilloscopes but you can cheap out on the DMMs and PSUs as long as you avoid ebay ( i consider most ebay items to be fake or low quality). Getting used is an option and many oscilloscope brands will give educational discount. Soldering stations, you can get one thats decent and reliable but you can cheap out on the tips as you would expect to be replacing those often if your students are going to be newbies. The oscilloscopes will be considered irreplaceable but other things that can be considered replaceable dont need much budget on them and for the consumables. Dont forget you will be needing lots of banana and alligator plugs and soldering supplies and multicore isnt the only decent consumable brand for it, there are a few others that also have quality stuff for a good price. While EEVBlog says to get the smaller solders its better to have smaller and bigger solder so use the one thats best for the job. Small solder works best for surface mounts while bigger solder will be cheaper to use for soldering the usual holes and cables as thats where you expect to use more.

author: rstofer
author_rank: Super Contributor
timestamp: June 22, 2016, 04:07:31 pm
content: Quote from: nctnico on June 22, 2016, 12:16:16 pmYou want simple and reliable? Get an old analog scope. They don't do MATH and they don't do DECODE and they don't make mistakes. Sure, you can't decode an SPI bus but do you need to? For nearly 60 years I used analog scopes (I built my first from the ARRL Handbook when I was around 12 and I'm 70). I only bought a DSO for two reasons: First, I thought it would be useful to display (but not necessarily decode) the SPI bus (4 channels) and, second, because I could. My old Tektronix 485 that I bought off eBay for $200 has worked for robotics projects for the last 12 years.

author: rstofer
author_rank: Super Contributor
timestamp: June 22, 2016, 04:26:14 pm
content: For Arduino and simple robotics projects, scope specs aren't an issue. ANY 20 MHz scope or better will do the job. For motor control, the students will probably be looking at PWM with a frequency below 10 kHz. For servo control the needs are even less. The rep rate is 50 Hz and the pulse varies from 1.0 to 2.0 mS. There might be some SPI or I2C and while it might be nice to decode the stream, it isn't necessary. Low speed I2C is 100 kHz and high speed is 400 kHz - again, not a challenge for any scope. SPI can be pretty fast but not if it's coming out of an Arduino. In any event, the bus can always be run at a lower speed.While I personally believe the DS1054Z is the way to go, the detractors are quick to point out that you can get a scope that is twice as good for 3 times the cost. But we have an issue here. I doubt that the school is going to want to hack the 1054. Therefore, it will be just another 50 MHz scope with decent triggering and no decoding. As such, it's just a 50 MHz scope competing with other 50 MHz scopes that can't be hacked. I don't know how it compares in that situation.Since you probably won't buy a scope that includes decoding, we're right back to a basic scope and the used Tektronix scopes on eBay start to look pretty good. Of course they are only dual-channel (usually) but that's not really an issue. I wanted a 4 channel scope but I have gotten by for decades with just dual-channel scopes.Like this:http://www.ebay.com/itm/Tektronix-465B-Analog-Oscilloscope-w-2-Probes-/122022523618?hash=item1c691bf2e2:g:cXcAAOSwjXRXaW9f

author: nctnico
author_rank: Super Contributor
timestamp: June 22, 2016, 04:39:56 pm
content: Sorry but suggesting an analog scope for a modern school (?) lab is totally nuts! If you are going to work with Arduino then decoding is likely to be a good asset so let's compare a Rigol DS1054Z + decoding options versus a GDS2074E (decoding included in the price):The Rigol DS1054Z including all options costs US $1101 and it has 50MHz, 250Ms/s with all channels enabled, 6Mpts per channel and 16kpts FFT.The GW Instek GDS2074E costs $860 and it has 70MHz bandwidth, 500Ms/s with all channels enabled, 10Mpts per channel and 1Mpts FFT.If you don't need decoding then you can choose the GW Instek GDS1054B which has 50MHz bandwidth, 500Ms/s with all channels enabled, 10Mpts per channel and costs $377 which is cheaper than the Rigol DS1054Z.Now try again to show how the DS1054Z is a good deal. I can't imagine a school would use a hacked scope because what kind of message would that send to the students?The Rigol DS1000Z used to be a good deal but today it is yesterday's model with several flaws.All prices from Tequipment.net.

author: Fungus
author_rank: Super Contributor
timestamp: June 22, 2016, 04:44:59 pm
content: Quote from: rstofer on June 22, 2016, 04:26:14 pmGood point.Will you be hacking the scopes to unlock all features? If not... it changes the replies a bit.

author: rstofer
author_rank: Super Contributor
timestamp: June 22, 2016, 05:23:00 pm
content: Quote from: Fungus on June 22, 2016, 04:44:59 pmIf they're not going to hack the scope for options and bandwidth, I say it changes the replies a lot! Without the options, what's the point of a DSO? Just so you can get some potentially incorrect math on the screen? What would you even use math for in the context of Arduino and robotics? Is that kind of complication even necessary in a school environment for those topics? It's like shooting ants with a machine gun!It's a lot harder to get lost in menus if there are no menus! Think about the subject matter. Are all those buttons, knob and dials really necessary? Menus? Seriously? There are knobs and dials on my Tek 485 that I have never used.All you need is volts/div, time/div, trigger polarity and level. AC & DC coupling would be nice but DC only would be adequate - for the topics being discussed.If I weren't worried about letting the magic smoke escape, I would recommend the Digilent Analog Discovery and some laptops. They're going to have computers anyway if they're going to do schematics and PCB layout. With the Analog Discovery there is an entire electronics lab in a small box. Signal generators, power supplies (current and voltage limited), dual-channel scope, 16 channel digital IO/logic analyzer and a bunch of other stuff. My concern is that it isn't bullet proof but if the voltages used on the projects are down in the <12V range, there should be no problem. A little supervision goes a long way.http://store.digilentinc.com/analog-discovery-2-100msps-usb-oscilloscope-logic-analyzer-and-variable-power-supply/

author: Ice-Tea
author_rank: Super Contributor
timestamp: June 22, 2016, 05:47:46 pm
content: Quote from: rstofer on June 22, 2016, 05:23:00 pmYou're not a teacher, are you?I designed a few boards where one of the design goals was "fool and student proof". You have no idea how imaginative these rats are.

author: Fungus
author_rank: Super Contributor
timestamp: June 22, 2016, 05:54:47 pm
content: Quote from: rstofer on June 22, 2016, 05:23:00 pmUmmm ... "education"? Learning how to use a DSO. The most useful tool in an electronics lab.(after a working brain...)

author: rstofer
author_rank: Super Contributor
timestamp: June 22, 2016, 06:45:01 pm
content: Starting with a DSO is a lot like learning to drive in a Ferrari. The student is better off in a Yugo (on several levels).I have always liked the idea of 'stepwise refinement' (quoting Niklaus Wirth). Learn on a modest setup and then advance over time to more sophisticated equipment. Kind of like the transitions between a biplane and the space shuttle. "Small moves, Ellie, small moves."Another Wirth quote:"My being a teacher had a decisive influence on making language and systems as simple as possible so that in my teaching, I could concentrate on the essential issues of programming rather than on details of language and notation."We can extend that idea to the number of knobs, dials and menu selections. This is a beginner's class (apparently), complications just aren't necessary.And then there is the fact that we can get a really good analog scope for half the price of a low end digital scope.But I would still be inclined to get the DS1054Z...

author: ez24
author_rank: Super Contributor
timestamp: June 22, 2016, 08:03:38 pm
content: OP what are you doing about the computers needed to program the arduinos?Talking about hacking in a school environment is bad.

author: nctnico
author_rank: Super Contributor
timestamp: June 22, 2016, 08:06:20 pm
content: Quote from: rstofer on June 22, 2016, 06:45:01 pmNowadays you'll be laughed at if you learned electronics using an analog scope and for a good reason because you won't find them being used in R&D labs. Still I agree about the small steps bit and Tektronix has DSOs specifically aimed at educational purposes with training tools and extended help functions. For general purpose lab work they are utterly useless (outdated technology) but for learning how to use a DSO they could work OK.

author: rstofer
author_rank: Super Contributor
timestamp: June 22, 2016, 09:12:23 pm
content: I'm just learning about DSOs and I'm not finding the transition to be difficult. I still only twiddle 3 things: Volts/div, Time/div and trigger polarity/level. That's all I need from a scope. All the other stuff is interesting to look at but not terribly useful - to me. As a guy who plays with FPGAs, uCs and robotics. Sure, I like the 4 channels but I got along for a long time with just 2. I bought the 1054Z specifically for 4 channels and the idea that I ought to expand my horizons.But on the bench, I twiddle the same limited set of knobs that I used on the analog scope. In some ways, the menu system is slower. I actually have a 'switch' on my analog scope to change trigger polarity. I don't need to fool around with a menu. Trigger level is more intuitive on the DSO (it draws a little line) but both work the same. There isn't any difference in Volts/div and Time/div - just twiddle the knobs.I just don't see my having learned on an analog scope as a handicap. Same knobs, different colors... In the context of this lab, finding RMS, P-P, FFT and all that stuff is useless. Now, the pulse width measurements will be handy but, really, that's why the graticule is there. 500 uS/div, 3 div wide pulse -> a 1.5 mS wide pulse which ought to center the servo nicely. In such a system, measuring the width to 3 decimal places is useless. "About" is close enough!I know I'm swimming against the tide! As I look at multi-thousand dollar analog scopes being sold for $200 or less I get the idea that the market is rather limited. Everybody wants a DSO!

author: Lightages
author_rank: Unknown
timestamp: June 23, 2016, 04:28:02 am
content: When buying equipment for teaching, also keep in mind that you might want to teach about selecting the right equipment for the job. Buying the cheapest junk multimeter is likely to give the students the feeling that relying on junk for safety and reliability is ok.

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 23, 2016, 04:48:10 am
content: Quote from: Lightages on June 23, 2016, 04:28:02 amnot necessarily. You could always buy used fluke meters. Besides i dont think a kid would know that a particular brand is junk or good. Just dont introduce them to cheap chinese stuff especially if you want to show a bit of patriotismIts more to do with the use such as can they learn by using this equipment? And also the feel of the equipment that it does what they want to easily and does it well. Its one of the reason analog scopes are a vintage item.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 23, 2016, 05:17:51 am
content: Quote from: rstofer on June 22, 2016, 09:12:23 pmA downside of getting some analog 'scopes is that you would be unlikely to pick up four identical ones.The other thing is that good brands are old,affecting reliability------you can still buy new analog Oscilloscopes,but they are fairly basic ones,& are very overpriced.School lab 'scopes don't need to be spectacularly good------the Cossor things they had back in Tech School were very far from "state of the art",even in 1960,but we learnt the subject using them OK.I think I would go with the Rigols---the OP may get a discount for buying four.