Making a portable electronics bench equipment kit - Page 1
Forum section: electronics / testgear

author: nectron
author_rank: Newbie
timestamp: April 18, 2016, 12:39:53 pm
content: Hi,#ContextI'm a French mechatronics engineer with 3 years of experience in the aerospace industry (meaning I'm starting to need good equipment, but I don't have the experience of most users here). I've just moved in a small appartment in which I'd like to have an area to build and test homemade PCBs for pet projects (house automation and mechanisms controllers mostly) and some freelance job - no RF. I'd rather stay "mobile" and have my electronics lab tucked in a briefcase that I can carry with me when repairing something at a friend's, or when moving somewhere else. I think it's best for me to buy control-less and display-less equipment and use my laptop, which I always have with me, as a GUI.#ProblemThe first phase of absolute essentials, in my opinion, is:1) 2 channel 10-20Mhz digital oscilloscope2) Function generator, if possible linked to the oscilloscope, to easily get Bode plots and FFTs, measure inductances and capacitors etc.3) 2 DMMs4) Power supplies. I think 3.3V, 5V for digital systems, and +/-12V for opamp rails, as well as a capable 12V (20-30W?) for motors should do the trick. Must be current limited. Variable power supply if possible?5) Soldering station + flux + solder + miscellaneous tools + breadboard + single core wires#BudgetMy budget is around 350USD for 1-4. After much research on the web, I currently have in mind:1 and 2) Vellerman PCSGU250:https://www.velleman.eu/support/downloads/?code=PCSGU250&country=be&lang=en. It's the only one I've found which has a decent interface.3) EX330 and VC99?4) An ATX power supply which I modify to be able to limit the current would be an obvious choice, but the price of the PCB with the current limiter circuits is probably going to make it less interesting. Instead, why not buy a wall adapter and a couple of those cheap CC/CV modules on Ebay and add an inverter supply chip and/or a LDO. Example:http://www.ebay.co.uk/itm/111435416832?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT5) [Not covered by this topic]I really like the Digilent Analog Discovery 2, but I think it's not great bang for the buck knowing that it'll cost 450USD to ship it to Europe. And if anything breaks in that unit, everything's going to the trash...I've also found the Sainsmart DDS140 3-in-1 unit, but the datasheet is wrong and the interface is horrible.#SizeI'd like to think I could end up with a briefcase such as this onehttp://www.castorama.fr/store/Malette-aluminium-PRDm200095.htmlweighing 5kg max once containing everything.What is your opinion? Any better idea or suggestion?Thanks in advance,Regards

author: tggzzz
author_rank: Super Contributor
timestamp: April 18, 2016, 09:19:22 pm
content: Quote from: nectron on April 18, 2016, 12:39:53 pmEUR250+Vat:http://shop.trenz-electronic.de/en/27069-Analog-Discovery-2?c=81or EUR160+VAT academic price.You can create your own applications in JavaScript or there is a conventional API. They might be sold to clients as "tailored to your specific requirements".Not overly mechanically robust, but usable.

author: ez24
author_rank: Super Contributor
timestamp: April 18, 2016, 09:32:23 pm
content: Look at this - they mounted everything under the breadboardhttp://store.digilentinc.com/electronics-explorer-all-in-one-usb-oscilloscope-multimeter-workstation/$659 !workstation - that is the word I was looking for

author: ADT123
author_rank: Regular Contributor
timestamp: April 19, 2016, 05:08:47 am
content: Quote from: nectron on April 18, 2016, 12:39:53 pmNot familiar with the Velleman but looking on the web a few things worry meSampling rate is 25 MS/s - not enough for the 12MHz quoted bandwidth. Its more like a 5MHz oscilloscopeMemory depth is 4K - thats tiny these daysSoftware last updated 2012

author: tautech
author_rank: Super Contributor
timestamp: April 19, 2016, 05:17:45 am
content: 1 and 360 MHz Handheld DSO/DMM combohttp://www.siglenteu.com/pdxx.aspx?id=94&T=2&tid=2Of course you could use the DSO as a basic VM too.

author: nectron
author_rank: Newbie
timestamp: April 19, 2016, 05:07:03 pm
content: Thanks for your answers. Handheld oscilloscopes are a good idea, but I'm not a fan of those - I prefer to have a large screen take snapshots easily. Thanks tggzzz for the link, that's indeed a good price in Europe. Now I'm unsure if it's cost effective, see below.So after yet another good deal of research, I've selected the following:1) Soldering station: Hakko 907/T12 handle+tip (5$ on ebay) with acheap thermostat board cloned of the 936:I'll use a laptop adapter DC 19V 4A to power up the thing, which will also be used when not soldering to power...:2) 5ACC/CV modules with built in V and A meters.I'll addLM317 modulesto get cleaner supplies for analog circuitryAnd a negative charge pump such as theICL7660for symmetric supplies3) DMM: I'll buy aVC99and a cheaper smaller one to go with it.4) USB scope: I'm hesitating between theHantek6022BE, which is very cheap and a decent software thanks to RichardK on this very forum who developed Open6022BE, and thePicoscope2204A which has double the sample rate, a good software already built in (with serial decoding etc.), excellent reviews (praising its build quality), good trigger features and a very small size. It also has a function generator. Saying all that it really sounds like I should go for the picoscope and I'm cheap, right?What do you think?

author: Kilrah
author_rank: Unknown
timestamp: April 19, 2016, 06:14:13 pm
content: Quote from: ez24 on April 18, 2016, 09:32:23 pmThis is very cool! Not cheap though.

author: ez24
author_rank: Super Contributor
timestamp: April 19, 2016, 07:35:52 pm
content: Hi OPI am confused on what you want to do. The title says "building". This implies putting something together with some sort of fasteners. Like nails, glue, screws, tape, etc.At first I thought "build" and wrote a long answer (since deleted) on "building". Then I saw "soldering station" I realize you are just assembling together a set of tools and putting them in cases.Have you looked at the sticky's in the Beginners section? Also there are millions of posts on scopes.Prices start at $400 for a usable scope (1054) and anything under that is a gamble. I think you could get more advice if you set a price limit (and stick to it)You might consider asking another question on what you want to do. I feel "building" is miss-leading. Try "portable electronic test kit". You may get better answers. And put in a price limit and stick to it (this is hard to do). This might actually be an interesting question. If you do not want to do this let me know and I will, I think it would be fun to set a price limit AND a space limit.

author: artag
author_rank: Super Contributor
timestamp: April 20, 2016, 12:05:37 am
content: I'm not fond of pc-based instruments, but Saleae's logic analyser changed my mind, so I'm prepared to at least look at oscilloscopes. An oscilloscope is the one instrument I couldn't do without, so I'd certainly want something decent in a portable setup. But I agree - the handheld ones just aren't good enough. In fact, the older cheap benchtops like the Rigol and hantek are pretty poor, too.A friend of mine with less love for self-contained instruments really likes the Pico stuff, and I'm inclined to agree that it's pretty much the only decent USB scope manufacturer. The PC software is excellent (as far as PC software goesand the specs are reasonable. He particularly likes it for its ability to generate pictures for documents : he writes a lot of reports. Of course, most PC scopes do this, but the Pico is particularly good at it and doesn't have a horrible 'virtual panel' interface - it's written like a proper PC program. Only the price is offputting. I feel i could get a nice Tek or HP bench scope for that money !

author: nectron
author_rank: Newbie
timestamp: April 20, 2016, 10:17:17 am
content: @ez24: I have updated my original post to make it clearer, thanks. Note that I had already mentioned a budget and a target size. Finally, although in its simplest form it can be just a case full of test equipment, it's a very tight fit so I'll have to actually integrate the components nicely, hence "build" is not that far off. That's the reason why I went for a thermostat controller + soldering handle rather than a ready built soldering station.Guys, I've continued my research and I've found what appears to be an even better tradeoff as far as USB scopes go. The Owon VDS1022. Gyrodid a reviewwith teardown, and a bandwidth + noise test, and it is excellent value. There are videos available of the software for higher versions which I assume is the same as the one for the VDS1022. It still has a 5k buffer, but good trigger options. And it's available for 70€ on ebay from a UK reseller! Have we got a winner?

author: Performa01
author_rank: Super Contributor
timestamp: April 20, 2016, 11:30:13 am
content: 5k buffer? Seriously?I predict you'll run into some serious troubles rather soon.It have been (and obviously still are) DSO designs like this, with inappropriate sample rate and/or memory depth, that make some greybeards claim that analog scopes would be superior. Fancy triggers don't help if the acquisition is flawed by too low a sample rate in the first place. And with quasi non-existent memory, sample rate will drop very quickly as soon as you're using somewhat slower timebase settings. This would also drastically limit the trigger delay and zoom functionality, so that in fact such a DSO cannot even compete with an analog scope for the most basic tasks.All in all, 70€ might be tempting, but in the end it is still misspent as you'll very likely want something better pretty soon.

author: nectron
author_rank: Newbie
timestamp: April 20, 2016, 11:44:44 am
content: If the data is transmitted on the fly, does it matter? I thought that DSO's memory was only for single shots? If that's more of an issue for single shots of slow events, I'd define simple tasks as the charging of a RC or the establishment of the current through a RL, or impulse responses of resonant circuits, and typically the measurements we make in these cases are graphical, which 5000 columns for the entire screen allows, doesn't it? I agree that to capture an entire frame of very heavy serial data it may be insufficient, but for 70€ isn't that acceptable given that the system is truly portable?

author: Performa01
author_rank: Super Contributor
timestamp: April 20, 2016, 12:20:14 pm
content: Well, it depends on what software is available. I do not know that 70€ DSO you mentioned, but at least the PicoScopes can actually stream to a PC contiuously and they also provide an API so you can write your own analysis software in your preferred language. But streaming speed depends on the actual model and whether it has an USB 2 or 3 interface. For USB 2 it is limited to some 9.6MSa/s for PicoScope 2206A and higher models of the 2000 series (only 1MSa/s below).

author: nectron
author_rank: Newbie
timestamp: April 20, 2016, 01:13:03 pm
content: Apparently they use compression (maybe in the onboard FPGA) such that even the isolated version, which functions on USB1.1, allows real time. The manufacturer's specs say "real time sample rate".In the thread I've linked, there is also:" "...together with data compression needed to pipe the data via USB1.1 at decent refresh rate. It also results in very low PC overhead with minimal impact on running other applications even on a low-end PC."I'm not sure any compression is required. With just 5K/channel, even sending it all over (which isn't necessary in real-time modes), that's at least 100 screen refreshes/sec."Maybe I'm holding on to false hopes, but is it really as bad as you thought? It sounds like incredible value for 70€ brand new, compared to benchtop DSOs which start at ~300€ and are not portable.

author: Performa01
author_rank: Super Contributor
timestamp: April 20, 2016, 01:44:20 pm
content: Well, that buffer is always used, no matter what the acquisition mode is. It just means that for a single trigger event, you can only capture 5k samples. But on any repetitive signal, the trigger will fire again and again, as long as you're not in single shot mode. Consequently, the buffer will be filled with new data again and again. Depending on the max. trigger rate (aka Waveform Update Rate) of the scope, a huge amount of data can be produced even with a very short buffer.Even the slowest scope manages to provide more than 100 waveforms per second, so this already would be 500kB/s with 5k buffer size.The compression thing is quite common - it is automatic peak detect acquisition - but it only means that not the entire buffer has to be transferred to the PC in order to display an accurate representation of the waveform. If your virtual DSO screen is e.g. 1000 pixels wide, then you don't need more than 1000 samples to get a full resolution graph. The compression just makes sure that the maxima/minima in the waveform don't get lost in that process.But if you want to stream the data to the PC and then analyze them within your own application, you'll need all the data and compression isn't an option.In the end it really depends on your requirements. Determine what sample rate you need - it should be at least 10x the highest frequency of your signal.Then determine the maximum length of a sequence you want to capture.Just as an example, I once had to measure 50ns wide pulses with regard to a reference signal edge and there was a variable pulse delay up to some 50ms. To capture a 50ns pulse reliably, you need at least 20MSa/s. To cover 50ms at that sample rate, you need at least 1M points of sample memory. The measurement would then have an uncertainty of 50ns - if more accuracy like 10ns would be required, you'd need a 100MSa/s scope with >5M points of memory.Think of all test scenarios you'll probably have to deal with and calculate the required sample rate and buffer length to cover them all. Then you can determine what you really need.A scope is the base equipment for every EE. So getting something inadequate here is probably the least appropriate opportunity to 'save' money.

author: ez24
author_rank: Super Contributor
timestamp: April 20, 2016, 06:44:57 pm
content: Quote from: nectron on April 20, 2016, 10:17:17 amInteresting. Since it is small and cheap maybe you could get another cheap and small scopeDSO112http://www.amazon.com/DSO112-Oscilloscope-Display-Battery-included/dp/B01982W558/ref=sr_1_1?s=industrial&ie=UTF8&qid=1461177460&sr=1-1&keywords=dso+112I have one of these and it is accurate, easy, fun to use to 5 MHz. It can "see" up to 10 MHzIt is stand alone.If you get one make sure it has a battery. Cannot just buy one.Getting away from the soldering station opens up a new challenge.What is your time frame. Maybe this could be turned into a contest (no prizes).There was once a $100 lab challenge, but really too low to be any good.

author: nectron
author_rank: Newbie
timestamp: April 21, 2016, 12:11:11 pm
content: Performa01: Interesting, thanks for the application example. I'll personally only be using the scope with the built-in app. I'm aware these types of scopes have inherent limitations, which are basically the length of single shots for a given "time resolution", but that's a tradeoff I'm willing to make if the unit is cheap and very compact. I quite like the idea to have some basic electronics kit I can carry around in a case, even if that means I may not be able to monitor absolutely everything. In my case, most of the time I'll be able to slow down serial data to the point I can capture entire frames for debugging purposes, so I'm not too worried about buffer depths (I'm not saying it won't bother me at any point, just that the rare cases I'll need that do not justify a much bulkier and more expensive unit).ez24: As I said I'm not a fan of handheld scopes because of the displays, and the fact that it's easy to export data or take snapshots with USB oscilloscopes for the same footprint. Turning it into a contest is a great idea! My timeframe is ~2 months, but I can hold that for longer as I'm sure people will come up with much better ideas. How do I start a contest?

author: Performa01
author_rank: Super Contributor
timestamp: April 21, 2016, 02:03:07 pm
content: The memory depth always matters, not just for single shot capture. As I've stated earlier, it determines the maximum data you can acquire for any trigger event. With segmented memory, you can store the data of more than one trigger event at the same time, which can be awesome.In any case, the data is not normally streamed when the scope is in run mode. The buffer is filled, then transferred to the PC, then filled again and so on. Only roll mode at slow sample rates allows you to stream data continuously, but even then they only get displayed but nowhere stored other than the scope sample memory which you could examine after hitting the (virtual) stop button on the scope.To record continuous data streams, there is data logger software available, at least for the PicoScopes. With that you can continuously stream to and record on your PC, but only at relatively slow sample rates.Lets look at your application example, capturing serial data. From experience we know that sample rate should be at least 10 times faster than the serial clock, so that the decoder will work reliably (after all its just an asynchronous sampling of all the signals and then interpreting them). If for instance you want to decode UART at 1Mb/s, you need 10MSa/s sample speed. This should not be the limiting factor then. But you need at least 100 sample points for a single byte, and then there could be even some longer idle periods between message bytes, because the micro has to wait for new data. Even at a continuous transfer without any gaps, you've run out of memory after 50 bytes the latest. And that assumes you've positioned the trigger position to the far left of the screen and not let it sit in the center, otherwise it's only 25 bytes best case.And even if you think you only have to deal with short messages like this, having no headroom at all isn't much fun at work. And the next day, contrary to what you thought, you run into a situation where you need to look at 128 bytes telegrams ... ooops, out of luck.Memory is just the key to being able to make use of the advantages of a digital scope. If you have segmented memory, you can capture a bunch of serial messages and analyze them all at once after the capture. This requires even more memory of course.

author: nectron
author_rank: Newbie
timestamp: April 21, 2016, 04:40:22 pm
content: Oups sorry, I don't know why single shot stuck in my mind - I understand that it affects any kind of triggering. I'm just saying that my requirements for the scope are very loose - take a look at the context at the beginning of my thread: most of the time, I deal with basic 8 bit microcontrollers, which very seldomly use high datarates (simply because it's not needed). So really, I'm looking for any kind of scope that can allow me to monitor serial frames of say 128 bytes at 115kbaud. Anything higher than that, I'd go to the lab and use a real scope (for example to monitor the signals between a RAM chip and a ARM M4). If I can't slow the software down to troubleshoot it before speeding it back up.I understand what you are saying, and I completely agree (and I appreciate the examples and discussion). But engineering is about tradeoff, too. I'm looking for a low cost portable unit, and for that I'm willing to reduce the range of problems I can solve with the unit.

author: charlespax
author_rank: Regular Contributor
timestamp: April 21, 2016, 05:00:01 pm
content: Quote from: artag on April 20, 2016, 12:05:37 amI agree. My little 8-channel logic analyzer has been wonderful. It has wonderful software. You can also use the Saleae or one of its clones with the open sourceSigroksoftware.

author: ez24
author_rank: Super Contributor
timestamp: April 21, 2016, 05:27:18 pm
content: Quote from: nectron on April 21, 2016, 04:40:22 pmYou are not going to get any help on this forum regarding "low cost". Because it seems there is a difference in what low cost means. Low cost on this forum is $400 and it seems low cost to you is $80.Low cost USB scopes get trashed on this forum with the only exception being Pico.If you talk about a $20,000 scope then you will get some action here.What would benefit the forum is you buy your scope and do a review of it and post the results. If you are able to return the scope, it would seem a low risk adventure.

author: nectron
author_rank: Newbie
timestamp: April 21, 2016, 05:41:33 pm
content: Low cost for me is 150$, but I understand it can be understood as very low cost instead, as the first price for any benchtop oscilloscope is 300$.I quite liked the picoscope, but the Owon seems to have similar specs for half the price so I thought it was a better candidate.Dealing with high end equipment of high cost does not mean that you cannot give some educated advice to people with lower needs about low end equipment of low cost, that is what I thought when posting here - because with all these cheap ripoffs, it was difficult to take a decision. After all these discussions, I think that basically the equipment VS budget choice is Owon VDS1022 for < 90$, Picoscope 2204A for < 175$, Rigol DS1052E for < 300$.It sounds like I should make the jump from the VDS1022 to the 2204A if a 1Mhz function generator (20kHz square waves) and serial decoding are necessary features, and they are, so I will be buying the picoscope for 120GBP.That's the most critical item, but basically I was asking pretty much the same thing about the rest of the case - help on compiling the best equipment for the given budget

author: ez24
author_rank: Super Contributor
timestamp: April 21, 2016, 06:47:25 pm
content: Quote from: nectron on April 21, 2016, 05:41:33 pmI suggest start a new topic, something like"Picoscope 2204A vs Owon VDS1022 --- Opinions ?"I can tell you 99% are going to say PicoI hope you will buy the Owon and do a review. More reviews of low cost equipment is needed.

author: Performa01
author_rank: Super Contributor
timestamp: April 22, 2016, 12:07:04 pm
content: I never had any 2000 series PicoScope, but from the specs it looks like a 'me too' product on the very low end. Consequently, that Owon might not be much worse.I have stated earlier that I think it to be a waste of money on the Owon, but with the Pico 2000 even more money would be wasted. The only reason to get the Pico would be the software, which is the same for all PicoScopes (of course, capabilities and features will vary widely according to the scope connected), so this is a known factor at least and you wouldn't have to learn a new UI when you eventually upgraded to a better model - the real deal starts in the Pico 3000 series.Since your budget is limited, I actually think it would be better to give the Owon a try. It might be a good learning experience, showing you how much the limitations of such a scope affect your measurement tasks and eventually you'll be able to decide yourself what you really need. And it is better to pay 90 bucks instead of 175 for that learning experience.

author: rstofer
author_rank: Super Contributor
timestamp: April 26, 2016, 06:24:33 am
content: Earlier today I was comparing the specs of the Pico Scope 2205A and the Digilent Analog Discovery. There's a $200 difference in price with the PS being the more expensive and the specs don't compare well to the AD. The 2205A has a dual channel scope, a 16 channel digital interface (logic analyzer) and a waveform generator. The AD has a dual channel scope with a 14 bit A/D converter versus 8 bit for the 2205A as well as 16 channel digital interface, two arbitrary waveform generators,When you talk about 'portable lab', it seems to me that the AD needs a little more attention. It has some pretty remarkable specs for the money. The only reasonable way to compare the two devices is to see up a spreadsheet. Since I already have the AD, I don't have much interest in doing the work.

author: LariSan
author_rank: Unknown
timestamp: May 18, 2016, 08:42:53 pm
content: The shipping may be terrible from the US. It's a bit hidden, but there are distributors in other countries that should help with shipping costs!http://store.digilentinc.com/our-distributors/