DSO138 - Went for a Owon VDS1022I instead. - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: November 09, 2017, 11:56:23 am
content: Yes I know it's a cheap toy, yes I know it's cheap chinese rubbish, yes I know it's low bandwidth....Given that, is it enough to diagnose things like button bounce or digital rising edge clock issues? eg. "Why is my clock/counter jumping?" type debugging?I know an oscilloscope is an investment, but I don't think I will ever be in a position to spend £1000+ on a scope. If I do invest it will be a 200Mhz USB based one for £200-300. I'm not there yet though. I'm still in the volatile phase of the hobby and I could just get bored and drop the whole idea and move on in a few weeks or months. I can think of 100 and 1 things I can still use a DMM for, but not an oscilloscope. Hence why this cheap little gizmo looks attractive for limited hobby/beginner use cases.

author: ebclr
author_rank: Super Contributor
timestamp: November 09, 2017, 12:06:30 pm
content: Can you afford 36 pounds?https://pt.aliexpress.com/item/HANTEK-20MHz-Bandwidth-Real-time-DVM-PSO2020-USB-Pen-96MSa-s-LED-Light-3D2C/32781136163.html?spm=a2g03.search0104.3.8.mj9bKQ&ws_ab_test=searchweb0_0,searchweb201602_1_10152_10065_10151_10068_10344_10345_10547_10342_10343_10340_10341_10548_10541_10307_10060_10155_10154_10056_10055_10539_10537_10536_10059_10534_10533_100031_10103_10102_5670011_10142_10107_10173_5660011_10562_5740011_10084_10563_10083_10561_10566_10564_10565_10312_10313_10314_10550_10073_10551_10552_10553_10554_10557_5650011-10102,searchweb201603_25,ppcSwitch_5&btsid=52c85d36-6689-4486-9310-f596a3a94d8b&algo_expid=b6437a70-60b0-4c78-9a61-092337d7a40b-1&algo_pvid=b6437a70-60b0-4c78-9a61-092337d7a40b

author: daybyter
author_rank: Frequent Contributor
timestamp: November 09, 2017, 12:12:22 pm
content: I would take a look at the hantek 6022be thread in thus forum here. 20 MHz 2 channels for 50 bucks, or so.If you want to go dirt cheap read the 10$ diy scope thread at stm32duino.

author: Gyro
author_rank: Super Contributor
timestamp: November 09, 2017, 12:37:31 pm
content: I think the general forum consensus it that the DSO138 is definitely a toy, but actually quite a useful little toy if your budget won't stretch to more than £15, a fun (but quite tricky to solder) kit. Use the forum search and you'll find several threads.You can get reasonable USB scope performance for well sub-£100. daybyter has mentioned the Hantek 6022be, but the price of the OWON VDS1022 seems to have dropped quite a bit recently (as low as £63 if you buy from China on ebay). The 6022be is severely hardware limited, the VDS1022 has twice the sample rate (100Msps - still not great but for the price...) proper triggering in H/W etc. Definitely worth the price difference. Again forum search.https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR12.TRC2.A0.H0.Xvds1022.TRS0&_nkw=vds1022&_sacat=0Beyond £100 things get a bit more confused until you get to the default Rigol DS1054z at £300+Someone will be along shortly to suggest a second hand analogue scope.EDIT: The DSO138 is fine for button bounce but will be limited on looking at "digital rising edge clock issues" of any significant speed.

author: paulca
author_rank: Super Contributor
timestamp: November 09, 2017, 01:05:26 pm
content: Ok, interesting.The OWON VDS1022I is £115 UK seller, or £65 from China - What are the chances of a fake I wonder.The Hantech 6022BE is £41 UK seller.The OWON does look twice the spec, but twice the price.I'm in a worse position than having a greatly limited amount of funds. I'm in the position where I have lots of funds, I could probably buy a mid range fluke tomorrow, but I'm saving for a house deposit, so ever £x00 I spend today will be another month I need to wait to put the deposit down on a house. Case of "I could, but I shouldn't".

author: Gyro
author_rank: Super Contributor
timestamp: November 09, 2017, 01:23:16 pm
content: A dilema indeed, from the comments in your OP I was thinking that you could probably stretch to the Rigol but a house is always better, no contest!FWIW, I don't believe the owon has ever been faked, or the Hantek come to that.Edit: I noticed you mentioned the VDS1022I, that's the one with USB galvanic isolation, if comparing like-for-like then it would be the straight VDS1022 as the Hantek doesn't have isolation. I think that brings it down to £100 ebay UK. (VDS1022Ifrom China would be about £75).

author: ebclr
author_rank: Super Contributor
timestamp: November 09, 2017, 01:56:25 pm
content: Trust the Chinese, The goods are made in China, The UK guy is there just to rip off you

author: paulca
author_rank: Super Contributor
timestamp: November 09, 2017, 01:58:08 pm
content: It makes it difficult as £10-30 is a throw away item should I upgrade later. But, £100 when an actual basic investment osc is £200-300 is a bit more of a dilemma.That said, I don't think I have a use case that would need more than the £100 OSC. On my radar are just:* Digital discrete logic building up to maybe a Z80 learning rig - OSC will help diagnosing waveform integrity issues with clock pulses etc. Note that I probably won't really be interested in running any digital electronics are any particularly fast speed. Much more likely to be run at "human" speeds to I can watch and tinker, <10Hz clock. The Z80 maxes out around 3Mhz anyway, so 15Mhz bandwidth should be enough (I think).* Battery chargers / PSUs - Mostly current/voltage sense, selection and limiting with little use of an OSC except to check for transistor switching, noise diagnosis etc.* Home automation - Most of this will be MC or Raspberry PI / Arduinno stuff with limited OSC uses.So maybe the £100 OWON would be enough for the foreseeable anyway. It would upset me if I buy it and a month later have a use case that a £150 OSC would be needed for. If that makes sense.

author: paulca
author_rank: Super Contributor
timestamp: November 09, 2017, 02:03:57 pm
content: Quote from: ebclr on November 09, 2017, 01:56:25 pmYes this is about 70% true. If you want to be a retailer, even an ebay one, you have to add 50% or more profit. You have to pay import duty, VAT etc. So the price will rise. You are basically paying for someone to import it for you.Ordering from China in my experience, 19 out of 20 packages with no declared value or a value more than a few quid arrive fine. The 1 in 20 get stuck in customs for a week and I have to pay VAT and a charge to release them once they arrive in the local depot. Buying from a UK seller gets you them quicker and UK duty and VAT is already paid and customs passed.On the actual goods. There exists many cases in China where a factory makes a US or UK designed product, but slips the plans to the factory next door who down-rate the components, materials and design to make it for 1/10th the price and sell it. Sometimes they don't even pretend it's a fake. Often they work fine, but sometimes they fall apart. Their QA department is a 12 year old whose job it is to stick "QA Passed" stickers on the bottom and most end up just sacking them as well.

author: paulca
author_rank: Super Contributor
timestamp: November 09, 2017, 02:18:49 pm
content: Quote from: paulca on November 09, 2017, 01:58:08 pmHmm.. Realising a logic analyser might be better suited to some of this stuff.

author: paulca
author_rank: Super Contributor
timestamp: November 09, 2017, 02:28:07 pm
content: I hit Buy Now on the OWON VDS1022IThanks for the help.Expect a similar post on logic analysers in a few weeksI promise to search and scan Dave's Youtube channel first

author: Peabody
author_rank: Super Contributor
timestamp: November 09, 2017, 02:29:56 pm
content: I looked at the DSO138 but ended up buying the DSO150, which is a newer design. But in addition to the $21, I had to buy a real scope probe (it comes with an alligator clip probe) and a 9V power supply. So the total cost was more like $31. I have found it to be quite useful working with things like control logic, audio, steppers and servos, and have not needed anything more - so far. But I would definitely recommend buying some kind of scope. They let you see what's actually going on.

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 09, 2017, 03:11:54 pm
content: Just posted.https://hackaday.com/2017/11/09/review-jye-tech-dso150-oscilloscope-kit/

author: Peabody
author_rank: Super Contributor
timestamp: November 09, 2017, 06:05:57 pm
content: Quote from: Mr. Scram on November 09, 2017, 03:11:54 pmI got mine from Banggood, and I think they are likely to ship the latest version, which is what you want. Also, you will get a legit version there (there are already illegal knockoffs around).I agree with the review that the DSO150 design cries out for a battery-powered option (but it draws 120ma, so a 9V wouldn't last long), but there are threads in the JYETech forum about adding that. And of course the alligator clip probe is completely worthless. They should raise the price a few bucks and include a real 1X-10X probe. I think I paid about $6 for a probe that was far more capable than this scope, and JYETech could get a much better deal on a probe that matches more closely. I have also missed having a second channel on one project. it worked out ok, but would just have been easier with two channels. Maybe they will offer a two-channel version at some point.Well, anyone looking at this will want to get the version that has the SMD parts already mounted, so you only have to do the through-hole parts. Also, be particularly careful mounting the little daughterboard for the rotary encoder. It's easy to get it upside down or backwards.

author: Gyro
author_rank: Super Contributor
timestamp: November 09, 2017, 07:18:21 pm
content: Quote from: paulca on November 09, 2017, 02:28:07 pmPlease post your experience with it inhttps://www.eevblog.com/forum/testgear/owon-vds1022i-quick-teardown-(versus-the-hantek-6022be)/The more shared knowledge and experience, the better.Regarding logic analysers, you could do worse than simply picking up one of the cheap 8 bit 24MHz clones for now - from about £7 in the UK (or about £3.50 from China). To be ethical, use it with the very well featured, open source, Sigrok Pulseview S/W rather than the proprietary Saleae. It will give you the protocol decoding and memory depth that you are missing on the scope. It obviously isn't going to span a full Z80 bus (speed would be ok though), but at the price they're really a no brainer.P.S.Good choice on the 'I' version, it will be very useful if you're playing with PSUs, monitoring current sense resistors etc. Just remember that the USB galvanic isolation is there to allow you to avoid ground loops, PC damage, float on low voltage supply rails and so on - just don't do anything silly like trying to float it at mains potential. It might survive but I very much doubt that you would!

author: paulca
author_rank: Super Contributor
timestamp: November 09, 2017, 08:51:41 pm
content: Quote from: Gyro on November 09, 2017, 07:18:21 pmI read "extra PC Protection" on the item description and looked at my circa £2000 pride and joy PC and thought... it's worth the extra £20.As to what exactly floating means in these terms I'm a bit lost. It's on my agenda to read up on it. I'm assuming it something to do with having two voltages which are not sharing a common ground. Does that make them "floating" when compared to each other? Anyway, I'll read up on it.

author: Gyro
author_rank: Super Contributor
timestamp: November 09, 2017, 09:26:12 pm
content: Yes, good reasoning.It basically means that there is no electrical connection between the ground clips on the scope and the USB cable ground wire and shield. The power goes though a transformer isolated DC-DC converter and the USB signals thought an inductively coupled USB Isolator IC...http://www.analog.com/media/en/technical-documentation/data-sheets/ADuM3160.pdfYou can see them in the teardown photos.Say you accidentally connect a probe ground clip to the positive of a 5V@10A grounded PSU, the PC is isolated and protected. Without it, the 10A would go via the USB ground, through your nice 'soon to be ex-PC' and back through the earth lead. An extreme case but you get the idea.A useful side-effect is that you can use it (with care) across a current sense resistor on a low voltage supply rail to monitor current. Ideally you'd do it in the ground return line, but your measurement isn't affected by currents running through the USB ground. You don't pick up noise through the USB ground either.Note that the ground clips of the two input channels are still connected together (and to the case) as you'd normally expect with a scope. The isolation happens at the USB interface.

author: ebclr
author_rank: Super Contributor
timestamp: November 10, 2017, 09:13:18 am
content: "Their QA department is a 12 year old whose job it is to stick "QA Passed" "This only works on your dreams, I fly to China at least 2 times per year, and this affirmation is false,

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 10, 2017, 09:55:27 am
content: Quote from: ebclr on November 10, 2017, 09:13:18 amIt would really help to explain why something you state is true, rather than just stating it. This has happened in other threads too. Just saying someone is wrong isn't making any sort of compelling argument. Tell us how it really is, according to your experiences.

author: ebclr
author_rank: Super Contributor
timestamp: November 10, 2017, 10:33:22 am
content: Perhaps you are right. but those xenophobic comments make me crazy

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 10, 2017, 11:11:13 am
content: Quote from: ebclr on November 10, 2017, 10:33:22 amI understand it to be about the counterfeiting problems that exist in China, not Chinese in general.Blueskull has provided some very interesting insights into the actual siuation in China, and has shifted opinions because of them. You might do the same if you just explain how you see it, rather than getting mad.

author: paulca
author_rank: Super Contributor
timestamp: November 10, 2017, 11:33:00 am
content: Quote from: Mr. Scram on November 10, 2017, 11:11:13 amThank you.I have nothing bad to say about China or Chinese people, but there is counterfeiting on a mass scale. Also the super cheap, low quality, untested manufacturing practices are not a reflection of the chinese but a reflection of the West's consumerism and desire for such things at such prices. They make cheap tat because we will buy it.If you talk to distributors of various products who get stuff made or customized in China they usually add a QA process and send rejects back.

author: ebclr
author_rank: Super Contributor
timestamp: November 10, 2017, 11:46:02 am
content: The problem is that some people wanna buy a 1 dollar multimeter and expect a Fluke quality, They get what they paid for.But these do not mean that there only exist fake things and bad quality, They do what you asked and paid for, and in a general way is a much better relationship with quality/price available, There you have the freedom to chose from A to Z, If you get something fake probably you are paying 1/10 of the price and expecting a miracle happens.

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 10, 2017, 11:52:04 am
content: Quote from: ebclr on November 10, 2017, 11:46:02 amThis is exactly what I've stated elsewhere on the forums. Chinese manufacturers make crap for the western market because we are happy to pay for crap, and often only will pay crap prices. It's a simple matter of demand and supply.There might be some added cultural confusion where manufacterers substitute components in later production runs, especially when pressed for price, and how different views exist on how acceptable this is.

author: paulca
author_rank: Super Contributor
timestamp: November 10, 2017, 12:56:36 pm
content: The other thing of course is that faulty items are next to impossible or non-economically viable to return.In the UK however, if you were to launch a business manufacturing similar untested, cheap tat, trading standards would shut you down eventually.Ebay retailers selling the Chinese cheap stuff are taking the punishment because under UK distance selling rules they have to accept returns for refunds, even for fully working items. This is (and paying VAT and not getting stung by customs) is why I tend to pay the extra 30-50% and buy from a UK seller.

author: paulca
author_rank: Super Contributor
timestamp: November 11, 2017, 02:23:39 pm
content: So the VDS1022I arrived. Had a bit of a faff installing the software as I downloaded it rather than using the coaster that came with it.Fired it up and probed my little comparator circuit. After an initial flapping about on my part I figured out the basics.So I could observe button bounce:After adding a bypass cap across the microswitch:Osculation at trigger voltage:Of interest (maybe), when I run this comparator in a simulator I cannot get it to osculate. I'm assuming this is due to simulation versus real world.... or the amount of RF and other noise in my man cave, which the oscilloscope also showed, but I didn't capture the waveform image. I expect the osculation frequency above is the same as the RF noise I seen with an discconected probe earlier.

author: Gyro
author_rank: Super Contributor
timestamp: November 11, 2017, 03:39:46 pm
content: QuoteWell cost aside, that's one advantage of purchasing from the UK - rapid gratification.The latest version of the S/W, from all reports, should be V1.0.28.I put together a list of helpful(?) shortcuts a long while back, most of them aren't in the documentation...https://www.eevblog.com/forum/testgear/owon-vds1022i-quick-teardown-(versus-the-hantek-6022be)/msg827103/#msg827103Shout if you find any more.QuoteYes, that's where stray capacitances, layout, decoupling, noise etc. (even the effect of a scope probe) come into play