PCB scope - reviews?

WhiteSpace

Well-known member
I would be interested in any feedback on the PCB scope available on the Picaxe store. I can’t justify buying an oscilloscope, but spotted this when I was looking at the Store earlier today. I’ve been wishing over the last few days that I could see visually the pattern of ADC readings coming in to the Picaxe, and have also thought several times over the last few months that it might be useful to do the same for serial, IR, PWM and other messages flying around. If I understand correctly, a scope would allow me to do that. I can’t see much comment on the forum. All thoughts gratefully received, thanks!
 

lbenson

Senior Member
I don't need to use my DPScopeSE very often, but it's illuminating when I do. I like that it's so tiny, especially compared to the 70-pound used monster I had 40 years ago.

A few days ago I wanted to look at the timing of an AC "cycle slicing" program which was attempting to capture a zero-crossing trigger of a 60Hz (North American) AC signal (tested using a 12V AC wall plug transformer) to fire a triac for an increasing period within the 8.33ms half-cycle time (120 half cycles per second).

This screen shot from DPScopeSE shows that the triac on-time (red signal) was ramping as desired after being triggered by the zero-crossing trigger (blue):

AC Cycle Slicing.jpg
Here's the PICAXE code. Running at SETFREQ M16, "PAUSE 1" takes 317 microseconds; incrementing to PAUSE 2 adds 250 microseconds. The program delays for a decreasing time before firing the triac to provide a "soft start" to a (simulated) A.C. motor. The scope showed that on my first pass, the delay was too long, running over into the next half-cycle. I reduced the delay until I could see the desired effect above.
Code:
' 08ZeroCrossFire.bas
#terminal 19200
'#terminal 9600
'#terminal 4800
#no_data

symbol pauseTime=b1 ' from 32 to 1; at 16mHz, 8ms to ~ 250uS
symbol i=b2 ' FOR loop counter

symbol pFire=C.4
symbol PAUSEMAX=26 ' was 31--too long
symbol NREPEATS=32 ' 15 for 2-second ramp

setfreq m16
'setfreq m8
pause 2000
pauseTime=PAUSEMAX
high pFire
pause 4000
low pFire
pause 4000

do
 do: loop until pinC.3=0
'  pause pausetime ' debounce
 do: loop until pinC.3=1
 low pFire
 pause pauseTime
 high pFire
 inc i
 if i > NREPEATS then
   i = 0
   dec pauseTime
   if pauseTime = 0 then
     low pFire
     pause 8000 ' 2 seconds on low
     high pFire
     pause 8000 ' 2 seconds on high
     low pFire
     pause 8000 ' 2 seconds on low
     pauseTime=PAUSEMAX
   endif
 endif
loop
 
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premelec

Senior Member
DSO138 for $25. ppd Ebay is a good deal for fundamental measurements - I bought one as a kit and don't recommend that as assembly instructions were not very good and it took a while... see:

 

AllyCat

Senior Member
Hi,

Personally, I have the original "DPScope SE" which uses identical software and is basically the same, but built inside a "box" with connectors for 'scope probes, etc.. For example, I used it for a forum thread HERE (end of post #1).

It has several strengths and weaknesses: Firstly, it has two channels (plus an External Sync capability); it's amazing how often a second (displayed) channel is useful and sometimes it's absolutely essential. Also, as it uses your computer's screen, it's easy to take a screenshot (Print Screen), the "User Interface" is quite good and it has a storage / persistence capability for slower signals. There are probably other advantages but I had better mention a few disadvantages:

Since it connects directly to your computer (USB connection for data and power) there is a slight risk that you might "destroy" the PC if you do something really bad. Unlikely, particularly for typical PICaxe projects, but it could be a very expensive mistake. Secondly, it is a rather slow "Sampling" 'scope; which means that for "higher" frequencies (potentially not far into the kHz region) it needs a "periodic" (continuous) waveform and a reliable sync / trigger signal. Of course that was also mainly true for traditional analogue 'scopes, but it's rather easier to "confuse" yourself with the subsampling artefacts of a digital scope.

Cheers, Alan.
 

WhiteSpace

Well-known member
Thanks very much all - I think i’ll give it a try. I found more stuff on the forum when I searched dpscope, which generally seems positive.
 

papaof2

Senior Member
I work with small solar power designs and basic US line voltage (110-120volts) inverters so I have a DSO138 that's powered by a 5 volt powerbank and a 5v to 9v boost converter so it's totally isolated from line power and ground. It's all low frequency "stuff" and mostly looking at continuous waveforms so the DSO138 with a 10:1 probe works very well for that. I also have a 4 channel, 100MHz Tektronix scope for higher frequency work (found on Craig's List for $100).
 

Flenser

Senior Member
Has anyone tried one of these Ultra Thin Scopes?
I have no experience with this scope but the price looks too good for the quoted specs to be true.
Rigol DS1052E 50MHz 1GS/S price AU$376.73 @TEuipment.net
Ultra Thin Digital Tablet Oscilloscope 2CH 100MHz Bandwidth 1GSAU$199 @Cheapest on ebay.com.au

The Rigol scope has a very good reputation as a cheap hobbyist scope on the eevblog forum.
I'd do my research before buying this scope.
 

PhilHornby

Senior Member
I’ve been wishing over the last few days that I could see visually the pattern of ADC readings coming in to the Picaxe, and have also thought several times over the last few months that it might be useful to do the same for serial, IR, PWM and other messages flying around. If I understand correctly, a scope would allow me to do that.
For working with Analogue signals, that vary with time, you need a 'scope - any scope, being better than no scope :) . That probably fits the bill for your ADC readings, but for the other examples you gave (Serial, IR PWM etc), a Logic Analyser might be more suitable. This web page explains the difference.

You always get what you pay for, of course, but I found one huge difference between PC-based 'scopes and real ones - and that is in usability. It is I find it so much easier to twiddle with physical knobs and switches, than it is to hunt for the mouse and start interacting with a virtual version.

My personal oscilloscope journey started with the Topward 7021, when Maplin started selling them in the late 1980's. ISTR it was less than £300, but allowing for 30 years inflation, that was still a lot of money. Eventually, I upgraded/downgraded/changed to the Hantek 6022BE, which as mentioned earlier, being PC-based, was quite awkward to use. My current pride-and-joy, is a Siglent SDS 1052 DL - which currently retails at ~£230. In real terms, that is much cheaper than the Topward was and has far more functionality.

Logic Analysers like this one, can be had much more cheaply - but careful research is required, as to which analysis software can be used with them - and which Operating Systems they run on.
 
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WhiteSpace

Well-known member
Thanks @PhilHornby - I'm not sure that I can justify the sort of outlay that seems to be needed for a decent "real" oscilloscope at my current stage of starting out. The PC-based version that I saw by chance in the Picaxe store seemed to be ideal - doing most if not all of what I need (subject to the limitations that you pointed out) but at a very modest price. If I understand correctly, it also includes a logic analyser. Thanks everyone for the very useful comments.
 

lbenson

Senior Member
It is so much easier to twiddle with physical knobs and switches, than it is to hunt for the mouse and start interacting with a virtual version.
Very much a matter of opinion, and probably of experience.
If I understand correctly, it [the picaxe store DPScope] also includes a logic analyser.
Right--4 channels. There's also the convenience of something that's only about 4 square inches and weighs next to nothing. I can use it sitting in my easy chair. And the price was right.

That's certainly not to say that it's suitable for all needs, but it can do a lot of what the ordinary hobbyist needs.
 

premelec

Senior Member
Like papaof2 I've got a Tek, a Rigol and a DSO138 each works for various tasks... that said there must be a simple add on oscilloscope and app for a smart phone by now as I've seen ads for very sophisticated apps... even I have a smarty phone [though I barely know how to use it]. Perhaps a cardio monitor could be adapted to straight oscilloscope use...
 

womai

Senior Member
Hello, here is the creator of the PCB Scope / DPScope SE speaking (there is no difference in functionality or performance between these two, they also use exactly the same software. The PCB Scope is simply a bare-bones version, by using surface mount components and omitting "real" probe connectors and the housing I was able to greatly reduce cost.

Whitespace, what you are looking for should indeed be possible to handle with the PCB Scope. Worst case, if at some later point you find out you want to go for a "big" scope not much is lost learning using the tiny PCB scope, I would consider it a good way of learning the basic functions and usage of any oscilloscope.

The Rigol scopes are a really good offering, build quality is excellent (have two of them myself), but of course price tag is another league (~300 Euros and up) than the PCB Scope. Hantek I don't really recommend, at least stay far away from the lowest-end models like the 6022 which have severe shortcomings (known from own experience, I once took one apart; explaining them here would get me too far but they make them unusable for non-repetitive signals; basically they lack any real trigger).

I would not recommend any of the single channel toy scopes, there are just too many occasions where you need to display two signals at a time (e.g. to see the timing of one relative to the other).

The PCB Scope's sampling rate for one-shot signals is indeed limited (50 kSa/sec means it is good for signals up to a few kHz). For repetitive signals the euqivalent time sampling mode (transparent to the user otherwise, scope switches automatically for faster time settings) enables you to look at faster (higher frequency) signals.

That said, if your signals are digital (like e.g. pulse width modulation, or serial data) it us usually better to use the logic analyzer mode; it can only distinguish between logic high and logic low, but offers much higher single-shot sampling rate (up to 1 million samples per second, so easily able to capture rather fast digital signals) and also larger record length (800 samples).
 
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Buzby

Senior Member
I would not recommend any of the single channel toy scopes, there are just too many occasions where you need to display two signals at a time (e.g. to see the timing of one relative to the other).
I fully agree !.

A single trace is very useful most of the time, but when you need to see a relative time, a dual trace is essential.

The only low-cost dual trace with onboard display I know of is the Gabotronics Xscope. I've got one permanently fixed on my breadboard, but I wouldn't reccomend it. The user interface is 4 buttons, and a real pain to use. However, it does also support a PC display which is much easier to use, but if you are going to use a PC display only, the PICAXE PCB Scope is just as good and cheaper. ( I've got one of them as well. )

Cheers,

Buzby
 

kranenborg

Senior Member
Nice to see that Womai is around om this forum! I still use his DpScope (Version 1) which is the "big brother" of the PCB Scope / DPScope SE, as a capable 2-channel scope, and I am very satisfied with it. Womai, do I get it right that the PCBscope is currently the only version left that you are still supporting?
/Jurjen
 

WhiteSpace

Well-known member
Thanks very much @womai. I ordered the PCB Scope a few days ago from the Picaxe store, so I'm looking forward to trying it out when it arrives.
 

womai

Senior Member
Nice to see that Womai is around om this forum! I still use his DpScope (Version 1) which is the "big brother" of the PCB Scope / DPScope SE, as a capable 2-channel scope, and I am very satisfied with it. Womai, do I get it right that the PCBscope is currently the only version left that you are still supporting?
/Jurjen
Yes due to several different reasons it does not look like I will be able to offer the scopes and kits now or in the future. (also my visits to this discussion board have become rather rare, even though I really enjoy the positive and helpful atmosphere here!). Of course I will still support all models in the sense that I am available to help n case of any questions or problems. I am also considering making at least the pre-programmed microcontrollers and the printed circuit boards available for anybody who would like to build his/her own DPScope or DPScope SE (the DPScope II is unlikely because it is much more complex to put together and bring up). So I am happy to see that Rev-Ed can at least supply the PCB scope as a low-budget entry into the world of oscilloscopes for hobbyists. (side note - I do not make any money on the sale of the PCB scope, so don't take my comments as self-serving publicity!).

By the way, my website moved to http://dpscope.freevar.com/ (no longer www.dpscope.com).
 

WhiteSpace

Well-known member
Well my PCB Scope has just arrived and I'm sitting admiring it! I have a couple of really very stupid questions, though. I can see that I need to solder one or both of the two rows of header pins supplied with it onto the row of holes marked CH1, GND etc. Does it make a difference whether I solder into the column headed J2 or J1, and does it make a difference whether I use the turned pin header or the square pin header? The photos on the store seem to show one row of header pins soldered downwards and the other soldered upwards. And then how do I connect something producing a signal to the relevant pin of the scope? If say I want to see the signal coming off a Picaxe pin that is going high and low to flash a LED, do I just connect a jumper from the relevant Picaxe pin to one of the 4 digital pins on the header? I've looked through the manual and can't see anything. Thanks
 

womai

Senior Member
j1 and j2 doesn't make a difference. The turned header pins have a smaller diameter and will fit better into the breadboard so this is the one to be mounted pointing downwards. The square pins are too large and would damage the breadboard over time but they fit standard jumper cables (coming in from above) so mount this header pointing upwards. Of course you are not required to install both headers if e.g. you never use a breadboard.

To display a signal connect it to the Picaxe as described AND connect Picaxe ground to scope ground GND. If you feed the signal to the logic analyzer input you must then use datalogger mode or logic analyzer mode. When connecting to the analog (scope) inputs CH1 or CH2, use datalogger mode or scope mode. But in all cases remember you also need to make the ground connection.
 

Eng460

Well-known member
Hi Womai, thank you for looking in again.

I purchased the OSC001 PCB Scope a few years back when the local store had it on display when I was buying something else. I could not find the software through my initial searches, so put it aside until “later.” You have reminded me it is still in my parts box, so I retrieved it once again.

The instruction set says Version 1.0 12/13, and the board says V 1.1 (Apr. 2013). I presume I will now find the software via the new website, though it’s probably no longer new. I am sure I just gave up too easily, and was probably distracted by other things at the time. (Edit, just looked at your site, which version should I follow for my ancient version with Windows 10?)

An initial question though, the turned pin header supplied is one shorter than the square pin one. Do I need to find a header with the extra pin? Or which end do I install the short one on? I must be missing something obvious here.

I will solder it up, and post again to let you know how I get on. I am looking forward to seeing how it goes. It’s quite timely for another project I am working on.

Thank you for developing a great little device, that will help me learn about using a scope, and in reality, probably do everything I will ever need.

Eng460
 
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womai

Senior Member
Make sure you install the correct software, i.e. the one for the DPScope SE, not the one for the "normal" DPScope. There is only a single version for your scope, found here:


The headers should both have the same number of pins and fill all available holes on the J1 or J2 footprints of the board, if they don't then somehing went wrong.
 

Eng460

Well-known member
Thanks, Womai,

I don’t know what went wrong back when I bought it, I went back to the Picaxe data sheet page and everything seemed to be there. I must have had a seniors moment! Downloaded and installed the software without a problem.

I will solder in the headers I have, and see what I can find for the extra pin.

Now to heat up the soldering iron and get those headers in place. But I hear that it’s dinner time first, so it might be tomorrow. I will come back and post when I have it done.

Eng460
 

grim_reaper

Senior Member
Hi Womai - I have a quick question about the DP Scope SE software - although from what you've already said I think I know the answer!
Do you have any plans to bring the software up to date? I'm sure you're aware that VB6 COM applications are somewhat legacy and MS might cause them to fall over with any pending update to Windows 10. Have you thought about putting the SE version onto GitHub (or similar) and letting the community update it?
 

womai

Senior Member
I might make the software publicly available if it makes sense. So far it still seems to work perfectly fine on all Windows versions, of course apart from its somewhat "classic" look and feel, thus at the moment no plans for any update or conversion which would be quite some work. That said, over the years I found out that "letting the community update it" (or "letting someone else convert it to e.g. Linux/Max/...") sounds great in the beginning but up to now never resulted in something even remotely usable... people tend to greatly underestimate the effort required to overhaul some foreign piece of software despite me always warning them beforehand. As a result, initial enthusiasm quickly fades and never got (at best) beyond a very basic "proof of concept".
 

grim_reaper

Senior Member
Oh I completely understand - I've spent a large portion of my career updating industrial software from VB6 to .NET and I know indeed that it's quite some work (or a massive amount of hard graft and mental pain to be more accurate).
I was only suggesting/asking for your thoughts - and don't misunderstand me - the software as it stands works perfectly well on my system. I just tend to notice the slight difference in fonts and the lack of window resizing whenever I open it up!
 

Eng460

Well-known member
I have now soldered their pin headsets on to the board, downloaded and installed the software. The turned pin header strip was only nine pins, something went wrong there somewhere, but I was able to find another header off cut that I was able to cut one pin from. Held it properly in line with a socket strip while I soldered it so all lined up.

It all powered up ok, With the little green light shining steadily, but the software still could not find the device. I tried another cord with success. Perhaps the first one was faulty, or possibly even supplied with a device that only needed power. Who knows.

I had a Picaxe circuit all set up on the breadboard, but no suitable spare space to insert the PCScope board, so O soldered two headers socket strips onto a small piece of veroboard, and was able to plug in the scope and connect to the Picaxe board with wire links and successfully displayed some wave forms and made some measurements.

A very pleasing result and a little instrument that looks like it will be most useful for my needs. It may be all I will ever need. At the very least it gives me a chance to learn about using an oscilloscope, even if this eventually leads to my needing to buy a stand alone unit with better specifications. But first some reading on the manuals and the other linked documentation.

Thanks Womai, for all the effort you have put into developing this little instrument.

And thanks to Picaxe for selling it (complete with the software download and documents) as I may never have found it otherwise.

In answer to the original posters question, now that I have it up and running, it’s highly recommended. If you ever wondered if you need an oscilloscope, this is a great way to experiment with a really useful entry level instrument at a very reasonable price. It might be all you will ever need, or at the very least you will know a lot more about what you need before you spend a lot more money.

Eng460
 

womai

Senior Member
It all powered up ok, With the little green light shining steadily, but the software still could not find the device. I tried another cord with success. Perhaps the first one was faulty, or possibly even supplied with a device that only needed power. Who knows.
Yes most likely cause for a USB cable not working with the scope is that the cable is just for power (charging), i.e. it lacks the data lines for communication. Frequent giveaway is that the cable diameter is very small.
 

Buzby

Senior Member
A very pleasing result and a little instrument that looks like it will be most useful for my needs. It may be all I will ever need.
Yes, it's a great little device at a fantastic price.

To see a list of low-cost scope products, see here : http://www.gabotronics.com/resources/hobbyists-oscilloscopes.htm

( This list is a bit out of date, but many of the devices are still available, and a few links are to instructions for homebrew DIY scopes. )

Cheers,

Buzby
 
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