Simple oscilloscope for Picaxe work - finally finished! (DPScope SE)

womai

Senior Member
"Only" 18 months between proof of concept and final design of what was supposed to be a minor diversionary effort on the side... but finally I finished the DPScope SE project. For those interested in the history, look at these two threads:

http://www.picaxeforum.co.uk/showthread.php?15814-Interest-in-very-simple-but-usable-oscilloscope

and

http://www.picaxeforum.co.uk/showthread.php?17938-Your-opinion-counts-questions-regarding-simple-but-usable-oscilloscope

The final design turned out very different from the initial concept:

PIC12F683 (8 pins, 20 MHz) --> PIC18F14K50 (20 pins, 48 MHz)
one channel --> 2 channels + ext. trigger
nothing else --> 4-channel logic analyzer
RS-232 connection to PC --> USB for power and data
bare board --> half-custom enclosure

... and all that AFTER I recovered from some temporary feature creep! :)

The webpage is here:
http://www.dpscope.com

or head directly to the software and documentation (assembly guide is complete, but user manual will follow in a few days, as will a detailed description of the circuit schematic. Pictures aren't there yet either):
http://www.dpscope.com/downloads_se.html

Enjoy!

Wolfgang

PS: Sitebuilder gives me some grief, quite often the top navigation bars on my modified site get messed up with duplicate/wrong labels etc. Let me know if you experience the same. Does not seem to be a browser issue as IE and Firefox suffer similar problems... but too late to spend a few more hours fixing that today.
 

Svejk

Senior Member
Well done Wolfgang!

I can't wait for it to arrive! One small thing tough: the paypal directs to deutch version of Paypal.

Regards,
S

Edit: can you autograph it?

Edit2: small error:
mistake.jpg
 
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womai

Senior Member
Yeah, since I now live in Germany I opened a German Paypal account. Haven't found out yet how to default to English for payment confirmations.

The mistake in the menu bar is exactly what I experience - looks perfectly fine in the editor, and shows up fine 30% of the time in the browser. Something gets confused so it uses the wrong label. Will work on that this week but really looks like a bug in Sitebuilder.

Where do you want me to sign? (back panel?)
 

pilko

Senior Member
@ womai,
The "buy it" link on the home page takes the reader directly to the DPScope rather than the DPScope SE. It may cause some confusion.

pilko
 

womai

Senior Member
Yeah, the labels on the top navigation bar get completely mixed up. I really have to work on this. Hope I don't have to re-do the whole webpage. The underlying links are correct though (you see them when you hover the mouse pointer over the respective menu navigation bar item). To get the DPScope SE buy-it page you need to selecte "DPScope SE" on the left side navigation bar (big grey rectangular buttons), or use this direct link:

http://www.pdamusician.com/dpscope/buy_it_se.html

Wolfgang
 

premelec

Senior Member
Looking at the schematic it would seem you could build this wonderful little unit with SMDs in a USB stick - the only problem being the RCA or BNC jacks being so big.... When I assembled a DDS with SMD stuff a few years ago was that IF [when...] I dropped a component on the floor I could never find it again...
 

inglewoodpete

Senior Member
Looking at the schematic it would seem you could build this wonderful little unit with SMDs in a USB stick - the only problem being the RCA or BNC jacks being so big....
You've just given Wolfgang an idea. Actually, it should be possible, with 3 RCA connectors on one side of the board and the other SMD components on the back...
When I assembled a DDS with SMD stuff a few years ago was that IF [when...] I dropped a component on the floor I could never find it again...
I have the same problem when I drop through-hole components on the floor!
 

womai

Senior Member
Looking at the schematic it would seem you could build this wonderful little unit with SMDs in a USB stick
Yeah, but then it would not longer be a beginner's project... (except that beginners tend to be younger, have better eyes, healthy backs, and thus less problems finding and picking up dropped SMD components :) Second issue, with the unit rigidly attached to a USB port (as opposed to connected by a flexible cable) I'd be afraid of mechanical damage to the USB port (and the computer) if you pull on the scope probes once too often.
 

premelec

Senior Member
Oh my you are up already and I haven't gone to bed yet - and I've found ICs embedded in my rubber soles occasionally... it's the hot de-soldered ones embedded in my finger I really hate - but at least they are sterile! [and the solder bits pick out of the cauterized holes pretty easy...] :)

On the SMD unit I'd just put some probe wires to it and logic input wires-- however no hurry - it'll evolve over the next 18 months.
 

inglewoodpete

Senior Member
... with the unit rigidly attached to a USB port (as opposed to connected by a flexible cable) I'd be afraid of mechanical damage to the USB port (and the computer) if you pull on the scope probes once too often.
I imagine that an SMD version would be machine assembled. I agree about the stresses on USB ports. However, its just a matter of thinking outside the square - I have a 4-port USB hub that came with an integral 3-cm lead to the USB plug. Flexible but not untidy.
 

smeagol

Member
Question re Probes simple vs proper scope probes.

I assume that proper scope probes offer an advantage at higher frequencies, better rejection of interference etc.

So with the limited frequency response of the DPScope SE would you see much difference between the two types of probe, apart from the attenuation offered by the 1:10 option?

Cheers
Gavin
 

womai

Senior Member
The scope probes offer advantages in a few respects:

- Wider range - 10x higher voltage range.

- Higher bandwidth (mostly in 1:10 mode, where they offer 20 MHz; about 5 MHz in 1:1 mode) and lower capacitive load on the circuit (in 1:10 mode) compared to grabber cables. For the DPScope SE and the DPScope this is of no importance, their bandwidth is too low (300 kHz and 1.3 MHz, respectively) to see the difference.

- More flexible means of attachment - hooks, pointy end, etc. Easier to hold. IMHO this is together with the voltage range the most important feature.

Both scope probes and grabber cable use coaxial cable so both are very well shielded; the grabber probes slightly less due to the very end where the two wires are separate.
 

Bill.b

Senior Member
Hi Wolfgang

I attempted to install the software for the osilloscope , received message 'Setup cannot continue because some system files are outof date on your system .... ' clicked on YES then rebooted computer. Ran setup again with the same results. repeated this four times.

my system is Intel duel core processor 2.1meg XP service pack 3

any suggestions.


regauds Bill
 

womai

Senior Member
Thanks for the feedback, constructive criticism is always appreciated. I am developing on a Win7 system so if the installer creation takes any system files then this could explain what you see. I am still in the process of cleaning up the installer package. I'll probably also put the bare .exe file of the software online so worst case you can just copy this into a folder of you choice and create a desktop shortcut to it. Bare with me, right now I am struggling with the d*** Sitebuilder - refuses to create working navigation bars.

Wolfgang
 

womai

Senior Member
Good news, I managed to fix the webpage - had to rip out all the navigation bars and recreate them from scratch. On the upside the new layout is a bit cleaner. Detailed design (circuit) description, pictures and user manual are still on the to-do list.

Now off to working on the installer and fixing a few things in the assembly guide.
 

womai

Senior Member
I put a new software installer online. At least on my two (Win7) machines it now install cleany without error messages.

In addition I put the bare .exe file online as well. Use this if the installer gives you trouble. Windows should already have all the other components by default anyway.
 

womai

Senior Member
Yeah, as I said, "Detailed design (circuit) description, pictures and user manual are still on the to-do list." I re-used the pages from the original DPScope and kept the picture legends as placeholders - but the actual pictures will be from the DPScope SE of course.
 

womai

Senior Member
I updated the installer - removed all files that I think should be already part of Windows anyway. I'd appreciate if people could download it (http://www.dpscope.com --> DPScopee SE --> Donwloads) and let me know if it works not or not (if not then I'll probably have to throw out even more stuff).

Thanks in advance

Wolfgang
 

womai

Senior Member
Are you sure you downloaded the new file? (Often my browser does not automatically refresh). It should be called DPScopeSE3.zip (the old one was DPScopeSE2.zip). Anyway, I just put yet another version online, please download this one and try (the file is called DPScopeSE4.zip). I threw out everything that the installer creator would let me. So if that one does not work (while the bare EXE apparently does) I'll have no choice but to look for a better installer creator.
 

greencardigan

Senior Member
No error this time although it didn't seem to install anything. Although that could be a something to do with our security at work here.

Yep, i tried DPScopeSE3.zip previously.
 

John West

Senior Member
No error this time although it didn't seem to install anything. Although that could be a something to do with our security at work here.

Yep, i tried DPScopeSE3.zip previously.
Might be the security settings at your job, but did you look in the Programs menu from the Start button? I found it there. It failed to load on my machine the other day, but this time (now SE4 version) it installed just fine but only shows up in the program directory, i.e. it has no Desktop icon, which is fine by me. All of my desktops are too overcrowded, even my PC Desktop. The bane of my existence.
 

womai

Senior Member
Or maybe because there isn't much to install - just the main EXE and the uninstaller - so it may have gone too fast to see anything. Should be easy to try - uninstall and make sure DPScope.exe has disappeared, then install and try to launch the program.

To all who have bought the kit - I'll ship tomorrow morning. Hopefully all the installer issues etc. will be sorted out before anybody receives and builds his/her kit!
 

BillyGreen1973

Senior Member
Just to let you know..
the SE4.zip installed and works just perfect on my work laptop (Celeron M 1.5Ghz, 512Mb RAM, WinXP SP3).
Once again, many thanks,and I look forward to building it and testing it out as soon as it arrives.
 

John West

Senior Member
I've been playing with the latest version of code for Wolfgang's DPScope SE. Wow! It now includes a large DMM-like display with a selectable choice of just about whatever data value you wish it to display, High value, low value, DC mean, AC RMS, frequency, period, duty cycle, rise time, fall time. Just wow! This thing is pretty handy.

I can finally make circuit measurements and adjustments without wearing my glasses. For us old guys, that's a big deal. Much of my regular bench-top test gear may wind up getting set in the corner and forgotten about unless I need high frequency or precision measurements. Congrats, Wolfgang. It's good stuff.

Now, if I could just find my PICAXE circuit....
 
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John West

Senior Member
Scope party! :)

Be sure and let Womai know if there are any problems or confusions with the assembly instructions. He's trying to make the scope construction as easy as possible.
 

smeagol

Member
OK finished the build, all went smoothly apart from the drilled snap off points at the rear of the main board. They were a bit proud so that the rear panel would not fit into the case. A bit of filing cured this but it's worth checking before mounting the components.

Unit passed self check OK and completed both stages of offset adjustment, 2nd stage took a bit of fiddling as the presets are a bit coarse but no real problem.

Now bear with me as it's about 30 years since I touched a scope so I may (probably) be asking stupid questions.

Channel 1 and 2 show 0V when probes are shorted. When probes are not shorted I get an offset of 2.75V on Channel 1 and 2.84V on channel 2. I don't have anything handy to generate a waveform but connecting a battery across the probes gives a correct DC reading on both channels. Is this normal?
 

John West

Senior Member
That sounds wrong to me. Check without the scope probes (just let the inputs float.) If it's still off, double check the resistor values at the probe input connectors. I'm on my way out the door to get to work on time, so sorry I can't be of more help now.
 
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