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Post by rodney on Dec 17, 2019 23:20:38 GMT
HI all, I'm building up a DSO138mini oscilloscope as an AE module over the next week or so. I'll document the process here and turn it into a proper tutorial.
the page describes a daughter board and alternative firmware to add another channel to the DSO138. I have a standard DSO138, but the power supply is 9v, so a little awkward and a bit larger for transforming into a module. I am not yet sure whether this daughter board would also be compatible with the DSO138mini (which runs off 5v).
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Post by rodney on Dec 19, 2019 4:44:13 GMT
Some pix for Size comparison:
The DSO138mini has some proto board space so I plan to use that to mount the header to connect to the AE rack's bus cable to get power and break out the bus clock etc. The DSO can also take an external trigger, so it might be fun to gate the scope from elsewhere in the synth:  |
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Post by rodney on Jan 3, 2020 0:01:02 GMT
So, chugging into the new year...
Here is the first iteration. It plugs into the bus and has one AE jumper patch input.
I plan to rework the 3D printed case which is a bit crappy at the moment. I want to make it more curvy and old-sci-fi but, realistically, square barely fits the 75mm space so it might stay like this one.
I will also add a jack and maybe RCA connector for external inputs.
| 10pin male header for AE bus cable soldered to the bottom of the analog board. Here, I'm only using the +5v and GND rails. | 
| On the other side of the board, the battery connectors are wired to the back side of the AE bus connector. |
I made the following changes to the standard DSO138mini board: - Added 2x5pin (10pin) male header for AE modular bus connector (the board has a convenient proto area for this kind of thing).
- Removed the input connectors (both BNC and JST connectors) and wired in a single female jumper header.
- Removed the power connector and wired directly to the AE bus connector instead.
- Removed the Power switch and bridged the pads to make it permanently ON.
- Replaced the 90 degree slide switches with vertical ones to poke through the panel instead of stick out the side.
- bridged JP4 jumper.
I need to do some maintenance and re-calibration of my 3D printer before doing the final panel. I'm trying not to waste plastic but it's hard to get all those fiddly measurements right. A good way is to only print a thin sheet of the parts of the model that need to line up with things in the real world. Then it's easier to see my mistakes before committing to a 6-12 hour high resolution print.
In practice though, vertical resolution does not matter much since we are mostly looking at the top layer, so I'll probably stick with 0.3mm per layer.
I will probably also print it in two parts that slot together in order to reduce the need for rafts and support material.
I will probably add ribs to stiffen the plastic panel (I'm using PLA but ABS would be slightly more bendy). I am still deciding whether to add clips for the board or to use screws.
If anyone wants to have a go at this project, I'm happy to share the .stl files and the OnShape cad project link, I just want to clean up the geometry and parameterize some aspects of the model for easier tweaking first.
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Post by timb0bsteve on Jan 3, 2020 23:20:12 GMT
I love this. I was looking to do exactly the same, but I wasn't sure it was possible without using a 9v-to-5v DC-to-DC converter or something. I'm not very confident with electronics yet and I'd really hate for that inexperience to kill my AEM :-(
Perhaps I can pick your brain a bit about how it's done?
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Post by rodney on Jan 4, 2020 1:28:05 GMT
I love this. I was looking to do exactly the same, but I wasn't sure it was possible without using a 9v-to-5v DC-to-DC converter or something. I'm not very confident with electronics yet and I'd really hate for that inexperience to kill my AEM :-( Perhaps I can pick your brain a bit about how it's done? Happy to help.  Can you wait a week or two for me to finalise this build and make this thread into a proper guide?
I think it is possible to get a ready-assembled DSO138mini board (not the DSO138) as, if you are not practiced at soldering, there are a lot of parts to put together. You'd need a de-soldering tool to remove a few sockets etc.
So far, this mod involves 2 wires, 2 additional components and 15 solder connections. (including the unused pins on the bus connector just for strength).
Do you have access to a 3D printer?
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Post by timb0bsteve on Jan 4, 2020 22:20:20 GMT
I'm not too fussed about 3d printing a case for it, I was just going to roughly mount it.
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Post by rodney on Jan 6, 2020 5:26:07 GMT
I'm not too fussed about 3d printing a case for it, I was just going to roughly mount it. In that case, it might be possible to add some cut board, or maybe spare circuit board, to mount it 'bare' in the AE modular case? You might be able to fit either an RCA or a jack socket for the input and still have enough space for a single female header pin for AE modular patching input. If you buy the 'J' variant of the design, I'd consider replacing the switches with ones that point straight up instead of at 90 degrees. Other than that, it should be fine to follow the instructions. If you are not confident about soldering, I'm sure there are ready-made ones out there for pretty much the same price.
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Post by rodney on Jan 6, 2020 5:34:56 GMT
As a quick hack to hold the module onto the panel without putting screws through my flimsy plastic job, I cut some strips of polyethylene from a drink bottle and poked holes in them for the panel-mounting hex bolts.
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Post by rodney on Jan 6, 2020 6:12:53 GMT
Oh, I forgot to post video...
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Post by rodney on Jan 6, 2020 20:34:25 GMT
... and the final thing (for now) labeled and installed. I can finally say I have spilled over into the second rack case! (creating a yawning gap to induce another flare-up of Gear Acquisition Syndrome) 
I'll leave this project for a while now and just use it. I'll eventually replace the 3D printed panel with a more solid print (I kept it simple and thin for speed of iteration). I'll also add a phono connector for external inputs and use screws to connect the panel to the board instead of scraps of PET bottle.
Much later, I'll see if it's possible to apply a hack to make it 2-channel. That needs a bunch more components and a change of firmware (mentioned and linked earlier in this thread). There should be enough space on the board, but maybe this mod only works for the original DSO138 and not the mini model shown here.
I actually have a nicer printed case design for the original 9v DSO138 if anyone wants to try it. It needs the same connectors removed and you'd have to run a separate +9v line straight from the Master module.
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Post by rodney on Jan 6, 2020 20:43:17 GMT
I'm seeing these online for about nine euro with free postage, so it's a good project for someone with intermediate soldering skills. The tricky SMD parts are all done for you on the main board. The DIY part is all analog through-hole construction with friendly use of space. I'm sure there are pre-built and tested versions out there too.
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Post by slowscape on Jan 6, 2020 23:16:30 GMT
This is an awesome project! The money is no problem, the time on the other hand... I could use more of that  Remind me, is this the oscilloscope that can stream data to a computer?
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Post by NightMachines on Jan 7, 2020 19:56:54 GMT
Spectacular!!!! And thanks for the shop link. Just ordered myself the kit and I look forward to put this in my new AEM case when it arrives. I like the large screen on it and having a built-in scope is a lot more convenient than an external one for quick waveform visualization.
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Post by rodney on Jan 8, 2020 10:46:33 GMT
This is an awesome project! The money is no problem, the time on the other hand... I could use more of that Remind me, is this the oscilloscope that can stream data to a computer?
yep! can send via USB (and be powered by usb) |
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bert
Junior Member
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Post by bert on Apr 5, 2020 16:07:35 GMT
Cool. I had exactly the same idea :-) I've found that it works best when you trigger it externally. The DSO138mini can automatically find the base frequency, but with complex waveforms this doesn't work well (or you need to tweak the settings with the buttons to make it work). Instead I recommend connecting the "pulse" output of one of your VCO's to the "PB15" input of the DSO138. Connecting the bus straight onto the board hadn't occurred to me yet. I think I'm gonna do the same. I'm struggling with one thing: what is the best way to attach the board to a 4U front panel in order to fit it nicely in the AE case? Has anyone given this a thought? I'm currently powering the thing with a USB cable. I can't get it to work with the battery input. Is that why you bridged the JP4 jumper? EDIT: OK just found out about the other thread about the DSO138 :-) Seems like a lot of thought has already gone into it. Has anyone successfully integrated it into the AE case yet? |
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Post by rodney on Apr 9, 2020 8:32:30 GMT
Cool. I had exactly the same idea :-) I've found that it works best when you trigger it externally. The DSO138mini can automatically find the base frequency, but with complex waveforms this doesn't work well (or you need to tweak the settings with the buttons to make it work). Instead I recommend connecting the "pulse" output of one of your VCO's to the "PB15" input of the DSO138. Connecting the bus straight onto the board hadn't occurred to me yet. I think I'm gonna do the same. I'm struggling with one thing: what is the best way to attach the board to a 4U front panel in order to fit it nicely in the AE case? Has anyone given this a thought? I'm currently powering the thing with a USB cable. I can't get it to work with the battery input. Is that why you bridged the JP4 jumper? EDIT: OK just found out about the other thread about the DSO138 :-) Seems like a lot of thought has already gone into it. Has anyone successfully integrated it into the AE case yet? The case I made is 3 units across. I will definitely add a trigger input. I will also try to properly calibrate it to measure things more accurately. At the moment, I'm happy just seeing simple waveforms and enjoying the mess of complex ones as pure bling. |
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bert
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Post by bert on Apr 9, 2020 9:31:03 GMT
Yes, I also realized it can just fit in 3U :-)
By the way I'm afraid mine is broken. I must have done something wrong while connecting the AE bus to V+, because a voltage regulator has gone up in smoke and now there is a lot of interference in the signal. I guess it's because initially I had the wrong polarity (beginner's mistake), although I'm not sure of this. I've ordered a new one cause they're so damn cheap. (But I hope I won't fry that one too.)
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Post by young Protoboard on Apr 9, 2020 17:04:46 GMT
I must have done something wrong while connecting the AE bus to V+, because a voltage regulator has gone up in smoke [/div]
MSRE
Press F to pay respects
F
You talking about a voltage regulator like an LM317? Or an outlet-to-barrel-jack AC-DC regulator? I need to make sure I get the cinematics in my head right.
A while back I was helping construct a radio telescope for my university's astronomy department and the team leader tried to test the controller board by inserting bare wire into the wall outlet. That circuit was expecting a 12V current-limited DC signal and what they received was 120V AC of "Oh wow, that sure was a loud noise. Do you smell something funny?"
Since then I've considered every MSRE I've witnessed and performed a positive learning experience, provided that they were spawned from less-egregious (and less costly) error than my acquaintance on that day.
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bert
Junior Member
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Post by bert on Apr 9, 2020 18:23:51 GMT
Yes, the small variant. It wasn't that spectacular :-( But still, I hope I learned from it.
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Post by rodney on Apr 10, 2020 4:39:59 GMT
MSRE
Press F to pay respects
F
You talking about a voltage regulator like an LM317? Or an outlet-to-barrel-jack AC-DC regulator? I need to make sure I get the cinematics in my head right.
A while back I was helping construct a radio telescope for my university's astronomy department and the team leader tried to test the controller board by inserting bare wire into the wall outlet. That circuit was expecting a 12V current-limited DC signal and what they received was 120V AC of "Oh wow, that sure was a loud noise. Do you smell something funny?"
Since then I've considered every MSRE I've witnessed and performed a positive learning experience, provided that they were spawned from less-egregious (and less costly) error than my acquaintance on that day.
[/quote][/div]
I'm assuming MSRE is Magic Smoke Release Event?
I'm planning to set up my AE power supply to test my system's current draw with a multimeter to avoid future MSRE as the Master module's heatsink is getting very hot. I don't think it's the DSO138mini but better safe than sorry. It may be one of th eother unorthodox things I've done to the poor thing.
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bert
Junior Member
Posts: 54
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Post by bert on Apr 10, 2020 9:11:45 GMT
OK keep us posted.
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Post by young Protoboard on Apr 11, 2020 3:37:57 GMT
I'm assuming MSRE is Magic Smoke Release Event? I'm planning to set up my AE power supply to test my system's current draw with a multimeter to avoid future MSRE as the Master module's heatsink is getting very hot. I don't think it's the DSO138mini but better safe than sorry. It may be one of th eother unorthodox things I've done to the poor thing.
Yup! Please share your findings-- I've been curious about AEM power draw and have yet to meter any modules or systems. |
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Post by woestijnmeeuw on Apr 29, 2020 15:37:18 GMT
Replaced the 90 degree slide switches with vertical ones to poke through the panel instead of stick out the side.
Can you specify the new switches? Thnx!
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Post by rodney on May 2, 2020 0:21:05 GMT
Replaced the 90 degree slide switches with vertical ones to poke through the panel instead of stick out the side. Can you specify the new switches? Thnx! I just happened to have an older DSO138 kit on hand so I could just swap out the switches. they are a fairly standard type though and more common than the 90 degree ones. You may need to measure your switches and search some catalogs.
If you have not yet ordered your DSO138mini, I'll see if I can measure the switches and help specify the right replacement.
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Post by woestijnmeeuw on May 3, 2020 22:18:51 GMT
Replaced the 90 degree slide switches with vertical ones to poke through the panel instead of stick out the side. Can you specify the new switches? Thnx! I just happened to have an older DSO138 kit on hand so I could just swap out the switches. they are a fairly standard type though and more common than the 90 degree ones. You may need to measure your switches and search some catalogs.
If you have not yet ordered your DSO138mini, I'll see if I can measure the switches and help specify the right replacement.
Thnx! I'm already in the final phase, building the mini with the AEM frontpanel and I'm trying to modify the 90 degree switches :-) I will share some pics when I'm done. |
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