Products > Test Equipment
LaPOD: Low cost Logic Analyzer probe for MSO5k, DHO900 and more!
oliv3r:
--- Quote from: ebastler on November 06, 2023, 10:21:35 pm ---
--- Quote from: oliv3r on November 06, 2023, 09:46:52 pm ---The wiggles above the voltage dividers are needed, because the center two channels come from the top of the chip, so need to go all the way from the top, to the bottom.
--- End quote ---
No, I don't think they are needed. They are in channels 0 and 3, right? And now you have created additional wiggles in channels 1 and 2 just above the 2*4 plug. They pretty much even out, so just do away with all four of them -- that's what I meant.
--- End quote ---
So on the top-size, from the chip to the resistor/capacitor network, there's a wiggle to compensate for the length of channel 1 & 2 which come from the top of the chip, and run on the bottom side. So all traces from the chip, to the network are all 4 in identical length. The wiggles after the network, is to match the length of the outputs going to the 2x4.
There is one thing that isn't properly matched though, just because I don't know how, and that's the length of the wires in the network, they should be the same but I wouldn't be supprised there's an error inthere, especially in the lm7234 pod, as the network isn't oriented identically, to make things fit better (0&3 and 1&2 are identical though). And since the parts aren't perfect tetris blocks (resistors and capacitor 2012's have different sized pads ... go figure.
One tiny advantage of not putting the PCB underneath the connector btw, is that we can put in the connector a bit lower, allowing the pod to be not as fat. I even thought of doing the same as with the 50pin connector, and use an SMD layout, for a straight throughole part and side-mount it ... should fit?
Does require clipping some sticking out legs though ...
ebastler:
--- Quote from: oliv3r on November 07, 2023, 07:30:58 am ---So on the top-size, from the chip to the resistor/capacitor network, there's a wiggle to compensate for the length of channel 1 & 2 which come from the top of the chip, and run on the bottom side. So all traces from the chip, to the network are all 4 in identical length. The wiggles after the network, is to match the length of the outputs going to the 2x4.
--- End quote ---
I think we are still not talking about the same traces. Referring to the attached montage, I was looking at the length-matching wiggles indicated by the two smaller circles. They seem to be for channels 0 and 3. And now you have added the wiggles for channels 1 and 2, indicated by the larger circle. These four seem to be of very similar length -- so can't you simply remove all four of them?
Edit -- some further, unrelated comments:
* I like the lowered position of the 2*4 connector; makes the vertical alignment nice and symmetrical.
* Don't forget to change the channel numbers on the top and bottom silkscreen to 0..3!
* Please correct the top silkscreen to say LMH7324.
UK:
Finally, guys, I found a solution for vertical 50p headers!
Firstly, such headers are not rare at all, it’s just that most manufacturers do not mark them as elevated or extra tall.
Secondly, there not many have in the lineup version 2x25.
Even Pololu produce such headers already many years but only in 2x20 version.
BUT if you try to search directly PC104 long pin, you can get a ton of them, its Chinese OEM headers which are very widely available on many markets... amazon, ebay and of course most cheap prices on aliexpress. There exact option 2x25, but as a rescue option 2x5 also available (that may be staked in row by 5).
The main interesting part is that its high may be easily raised just by adding a plastic part salved from common pin header (pic from Pololu nicely illustrate that).
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So now we have an all option for vertical 50p and vertical HDMI sockets ;)
And as for the vertical HDMI sockets looks like Rigol use C2682172 in their DHO scopes, you can cheek it here... but I think C5204145 definitely more robust.
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PS
--- Quote from: oliv3r on November 07, 2023, 07:30:58 am ---...is that we can put in the connector a bit lower, allowing the pod to be not as fat.
--- End quote ---
Extremely like the idea of low-ride 8p socket position! :-+
ebastler:
--- Quote from: UK on November 07, 2023, 03:34:20 pm ---BUT if you try to search directly PC104 long pin, you can get a ton of them, its Chinese OEM headers which are very widely available on many markets... amazon, ebay and of course most cheap prices on aliexpress. There exact option 2x25, but as a rescue option 2x5 also available (that may be staked in row by 5).
--- End quote ---
Yes, these should work. They don't even need a spacer permanently installed, I think, since there are so many pins to keep them stable. But of course you need some spacer or alignment aid during soldering, to make sure you solder them in at the right height.
These connectors do not have the little tab which ensures you can't plug them in the wrong way. So the PCB will need some clear lettering on the front to show the user which side is up.
EDIT: Or rather, the 3D-printed enclosure will need to provide that lettering. Or one can try and glue a little plastic tab onto the connector which matches the notch on the scope side.
UK:
--- Quote from: ebastler on November 07, 2023, 03:47:32 pm ---These connectors do not have the little tab which ensures you can't plug them in the wrong way.
--- End quote ---
Yep, it's definitely not a problem and it just could be a part of the shell.
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I've made a try to calculate the best dimensions for 2х2 PCB, which taking into account all shell clearances and possible margins, should have a perfect fit with both of the scopes!
Also, I want to point out that 50p header should have a slight vertical offset.
To be honest, now I'm even more interested in the version for DHO900 since I plan to get this cute little scope during the winter holidays :-[
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