Author Topic: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes  (Read 53723 times)

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Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #100 on: March 27, 2021, 10:11:14 pm »
one of my friends said also look inside HDMI and Displayport cables, they should also contain 4 twisted pairs and a bunch of thinner single wires,
however i dont like to trash this type, since we use them for our PC stuff,
VGA cables are no good, the video wires are too thick and there are only 3 of them, and the rest of the signal wires are too thinn, for this project,
but could be perfect for other projects, so have a look in the electronic dumpster near you :-)
Radioamateur OZ2CPU, Senior EE at Prevas
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Offline mawyatt

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #101 on: March 27, 2021, 11:47:47 pm »
Nice  :-+

We've used some Cat5 cable before which is small (~AWG 26) twisted pair but this was for precision analog use, it's solid copper and much too stiff for probe use. The 3M flat twisted ribbon type is smaller with AWG 28 wires (stranded) and flexible.

Best,
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 

Offline natman69

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #102 on: March 28, 2021, 09:29:48 am »
I agree that ethernet solid cables are too rigid for probe use but they can come also in stranded and very flexible versions with AWG 24-26. They are cheap and available in every shop.

Will this DIY probe be available as a kit? Any plan to sell it to eevblog users?

Anyway, really thank you for sharing this project!
 

Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #103 on: March 29, 2021, 10:10:25 am »
>Will this DIY probe be available as a kit? Any plan to sell it to eevblog users?

sure, see post 1
it is actually just PM me if interested :-)
right now the first few kits are send out,
during next week the design is expected to be fully approved
and i start shipping the rest, i still have pcb's stocked
i sell them real cheap .
have you smd parts ?
solder skils ?
3D printer ?
if not I can help with that too, for a little extra fee,
but the cables and test hooks, you need to get and solder your self.

YES Ethernet cables do come in flexible cores, but they are still a bit too thick
and to my experience not that good for soldering, the plastic melts too easy
Radioamateur OZ2CPU, Senior EE at Prevas
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Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #104 on: May 04, 2021, 07:07:27 am »
latest news, only a few are left now :

All the 3 loose pcbs = 10$
(the 4 layer scope pcb is sanded to correct connector end angle)

option, all the smd parts and the pin rows mounted, add 10$

option, all the 3D printed parts and screws, add 10$
(STL files are for free, incase you got a 3D printer or know one locally)

postage 5$, untracked, no insurance.

twisted pair cables, not included
(i recommend to use DVI cables, perfect diameter for the job, cut all wires exactly 50cm long)
twisted pair soldering, you need to do this your self.
test hooks with small female connectors, not included, see ebay and similar.
Radioamateur OZ2CPU, Senior EE at Prevas
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Offline FrancisM

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #105 on: May 04, 2021, 08:04:55 am »
@ oz2cpu,

PM sent
 
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Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #106 on: May 04, 2021, 06:25:54 pm »
thanks FransisM all done, packed and send..
To any one else. mail via this system dont seem to be working at the moment, nothing show up, and no notifications too,
so please use normal emails : my username at gmail dot com

Radioamateur OZ2CPU, Senior EE at Prevas
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Offline Bad_Driver

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #107 on: May 06, 2021, 07:00:19 am »
Good Morning OZ2CPU,

yesterday the PCBs arrived! Looks very good! I'm impressed by your SMD soldering capabilities, I tried some 8050 yesterday and two jumped into Nirwana .... :palm:
I need much more practice....  |O
Unfortunately my 3D printer isn't working anymore. Last part I have finished was your SDS2000x+ blind plug, fits perfect!
After long investigations and part changing it seem to be the thermistor on the hot end. Now I'm awaiting a DuPont crimp tool from Aliexpress
for final repair. I keep you informed when I got the probes running, the tips are still on their way.

Thank you very much for this great piece of engineering! Keep you informed about my progress.
 

Offline mawyatt

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #108 on: May 06, 2021, 02:18:01 pm »
Haven't had time to do much with the LA since another project has taken over our available time, but hope to get back on this soon.

However, we can verify that Thomas (oz2cpu) LA Probe works well with standard 10 line ribbon cable (8 active, 2 ground), the twisted pair cable we have is a little too wide so used ribbon cable instead. Don't have a high speed pulse generator, but did verify that using a sine wave input from a AWG the Probe works to ~100MHz with ribbon. You do "see" a small amount of crosstalk, but that's expected, with twisted pair the crosstalk should be eliminated. Also can verify the 3D files print nicely.

Still waiting for a proper crimp tool and doublewide 16 connector "shells" for Dupont connector pins, so just used a single wide 8 "shell" and soldered the connector pins. As shown this supports the 8 active lines, and the ground lines are just a single Dupont connector.

Anyway, hat's off to Thomas (oz2cpu) for developing this DIY PA Probe for the Siglent Scope and making it available to others :clap:  :-+

Best,

Mike
Curiosity killed the cat, also depleted my wallet!
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Offline FrancisM

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #109 on: May 14, 2021, 08:37:09 am »
I acquired my 2104x+ three months ago and was surprised to discover that all the active parts for the LA were already inside the scope. Being a hobbyist and newly retired, I found it interesting as I never used myself such a piece of gear. Too expensive at the time.
I asked Thomas (oz2cpu) for the pcbs and all the parts he could provide.

In the mean time, I had to activate the needed option. I spent some time to dig into a thread about it and found all I had need for.
It was way more easy than expected and I ended up with a fully liberated scope !!!
I also built a test jig MCU based to have something to play with. I started with the PIC16F84 at it's beginning and now, mostly use PIC18F series wich satisfy my needs. Just a single pulse on each bit of two IO ports in a loop, to be sure I haven't mixed things up.

A smart guy made the soldering job of the tiny parts for me. I just had to solder the wires and close the boxes.
It worked like a charm at start.
The nice thing is I can see both digital and analog level of the same pulse.
I had some fun playing with the trigger and the options available.

Next step will be troubleshooting of a Z80 cpu board from the eighties. It fails to control water temperature in a coffee machine.

Thomas, without your offer wich was a bargain, the LA would have never been used on my scope. Some tens of MHz and half a meter length is all I have need for. It won't have an every day use so the official probe wasn't an option.

Thanks for all your effort,  :-+
Francis
« Last Edit: March 21, 2023, 05:07:39 pm by FrancisM »
 
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Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #110 on: May 14, 2021, 10:17:09 am »
Fantastic looks like you nailed it :-)
did you try to use the SKEW settings ?
with this you can trim the LA delay to match that analog channels
Radioamateur OZ2CPU, Senior EE at Prevas
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Offline techneut

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #111 on: May 14, 2021, 12:52:26 pm »
I was looking for cables and came across a scart cable. In it are 6 small flexible coax cables 50 Ohm. Is it worth the trouble to strip this cable and use them or is it not any better than twisted pairs? I would probebly need to change the 120 Ohm resistor value?
 

Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #112 on: May 14, 2021, 01:13:25 pm »
scart coax is 75 ohm, so yes, all 120 ohm, needs to be 75
this way each side of the coax is terminated with 75, and you should expect as little as possible ringing, and better timing.
I prefer to use a high impedance as possible, twisted pair is about 120 ohm, and this way you load the signal source less,
that is also what you want.
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Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #113 on: May 14, 2021, 01:59:46 pm »
LATEST NEWS : MY STOCK IS EMPTY.
I DO NOT PLAN TO MAKE AND SELL MORE.
ALTIUM AND GERBER FILES ARE NOW IN THE THINGIVERSE LINK.

MAKE PCB and 3D files for OWN private use is alowed.
MAKE and sell PCB or 3D files, or fully assembled product, ONLY alowed if the sale price ONLY cover actual expenses.
it is NOT alowed to modify this design and distribute any part of it as your own.
Radioamateur OZ2CPU, Senior EE at Prevas
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Offline techneut

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #114 on: May 14, 2021, 02:02:03 pm »
scart coax is 75 ohm, so yes, all 120 ohm, needs to be 75
this way each side of the coax is terminated with 75, and you should expect as little as possible ringing, and better timing.
I prefer to use a high impedance as possible, twisted pair is about 120 ohm, and this way you load the signal source less,
that is also what you want.

That is what I expected 75 Ohm but I used the TDR with a variable resistor at the end of the cable and it was 50 Ohm. For analog video (< 5MHz) it doesn't realy matter. The BNC's used in analog video are also 50 Ohms. Only with SDi (540 MHz and higher) came the 75 Ohm BNC.
 

Offline FrancisM

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #115 on: May 14, 2021, 04:46:42 pm »
Thomas,

I learned what deskew is with my first digital scope some years ago. And I saw you using it while testing your probe earlier in this thread.
A friend of mine is amused to tell me that most of my gear is running close to DC, so I will leave it at 0ns.

This morning, I made some further testing on a Z80 cpu board. And as almost always, it started with a bad electolytic on the PSU. The +5V is a buck converter (L4960) and it's output cap measured less than one tenth it's original value, not speaking about esr. There was a lot of garbage on top of the 5V and it's probably the only issue. After replacement, the ripple was down to a decent value. The thing runs at 100kHz and I used a Panasonic FR.
So far, so good.

I was told the board fails to read temperature of a sensor. I can see an ADC0844 and some opamps connected at it's inputs. There's a span adjustment like in the datasheet and the opamps make the zero shift. It's a four layer board and I have no manual but the sensor seems to be connected to ch1 and ch2 through two opamps.

I connected your probe to the ADC data and control lines. Once triggered, the timings are clean but a read always outputs a 0FFh even with the sensor(PTC) connected. I then triggered on a write to get the mux mode control byte. It reads 04h wich is not what I expected. It translates to channel 1 in single ended mode while I thougt it to be in diff mode. The board doesn't seem to initialize as it should, probably an external missing stimuli. It will be replaced where it comes from with everything connected to it.

I had fun playing with my scope.

All the best,
Francis

« Last Edit: May 14, 2021, 05:58:48 pm by FrancisM »
 

Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #116 on: May 14, 2021, 06:09:53 pm »
great, yes Z80 speeds is quite a facter away from this scope capeabilities,
but you are having fun, and learn how to use it as hardware and software debugger,
the more you dig into the z80 board, you be amazed how easy it is to find and fix all the problems.
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Offline pzw

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #117 on: May 15, 2021, 05:15:00 pm »
I guess I was one of the lucky people getting one of the last sets! The PCBs look great, and well assembled!
One small hint for whoever will decide to make their own PCB; The inner layers of the PCB with the edge connector will be exposed when the edge is sanded under the correct angle. Not that it will create any issue, since I do not see how the exposed copper can short out anything. But if the internal layers are made about 1.5 - 2.0mm shorter at the edge connector end, this inner layer will never be exposed.

Now I am on the hunt for an old DVI cable, or maybe I just need to buy a new one ;-) .

Thanks again to @on2cpu for the nice PCBs and quick shipment!
 
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Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #118 on: May 15, 2021, 05:42:33 pm »
Fantastic usefull comment
if anyone like to take this up in the near future
and maybe dont own an Altium license, just pm me,
all files , gerber, and altium, are in the thingiverse link.
Radioamateur OZ2CPU, Senior EE at Prevas
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Offline techneut

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #119 on: May 15, 2021, 07:28:12 pm »
My pcb's arrived today and they are looking good. I'm waiting for the slow boat from China for the components and in the mean time checking out other scart cables for coax. We still have a lot of them at work.
 

Online tautech

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #120 on: May 16, 2021, 08:50:58 am »
Spotted in another thread is a better description of flat ribbon coax cables like OEM's use for these LA probes:
Google: micro-coaxial ribbon cable

Lots out there and will be interesting to see what motivated hunters of such products can find.  :popcorn:
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Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #121 on: May 16, 2021, 11:25:03 am »
thanks for the hint, did a little googling :-) looks like it is clearly possible to get very thinn coax, and even in ribbon style,
however  : expect it will be a lot more work to hand solder, lower impedance..
and a lot more expensive / hard to get.
with the twisted pair : easy to get, chep, and easy to solder, and there is no detectable crosstalk..
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Offline oz2cpuTopic starter

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #122 on: May 16, 2021, 11:28:02 am »
NEW updated files :

the scope plug in pcb is now in V2.0
files are at the thingiverse link

V2.0 released 16 may 2021
 inner layers pulled back at gold finger ends,
 this way gnd copper will not be exposed when edge milled.
 0R resistor removed, the idea with this resistor : to be able to use the plug in pcb alone,
 if this feature is needed, use V1.0
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Offline mawyatt

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #123 on: May 16, 2021, 01:07:05 pm »
Great work!!

A couple notes regarding the newer PCBs. Don't see a spot for the lead cap in the POD PCB, this is in parallel with the high value resistor. When we assembled your POD PCB we had to stack the cap on top of the resistor, not so easy with 0603 SMDs. Also the terminating resistor at the scope side BASE doesn't actually terminate the transmission line since the input to the scope is relatively high Z. In fact the input terminating resistor doesn't do this either since the input probe lead is a large series inductance due to the actual probe leads, not to mention the ground lead inductance. The isn't as simple as just terminating with the line impedance at either end, look at my earlier post that shows the simulation which attempts to get a waveform at the scope connector that "looks" like the waveform tautech provided from the OEM LA. Figuring that "IF" the waveforms look similar, then the LA networks should be similar and the performance similar, I know at lot of "IFs" ::)

For these reasons when we did our PCB version we included the addition components to allow better control of the impedances "seen" at the input and output of the transmission line, wether it's a micro-coax, twisted pair, or simple ribbon cable.

Still waiting on the Dupont crimp tool, and sidetracked on another involved project (64 channel MMW phased array controller based on a new integrated technology voltage controlled transmission line for the delay elements), so hope to get back to this LA project soon.

Disregard the 0.1uF cap values shown in the schematic, obviously these should be in the few pF range!!

Best,
« Last Edit: May 16, 2021, 01:11:47 pm by mawyatt »
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Offline Bad_Driver

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Re: DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
« Reply #124 on: May 18, 2021, 02:36:57 pm »
I checked different old monitor cables as well. Old VGA cables have 3 thin coax with 75 ohms (measured) inside and other thin twisted cables.

But I will stay with twisted pair cables from DVI cables as suggested by Thomas. My interests are more on the "DC side" of digital electronics.
But it would be interesting to see if there are real differences with different cables and terminations up to 500 MHz. May be someone
tries it.

Unfortunately my 3D printer seems to suffer from a defective main board and needs much more efforts than I can spend these days.
So I cannot print the shells for the PCBs.  :phew: Hope to overcome this issue and be able to finalize the logic probe set. The tips arrived from Aliexpress.
 


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