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TM500/TM5000 extender project

Ke-Fong Lin
 

Hi everyone,

I've made some progress for the TM500/TM5000 project:

https://drive.google.com/file/d/14WSoPeQoIwup4532_YnxUz44PVxAYJ8T/view
https://drive.google.com/file/d/1E7RxXXPg_3-Kwd652mFbe5g-4zoBeAN_/view

The purely "extender" part is done, that is the PCB edge connector plus solder pads to connect.
Left to do, is the debugging part: PWR power-good signal for TM5000 (only 1 transistor and a few resistors) and final layout of the PCB.
Basically, everything on the right of the solder pads.
The big cutoff in the PCB is intended to act like a handle, much as what cyrob (Philippe Demerliac) has done for his TM500 projects.

Hardest part was to draw the PCB edge connector footprint into kicad. The polarity cut-off was particularly tedious.
However, python scripts can also be used to generate footprints, that's what I did for the solder pads. It is easy, fast and above all precise.
With the experience gained here, a 7000 series plug-in extender would be an easy addition.

Note that only the "mandatory" cut-off is here, not the function specific ones.
To be honest, it is particularly tedious to enter the coordinates manually. Yet it would be possible to write a python script to do so.
With so many cutoffs, as in Tek's "official" extender, I'm worried that the edge connector would be fragile.
Also, it would be only a minor inconvenience to not support the function specific cutoffs.
So I decided to have only the one cutoff absolutely needed.

The connectors are Molex KK 2.54mm series. I had good results with them in previous DIY projects.
They are readily available at mouser or farnell, and not expensive. Only drawback is they need a crimping tool for wires.

I've done a quick quote with this work in progress. JLPCB has it at around 22 euros for 5 pieces and 5 euros shipping.
Gold plated edge connectors + chamfer included.

I plan to have it everything ready for next sunday for a first try.
And put everything on github when done.

Best regards,

John Griessen
 

On 2/9/20 6:40 PM, Ke-Fong Lin wrote:
Hardest part was to draw the PCB edge connector footprint into kicad. The polarity cut-off was particularly tedious.
However, python scripts can also be used to generate footprints,
If you write scripts, pcb-rnd would maybe be a better way for you to spend time -- it's aimed at
engineers that use linux/unix to create circuits, circuit models, documentation, as chip designers do,
but mainly for boards. (At least until 3D printed organic transistor resistor capacitor inductor circuits are easy to specify and buy).

Brian Cockburn
 

Will the two connector footprints - male edge connector and pads for mating socket - be available as public Kicad libraries please? I can see that other people in the future being able to use these for their projects and being gratefull not having to pointlessly re-implement your great work.

Ke-Fong Lin
 

Everything will be available on github, including the footprints of course.
In fact, it is more the python scripts that are really useful. It is much faster, less error-prone, and precise than manually drawing.

As for pcb-rnd vs. kicad, I've already started to learn and use kicad.
Also, it seems that kicad has more developers and some institutional support (CERN?), along with a larger community.
So I'll settle on kicad.

Paul Amaranth
 

I made up a script to generate edge connector footprints for Geda.
If anyone wants it drop me a note.

Paul

On Sun, Feb 09, 2020 at 11:04:50PM -0800, Brian Cockburn wrote:
Will the two connector footprints - male edge connector and pads for mating socket - be available as public Kicad libraries please? I can see that other people in the future being able to use these for their projects and being gratefull not having to pointlessly re-implement your great work.





!DSPAM:5e41009e9591577342676!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix & Windows

Ke-Fong Lin
 

Hi everyone,

The PCB is ready! I've updated the preview and the schematics.

https://drive.google.com/file/d/14WSoPeQoIwup4532_YnxUz44PVxAYJ8T/view
https://drive.google.com/file/d/1E7RxXXPg_3-Kwd652mFbe5g-4zoBeAN_/view

In particular, I've added a small circuitry to generate the "power good signal" for the TM5000 modules.
It's basically a voltage divider from 8V to 5V, and an NPN buffer. The PWR specifies a full load (16mA) of TTL high (+5V).
A small drawback is that it always draws around 2-3mA even if not to needed (inserted in a mainframe).

Can some of you do a review of the schematic? Or give some comments or suggestions?
For those really curious, I can send the complete kicad project, just ask. Final version will be an github of course.
For a pure extender use, there is just some wiring to be done. Otherwise, I'll have to provide some sort of BOM.
I also have to write a small "documentation".

Plan is to send the PCB to fabrication (JLPCB) this week-end, after feedbacks.

Best regards,

Abc Xyz
 

Nice Board!

On Wed, Feb 12, 2020, 2:20 PM Ke-Fong Lin <anotherlin@...> wrote:

Hi everyone,

The PCB is ready! I've updated the preview and the schematics.

https://drive.google.com/file/d/14WSoPeQoIwup4532_YnxUz44PVxAYJ8T/view
https://drive.google.com/file/d/1E7RxXXPg_3-Kwd652mFbe5g-4zoBeAN_/view

In particular, I've added a small circuitry to generate the "power good
signal" for the TM5000 modules.
It's basically a voltage divider from 8V to 5V, and an NPN buffer. The PWR
specifies a full load (16mA) of TTL high (+5V).
A small drawback is that it always draws around 2-3mA even if not to
needed (inserted in a mainframe).

Can some of you do a review of the schematic? Or give some comments or
suggestions?
For those really curious, I can send the complete kicad project, just ask.
Final version will be an github of course.
For a pure extender use, there is just some wiring to be done. Otherwise,
I'll have to provide some sort of BOM.
I also have to write a small "documentation".

Plan is to send the PCB to fabrication (JLPCB) this week-end, after
feedbacks.

Best regards,



Dave Daniel
 

I noticed that you don’t have anything to strain-relieve the wires. I’d add some holes through which cable ties could be run to capture the wires.

DaveD

On Feb 12, 2020, at 17:20, Ke-Fong Lin <anotherlin@...> wrote:

Hi everyone,

The PCB is ready! I've updated the preview and the schematics.

https://drive.google.com/file/d/14WSoPeQoIwup4532_YnxUz44PVxAYJ8T/view
https://drive.google.com/file/d/1E7RxXXPg_3-Kwd652mFbe5g-4zoBeAN_/view

In particular, I've added a small circuitry to generate the "power good signal" for the TM5000 modules.
It's basically a voltage divider from 8V to 5V, and an NPN buffer. The PWR specifies a full load (16mA) of TTL high (+5V).
A small drawback is that it always draws around 2-3mA even if not to needed (inserted in a mainframe).

Can some of you do a review of the schematic? Or give some comments or suggestions?
For those really curious, I can send the complete kicad project, just ask. Final version will be an github of course.
For a pure extender use, there is just some wiring to be done. Otherwise, I'll have to provide some sort of BOM.
I also have to write a small "documentation".

Plan is to send the PCB to fabrication (JLPCB) this week-end, after feedbacks.

Best regards,


John Griessen
 

On Feb 12, 2020, at 17:20, Ke-Fong Lin wrote:
For a pure extender use, there is just some wiring to be done. Otherwise, I'll have to provide some sort of BOM.
Please tell us more about how laborious that wiring is in various ways you have made it possible.
How do you see using the 7 through hole connectors? Are there 7 mating connectors you plan to supply
to users who might have difficulty getting just one of them?

Arie de Muijnck
 

Add a pin 1 marker (small triangle)  to J4...J10. It might same someone a lot of trouble.

If +8_11.5VDC is max 11.5VDC then the voltage on TTL_HIGH can be max 7V, way too high for TTL.
Better use a 5.6V zener instead of R2.

Regards,
Arie

On 2020-02-12 23:20, Ke-Fong Lin wrote:


Hi everyone,

The PCB is ready! I've updated the preview and the
schematics.

https://drive.google.com/file/d/14WSoPeQoIwup4532_YnxUz44PVxAYJ8T/view
https://drive.google.com/file/d/1E7RxXXPg_3-Kwd652mFbe5g-4zoBeAN_/view

In
particular, I've added a small circuitry to generate the "power good
signal" for the TM5000 modules.
It's basically a voltage divider from 8V
to 5V, and an NPN buffer. The PWR specifies a full load (16mA) of TTL high
(+5V).
A small drawback is that it always draws around 2-3mA even if not
to needed (inserted in a mainframe).

Can some of you do a review of the
schematic? Or give some comments or suggestions?
For those really curious,
I can send the complete kicad project, just ask. Final version will be an
github of course.
For a pure extender use, there is just some wiring to be
done. Otherwise, I'll have to provide some sort of BOM.
I also have to
write a small "documentation".

Plan is to send the PCB to fabrication
(JLPCB) this week-end, after feedbacks.

Best regards,

Ke-Fong Lin
 

Hi everyone,

For strain-relieve, I've consider it but:
* this will make the PCB bigger however that's not so much of a problem;
* the solder sides will be at the back, whereas front side, the pads act like touch points;
* the extender is for hobby use (repair/calibration), probably only during week-ends, not intensive professional use.

Regarding the 7 connectors, they're standard 2.54mm (.1in) Molex connectors. Readily available at Mouser and Farnell.
There are cheaper alternatives at Tayda electronics or even aliexpress.
If you don't plan to do debugging without mainframes, then none of the extra circuitry is needed.
I'll write a small README along with a proposed BOM.

As for the power good (PWR) high TTL output, it is intended only for TM500x modules which expect regulated 8VDC.
The markings on PCB specify the regulated TM500x voltages.
TM500 supplies filtered but regulated voltages, tolerance of +7.6V (fully loaded) up to +16V!
It is not a problem as these older modules don't use PWR. But it draws around 2-3mA.
In fact, some TM500x modules (AA5001 for example) don't even check PWR when they should.

Best regards,

Ke-Fong Lin
 

Hi everyone,

The PCB came back today from JLCPCB. With the covid-19 it may have been a week or so later than expected, but here they are!
I've add a new photo: https://groups.io/g/TekScopes/photo/239639/0?p=Created,,,20,2,0,0

I've done some quick test, the PCB edge connector fits properly in my TM503. I would need to check my TM5003 but I guess it won't be a problem.
The edge pads are a bit longer than needed, this may be due to the 1.2mm allowance for chamfer, or may be because I've also taken as reference 5000 series scope plugins, which have longer pads than TM500/TM5000.
The solder pads for the extending cables have quite tight tolerance, 22AWG fits closely, no floating expected during soldering.
The handle is quite tight, I can barely fit my fingers and my hands are small. But offer correct great and it may just be adequate enough.

Except from a few scratches, the quality from JLCPCB is good, especially the through hole platings, not much to say about.

Plan is to do the thorough testing this weekend: Both as extender and "debug" device with a bench power supply.
And when stuff is confirmed working, release v1.0 on github.

I've received 5 prototypes PCB, if some of you wanna try and help me debug. I can send you one for cost of shipping.

Best regards,

Ke-Fong Lin
 

"The handle offer correct grip"