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Grogster
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Posted: 19 April 2018 at 9:32pm | IP Logged Quote Grogster

As a follow-on from my other HC-12 thread, here is what I have so far for the programmer/tester.







The board is 50mm square, and incorporates a 1455 USB interface for the serial. As this board is HC-12 specific, I have not bothered with the ICSP pins or the SELECT tact, as all I wanted was just a plain old USB-serial adaptor on-board so I did not have to hunt around for one to plug into it.

Two mini slide switches control the unit, with one being connected to the HC-12's SET line to easily allow you to hop in and out of setup mode. The other slide switch turns the power off and on to the HC-12 module.

The two slots above the module, and one below, allow for module restraint by way of a wide rubber-band, that you cut so it is one long length of rubber strip. The end by the switches is fixed, and the other end is threaded through the upper two slots, so you can easily loosen it, insert a module to test or program, and pull the rubber-band though the two upper slots, which will pull the module down on the pogo pins. The rubber will grab on the edges of the slotted holes, holding it in place for the duration of the testing or programming. That's the idea, anyway.

Rubber is a conductor of static electricity, so I will have to test this idea a bit more, but I don't see there being THAT much friction to charge up the rubber band, but perhaps elastic would be better.

As well as allowing you to easily program an HC-12 module WITHOUT soldering any pin-strips to it etc, it will also allow you to send it test data that it will transmit which can quickly and easily be checked for frequency with the likes of a UHF scanner radio. Here is the scanner radio I use - US$35.

The pogo pins are P75-E2 type, and 100 of them can be had for US$2.
Having a conical head, these ones self-centre in the holes on the module, and it also makes for quick alignment of the module on the pins, as they 'Want to be together' - isn't that sweet....

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kg4pid
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Posted: 20 April 2018 at 3:21am | IP Logged Quote kg4pid

Maybe I missed it, but does this board have a place for an antenna or are you going to use an external antenna?
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Grogster
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Posted: 20 April 2018 at 10:00am | IP Logged Quote Grogster

For the purposes of testing, you usually don't need an antenna.
You could put an external one on the U.FL socket if you needed to use it to range-test, but that is not really the purpose of the board. Having said that, it would be a good idea to have a hole in the PCB so you can put a simple wire on if you want. Thanks for the tip.

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Grogster
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Posted: 30 April 2018 at 8:38pm | IP Logged Quote Grogster

Here is a photo of a completed unit:





The rubber-band idea was a failure.
The pogo-pins have enough force collectively, to pull the rubber-band back through the slots. Oh well - was worth a try. For now, I am just holding the HC-12 on the pins - that works, but means you lose one hand, so I am working on some other method. Because there are five pogo pins at one end, but only two at the other, you need more force at the connections end then the antenna end - should have seen that before - oh well.......

The board works fine to read, program and test the modules though. I just need to think of a more suitable module restraint system.

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Azure
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Posted: 30 April 2018 at 11:13pm | IP Logged Quote Azure

A little swing lever made of plastic with a hole at one end and a slot at the other. Swing it away to change modules, swing it in over a module push it down (against the pogo pins) and into a retaining screw which has a washer on top for the slotted end to go under.

Both screws raised up from the pcb with nylon spacers.

I you used washers (maybe need nylon ones gainst PCB) you might be able to use the rubber band slots for the screw holes. You could use a nylock nut to keep the screws at a set tension and a little spring (above the lever pushing down on it using a longer screw) if you want more pressure.

If that makes sense.

That's what I was thinking of doing (when I read the rubber band idea , that is when I eventually get one.
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plover
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Posted: 30 April 2018 at 11:30pm | IP Logged Quote plover

I do love that testing arrangement (and I do not have an HC-12)

Can't help to suggest sort of springy piece of say hardened fence wire using the two nice slots. Flat piece of spring from an old wind up alarm clock, I seem to remember I have such in my scrap bin.


May well require a bit of insulation. Hmmm piece of single strand copper mains wiring.

Board kit available in the shop?


Edited by plover on 30 April 2018 at 11:34pm
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Andrew_G
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Posted: 30 April 2018 at 11:59pm | IP Logged Quote Andrew_G

Hi Grogs. Is it not possible to put a flatish weight (insulated of course) in the "sweet spot" on the module?
Given that there are pads to which the coil antenna can be attached is it possible to re-design or modify the PCB so a pogo pin, with an antenna attached, connects to one of these?

Cheers, Andrew
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CaptainBoing
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Posted: 01 May 2018 at 8:35pm | IP Logged Quote CaptainBoing

Grogster wrote:
For the purposes of testing, you usually don't need an antenna.
You could put an external one on the U.FL socket if you needed to use it to range-test, but that is not really the purpose of the board. Having said that, it would be a good idea to have a hole in the PCB so you can put a simple wire on if you want. Thanks for the tip.


how about a pogo pin with a 86mm (1/8th wave) "squiggle" on the PCB?

Edited by CaptainBoing on 01 May 2018 at 8:36pm
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Grogster
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Posted: 01 May 2018 at 8:40pm | IP Logged Quote Grogster

@ Azure - I think I see what you are getting at. I will have a play with the idea.
@ plover - Not available on the website. I can put it up there if anyone is interested.
@ Andrew_G - I like the weight idea - I will look into that. That might be all we need. The board caters for an external wire or helical antenna - there is a pogo-pin in place for that:





EDIT: Here is another shot of the board without HC-12 module:





There is a pogo-pin for the antenna connection, coming out to a PCB-based coplanar wave-guide set for 49.93-Ohms, which was as close as I could get to 50-ohms.


Edited by Grogster on 01 May 2018 at 8:57pm


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MicroBlocks
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Posted: 02 May 2018 at 5:18am | IP Logged Quote MicroBlocks

If you have one of these:



You could remove the microscope and replace it with a pencil or mabe a dowel and use it as a clamp. :)




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Grogster
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Posted: 02 May 2018 at 10:18am | IP Logged Quote Grogster

I don't, but all ideas are ideas!
Thanks.

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Andrew_G
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Posted: 02 May 2018 at 10:52am | IP Logged Quote Andrew_G

Hi Grogs,
I hadn't appreciated that there IS a connection for an antenna on the PCB.
With that I suggest all you need now is one of these:





Cheers,

Andrew
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