[HBQRP] Magnetic loop project, automatic tuner vid.

[Arnie Grubbs]

Hi group,

I hope that this is of some interest to the group, as the HBQRP mag loop project continues!
On the Yahoo,  MagLoop e-group one of the guys posted a vid of his homemade loop tunerand I have to say, it looks very nice.  Its made using an ardrino controller, so thecomputer part is "open" to anyone to write their own code.  I think he will be puttingthe code out there for anyone to use if they wish, after he cleans it up a bit.
Heres a link to the vid.  

http://youtu.be/L7Od9lhrZi8

and here is the note that the builder posted on the e-group after there werea few people asking about the device.. I'll add it at the end of my note.

Also,  I am looking forward to the meeting coming up this weekend.  I hope to see everyone there, and also our 'special guest'.
I have not made much progress on my loop yet, due to some things at work and also things thatneeded to be done before leaving for the Dayton Hamvention next week...I do want to try to get something done this spring, if spring ever gets here and it warms up!

Also, PLEASE, everyone remind Darwin that the meeting is this weekend and to bring the KX1 that he has been building for me..    



73 - Arnie KA0NCR


Re: QRP Mag Loop and FT817
    Posted by: "Bernie" berniemcintosh at yahoo.es berniemcintosh
    Date: Wed May 8, 2013 3:32 pm ((PDT))


Thanks for all the very nice feedback.

The truth is that I spent a bit more time on the project recently  than
is consistent with maintaining a life of domestic bliss.  I need to give
it a little break before I get project documentation pulled together.
Also need to debug the code to the proper standard before making it
available as an open source package.

Briefly though, there is nothing particularly special about the control
side. Its an Arduino with:


    * two pins interfaced to the FT817 CAT  port,
    * two pins connected to a rotary encoder,
    * a set of switches used for simple commands and for changing mode of
operation (most of which are not used yet),
    * a stepper motor  (quite a big one for this job, but with steppers
bigger is always best),
    * a 12v stepper controller interfaced to two pins of the Arduino
    * A small psu module for 5v supply
    * A little power distribution PCB
    * An LED interfaced to a pin of the arduino
    * A shop bought LCD display with control board - I2C interface direct
to the arduino
    * A limit switch interfaced to a pin on the arduino

A word about the stepper driver - I used my own stripboard circuit with
a basic stepper driver chip.  But I wasn't happy with the accuracy when
I was powering the motor off in between moves (necessary because it can
pull a continuous 600mA if you don't do this). So I bought an off the
shelf "chopper" controller with 16x microstepping capability.  The old
board is still mounted in the case as it had some useful wiring
connections on it that I didn't want to bother moving.

Microstepping might be great for some applications but the accuracy
needed for this project is actually quite high and I couldn't get  the
microstepping features working wel enough.   So I use half stepping and
disable the motor in between moves. It works perfectly. The moral of the
story is though, that I would advise against using microstepping as a
means of getting good resolution and fine control of the capacitor. Make
sure you have enough mechanical reduction in place. I do. But only just.
If I was starting from scratch  I would have more mechanical reduction
in place than I do at the moment.

I'd be interested to know if anyone else has tried microstepping their
motor and if it was accurate enough?

You'll notice that I used ethernet plugs on both controller and tuning
boxes. The idea is that when I build my QRO loop, I can just plug in the
existing controller to the new loop.

On the CAT side, several folk have asked if it would be difficult to use
other rigs.

The controller only uses a few rig functions

1. Get the mode that the rig is currently in.
2. Set the mode of the rig (AM for tuning, then back to the original
mode)
3. Get the freq the rig is tuned to.
4. Get the SWR
5. transmit/receive
6. Get the current Smeter reading (not needed but looks nice !)

They are available from both kenwood and icom radio CAT ports, so yes,
it shouldn't be a bother to reprogram for other radios.

These kind of projects tend to revolve around what bits you have, and
what bits you know how to use. The mechanical stuff can be found from
stores online that cater to the hobby robotics market. At this level,
most microcontroller boards are more or less similar and can be
interfaced in similar ways.

Thanks again for all the nice comments.   Its something to show the XYL
to demonstrate that my being AWOL for a few weeks of shack construction
work  was worth it. [;;)]

73


Bernie
GM4WZG