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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 2nd Aug 2019, 4:39 pm   #21
ajgriff
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Default Re: Drawing circular log scales?

As someone who has attempted this kind of thing with more conventional drawing/graphic design software I'm very impressed with Terry's work and Abacomb Front Designer. Unfortunatley, I don't think I could justify the cost of buying the package for the odd occasion it would be used. Having said that about 40 doesn't seem too outrageous.

Alan
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Old 3rd Aug 2019, 2:51 am   #22
Terry_VK5TM
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Default Re: Drawing circular log scales?

Quote:
Originally Posted by mole42uk View Post
Hi Terry, that is fabulous! Thank you, I'll be able to finish rebuilding the signal generator...
You're welcome.

Alan,
You'd be surprised at what uses you may end up using the Front Designer software for.

I've used it as above for various scales and dials, front panels (both custom and replacement), site plans for building and even A3 sized 'elf'n'safety signs for the Mens Shed, amongst other things.

As an aside, this sort of thing (the dial face) can be done (and is in industry) with ordinary CAD software, even the free ones. I just prefer Front Designer as it has much less of a learning curve than full on CAD packages.
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Old 3rd Aug 2019, 9:23 pm   #23
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Default Re: Drawing circular log scales?

The only freeware package I can recommend for this sort of thing is Galva, written by Jean-Paul Gendner, F5BU.
http://www.f5bu.fr/galva-about/
It's a script-based program so you just define things like start number, end number, log or lin, and you can draw scales for almost anything, including very complex multi-meter scales.
I have used it to restore the dial from a 1970 KW2000 transceiver, for instance, which has an irritatingly non-linear dial.
I highly rate it.
-Jeremy

PS, I also use Front Designer and have done some huge front-panel layouts with it. Much easier for entire front panels than Galva.
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Old 4th Aug 2019, 6:00 am   #24
ajgriff
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Default Re: Drawing circular log scales?

I'll have a play with Galva. Thanks Jeremy.

Alan
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Old 19th Aug 2019, 7:23 pm   #25
tb10_flyer
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Default Re: Drawing circular log scales?

I thought I'd refresh my old Galva skills my trying to replicate the OP's dial based on the photograph shown in Post #12. The first PDF shows a log scale in blue superimposed over the photograph. Clearly there are differences which indicate the original instrument scale is NOT logarithmic, and probably cannot be accurately represented by any mathematical function. So, using the 'measurement' technique suggested by Jean-Paul Gendner in his Galva Help file, by Jeremey <Pamphonica> in Post #23 and by myself in previous designs. the second PDF shows in red a perfect match. If Richard <Mole24UK> is still looking for a true restoration of the original scale, this will provide the art work. I have assumed that the '1' and '10' marks correspond to the full CCW and full CW rotation of the dial, through the measured 285 degrees.

Now, I wonder whether the empirical nature of the original dial may be because the resistance(?) of the control component was only an approximation to logarithmic progression as, I think, is usually the case with most log-law devices.

Mike
Attached Files
File Type: pdf Log Dial 3 - LOG scale.pdf (178.8 KB, 20 views)
File Type: pdf Log Dial 3 - MEASURED scale.pdf (184.1 KB, 25 views)
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Old 20th Aug 2019, 6:12 am   #26
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Default Re: Drawing circular log scales?

That’s interesting, the designers at Radford must have made the dial to fit the log law of the Bourns potentiometer they used.

I’m away on holiday but as soon as I return I’ll pick this up again.
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Old 7th Sep 2019, 8:25 am   #27
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Default Re: Drawing circular log scales?

The project progresses, not quite as soon as I wished, because work made huge demands after my holiday!

I have now 'borrowed' a Windows machine, used your Galva script and printed a version of your modified log scale. I also have the piece of 2mm anodised aluminium and the photo-resist film so that I can etch the scale.

Before I commit to the final version, I'm going to use the paper print on a dummy dial and measure the output frequency against the new markings. That should prove the theory about the variation of the Bourns pot logarithmic law against a genuine logarithmic scale.

I did not think that this dial would have taken quite so long to reproduce!
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Old 6th Oct 2019, 1:24 pm   #28
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Default Re: Drawing circular log scales?

Right, more progress. I have used a paper copy and checked Mike's modified logarithmic scale on the actual machine, and it is accurate - well as accurate as my old test equipment and eyes can determine.

Now I need to get the scale etched onto the aluminium and the Radford LDO will be ready for action....
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