For years I've struggled making circular scale graphics to use in Front Panel Designer. The often-suggested way is to created the graphic in an external program and then import it into FPD as a .HPGL file. However, the only package that seems to be able to do that is Inkscape. Apparently you can do it by installing a 'virtual Post Script' printer and then tricking the likes of Illustrator to use it to print to a file. I had a go at that but, frankly, life is too short.

I've abandoned Inkscape of late and have migrated all of my panel designs over to Illustrator. I tried exporting a drawing in every single format that Illustrator can chuck out but none of them are liked by FPD so that is a dead end.

Instead I thought I'd see if I could coax FPD's somewhat limited feature set into doing the job. As it turns out, it's object rotate function has a couple of nifty feature that make it quite useful.

Create the graphic that will be used to make up your circular scale:

 

he object becomes your top-centre division on your scale. Select the object and choose "Selection -> Rotate":

Here's where you need to pay attention. Set the Rotation Point Y offset (DY, highlighted in green) to the radius of your circular scale. In my example I've used "-10.00mm" which will eventually give us a circular scale based around a 20mm diameter circle. The value is negative to rotate the objects downwards. You then need to set the angle of Rotation (coloured blue). You need to calculate this yourself based on the overall angle of rotation of the control/scale (for example, most Alpha potentiometers have a rotation angle of 300 degrees) and the number of divisions you want. I'm using -20.00 degrees here which will give 18 divisions (360 / 20). For some reason, negative rotation values make the object rotate clockwise which seems counterintuitive to me. The important bit is the "Apply action to copy" setting. You need this on so that Inkscape will rotate a copy of the object rather than just rotating the original.

Here's where you need to pay attention. Set the Rotation Point Y offset (DY, highlighted in green) to the radius of your circular scale. In my example I've used "-10.00mm" which will eventually give us a circular scale based around a 20mm diameter circle. The value is negative to rotate the objects downwards.

You then need to set the angle of Rotation (coloured blue). You need to calculate this yourself based on the overall angle of rotation of the control/scale (for example, most Alpha potentiometers have a rotation angle of 300 degrees) and the number of divisions you want. I'm using -20.00 degrees here which will give 18 divisions (360 / 20). For some reason, negative rotation values make the object rotate clockwise which seems counterintuitive to me.

The important bit is the "Apply action to copy" setting. You need this on so that Inkscape will rotate a copy of the object rather than just rotating the original.

ou should end up with something like this:

Here's the handy part! With the cloned object still selected, choose "Edit -> Repeat Rotate"

And Inkscape will repeat the rotation you just setup. Do this as many times as you like/need until you end up with something like this:

Note: it's even quicker if you remember the Repeat Rotation shortcut key, in OSX it's CMD+R

Note: it's even quicker if you remember the Repeat Rotation shortcut key, in OSX it's CMD+R

So, that gives us one half of the scale. To make the other half, select the original object again at the top. Choose "Selection -> Rotate" again but this time set the Rotation angle to a positive value, here in my example it's 20 degrees (highlighted in red). Don't forget to set the DY value (green) and make sure "Apply action to copy" is still selected.

Use the "Edit -> Repeat Roate" command again to populate the other half of the scale and you'll end up with this:

ou can then group them all together (drag-select, SHIFT+G) and then drag the group to line up with your drill hole:

Lovely!

In my example I used a circle so it's not obvious that as well as rotating the position, the object itself is rotate to orientate correctly to the circle. This works with any kind of object, even text (though you have to do each letter individually!)





FPD Front Panel Designer scale circle circular array DIY panel modular

Published on by Neil Baldwin.