Hello everyone,
If there's still interest in the (still unfortunately bezel-less) LM3914 approach to this, here is the result of some further work I've done. You will see that, by mounting the display in a rather unorthodox fashion, I have kept the circuit within the 'footprint' of the display. There are now adjustments for the full scale sensitivity (the 100k pot) from 1.25V to over 12V, and the point at which the first LED comes on (the 5k pot) from 0.5V to about 1.5V. These two adjustments are independent, and ought to accommodate most expression pedal setups I think. V+ can be anything from 5-15 volts or more. The longest dimension of the display is almost exactly 1" (2.54 cm) for scale.
For the reasons explained in my earlier post, it is configured to work in 'dot mode', but if you wanted it to work in 'bar mode' (and are sure you can supply the necessary 150mA or so) just connect pin 9 of the LM3914 (the only pin not connected to anything else at the moment) to V+
The design works equally well for the red and green displays, and should be OK with the yellow ones too though I haven't got any of these to test it with.
Below is a (rough - I'm sorry) picture of the copper (green) side of the PCB with the components (red) indicated as well. Please note that the anodes of all 10 LED segments have to be connected together and to the pad marked 'led+' on the PCB.
If anyone wants a high definition version of the layout (suitable for printing transparencies to make the PCB) it is here:
http://www.personal.leeds.ac.uk/~edu6nwn/midistuff/ledbar.lay,
but unless you have the PCB design software "Sprint-Layout 4.0" you will need to use this:
http://www.personal.leeds.ac.uk/~edu6nwn/midistuff/viewlayout40.exe to view and print it.
Please note that I have no interest in making any of these boards/assemblies in quantity since a) it's very boring and b) neither my eyesight or
manual dexterity is really up to it any more. However, I might be persuaded to provide a very few for regular forum contributors if asked
nicely enough. I've not costed them, but could do if necessary on a not-for-profit basis.
Nick
ps It might be appropriate to move this thread to the 'DIY consoles' section?