COMPLETED First, thanks to all for your ideas that did help me figure it out. I managed to construct a working model of a light up string action gauge, so here is what I did and pictures. Not real ‘refined’ but quite effective. Picture ONE – the measuring Shim. This was the most time consuming due to very small tolerances. I made a 1/16” thick x 4” long x 1/2” wide shim out of a very hard wood, this case Bocote. The length was determined so the shim would float on adjacent frets up and down the fret board either side of my target fret, the octave. I cut a starter slot with exacto saw, then widened it with the tip of a rat tailed mini file to give a good nest to the paperclip for glueing – superglue. File, then measure with micrometer, so that when the paperclip was flatly nested in the slot it was exactly .075” (my target string height) when under the string. Measure check, measure check, and so on. That was the time consuming part. Obviously 1/16” would flex between frets, and hard to hold. So I milled a flat upright brace to solve both problems. I cut a slot on the back side of the brace, and across the bottom, so that the upright portion of the paperclip would nest inside it to avoid contact with adjacent strings, and span the paper clip along the bottom of the brace, as well as easy to hold. I put the measuring portion of the paperclip approx in the middle of the device so I could turn it around for the last outside string. Otherwise it was gettting too close to the fret bevel to float reliably flat. Done.
Picture TWO – wired and mounted with the electronic components:
1. Wood Block just to make it more of a unit rather than wires runnng everywhere.
2. Two screw connectors scrounged from an old wall receptical to eliminate soldering. I just glued them on the block. Close enough together so the leads from the LED would reach.
3. Battery box from Amazon with hot and neutral leads and on off switch, holds 2 AA batteries. 5 of them cost about $7.
4. 5 mm LED light. Amazon, pack of 100 in 10 colors. Hot lead on light about 1/8” longer than neutral lead for identification purposes. Also about $7
5. Tester leads with alligator clips from Autozone. $2.99. I bought two of them so I’d have enough red wire. One is enough though if you don’t mind using black for a hot wire.
Picture THREE – wired and working device. (NOTE- PICTURES POSTED IN REVERSE ORDER FROM NARRATIVE)
Wiring scheme:
Black lead from battering box, AND the neutral lead from LED, to neutral screw.
Red long test lead with clip to the battery box red wire. This clips to the tuner.
Red shorter test lead, AND hot lead from LED to the hot screw on the block. For connecting to shim.
This completes the circuit, and when string touches the paperclip, the light comes on.
Note worthy things that made me say “ hmmmm”:
1. The light will flicker as you move toward the target fret. I called it good when I got a steady light when slightly moving the shim. Checked with feeler guage to make sure. Yep.
2. If you use a Zero fret, clipping to any tuner will cross over it and energize all strings for light.
3. I can use this one measurement (.075”) to tell how much I need to lower string action. I start a tad high. Considering the plane of the frets as the Base, I did some calculations and found that for every 1/2” length either side of the target fret, the action is plus or minus 3/1000ths. Since the angle from nut to bridge is a constant, this applies all up and down the fret board. Formula used for that (from a friend) is Base length x .005555. So, a light 1” past the target fret is 6/1000ths too high as example.
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Oh well! it doesn't hurt to have things reiterated. ![[:Y:]](./images/smilies/smiley20.gif "Thumbs Up")