Building the circuit support plate for the amber front running light was entirely too fiddly:
This was definitely easier:
Two pins fit in the small holes to align it with the LED heatsink, with an M3 stud and brass insert holding it in place:
The rectangular hole around the insert let me glop urethane adhesive over it to lock it into the plate, with more goop on the screw and pins to unify heatsink and plate.
The LED wires now emerge from the heatsink on the same side of the plate, simplifying the connections to the MP1584 regulator and current-sense resistor:
The paralleled 5.1 Ω and 3.3 Ω resistors form a 2.0 Ω resistor setting the LED current to 400 mA = 1 W at 2.6 V forward drop. They’re 1 W resistors dissipating a total of 320 mW and get barely warm.
The resistors and wires are stuck in place with clear adhesive, so things shouldn’t rattle around too much.
The OpenSCAD source code as a GitHub Gist:
| // Circuit plate for Tour Easy running lights | |
| // Ed Nisley - KE4ZNU - 2021-09 | |
| /* [Hidden] */ | |
| ThreadThick = 0.25; | |
| ThreadWidth = 0.40; | |
| HoleWindage = 0.2; | |
| Protrusion = 0.1; // make holes end cleanly | |
| function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit); | |
| ID = 0; | |
| OD = 1; | |
| LENGTH = 2; | |
| inch = 25.4; | |
| //---------------------- | |
| // Dimensions | |
| // Light case along X axis | |
| LightID = 23.0; | |
| WallThick = 2.0; | |
| Screw = [3.0,6.8,4.0]; // M3 OD=washer, length=nut + washers | |
| Insert = [3.0,4.2,8.0]; // splined brass insert, minus splines | |
| InsertOffset = 10.0; // insert from heatsink end | |
| PinOD = 1.6; // alignment pins | |
| PinOC = 14.0; | |
| PinDepth = 5.0; | |
| Plate = [50.0,LightID,Insert[OD] + 4*ThreadThick]; // overall plate size | |
| WirePort = [10.0,3.0,2*Plate.z]; | |
| NumSides = 2*3*4; | |
| //---------------------- | |
| // Useful routines | |
| module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes | |
| Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2); | |
| FixDia = Dia / cos(180/Sides); | |
| cylinder(r=(FixDia + HoleWindage)/2, | |
| h=Height, | |
| $fn=Sides); | |
| } | |
| // Circuit plate | |
| module Plate() { | |
| difference() { | |
| intersection() { | |
| cube(Plate,center=true); | |
| rotate([0,90,0]) | |
| cylinder(d=LightID,h=2*Plate.x,$fn=NumSides,center=true); | |
| } | |
| rotate([0,90,0]) rotate(180/6) | |
| translate([0,0,-Plate.x]) | |
| PolyCyl(Screw[ID],2*Plate.x,6); | |
| rotate([0,90,0]) rotate(180/6) | |
| translate([0,0,-Plate.x/2 - Protrusion]) | |
| PolyCyl(Insert[OD],Insert[LENGTH] + InsertOffset + Protrusion,6); | |
| translate([-Plate.x/2 + InsertOffset + Insert[LENGTH]/2,0,Plate.z/2]) | |
| cube([Insert[LENGTH],Insert[OD],Plate.z],center=true); | |
| for (j=[-1,1]) | |
| translate([-Plate.x/2,j*PinOC/2,0]) | |
| rotate([0,90,0]) rotate(180/6) | |
| translate([0,0,-PinDepth]) | |
| PolyCyl(PinOD,2*PinDepth,6); | |
| for (j=[-1,1]) | |
| translate([0,j*(Plate.y/2 - WirePort.y/2),0]) | |
| cube(WirePort,center=true); | |
| } | |
| } | |
| //- Build it | |
| Plate(); | |
