load-cell-scad

OpenSCAD models of common bar load cells and HX711 amplifier boards, for designing scales, mounts and enclosures around them. Each part is a data row, so the hole positions you design against come from the same numbers that draw the part.

Use it

include the data file, which brings in the rows, then draw a row:

include <load_cells.scad>
load_cell(LC_TAL220);

include <amplifier_boards.scad>
amplifier_board(AMP_HX711_generic);

Use include, not use: the LC_* and AMP_* rows and the load_cells and amplifier_boards lists are variables. To draw every load cell:

include <load_cells.scad>
for (i = [0:len(load_cells) - 1]) translate([0, i * 25, 0]) load_cell(load_cells[i]);

Load cell	Bar (mm)	Mounting holes
LC_TAL220	80 × 12.7 × 12.7	M5 at one end, M4 at the other
LC_TAL220B	55 × 12.7 × 12.7	one M5 at each end
LC_TAL221	47 × 12 × 6	two M3 at each end
LC_komputer_10kg	75.2 × 12.7 × 12.7	M4 at both ends
LC_komputer_5kg	80.2 × 12.7 × 12.7	M5 at one end, M4 at the other

A load cell is centred on the origin, its length along x and its mounting holes along z. load_cell(type, load_cell_color, sensor_color) sets the colours.

The boards are AMP_HX711_generic (33.5 × 20.5 mm, a 6-pin and a 4-pin header, two 3.15 mm mounting holes) and AMP_HX711_sparkfun (31.2 × 23.4 mm, two 5-pin headers). A board lies on z = 0, centred on the origin. amplifier_board(type, headers, header_pin_length) leaves the header blocks out with headers = false and the pins out with header_pin_length = 0.

Designing around a part

The accessors return a row’s fields, so a mount can follow the part:

include <load_cells.scad>

// Clearance holes for every mounting hole of a TAL220, in a 5 mm plate
difference() {
  cube([90, 20, 5], center = true);
  for (g = lc_screw_holes(LC_TAL220), p = [g[1], g[2]])
    translate([p.x, p.y, 0]) cylinder(d = g[0] + 0.4, h = 6, center = true);
}

examples/scale_mount.scad builds a whole single-bar scale this way: a base and a platform, each bolted to one end of the cell, for any cell in the library.

Load cells: lc_name, lc_cell_dims, lc_sensor_dims, lc_center_cutout, lc_screw_holes, lc_side_cuts. Boards: amp_name, amp_pcb, amp_colour, amp_chip, amp_headers, amp_mount_holes, and amp_pin_ys(n) for the pin positions in a header of n. The row formats are at the top of load_cell.scad and amplifier_board.scad; add a part by adding a row to load_cells.scad or amplifier_boards.scad and to its list.

Checks

just test takes about 3 s on OpenSCAD 2026.10.15. For every load cell it checks that:

• it renders as one piece, the bar plus its two gauges;
• every mounting hole, both bores, and the TAL221’s slot and side notches go right through at their stated size: a pin 0.05 mm under size passes and one 0.2 mm over doesn’t;
• each hole keeps at least 1 mm of metal to the bar’s ends, sides and bores;
• the gauges cover the bending section.

For each board it checks its size, that every header pin passes through its hole, and that the mounting holes go through at their stated size.

just images renders the pictures.

Licence

MIT; see LICENSE.