How to build an electric safety box for components above 25V

thijs · September 2, 2026, 12:14am

Based on contributions by 21142173.

If your SMR project uses any component running at 25V or higher, it must be housed in an electric safety box before you’re allowed to power it up. This guide covers the assembly; see the Rulebook for the full electrical safety rules.

What you need

An electric safety box (available in the robot lab)
DIN rail(s)
Cable glands and blanking plugs
Terminal blocks, including grounded terminal blocks
Cable shoes (for bare/stripped wires), available in the workshop
Bolts, for components without a DIN-rail connector

Steps

1. Place the components in the box

Use one of the electric safety boxes available in the robot lab. Place one or more DIN rails on the metal bottom plate, then attach that bottom plate into the corners of the box. Mount your components on the DIN rail(s); if a component doesn’t have a DIN-rail connector, bolt it directly to the metal bottom plate instead.

2. Prepare the box for wiring

Every cable that leaves the box must be fed through a cable gland and connected to a terminal block for strain relief. Fit cable glands into the holes on the sides of the box, and close any unused holes with blanking plugs. Mount terminal blocks on the DIN rail, placing signal/power terminals between grounded terminal blocks.

Grounded terminal blocks:

3. Wire the components

Plug in cables that already have a connector. For bare (copper) wires, crimp on cable shoes before connecting them — these are available in the workshop. Check that the cable’s diameter is suitable for the current your application draws.

4. Get it checked and approved

Before powering up your box, an authorized teacher (electrical safety officer) must inspect it and issue a pass. Only use the box once you have that pass.