GDT for 24VDC Industrial Field Wiring Surge Protection

Question

Problem: GDT for 24VDC Industrial Field Wiring Surge Protection. Solve this hands-on electronics task on EWskills.

Accepted Answer

1. Component Purpose

Long 24VDC field cables running across factory floors and outdoor cable trays act as antennas for lightning-induced surges. These surges can damage the controller’s input circuitry, TVS diodes, and ICs.

A GDT at the controller input acts as primary (first-stage) protection. It absorbs the high-energy portion of the surge. A downstream TVS diode (second stage) then clamps any residual voltage to a level safe for the board components.

The 75V spark-over is well above the 24VDC supply range (up to 30V with tolerance), so the GDT stays inactive during normal operation.

Required: 75V Spark-Over · ≥5kA (8/20µs) · 2-Pole · Surface Mount · Littelfuse · RoHS

2. How to Find It on DigiKey

Go to DigiKey.com → Circuit Protection → Gas Discharge Tube Arresters (GDT)

Apply these filters:

Voltage - DC Spark Over (Nom) → 75V
Impulse Discharge Current (8/20µs) → 5kA or higher
Number of Poles → 2
Mounting Type → Surface Mount
Manufacturer → Littelfuse Inc.
Part Status → Active

Tip: In a two-stage protection scheme, a decoupling element (usually a small inductor or resistor) between the GDT and TVS diode ensures proper energy coordination — the GDT fires first and handles the bulk energy, while the TVS handles the fast residual.

3. Key Specifications & What They Mean

Specification	Required	Why
Spark-Over Voltage	75V	Above 24VDC max (30V); surge-only firing.
Surge Current	≥5kA (8/20µs)	Lightning protection for long field cables.
Number of Poles	2	Protects 24V line and return together.
Mounting	Surface Mount	Compact board layout.
Manufacturer	Littelfuse	Company AVL requirement.
RoHS	Yes	Compliance required.

4. Selecting a Safe, Production-Ready Part

The filtered list will show matching parts. Before you pick one, check: Is it Active? Is stock available? Is the manufacturer reputable? Is a datasheet available?

Full checklist: How to Select a Safe, Production-Ready Component — EWskills Guide

5. Filtered DigiKey Link

➡ View Matching Parts — Littelfuse, GDT, 75V, ≥5kA, 2-Pole, SMD

47. GDT for 24VDC Industrial Field Wiring Surge Protection