DC Motor Relay Selection

Question

Problem: DC Motor Relay Selection. Solve this hands-on electronics task on EWskills.

Accepted Answer

1. Component Purpose

The controller needs to turn a 12V DC motor ON and OFF. A relay isolates the motor’s high-current circuit from the low-current controller, and provides a clean mechanical ON/OFF switch.

DC loads are harder on relay contacts than AC loads. AC current crosses zero 100/120 times per second, which helps extinguish the arc when contacts open. DC current has no zero-crossing, so the arc persists longer and erodes contacts faster. This is why adequate current margin is important.

Required: General Purpose · 12VDC coil · SPST-NO or SPDT · ≥5A contacts · DC rated · Non Latching · Through Hole

2. How to Find It on DigiKey

Go to DigiKey.com → Relays → Power Relays

Apply these filters:

Coil Voltage → 12VDC
Contact Form → SPST-NO (1 Form A) or SPDT (1 Form C)
Contact Rating (Current) → 5A or higher
Coil Type → Non Latching
Mounting Type → Through Hole
Termination Style → PC Pin
Part Status → Active

Tip: When checking the datasheet, look for the DC contact rating specifically. Many relays are rated 10A at 250VAC but only 5A or 3A at 30VDC.

3. Key Specifications & What They Mean

Specification	Required	Why
Coil Voltage	12VDC	Matches driver supply.
Contact Form	SPST-NO or SPDT	Only NO switching needed.
Contact Current	≥5A	Motor draws 3A; DC arc needs extra margin.
Switching Voltage	12VDC rated	Must be rated for DC switching.
Coil Type	Non Latching	Standard ON/OFF control.
Mounting	Through Hole, PC Pin	Standard PCB mount.
Temp Range	−40°C to +85°C	Industrial conditions.
Safety Approval	cURus or equiv.	Product certification requirement.

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 — 12VDC Coil, SPST-NO/SPDT, ≥5A, DC Rated, Through Hole

55. DC Motor Relay Selection