DC SSR Load Switching

Question

Problem: DC SSR Load Switching. Solve this hands-on electronics task on EWskills.

Accepted Answer

1. Component Purpose

Like the AC SSR, a DC SSR switches loads without mechanical contacts — giving silent operation and long life for frequently switched loads.

DC solid state relays typically use a MOSFET output (often called PhotoMOS or photorelay). Unlike AC SSRs that use TRIACs, MOSFET-output SSRs work with DC loads and have very low ON-state resistance (≤100mΩ), which means minimal voltage drop and power loss.

Required: SSR/Photorelay · SPST-NO · DC Output · 5V input · ≥24VDC load · ≥3A · Ron ≤100mΩ

2. How to Find It on DigiKey

Go to DigiKey.com → Relays → Solid State Relays

Apply these filters:

Output Type → DC
Voltage - Input → Range includes 5V
Voltage - Load → 24VDC or higher
Load Current → 3A or higher
On-State Resistance (Max) → 100mΩ or lower
Circuit → SPST-NO (1 Form A)
Part Status → Active

Tip: On DigiKey, DC SSRs may appear under "Solid State Relays" or as "PhotoMOS" / "Photorelays". Both are valid for this application.

3. Key Specifications & What They Mean

Specification	Required	Why
Relay Type	SSR / Photorelay	MOSFET output for DC switching.
Circuit	SPST-NO	Single NO output channel.
Output Type	DC	Switching 24VDC load.
Input Voltage	Includes 5V	Controller signal compatibility.
Load Voltage	≥24VDC	Must handle 24V load voltage.
Load Current	≥3A	Load is 2A; 1.5× margin.
On-State Resistance	≤100mΩ	Low Ron = minimal loss and heat.
Temp Range	−40°C to +85°C	Industrial conditions.
Safety Approval	UL/CSA/TUV	Product certification.

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 — DC SSR, 5V Input, ≥24VDC, ≥3A, Ron ≤100mΩ

59. DC SSR Load Switching