The DC SSR project was commenced at the request of Scott Nething, who wanted to control some DC Devices for Halloween. We worked on this project and had some prototype boards working for the shows, and I have subesquently tested the DC SSRs with LED MR16s, and dimmed them using a RENARD Controller using PWM code.

There have been three revisions to the board design.

Version 1.0 original board design (with 78L05 silkscreen errata)

Version 1.1 Original board design with corrected 78L05 overlay)

Version 1.2 Updated board design with Fuse protection and dimensions to fit TA-200 enclosures.

SSRez Features

  • Designed to fit in the TA-200 Enclosure
  • Designed to be compatible with many controllers e.g REN64
  • Made with 2oz Copper boards for 7A total capacity
  • RJ45 Jack layout for Top or Side Load for flexibility
  • On board 5V Logic Power LED
  • MOSFET layout designed with Heat Sinks in mind
  • Separate Terminals for each wire making the connections easier
  • Wiring "channel" makes the connections easier
  • Fuse Position and layout allows for the Optional Fuse Cover
  • Supplied as a bare board (from wjohn) or as a kit from WLC Store Link


The board is a simple design, and follows the standard connection for an AC SSR COOP board. The RJ45 Socket provides the connection from the DC SSR to the Controller. The LED on the board indicates 5VDC is being supplied from the Controller to the OPTO.

The OPTO, which is different to the MCO3023Ms used on the AC SSR, is a K84PH, 16 pin DIP IC. I purchased mine from Mouser. 782-K847PH was the Mouser Part # and they cost $1.02 each, and here is the Datasheet The OPTO provides DC isolation from the Controller to the DC load. this is a safety feature, though some would suggest it could be deleted, I felt that with storms and electrical noise, it makes sense to isolate the PC and controller from the Lights.

The load switching is provided by MOSFETs. The original MOSFET used was a STF20NF06 and here is the datasheet. The original MOSFET was plastic tab isolated.

an optional part is the Mouser, RFD14N05L, as part # 512-RFP14N05L and here is the Datasheet

There is a regulated 5V DC supply for the OPTOs, provided by either a 7805 or a 78L05 on the PCB. the PCB has mounting holes for either the TO-220 or TO-92 case style.

Euro style screw connectors are specificed for the board, and they are grouped in pairs (+/-) to make connections easy.

The DCSSR is designed to switch DC loads between 0 and 35 Volts. The MOSFETs are rated to great than 10 Amps each, however as fitted to the PCB, I would limit to individual channel load to 2 to 3 Amps max. A suitable heatsink will be required.

Schematic Diagram

There are two schematics available, V1.0/1.1 and V1.2

A DCSSSR V1.1 diagram of the DC SSR is available.

A DCSSSR V1.2 diagram of the DC SSR is available.

Parts List

The PCB is available from wjohn on the Forum.

511-STF20NF06 4
782-K847PH 1
660-CF1/4C681J 5
660-CF1/4C471J 4
660-CF1/4C103J 4
604-WP7104IT 1
571-5202514 1
863-MC78L05ACPRPG 1
538-39890-0302 5
571-3902614 1
80-C322C104Z5U 1

571-3902614 is an optional IC socket, the rest of the parts are the Mouser part # and quantity required.

Click on this link to load a Mouser BOM

Completed DC SSR

Version 1.0 completed board

PCB Overlay Version 1.2


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