The 12v PSU is just a variable control DC power supply that I used to trigger the relay. Mains -> 24v is the LED power brick & controller. The mosfet and relay are between the 24v and the LED strip.

Energizing the relay does cause the 24v to drain to the LEDs, but they are dimmer than if I just energize the LEDs without the relay/mosfet between them.

I'd be happy to understand what I did wrong. Like I said, I thought a mosfet would have worked, but I'm not experienced enough in EE.. I only have surface level knowledge.

Here is a link to a poorly drawn diagram on my phone.

I had also tried this much beefier mosfet from an car amplifier, but encountered the same problem.

Great suggestion. It never occurred to me to use an SPDT relay - I have a bunch laying around. I checked and your solution works. Thanks for the help.

That didn't even occur to me, I have a bunch of SPDT relays. I just went and tested it and it works great. Thanks for the help.

FWIW, I also asked in the electrical engineering sub-reddit, but they have less traffic. I figured it is still technically a DIY question as I have no EE experience outside of DIY.

I was under the impression (maybe mistakenly) that I was able to get around the relay voltage drop by using the Mosfet. I had hooked up the gate pin to the output of the relay, the source pin to the PWM source and the drain pin to the LEDs. I guess I thought once the FET was open, the voltage would flow through it as if the relay wasn't even there.

I'm mostly just trying to solve this problem with things I have on hand because I've spent too much this year switching over to addressable pixel LEDs. I know I can technically buy a dmx receiver that outputs PWM for LEDs, but I'd unfortunately need several for different voltage strands.

Thanks for the help though.