24V power supply SRS / relais extension box for 3d printer

prusaprinters

<p>I made a box to mount on a separate 24V power supply</p> <p>Until now, my 3d printer has been given 12V to the heat bed, so it takes approx. 20 minutes to heat it up to 100 C (while covering it with some insulation on top).</p> <p>After that it struggled keeping that temperature.</p> <p>When i designed and built my printer, everything has found a place in the very compact base of the printer, so there was no space left for an extra power supply.</p> <p>I left the 24V power supply out of the printer housing and left it separate, but only with one cable connected to the printer.</p> <p>The box houses a solid state relais, a heatsink and a fan. You can mount the SRS two ways; with the top or bottom facing the square hole (in case you don't use a fan or heat sink)</p> <p>The cable contains the following signals:</p> <ul> <li>220V AC mains</li> <li>AC mains earth</li> <li>12 VDC to power the relais (normally connected directly to heatbed)</li> <li>"12 VDC" earth</li> <li>24 VDC to heatbed</li> <li>"24 VDC" earth</li> </ul> <p>The fan in the box is powered by the fan voltage already supplied for in the power supply</p> <p>Because this PS is powered by the 220V signal behing the on/off switch on the printer itself, it automatically powers on when the printer is powered on.</p> <p>--- IMPORTANT NOTE: ---</p> <p>The setup with the solid state relais did not work out ok!!</p> <p>I let Marlin control the heatbed with PID settings and while i used a fan and heat sink on the SRS, the thing completely melted down :-(</p> <p>Now i have replaced the SRS with a 30A car fuse and let Marlin control the bed using the bang-bang method instead of PID (to prevent relais switching too much).</p> <p>It works perfectly now, and also eliminates the use of a fan and heatsink! :-)</p> <p>Bed heats up to 100 C in approx 5 minutes now, is very stable and even 120 C is no problem!</p> <p>Note that my heat bed is not a regulat 12V heat bed, it can be configured for 24V when connected differently, so that's what i have done ;-)</p> Category: 3D Printer Accessories