MakerFarm 8" i3v Prusa build by Printbus

[printbus]

Does your bed heat indicator LCD work? I noticed the wiring seemed different than that shown on the reprap wiki photos. Great looking build.

Thanks for the build comment!

I assume we're talking about the LED on the heat bed? Yes, it works. I didn't think to look at the reprap wiki on how to wire it up. I assumed the two parallel pad sets were for resistors - Without crunching the math, I figured maybe there was a power dissipation issue with using just one small surface mount resistor to provide the current limiting, and the intent was to put two resistors in parallel. I now see the wiki says to put two LEDs there in opposing polarities so that you know one of the two will light up. I just powered up the bed and when the LED didn't come on the first time, I unsoldered it and flipped it around. As long as the LED and resistor are both in series, it doesn't matter which one is "first".

When I reversed the LED, I also changed it so that the legs of the LED bend up at the edge of the heat bed. That way the LED sticks up above the heat bed and is visible from the front of the printer. All that said, there isn't much point to the LED. I hear the heat bed relay clicking on and off, and it's obvious soon enough whether the bed is warming up. As mentioned in the build post, I just added the LED since the heat bed had provisions for it.

EDIT: Before someone points this out, yes, the LED body is shaped so you can tell the + (anode) and - (cathode) leads apart. For some reason (too late at night perhaps?), I ended up soldering the LED on backwards even though I knew which way things had to go. Having probably wired up hundreds of LEDs before, it was embarrassing to see the LED not work right off the bat. Also, if the LED doesn't come on since it is reversed, one could also just swap the wires for the heat bed at the heat bed relay or RAMPS board. Polarity doesn't matter to the heat bed.