Maximize bed output using smart PID limiting
I'm currently making a custom heated bed for my printer and had a really good idea: What if you could make use of the unused power when your bed is being heated?
My power supply is a 12V/10A brick power supply, not a lot of juice, but gets the job done. My heated bed is currently 3 Ohms, so it will only ever draw 4A, and when I only print in ABS heating up to 100 deg every time is quite time consuming. But what if I dropped the resistance on my new heated bed, increasing the current to something like 8A for a little overhead, and disabled my steppers while I cranked the heat up? I think I could do this with start codes at the moment, but it would be real neat if you could do something like the following: When the heat bed is on, max PID out is 255. When the hotend is enabled, reduce this by 50, X/Y/Z,E axis being enabled reduces this by 25 each (all user configurable variables dependent on setup). This way while you're printing you're basically back to your standard heating capabilities, but when everything is off you can heat up real quick.
I'm not an experienced programmer but if I was this would be so handy that I would definitely write it in myself. At the moment I'm going to see what I can do with custom start codes. This is probably something that would be a bit tricky to configure for users, so it would probably only affect custom builders. People could say to just run an AC heated bed, but I'm not running 240V wires through my printer, thanks.
I'd love to know what people think about this idea.