Just a quick update on this :
Before going too far in laying down tracks i wanted to validate and refine the math for accurately working out the required trace width & length to get the resistance and power output needed - and as close to dead-on as possible in the first try -
Its actually a tricky problem because we're starting with a fixed area and want a to optimize the track design for a given power area density and thus resistance.
So i've been playing around with equations in Excel to do this and i think i finally have something that works well and correlates closely with published numbers and equations / calculators you can find for working out the track width for a given current /length/ temp rise as is the more common scenario.
So a consequence of this is that i believe it wont be hard to not only optimize the layout to support several voltages as i'd hoped,
but also to do a single layout for both the Hadron size and the Quantum size: in other words, the Quantum heater forms the center section of the full size Hadron heater -
To convert a Hadron heater to Quantum size you just "cut along the dotted lines".
This is a good thing considering the lower demand for the Quantum; this way the risk and variability in providing a Quantum-optimized version is eliminated.
Now since the Quantum is about 36% the area of the Hadron, to get the same power density across the surface,
if the Quantum size is 100W (at room temp), the the Hadron will be 280W.
In theory that's what you need to get a reasonably quick warm up time and the ability to reach over 100C temperatures.
Now 280W at 12V is over 23A - which does limit your power supply options - so there is some tradeoff required here.
However, if you use the 24V terminals at 12V instead, then you end up at close to 100W again with only about 8-9 amps needed, so that may be the best way to support a lower current mode for those that don't have a 23A power supply.
Another possibility for the more technically adventurous is to hook up the 5V and 12V in series (requires hacking into your ATX supply a little ) so 17V into the 24V terminals gets you 140W at the same 8-9A.
Any comments on this?
The other cool feature i'm probably doing here is to provide and option to connect these through a single piece of flat flex cable, like you would find in just about every printer -
The benefit here is that it has for all intents an infinite fatigue life and more importantly zero drag on the fast-moving build carriage mechanism and very little chance of snags.
The connector will be on the underside of the plate, at the right front corner of the Quantum heater section, pointing towards the back of the unit.
A small board that can be bolted to the makerslide beneath the build carriage fixes the other end of the flex cable, and provides heavy duty screw terminals and the optional temperature controller (with an ATX power supply connector as well).
It will also be designed so the flex cable exits towards the back, so it loops 180 degrees allowing a very neat and tidy installation with the flex cable mostly out of view.
The flex cable and adapter board would be a separate optional add-on; all the boards will include 1/4" "Quick-Fit" style lugs for the power connections and something more appropriate for the thermistor /led connections - not sure what yet though, open to suggestions there.