@Neil_Darlow I’m more practical than that, I’m not into erecting such barriers in my way. I would have no great concern putting printer electronics into the wild. I know I shouldn’t do it alone though, one more board with one designer in the wild is a bad thing.
@Nils_Hitze I’d be happy to join that group.
Something else that could be integrated into octoprint is an infrared camera with the “motion” app. This would allow you to set triggers if too much heat is outside of a given zone and optionally, you could have it check on the hotend and heatbreak by homing and then using a special map to make sure too much heat has not leaked to the heatbreak.
Infrared cams are pretty expensive afaik
@Nils_Hitze I heard you can remove a filter from a number of webcams and they will have at least some heat vision. I came across that tid bit while researching touch panels.
Extreme (and unreliable) idea to protect against simple design errors.
He is probably a solidoodle user. The solidoodle electronics are shown in : http://www.solidoodle.com/wp-content/uploads/2013/06/boardcover.jpg
Heating the bed via a molex kk (clone ?) is asking for problems.
@Ashley_Webster @nop_head has made some improvements to the Melzi he supplies. He has better rated screw connectors and lower RDSon MOSFETS than the original design. It’s not perfect but better than most.
@erik_vdzalm and myself are working on our own hardware which, I hope, will incorporate some useful features (but at a cost).
@Ashley_Webster It is difficult to recommend a safe board. Most boards have simple errors like connectors that are not rated for the used currents, layout problems for high current traces etc. These could be fixed by changing the connectors or using 24V.
All boards I know have a problem if the mosfet fails. Then they can’t switch off the heater.
The power supply is also very important. Most kits use a low cost china power supply. These supplies can be vary dangerous. Do not trust the safety markings on a noname powersupply.
I think the powersupply is the biggest fire hazard in the printer.
@erik_vdzalm My thoughts on MOSFET failure handling would be two series-connected devices. The secondary device would be connected to a disabling signal common to all outputs. This, of course, would not handle both MOSFETs failing but that should be a rare occurrence.
For an industrial application I’d have a relay on the 12/24V supply to all the power devices. Or we could use the PS_ON pin on server/ATX supplies. Marlin drives this in some circumstances but not intelligently at all,it also needs to look at PWR_GOOD.
@Bracken_Dawson I don’t like the idea of killing the PSU. Once you do that you are left with a lifeless mass that can’t even report the fault. I’m not sure that introducing contact resistance into a high current path (with a relay) is a good idea either.
@Bracken_Dawson Your response was “that’s why you power the MCU and thermistors from 5Vsb.”
Using the USB power is no option for many printers and should not be needed for the electronics to run.
Boards that need USB for the power, and have a SD-card or ethernet are not very good designs.
@erik_vdzalm , I see now.
5Vsb comes from the PSU and is always on.
5V from USB and either the USB phys or the seial lines should be isolated from the prtiner electronics. Nobody does this right now.
@Bracken_Dawson In the hands of the RepRap community you can’t make assumptions about how a user will connect your hardware. What if a user substitutes regular 5V for your expected 5Vsb? And I don’t regard “That’s his problem!” as an answer.
@Neil_Darlow How do you stop them programming firmware which doesn’t cut power via your on-board relay or whatever else you come up with?
I value freedom to wire it up how I want. The best you could maybe do is ship with an appropriate PSU and good instructions.
The worst thing you could do is closed source your firmware and smatter it with proprietary connectors.
If the user substitutes the 5Vsb for regular 5V, nothing bad will happen at all.
If the user substitutes the switched 12V for regular 12V, or bypasses PS_ON, that’s his problem.
