Results of Testing Heater Fault Interlocks / PS_ON
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@DocTrucker said in Results of Testing Heater Fault Interlocks / PS_ON:
I've got a Duet 3 and will run these tests as soon as practical (machine not ready yet) as it appears the exact behaviour of RRF3 is not clear. I would assume it is no worse than RRF1, but tests will verify.
Thanks, but I suggest you hold off doing that until RRF3.01-RC4 is released, so that I know that the results you report are up to date. Please note that M143 parameters have changed in RRF3. The simple case of just setting a temperature limit has not changed, but the more complex cases have.
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@dc42 will do. I expect you will have that ready before I am, or at least before I've got my head around the RRF1/2 to RRF3 config changes!
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Thanks @DocTrucker, this is very useful. I will try to replicate the triggering of PS_ON by heater failure. Having a relay switching off the heaters is a good idea and straight forward.
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@zapta I've just got the standard 30W heater and 100W heatbed, so they are well within the capacity of the arduino relay boards and they come with the added perk of being conveniently mounted with all necessary flywheel diodes. I doubled up two sets if contacts per heater and added fuses below the rating of the relays.
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@DocTrucker, my bed heater is 24V 350W so I need a larger relay. DC relays are harder to find but this one seems to be a good fit https://www.digikey.com/short/z8wc8f
What kind of relay do I need, NO or NC ?
Good point about the diode, PS_ON doesn't have a protection diode so I will add it on the coil. I presume also that a SPST relay can also work since the +24V ends of the nozzle and bed heaters can be tied together.
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Visit your local car parts store (or dumpster). They have plenty 12V & 24V relays capable of switching 30Amps, and starter solenoids capable of switching a whole lot more.
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@DaBit, you are right, and at much better prices than Digikey. E.g. https://www.amazon.com/Ehdis-Automotive-Starter-Footprint-Terminal/dp/B01IV7D1Q8
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@zapta Use the NO contacts, pass a permanent posative to one side of the coil and the ground side to PS_ON. If the permanent posative comes from a seperate power supply to VIN and/or external 5V supply to the board ensure the negative poles of all the power supplies are tied. Some automotive relays have flywheel/flyback diodes but not many.
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@DocTrucker, I was able to replicate the PS_ON trigger on heater exception but only while printing. In a non printing state PS_ON failed to respond to a heater exception. Can you try replicating on your machine? I think this is a safety issue.
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While in idle, set the nozzle temperature to 200C. (I used the PanelDue to do this, can be done also with the Web UI).
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Let the nozzle reach it's target temp.
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Short the nozzle power mosfet (e.g short the E0 (-) output to the ground of the power supply), and watch how the nozzle temperature keep rising above 200C.
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At some point, the duet will try to stop the heaters and give a failure message. Disconnect the mosfet short immediatly.
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Observe if PS_ON got triggered (that is, your relays will go off).
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@zapta PS_ON interlock while idle has been om the wishlist for a long time. The argument is you are expected to be by your machine while idle. In my books that doesn't hold because if you're away from the machine during a build, then you are unlikely to be by it at the instant it finishes.
Another interesting observation. People on here can get twitchy when running more than 30W on the hot end. Slice Engineering's Mosquito has a default 50W offering!