@veti said in RepRapFirmware 3.0:

@dc42 said in RepRapFirmware 3.0:

The current plan is 30V or perhaps 36V. It's difficult to find 5V buck regulator chips that accept higher than 40V input.

why not says that for input above 30V the 5V line has to be supplied via the ext 5V?

I think that the board could have separate V_MOT and V_IN terminals.
The V_MOT could accept higher voltage which would go solely to the motor drivers.
The V_IN could accept 25-30V max as you will probably need 12/24V for the hotends or fans anyway, or for other automation purposes in CNC. This is how I usually do in custom machines I design.

Those who don't need higher voltage or anything special just have to connect the V_MOT and V_IN parallel, those who need it could use two power supplies.

@dc42 said in Quad head idex:

Please explain how four heads on two carriages (not 4 carriages) could print the same part at the same time.

By "same part", do you mean different parts of one piece, or 4 different copies of one print?

I think he meant 4 copies, and maybe 2 X carriages per 2 Y rails.

But... If that's the case, why it would need any electronic solution? You could mechanically couple the 2 rails at 1/2maxY distance apart, with 2 carriages at 1/2maxX distance apart, making a 4 quadrant bed, so each quadrant would be 500x500.

@alexander-mundy said in SSR failsafe:

For my clarity, in some other countries neither of the 2 current carrying conductors are intentionally grounded in general purpose outlets?

I live in Hungary (but many places in the EU are similar too). We use three-phase Y connected distribution system where the central point of the Y is connected to earth AND carried by wire as a neutral. The phases are 120 degrees apart. If you use three phase power, those connectors are polarised, the order of L1, L2, L3 and location of N, PE are guaranteed.

If your house have only one phase, you will get one of the three, plus N. It is clear (should be...) through the whole house which is which. If you wire something directly in the distribution cabinet, you could rely on it. However, the one-phase consumer socket, Schuko isn't polarised. There is a standard that wire the L on the left side, N on the right on the socket, but the plug is intentionally symmetric, mechanically reversible, so you can't guarantee which wire is which in an equipment - the distinction ended at the wall.

Plus, because it is symmetric, the electricians rarely even care which is the live, even in the socket, so even there is a standard, better to expect nothing...

Polarised one-phase industrial sockets do exists, but it is rarely used, you'll never see it in a house.

HW check ideas, since you have an oscilloscope:

• Do any signal present on TMC's OA1 OA2 OB1 OB2 pins? (during move)

• What can you measure between BRA/BRB and GND? 1. Measure resistance without power, 2. check on scope during move.

• Between SRA/SRB and GND?

• You verified that the TMC's get 24V and the STEP signals. This is where everything gets interesting... But does them get GND?

Does the extruder motor move?

If you can not heat up, use "M302 S1" to allow cold extrusion.

T0
M302 S1
M83
G1 E+100 F500

@singhm29 said in SSR failsafe:

Quite alot of new terminology to take in here! Looks like adding all of this in will be a project itself lol here I was thinking adding in a thermal cutoff switch would do the trick.

It all depends on you use case. If you have a low powered bed heater, which can not reach unsafe temperatures, and you always supervise your printer (frequently enough) you may live without it. But in a 12V system, for a 12V bed, using just an automotive relay and a thermal fuse is dirt cheap and easy to wire - yet greatly increase the safety.

Once you go for high power mains voltage bed heater... I should say that this safety system is mandatory. It could heat to the melting point of aluminium in no time. Maybe while you come back to check your print, it is already on fire. And use quality parts. You don't want the safety to fail.

@doctrucker The fues's purpose is to protect against fire, not protecting against electrical shock. If somebody is that dumb that carelessly touch parts connected to mains voltage without safely disconnecting it first - that will be their responsibility. In many printers even the mains switch is SPST only, so you can't rely on that either.

If you work on a circuit, it is yours responsibility to disconnect and check it first. No insulation, no fences, no other systems will save you with 100% certainity. Many times maybe, but once in a life maybe something will fail. Not following safe (I call it common sense) procedures but relying on someone or something to protect you is looking for a disaster.

You need two fuses, not because they will blow up at the same time and disconnect both lines, but because it cannot be guaranteed that which line is neutral and which is live. There is a possibility of earth (chassis) short anywhere in the system. Especially common in heaters, the moving bed cable's insulation can break, the cable end may break off, the SSR may fail short to it's heatsink, etc... And if you only have fuse in one line, which happened to be the neurtal today, then it will not blow. This is the ONLY reason you need fuse in both wire, not because it will safely disconnect your printer to work on.

Maybe you misunderstood my text before, I am not advocating to use SSR for safety disconnect. Exactly the opposite, exactly you worte last. I recommend using it for control, because it is fast and reliable for that purpose, but using an independent (manually enabled and thermal cutoff + PS_ON disableable) double pole contactor to disconnect in case of failure.

@doctrucker Expensive is always depend on budget, but an SSR is somewhere in the same price range as a contactor.
I don't know where you live, but here in the EU you can buy quality ones for 20 EUR.

For example:
ABB AF09-30-01-11
24V (20-60V DC), 3xNO + 1xNC, Imax=25A

@dc42 I think you should not just count the value of the printer itself. If it starts burning, the disaster could be much more than that. If you take this in to consideration, a contactor for 15-20 EUR isn't that much of a cost. An SSR would not be cheaper either nor the kW-powered bed heater was, and the Duet board itself isn't that cheap, may be an overkill for a cheap printer. But we want serious things.

If I build something, I always build as industrial grade, idiot proof, safety first. I don't like underengineered things which I am not fully confident in.

Limiting the power of the bed heater so that it could not reach unsafe temperatures would defeat the purpose of the high power bed: heating up fast.

The UK plug is polarised, but for example where I live, the Schuko isn't. You still can use a GFCI, but just assume both wire as live fuse them both and break them both at mains switch or GFCI or safety relays, everywhere where galvanic isolation is expected to happen. Controlling a mains powered device with SSR or relay in one line is okay, but safely disconnecting it you should use double pole switching. 3mm distance between open contacts... Etc...

@doctrucker I recommend a relay/contactor too, but my idea which I am currently executing on my printer is to wire it in a self-latching start/stop circuit. Wire the thermal fuse (be it as one-shot or a bimetall one) in series with the relay coil power. Maybe you could use the PS_ON to control it too. This way you should not have to use a fuse which able to disconnect 10-20A at mains voltage. It would be a pain to wire with thick wires and insulate properly WHILE attach thermally and mechanically at the same time anyway.

You could use 12V/24V in the control circuit. Electronically it will give you several possibilities:

• It will trip on thermal runaway triggered by thermal fuse if SSR failed short or the firmware frozen.

• You could trip it by software via releasing PS_ON before it actually ran away, but something wrong detected according to diagnostics.

• You have to press a mechanical start button to activate. It will release on power-loss and never come back accidentally on power return.

• It will not oscillate if you use bimetal thermal switch