D8 MOSFET

I was powering up the printer and the heated bed was coming up to temp (70c) when all of a sudden sparks flew out the side with the wires. It was short and sweet and why it happened I can only assume the MK2B heated up and flexed against the aluminum bed and caused a short. What happened is that short blew out the MOSFET for D8 so the power was always on and the heated bed just kept on heating.

Here is a HUGE safety issue worry I have because if that, or the nozzle's, MOSFET blows like that there is absolutely nothing on RAMPS to stop it from burning down your house. I never once gave this a thought before last night but I do now see a strong case for worry and wonder what could be done to stop an ensuing fire if those MOSFETs ever give up the ghost?

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

That sucks. Why couldn't you fuse the ramps with an actual fuse of 25 or 30 amps. That way you would probably get a puff of smoke but not an inferno.

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DRobs86
That sucks. Why couldn't you fuse the ramps with an actual fuse of 25 or 30 amps. That way you would probably get a puff of smoke but not an inferno.

It has a fuse but even a fuse wouldn't help this issue and it is an issue for everyone with a Ramps. If you look at the circuit schematic the mosfets close to ground and are floating open. So, when one blows (all electronic things have a chance of blowing even on a good day) they blow closed (most fets die with source to drain fused so in a closed position) which just acts like a direct connection to the power supply. Short of a real thermal protection (like they use on coffee pots, etc...) it will just keep getting hotter and hotter until something bad happens.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

Its been a while since I looked at my RAMPS lately because hi do so much more milling than printingnthese days, but the RAMPS fuse is self resetting, correct? I am talking about an actual fuse from the power supply to the RAMPS so even if the MOSFETs were to fail closed the fuse would blow, leaving it unpowered.

For that matter, I'm not exactly sure why the fuse on the RAMPS isn't staying tripped in this condition.

I reiterate that I haven't looked at the RAMPS non a while though. If you have an idea for a safety improvement then you sure have my support.

Edited 1 time(s). Last edit at 12/22/2015 08:53PM by DRobs86.

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DRobs86
Its been a while since I looked at my RAMPS lately because hi do so much more milling than printingnthese days, but the RAMPS fuse is self resetting, correct? I am talking about an actual fuse from the power supply to the RAMPS so even if the MOSFETs were to fail closed the fuse would blow, leaving it unpowered.

For that matter, I'm not exactly sure why the fuse on the RAMPS isn't staying tripped in this condition.

I reiterate that I haven't looked at the RAMPS non a while though. If you have an idea for a safety improvement then you sure have my support.

Nope, the fuses never tripped and the power stays on because the mosfet is shorted (dead).

edit: Let me say that as far as the circuit goes nothing is wrong BUT there is as the mosfet will never turn off which means lifting ground up so the board stops heating so even with the safety measures in Marlin that says if you go over this temp to shut off it can't obey since the MOSFET is a direct short and is dead. There is the crux of the matter and why something like coffee pots use is needed for real protection. I never once gave this any thought until it just happened to me and I started thinking and looking at the only version of the RAMPS schematic I could find. Extremely dangerous in this situation.

Edited 1 time(s). Last edit at 12/22/2015 11:42PM by Dark Alchemist.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

There is a thread [forums.reprap.org] about safer mosfets that can be used which have a built in protection against this problem.

Also you might want to consider this fire safety device [forums.reprap.org]

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DjDemonD
There is a thread [forums.reprap.org] about safer mosfets that can be used which have a built in protection against this problem.

Also you might want to consider this fire safety device [forums.reprap.org]

I am the last post on that thread and I already purchased 5 IRLB3034 for less than 5 IRLB8743. Now this takes care of the heat (the original had been getting so hot it had stuck itself to the plastic D8 header) but it doesn't take care of the fact of the closed circuit. When I was removing the bad MOSFET last night I tore the pad off the bottom and the top of the middle pin which is the pin that is the on and off pin and is connected to the SMD led. Since that is the major pin I lay odds it was already weak due to the heat as I removed (just testing) D9's MOSFET and it came out cleanly. So, I need a new RAMPS (for safety concerns too) but I can't get a single ebay seller to answer me if the picture they are using is exactly what they are selling with the 35v capacitors. I use 24V so I have to have them or no dice.

Basically everything I purchased for my 2 year old printer come Feb that was from Sainsmart is all gone now except the Arduino which is fine. Live and learn and never again have I or will I touch Sainsmart.

Oh, and one other thing I am bidding on but will just buy is a new MK2B because this board has always been a thorn in my butt but I measure no shorts (though I no longer measured 3.6 ohms it is now ~4 ohms) but something on that board shorted as I saw the sparks then no sparks near the power connectors on the MK2B. Something flexed at around 70c and boom it took out the MOSFET but as I said earlier that MOSFET could go for any reason and at any time and without some physical protection I am now scared to leave any RAMPS based machine running while I am away or asleep. Not going to happen for sure so long print times are not going to happen.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

Run away power to a low power bed like the MK2 is unlikely to cause a problem as they struggle to reach much over 110C anyway. If you're worried about it, embed a thermal fuse in the insulation under the bed. High power beds and the extruder are a different story, and it's a worry for sure. The smoke detector power cutoff seems like a good bet.

RE fuses, I didn't like the way the bed supply was routed through the ramps just to go through the polyfuse. I took 12v straight to the bed via an inline blade fuse holder and that dramatically cut down on heating off the ramps board. It's still taking the return current through there, but the ground is common'd across both sets of 12v inputs, so you have more pcb trace and more wires carrying the juice. I'd recommend that as a simple safety upgrade for any ramps user. It's also easy to put a heatsink on the D8 mosfet, and with the combination everything is running cool now.

I still don't like the idea of the mosfets being on the ramps at all, so at some point I'll make an aluminium carrier for them and bolt it to the metal printer chasis.

Edited 1 time(s). Last edit at 12/23/2015 02:21PM by JamesK.

I use 24V and my plate goes to 136c easily. The only saving grace is the board struggles to go much higher. Now the issue is also the head because if that ever blew for whatever reason then your up a shit creek as that thing will easily, for me at least, go well beyond 300c and for a real J-Head that spells disaster.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

Overheating mosfets, lack.of sufficient 5V power, inadequately cooled stepper driver chips, no 24V capability, no software controllable stepper motor currents, no flow control on the USB interface - these are just some of the reasons why RAMPS sucks. Don't throw good money after bad, get yourself a decent modern 32-bit board instead.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
Overheating mosfets, lack.of sufficient 5V power, inadequately cooled stepper driver chips, no 24V capability, no software controllable stepper motor currents, no flow control on the USB interface - these are just some of the reasons why RAMPS sucks. Don't throw good money after bad, get yourself a decent modern 32-bit board instead.

Already have the mosfets on their way but no great loss if I don't use them but which board? There are a lot to choose from but I am not eager to spend for a smoothieboard (I see it is having some issues now too as of Nov, 2015 in special cases) and I did look around but I don't see many talking about anything other than RAMPS and Smoothieware.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

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Dark Alchemist
Already have the mosfets on their way but no great loss if I don't use them but which board? There are a lot to choose from but I am not eager to spend for a smoothieboard (I see it is having some issues now too as of Nov, 2015 in special cases) and I did look around but I don't see many talking about anything other than RAMPS and Smoothieware.

Duet is becoming popular, you will find it talked about quite a lot in the Controllers forum. It is the only board that provides a good built-in web inteface including fast upload to the SD card. Two versions are available, the 0.8.5 from think3dprint3d and the 0.6 from RepRapPro and from Replikeo.

I prefer all-in-one boards like Duet, but if you want a 2-board solution with plug-in drivers, there is Arduino Due + RADDS, although again you get limited 5V power and you have to set the motor current using pots on the drivers.

Edited 1 time(s). Last edit at 12/24/2015 02:26AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42

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Dark Alchemist
Already have the mosfets on their way but no great loss if I don't use them but which board? There are a lot to choose from but I am not eager to spend for a smoothieboard (I see it is having some issues now too as of Nov, 2015 in special cases) and I did look around but I don't see many talking about anything other than RAMPS and Smoothieware.

Duet is becoming popular, you will find it talked about quite a lot in the Controllers forum. It is the only board that provides a good built-in web inteface including fast upload to the SD card. Two versions are available, the 0.8.5 from think3dprint3d and the 0.6 from RepRapPro and from Replikeo.

I prefer all-in-one boards like Duet, but if you want a 2-board solution with plug-in drivers, there is Arduino Due + RADDS, although again you get limited 5V power and you have to set the motor current using pots on the drivers.

Those are some hefty price tagged controllers. I have seen some boards at 55-60 dollars that use the smoothieware and honestly I do not even know if this printer will work. It has been down since April and I am just replacing everything and starting over but its main issue was an unlevel bed. I wish I could use the aluminum spreader I bought but wasted money as it was too thin and thanks to that it shorted out my ramps (would have any controller board I imagine). I will probably end up getting the board mentioned on this thread as it is at least better than the RAMPS and not going to destroy my pocketbook in the process: [forums.reprap.org] I just need some more people to chime in and I am seriously trying to get away from Arduino based controllers as well.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

You can get a Duet 0.6 from Replikeo for $50. The build quality isn't as good as the boards from T3P3 and RepRapPro, but Replikeo seems willing enough to replace faulty boards if you are unlucky enough to get one.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
You can get a Duet 0.6 from Replikeo for $50. The build quality isn't as good as the boards from T3P3 and RepRapPro, but Replikeo seems willing enough to replace faulty boards if you are unlucky enough to get one.

Comparing the closed source/not closed source MBASE has X/Y/Z/E0/E1 for 56 delivered and the DUET 0.6 has only 1 less Extruder the leaning is towards the MBASE and I have read a lot of threads on it but little is said beyond the Smoothie people blasting it.

I want to dual extrude or at least have the opportunity (something even RAMPS 1.4 has) and I want to be able to continue to use Pronterface to do my printing. I will never have a Delta as I am not into them. So, for the price of a MBASE (give or take 10%) that allows me to dual extrude AND to continue using Pronterface what is there out there?

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

You can use Pronterface with every 3D printer board I know of, including Duet and Smoothieboard - although once you have used the web interface on the Duet, you will never want to go back to using Pronterface because the web interface is so much better.

Don't forget that if you use dual extrusion on a RAMPS, you lose the controllable fan output, and if you drive both heaters at once you will probably overheat the 5A fuse. So I don't consider RAMPS to truly support dual extrusion.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
You can use Pronterface with every 3D printer board I know of, including Duet and Smoothieboard - although once you have used the web interface on the Duet, you will never want to go back to using Pronterface because the web interface is so much better.

Don't forget that if you use dual extrusion on a RAMPS, you lose the controllable fan output, and if you drive both heaters at once you will probably overheat the 5A fuse. So I don't consider RAMPS to truly support dual extrusion.

I see nothing was mentioned to answer my question so I guess until these boards start to fall in price I will do one of two things and that is go back to a RAMPS 1.4 or get that MBASE for 60. I will probably fall back to RAMPS for now since it is only 10 delivered and hopefully I can get the MOSFET unsoldered on it without tearing a pad but the Chinese barely use enough glue for the copper and the copper is thin too.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

I replaced this with an IRLB3034 and within seconds it got so hot it burned a blister on my finger. 24V system ( 3.6 ohm MK2B ) and since RAMPS is from hell and there isn't anything else that doesn't cost an arm and a leg (yet still has various issues of one sort or another) I can say done.

Edited 1 time(s). Last edit at 01/12/2016 06:04PM by Dark Alchemist.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

By my reading of the datasheet I wouldn't expect it to get that hot so quickly. I'd check the gate voltage and make sure you're getting a decent 4.5V or better.

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JamesK
By my reading of the datasheet I wouldn't expect it to get that hot so quickly. I'd check the gate voltage and make sure you're getting a decent 4.5V or better.

First thing I did but too late the mosfet is dead. From all of my specs and if my house was 25c ambient (15-17c in there right now) that MOSFET should hit around 33-35c which is less than my body temp.

Which pin from the Arduino is driving the gate on that MOSFET? Do you, or anyone, know? I would like to check the Arduino directly.

Edited 1 time(s). Last edit at 01/12/2016 09:47PM by Dark Alchemist.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

As far as I can see, it's the pin marked 8 on the pwm connector at the top of the following image:

[www.electroschematics.com]

But the best place to measure the voltage is at the mosfet, in case there are any losses in the connections/traces on the RAMPS. It's the mosfet pin closest to the polyfuses.

Edited 1 time(s). Last edit at 01/12/2016 09:58PM by JamesK.

Good, I tested that before but not like I should have as I only tested if it was floating when turned off. Should be 5v when on but the problem is ramps will be completely removed so how do I fake it out so it just does what it is supposed to do if the RAMPS were still connected?

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

I haven't tried, but my first guess is that the firmware won't care that the ramps isn't there, at least for a short duration. if you have the thermal runaway stuff turned on that will shut everything down after a while, but you should have plenty of time to measure the voltage. On the other hand, the lack of thermistors might cause the firmware to refuse to do anything. If I remember right, you can fake the thermistors out in the configuration.h, but I'm not sure it's worth the effort. I'd still reckon it's better just to measure the voltage at the mosfet with the ramps in place.

The other thing I think you need to check is the resistance seen across the bed connections from the ramps end. A short in the cable or at the heater connections would fit the description.

Edited 1 time(s). Last edit at 01/12/2016 10:05PM by JamesK.

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JamesK
I haven't tried, but my first guess is that the firmware won't care that the ramps isn't there, at least for a short duration. if you have the thermal runaway stuff turned on that will shut everything down after a while, but you should have plenty of time to measure the voltage. On the other hand, the lack of thermistors might cause the firmware to refuse to do anything. If I remember right, you can fake the thermistors out in the configuration.h, but I'm not sure it's worth the effort. I'd still reckon it's better just to measure the voltage at the mosfet with the ramps in place.

The other thing I think you need to check is the resistance seen across the bed connections from the ramps end. A short in the cable or at the heater connections would fit the description.

Already tested at the gate and was perfect. As far as a short goes I replaced the wire to the bed and I measured the resistance and it is 3.6 ohms. Now with a dead short due to the fet being destroyed I am unsure what to do next as that is two fets dead (the original crappy one and the better one).

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.