BIGTREETECH EBB SB2209 or MellowFly SB2040 CAN Board thoughts

[ChicagoKeri]

Hi everyone!

OK, I built my Voron 2.4 with CANBUS and TAP, which is just asking for trouble. But that's OK, I'll fix it eventually....

So Initially I used a BTT EBB SB2209 CAN Toolhead board interfaced through a BTT U2C board to the Raspberry Pi4.  After some initial confusion, I got both boards flashed and communicating and configured.  I really liked the EBB SB2209 and had hoped to eventually put the optional Stealthburner LCD on.  The only downside seemed to be that the tiny 1.2mm pitch connectors are a pain to work with. The documentation is difficult, but adequate... if you can track down all that you need.

However, the SB2209 seems to have an appetite for Thermistors.   It seems that a thermistor was good for about one 5 hour long print, which would complete ok, but  subsequent prints would fail after 30-60 minutes with a "hotend not heating at expected rate" fault.    

The first time this happened, replacing the Heater element of the Dragon Hotend had no effect, and voltage at the SB2209 was a steady 24v with the problem occurring.  Replacing the Thermistor with an E3D one got me back printing... but soon, another failure!   So this time I used a generic thermistor, and again, after a 5-hour print.... fail.    So, I tried my early production REVO... it didn't even get one print, though these are known for failing thermistors.  

So, I thought, maybe something is wrong with the EBB SB2209....  I ordered another one, flashed and configured it, put in in without the Cable Cover so that it might run cooler and went back to the Dragon with a generic thermistor, which failed after a 5 hour print.

Next, I tried a new Red Lizard hotend with the new, integrated REVO-type  combined heater/thermistor and.... surprise, after a 5 hour long print, the next print Failed. It seems the temperature starts to climb, but before it reaches the target of 250C, it would get to maybe 220C, falter, start to drop and then Klipper shuts down.

Trying the new cable from the new SB2209 had no effect, and neither did wiring the 24v straight to the Power Supply. Again, steady 24v at the toolhead while the problem is occurring.

So, back to the Dragon, this time with a PT1000 sensor, which uses a different connector on the SB2209, and runs through a dedicated chip. At last!  It seems the PT1000 works.  However, after a few more long prints, Fail. Apparently the heater element is not heating enough. The temperature graph seemed more stable than with the thermistor failures, and again, the temperature will climb to about 160C then falter, drop to about 155C then Klipper shuts down, as expected.

So, finally, I bought the Mellow Fly SB2040.  Fewer features but sensibly sized connectors though not the standard ones that come on Thermistors, Stepper Motors or TAP wiring.  Also, the English language documentation is very poor. Prior experience with the SB2209 helped a lot.  But, eventually I got the SB2040 flashed, configured and wired up.  And it works!  The Revo and the Red Lizard remain dead but the Dragon has been working just fine with a generic Thermistor and heater cartridge.... no failures yet after a few weeks, the longest time that the 2.4 has run!

As a bonus, the Mellow Fly board is smaller and allows use of the LGX Lite Stealthburner variants, which I'm in the process of trying out with the hopes of getting reliable TPU feeding..

So, here's my thoughts.

I can only recommend the Mellow Fly SB2040. Although the documentation is poor, it actually works well once configured and the connectors are easier to deal with.  Also, if your Stealthburner variant is designed around Hartk's 2-piece board, it fits right in. On the downside, the included cable has silicon wiring for 24v, though the CAN wires are apparently PTFE.

I really wanted to like the BIGTREETECH EBB SB2209.  The documentation is better, though still difficult, the included cable seems better and the front board has connectors already in place, no soldering required.  The constant  Hotend failures across two different SB2209s leaves me very wary of this series.   Even if I just happened to have the biggest string of completely unrelated thermistor and heater failures that had nothing to do with the SB2209, (unlikely) it still won't  fit Stealthburner LGX Lite mods.  Of course it is possible, maybe likely that I somehow failed in installing or configuring the SB2209 but I did manage to get the Mellow Fly  SB2040 working on the first try...

The BTT U2C has been working just fine as a CAN interface, no troubles at all.  Yes, I know the Octopus can be used a CAN interface, but I prefer the U2C.

Voron TAP has also been working just fine. First layers are great, better than PRUSA Mk3s.  

 

[mvdveer]

17 hours ago, ChicagoKeri said:

I can only recommend the Mellow Fly SB2040

I am with you, as I said in this forum before, I am very partial to Mellow Fly products. Have 4 Vorons running on SB2040 Canbus boards on the toolhead. (Voron2.5 350, Voron2.4 300, Trident 250, Switchwire) After more than 100 hours printing on each individual printer - no issues at all. For installation, I started off with this guide and it has served me well.  Just installed an SHT36V2 on a micron build - don't think the documentation was any better than the Mellow Fly docs.

 

17 hours ago, ChicagoKeri said:

the Mellow Fly board is smaller and allows use of the LGX Lite Stealthburner variants,

Have the LGX Lite installed on the Voron 2.4 300mm build. However the mounts between the board and the lgx lite is a pain in the proverbial. Very fragile and easy to break. There are variants of the mounts out there, but could never get them to mount correctly in order to align the stealth burner body. Would be interested in your mod and how you did this.

17 hours ago, ChicagoKeri said:

OK, I built my Voron 2.4 with CANBUS and TAP, which is just asking for trouble.

Nah, all four mentioned printers have canbus and TAP - Works Great.

Thanks for a great write-up

[v1r3z]

 @ChicagoKeri

 

Thanks so much for the write up. I'm looking to get some help and ran into your post mentioning all of the same parts I have. Here's what happened to me: 

I just finished building my LDO 2.4 Rev C. I got the 2 piece ldo (hartk) stealthburner boards and noticed there was a soldering pad for the z probe (said 5v and 24v and a pad in-between) so I soldered the 5v to the pad because I also got the cnc tap and read the warning about it needing 5v not 24v. Well when I finally wired everthing I flipped the power switch and noticed my pi was flashing in sync with the 24v psu and the octopus, all 3 had leds that were in sync blinking. I panicked and flipped the main power switch. I had a feeling it was that soldering that I did, and also since the biggest source of power was from the hotend, I unplugged the power cables going into the breakout board from the hotend. I tried flipping the switch again... Everything worked! I did all my flashing and stayed up late setting up my printer.cfg. I was so happy. This is where i learn staying up till 4am is bad, I went and plugged in that hotend power cable thinking the issue was with the probe, i plugged it in while everything was still on and running... bzzzt... ... ... I watched in terror as my raspberry pi, my octopus, and the breakout board all let out the magical black smoke that makes it all work. I cried a silent cry of frustration and went to bed. 

The following paycheck I went online and purchased replacements. I got a new pi4, I got a new octopus 1.1, new hotend just in case, and a new tap just in case. and instead of getting the same ldo 2 piece boards, I pulled the trigger on the fly sb2040 canbus with the usb adapter. The shop I purchased from later told me they were out of the fly USB board and offered a bbt u2c 2.1, I accepted and here I am. I just got the parts in today and I'm really excited to get my printer up and running. 

I'm currently in the process of researching as much as I can before plugging stuff in this time. I don't want to burn anything this time.  So I'd like to get some help from someone who has done this. If there are any guides you have followed or if you can help me with how you have your set up some photos or some video clips lol ANYTHING! please...

 

[ChicagoKeri]

Here is a good guide by Teaching Tech on YouTube.... it's a bit fast paced, so expect to pause and jump back quite a bit.  The video does cover most of the setup.  

 

[ChicagoKeri]

I might have found something that explains why my SB2209 boards were eating thermistors at a prodigious rate (during long prints)!

It seems that static buildup can occur on the metal parts of the hotend, if they are not grounded in some way and this can damage sensitive thermistor circuitry.

Normally, I would have thought that the Thermistor is isolated from its metal sleeve ... but is this isolation capable of withstanding possibly thousands of volts of static charge built up over several hours of pushing plastic? 

Of course, being mounted in an all-plastic Stealthburner, the metal parts of my various hotends were  NOT  grounded in any way!  I suspect that some high value resistor, like that of an anti-static wrist strap, 1 megohm or so, tying the heatsink to 24v Negative would bleed off any static charge while preventing damage if a heater element or thermistor were to short out.

I just happen to have some 10 megohm resistors lying around so.....

Perhaps I'll re-install an SB2209 and see what develops. But I think that I will start grounding hotends from now on.

 

[WINEDS]

Thermistor circuitry really should have protection diodes at the input to clamp input to the rails?

 

https://www.utmel.com/blog/categories/diodes/clamp-diodes-principles-functions-and-applications

Edited February 14 by WINEDS

[ChicagoKeri]

1 hour ago, WINEDS said:

Thermistor circuitry really should have protection diodes at the input to clamp input to the rails?

https://www.utmel.com/blog/categories/diodes/clamp-diodes-principles-functions-and-applications

Ah, but say the input circuitry is sufficiently protected... it will protect the circuitry but not the Thermistor!  So, if the protection successfully shunts a static charge to ground, wouldn't that tend to zap the Thermistor itself?  Depending of course, where in the Thermistor the flashover occurs... if the charge flashes direct to a wire connected to a protected circuit or to ground, the Thermistor would probably be unaffected. But if the charge blasts through the Thermistor itself on its way to the ground, poof! Or, if the threshold point of the protection is higher that the destruction point of the Thermistor, poof!

Drat! Maybe I'll look into printing Stealthburner parts in conductive filament.... might be easier that sneaking wires in there...

[WINEDS]

I wasn't clear from reading your post if the thermistor or the signal conditioning circuitry was being zapped sorry.  Is your 0 volt tied to mains earth?  It's common practice in amplifier builds to tie 0v to mains earth via a cl90 ntc. This loosely couples 0v to mains earth but provides protection in the event of a fault.

That should stop your hot end from floating at some random high voltage.

https://www.google.com/search?q=cl09+ntc&oq=cl09+ntc&gs_lcrp=EgZjaHJvbWUyBggAEEUYOdIBCDkwNjRqMGo3qAIAsAIA&sourceid=chrome-mobile&ie=UTF-8#vhid=Y8kRX_QMq0Ys3M&vssid=l

But I'd try tieing 0v to mains earth first 

Edited February 14 by WINEDS

[ChicagoKeri]

I think this warrants a new thread!

 

[ChicagoKeri]

Okay, time for a Sanity Check.

Why did the BTT SB2209 eat a lot of thermistors on me? Apparently, static discharge from an ungrounded Hotend killed the thermistors.

Then... why has the Mellow Fly SB2040 apparently been immune to the exact same static discharges on the same Printer with the same Hotend(s), the same Stealthburner and the same filaments?

A study of the relevant circuitry is in order!

Fortunately, there are differences... I would be very puzzled if the circuit was identical.

The Mellow circuit is simpler, so let's look at that first:

In the standard, 4.7k pull-up configuration,  JP2 is Open, causing current from vRef to flow through all  resistors totaling 4.7k ohms, through JP4-1 to the Thermistor, through the Thermistor and to Ground at JP4-2. The voltage at JP4-1 will vary depending upon the resistance of the Thermistor, giving an indication of temperature. This signal is read by the MCU through a 1k resistor, R21.

The only protection for the MCU is R21, a 1k resistor and C22, a 100nf  (0.1uf) capacitor across the Thermistor directly. The vRef Voltage supply is protected by C22 and the 4.7k of resistors.  C22 will have little effect on the normal DC voltage across the Thermistor but will shunt short duration spikes to Ground. In operation, this simple protection scheme has not been a problem.  Any static discharges on JP4-1  might dissipate through C22 to Ground or through the 4.7k resistor chain to vRef. Some might get through R21 to the MCU but it doesn't seem to mind.... so far.

 

So, now onto the BTT SB2209. Wow, this looks more complicated!

 

So, let's see here... the primary operation is similar: vRef of 3.3v flows though R46 of 4.7k ohms (R45 not used in standard config). Voltage goes through P13-2 to the Thermistor, through the Thermistor and to Ground though P13-1. As with the Mellow, voltage at P13-2 will vary in time with Thermistor resistance, giving an indication of Temperature.  The MCU reads this voltage through R48 and R47, totaling 4.74k ohms.  Now here is where it gets a bit tricky for me:  The 100nf (0.1uf) capacitor C36 is no longer across the Thermistor input directly.  It is now "behind" R47 and R48 as well as... Two Diodes?

On the face of it, these Diodes should protect against any Negative voltage spikes that end up on the sense voltage, which is normally Positive. Why are there two? Oh, it's a single package with 2 diodes inside.  But.... any Positive-going spike (static, perhaps?) would have to get through either R47 and R48 to the capacitor OR overcome BAT54's reverse breakdown voltage (Vr) which is likely to be a Minimum of 30 volts???  Zap, Crunch, Bang and Poof goes the Thermistor?

Or perhaps any Positive-going spike is meant to be absorbed by the 3.3v vRef circuit?

Would not a better place for C36 be directly across the Thermistor, as in the Mellow? A small capacitor would have little effect on the normally DC voltage across the thermistor while allowing short-duration spikes to shunt to ground.  As it is, the protection appears to be focused on protecting the MCU itself, rather than the Thermistor.

 

Any thought or ideas? 

 

 

[WINEDS]

Maybe worth looking at both circuits with LT spice?

[Dirk]

How about asking btt tech support?

I will contact them and if they reply( Chinese new year, everyone is gone from the work cities to rural areas to visit parents) I will present this problem or give you their mail address

 

[Dirk]

13 hours ago, ChicagoKeri said:

Okay, time for a Sanity Check.

Why did the BTT SB2209 eat a lot of thermistors on me? Apparently, static discharge from an ungrounded Hotend killed the thermistors.

Then... why has the Mellow Fly SB2040 apparently been immune to the exact same static discharges on the same Printer with the same Hotend(s), the same Stealthburner and the same filaments?

A study of the relevant circuitry is in order!

Fortunately, there are differences... I would be very puzzled if the circuit was identical.

The Mellow circuit is simpler, so let's look at that first:

In the standard, 4.7k pull-up configuration,  JP2 is Open, causing current from vRef to flow through all  resistors totaling 4.7k ohms, through JP4-1 to the Thermistor, through the Thermistor and to Ground at JP4-2. The voltage at JP4-1 will vary depending upon the resistance of the Thermistor, giving an indication of temperature. This signal is read by the MCU through a 1k resistor, R21.

The only protection for the MCU is R21, a 1k resistor and C22, a 100nf  (0.1uf) capacitor across the Thermistor directly. The vRef Voltage supply is protected by C22 and the 4.7k of resistors.  C22 will have little effect on the normal DC voltage across the Thermistor but will shunt short duration spikes to Ground. In operation, this simple protection scheme has not been a problem.  Any static discharges on JP4-1  might dissipate through C22 to Ground or through the 4.7k resistor chain to vRef. Some might get through R21 to the MCU but it doesn't seem to mind.... so far.

So, now onto the BTT SB2209. Wow, this looks more complicated!

So, let's see here... the primary operation is similar: vRef of 3.3v flows though R46 of 4.7k ohms (R45 not used in standard config). Voltage goes through P13-2 to the Thermistor, through the Thermistor and to Ground though P13-1. As with the Mellow, voltage at P13-2 will vary in time with Thermistor resistance, giving an indication of Temperature.  The MCU reads this voltage through R48 and R47, totaling 4.74k ohms.  Now here is where it gets a bit tricky for me:  The 100nf (0.1uf) capacitor C36 is no longer across the Thermistor input directly.  It is now "behind" R47 and R48 as well as... Two Diodes?

On the face of it, these Diodes should protect against any Negative voltage spikes that end up on the sense voltage, which is normally Positive. Why are there two? Oh, it's a single package with 2 diodes inside.  But.... any Positive-going spike (static, perhaps?) would have to get through either R47 and R48 to the capacitor OR overcome BAT54's reverse breakdown voltage (Vr) which is likely to be a Minimum of 30 volts???  Zap, Crunch, Bang and Poof goes the Thermistor?

Or perhaps any Positive-going spike is meant to be absorbed by the 3.3v vRef circuit?

Would not a better place for C36 be directly across the Thermistor, as in the Mellow? A small capacitor would have little effect on the normally DC voltage across the thermistor while allowing short-duration spikes to shunt to ground.  As it is, the protection appears to be focused on protecting the MCU itself, rather than the Thermistor.

Any thought or ideas? 

Like @mvdveer says, above my and probably most others pay-grade. But nevertheless, very informative. And you wrote it down so that even I (basic knowledge electronics components), understood the line / logic you have followed. Thank you very much for that.
If the only difference between the two cirtcuits is the fact that the 0.1 uF capacitor is not protecting spikes to the thermistor, causing it to breaking down, it should be easy to add yet another capacitor or like you suggest modify the location of the capacitor (no idea if and how this will influence the other components on the circuit).

I have sent an email to BTT support, asking for information, if it is safe to use their CAN PCB after reading the information you provide. I am sure and hope, they will reply me soon. 

On another note, I have searched the net (just google) and I can not find anyone else experiencing this problem: 'thermistor destroyer' CAN-PCB from BTT. I think this is the first thing BTT support will tell me: 'we no have this problem'. 

I have purchased a CAN pcb from both BTT and from Mellow and will install first BTT (with Rapido UHF) and do several long prints and see if the same happens to me. You will not be the only one. Unless others have also had killed thermistors from using this CAN-PCB?

One other thing I wanted to ask: you mentioned printing with 'conductive' filament. What kind of filament should I think of? or was this a joke? 

 

[ChicagoKeri]

1 hour ago, Dirk said:

Like @mvdveer says, above my and probably most others pay-grade. But nevertheless, very informative. And you wrote it down so that even I (basic knowledge electronics components), understood the line / logic you have followed. Thank you very much for that.
If the only difference between the two cirtcuits is the fact that the 0.1 uF capacitor is not protecting spikes to the thermistor, causing it to breaking down, it should be easy to add yet another capacitor or like you suggest modify the location of the capacitor (no idea if and how this will influence the other components on the circuit).

I have sent an email to BTT support, asking for information, if it is safe to use their CAN PCB after reading the information you provide. I am sure and hope, they will reply me soon. 

On another note, I have searched the net (just google) and I can not find anyone else experiencing this problem: 'thermistor destroyer' CAN-PCB from BTT. I think this is the first thing BTT support will tell me: 'we no have this problem'. 

I have purchased a CAN pcb from both BTT and from Mellow and will install first BTT (with Rapido UHF) and do several long prints and see if the same happens to me. You will not be the only one. Unless others have also had killed thermistors from using this CAN-PCB?

One other thing I wanted to ask: you mentioned printing with 'conductive' filament. What kind of filament should I think of? or was this a joke? 

Hi! Thank you for your kind words. 
The thermistor destroyer effect was only under specific circumstances, during long prints and with an electrically isolated Hotend, mounted in a plastic Stealthburner.  Static buildup is the only thing I can think of that could have caused this effect. If course it could be something else.

As static is an actual effect, I think it wise to ground, or “earth” the metal parts of the Hotend.  

To that end, conducive filaments are a thing!  Not a joke. The stuff I ordered is intended as “static dissipative”, which implies a fairly high resistance value. Other ways to accomplish earthing are to install a wire and resistor or just apply conductive paint to the relevant plastic parts.  Conductive paint is widely used as shielding for plastic enclosure.

[Dirk]

18 hours ago, ChicagoKeri said:

during long prints and with an electrically isolated Hotend, mounted in a plastic Stealthburner.

Thanks for your answer(s).

I had already seen the specific circumstances you mentioned. But please correct me if I am wrong, are we not all (Voron printer users with SB) printing with a plastic stealthburner and with isolated parts except for the wires running out of the SB? 

And as soon as I fill my printing plate(350*350) halfway, my printing times are around a few hours to half a day. So not anything unusual.

I am very curious to the outcome and findings of your experiments/ diagnostics in the other thread. 

Thanks also for the conductive paint test / demonstration.

Your tests are surely better than my idea to simply try out the same setup and see if my thermistor gets destroyed 

But... I got an answer from BTT support. About the start of their day 8.00 am (3.00 night western European time). They write that the Chinese new year is over next week and that it is safe to use my Rapido with the BTT sbb2209 toolhead pcb. And some generic tips about grounding... See screenshot of the mail.

I will contact them again next week and ask very specifically about the circuitry.