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Sanguinololu V1.3B Mods

Posted by eslavko 
Sanguinololu V1.3B Mods
April 22, 2015 04:49AM

I'm in building proces for my 1st printer. For electronics I just ordered Sanguinololu V1.3B. But there are some bugs/mods proposed.
Sadly I can't find board layout (or gerbers) for that board.

I know that backfeeding USB with 5V is bad idea, and this should be solved.

But for heated bed and extruder there are just two pins on connector. I don't think that can carry 10A+ for hotbed. And there are some SMT mosfet with (for me) unknown marking 7R030/PE/407 B5/9868 And don't know if that can carry 10A without overheating too.

Does someone realy run bed heater from that board directly? What mosfet is this? RdsON?

Re: Sanguinololu V1.3B Mods
April 24, 2015 03:18AM

I finnaly managed to open pcb file.
As electronics is my area I can say folowing from what I see in board.

- used FET is PH7030L and has RdsON worst case 11mOhm (at 5V on gate) So if I assume 10A for heatbed that's mean over 10W of heat dissipation. And there are two FETs close together. So the board will overheat here. But as the heater doesn't work all the time in most situation the board should work fine just with some fan for cooling.

- There are no exact part number for MOLEX connector used in board. But I find only one MOLEX PCB connector rated for 5A per pin but doesn't fin on board. I find two choices and one has 3A per pin rating and other has 4A per pin rating. I do have 4A per pin type. From datasheet and experience I can say that connector will melt with 4A per pin current. Of course not instantly but over time. Declared resistance of contact is 10miliOhm so at 10A current each pin develop 5W of power dissipation. So 20W per connector.

- I don't know the thicknes of cooper on board and if it's standard 35um then the width is just ok for 10A. But there is more than 10A (Extruder, bed, and stepers). If board is with 70um cooper then this is ok.

- The weakest link is power screw terminal. The solder pad has thermals so the cooper area in this point is way to small to handle all currents. If the boar has 70um cooper then thermal arrea jus barely fit for 10A but nothing more.

- shamed that over so much iterations of new boards the 5V backfeeding problem isn't solved yet. Just two diodes.

Don't understand me wrong. The board is othervise ok, but have some isues that should be solved.
In my board I will do:
-Install 2 diodes to prevent backfeeding 5V to usb. (this can destroy USB port!)
-Solder heavy wire from FET sources (left 3 pins) to PSU
-Solder heavy wire from FET drain (tab) to heatbed/extruder
-Power heatbed/extruder directly from PSU not from onboard pwr connector.

Re: Sanguinololu V1.3B Mods
July 08, 2015 07:48PM
Hey there,

I am not very good at electronics, an amateur you can say with a will to learn something.

I am using this thing -> [reprap.me]
in between a 46A 12V PSU and my heatbed. This help the bed to get up to 110°C within 12 Minutes.
But I am worried if this little thing can do 46A for this period of time, the MOSFET can do it as far as I understood from the provided datasheet.

The extruder is not heatet *all the time*, after a couple of minutes it reaches its temperature and it will then heat with pauses.
You may limit the current via the firmware (I use marlin), that's probably the best thing you can do.
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