I have been working on designing the Teensylu2, a follow-up to my Teensylu controller board.
I’ve added some features that have been missing from the Teensylu board for some time.
A SD card slot has been added. A 2nd extruder has been added (including a 2nd motor driver, mosfet, and thermistor input). The Mosfets are now rated to handle much higher power, as well as the connectors. The main expansion header has been removed to make room. The 2nd expansion header remains for attaching a LCD.
Protection circuitry is on the fan, and USB input. There is no fuse for the 12v input.
The board is rated for a higher voltage supply. In fact its highly recommended to use a 24v supply as it will put a lower load on all of the components, your motors will run better, the connectors and mosfets will run cooler, and your heaters will be more efficient. Make sure you are using heaters made for 24v, using 12v heater with a 24v supply will most definitely start a fire.
The board is currently in Beta. It needs to be reviewed by the community. If you are capable of providing feedback, please let me know what you think of the design.
The design couldn’t have happened without the awesome work that Laine from printrbot did on the printrboard.
I am a firm believer in Open Source. It is the tool that will change the world. This board is released under CC-BY-SA. If you make a derivative of the board please release the source.
I work on this in my spare time, and don’t sell the design or hardware. I am currently looking for donations so I can purchase a full version of Eagle so I can release more cool things. If you wish to donate, please message me.
@Stephanie_A Is there any reason you do not use KiCad? It would go with your pro-opensource ethic very well. Thanks to efforts from CERN it now has push-and-shove routing ability and things like differential pair routing and RF tools.
I have tried to use kicad so many times, I just couldn’t figure it out. The tutorials for it is aweful and lacking, and the interface is difficult. I am still an advocate for open source, but when the product is so difficult to learn and use then it is hard for me not to look at alternatives. Eagle has a great open source community using it and even has licenses for an open source use (though I find it too limiting). In the end I like Eagle more, it’s easier to use, and it works for me. If I tried to make this design in Kicad it would have taken me weeks just to get a basic understanding of the interface.
@Stephanie_A Just the learning curve aspect. I understand. I am at the same point but see the 3D component modeling aspect being very useful when producing 3D printed enclosure designs. For that alone I consider the effort worthwhile.
I’ll give it another shot next version. I don’t want to turn this into a kicad vs Eagle thread, what I’m really looking for is feedback on the design. If you don’t have Eagle and would like to review the design, I’ll export the schematics to PDF and do screenshots of the PCB.
@Stephanie_A do you have any thermal vias for your MOSFETs? It looks from the board layout image that you are relying on the solder outline as your heat sink, which on one layer for that package will give you a Theta(j-a) of about 140 C/W. That will limit your current capacity. See this doc http://www.nxp.com/documents/leaflet/939775016838_LR.pdf for some ideas of how to put a separate heat sync “pad” on the other side of the board.
Hi @Chuck_McManis I put vias all around the hotbed mosfet, and 5 on each hotend. I can add more, but I can’t take up too much from the gnd plane that is interrupted by the mosfet. I also don’t know of any method to put vias under the pad, as it will wick away the solder paste. @Maxim_Melcher my recommendation to manufacturers is to use 2oz-in copper. I have not done any calculations on this design yet, max stepper motor output is 2 amps I believe.
The heatbed mosfet has a maximum amperage set by the connector. Its a 12A connector, so 24A is the absolute maximum. The mosfet is 1.4mOhm,so total power across it is 1 watt at the max. Sure it can handle 100 amps, but we wont get nearly that high. The connectors and traces are my bigger concern.
@Billy I don’t have the money to build it right now, I’m hoping that someone else could try.
I’m thinking I might change the z endstop to be a z-probe by using a mosfet as a level shifter (like the printrboard).