TeensyPrinter: a RAMPS-like board built around the Teensy 3.6
Posted by salfter
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TeensyPrinter: a RAMPS-like board built around the Teensy 3.6 March 25, 2019 03:48PM |
I started work on this a little while ago, aiming to produce a modular 3D printer board with something faster than an Arduino Due:
https://gitlab.com/salfter/TeensyPrinter
There's just enough I/O to handle three axes, three extruders, four heaters, five thermistors (bed, 3 hotends, and an enclosure), and a few other things. It borrows the emergency-stop feature from RAMPS-FD and extends it to include a "suicide" input controlled by the Teensy to ensure that heaters, motors, etc. are shut off in hardware if Marlin decides to kill the printer. Separate power inputs for motors/electronics, hotends, and the bed heater allow different parts of the printer to run on 12V or 24V (or, in the case of the bed heater, on AC if you use an SSR). Connections for the most common LCD controllers are included, so no adapter boards should be necessary.
At this point, the schematic should be mostly complete. Next task is to choose components so a BOM can be generated and a PCB can be laid out. I intend to use mostly surface-mount components, especially for the heater MOSFETs so the PCB can serve as the heatsink (similar to a RAMPS 1.6).
The design is licensed under the TAPR OHL, and developed in KiCad. I've already gotten a Marlin PR accepted to enable pin assignments to be moved around on the Teensy 3.6; this is just making use of that.
https://gitlab.com/salfter/TeensyPrinter
There's just enough I/O to handle three axes, three extruders, four heaters, five thermistors (bed, 3 hotends, and an enclosure), and a few other things. It borrows the emergency-stop feature from RAMPS-FD and extends it to include a "suicide" input controlled by the Teensy to ensure that heaters, motors, etc. are shut off in hardware if Marlin decides to kill the printer. Separate power inputs for motors/electronics, hotends, and the bed heater allow different parts of the printer to run on 12V or 24V (or, in the case of the bed heater, on AC if you use an SSR). Connections for the most common LCD controllers are included, so no adapter boards should be necessary.
At this point, the schematic should be mostly complete. Next task is to choose components so a BOM can be generated and a PCB can be laid out. I intend to use mostly surface-mount components, especially for the heater MOSFETs so the PCB can serve as the heatsink (similar to a RAMPS 1.6).
The design is licensed under the TAPR OHL, and developed in KiCad. I've already gotten a Marlin PR accepted to enable pin assignments to be moved around on the Teensy 3.6; this is just making use of that.
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Re: TeensyPrinter: a RAMPS-like board built around the Teensy 3.6 March 27, 2019 07:15PM |
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frankvdh
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salfter
Is there enough I/O on a Teensy 3.1 to drive even a single-extruder configuration? Each extruder needs three digital outputs (step, direction, chip select), a PWM output (heater), and an analog input (thermistor). Axis steppers need three digital outputs each.
Do you really need a Chip Select on every stepper? So long as you aren't actually sending step pulses, nothing will move. Maybe you can tie CS to be true all the time?
You can't configure TMC2130s without it. Each SPI slave needs its own CS line. (You could set them up for jumper configuration instead of SPI, but why?)
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Also, for mixing extruders like the Diamond, you only need one heater and thermistor for 3 or 5 steppers.
That's one way to do multi-material printing. It's not the only way.
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It needs 2-oz. copper to get heavy enough traces to handle up to 15A in some places
I suggest not directly powering the bed heater from the controller.
Driving something like the 600W AC heater I'm building into my Hypercube directly from the MOSFET on the board would be inadvisable.
For a printer with more modest needs (like an Anet A8 or some other smallish printer with a 100-120W DC heater), the onboard MOSFET is an option. Put 24V through it and you can get twice the power at the same current (or the same power at half the current).Basically, I'm not trying to restrict things to how I might want to configure a printer, but to maintain some degree of flexibility.
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Re: TPS: a RAMPS-like board built around the Teensy 3.6 March 27, 2019 11:46PM |
Getting all those connections out from under the Teensy was a bit of a challenge, leading to a somewhat large (150x120mm) board. I started out by laying out subsections: power and heaters, stepper drivers, thermistor inputs, LCD connector, etc. I rearranged pinout usage extensively on the Teensy to get like signals (that needed to be routed together) as close as possible. While there is a chunk of empty space where Lumbergh's mug resides (more on that in a minute), the rest of the board is relatively busy. It may be possible to shrink it somewhat, but I doubt it'd fit in 100x100mm without cutting something.
I also gave it a new name: TPS, the Teensy Pololu Shield. "T" for Teensy instead of "AM" for Arduino Mega, and then I just had to leave off the R at the beginning to get "TPS." It's a printer control board, and an Office Space reference.
Getting them produced in 2 oz. copper would run about $32 for 5 at JLCPCB; half of that cost is for the 2 oz. copper. They'll do 10 for about $40. 1 oz. copper would be $14 for 5 or $20 for 10, but there'll be more losses in the copper. (If you don't drive it to the limit set by the fuses (for instance, you use external MOSFETs and/or SSRs to switch heaters), you can probably get away with it...but at a per-board difference of $2 (qty 5), why skimp?
Edited 1 time(s). Last edit at 03/27/2019 11:58PM by salfter.
I also gave it a new name: TPS, the Teensy Pololu Shield. "T" for Teensy instead of "AM" for Arduino Mega, and then I just had to leave off the R at the beginning to get "TPS." It's a printer control board, and an Office Space reference.
Getting them produced in 2 oz. copper would run about $32 for 5 at JLCPCB; half of that cost is for the 2 oz. copper. They'll do 10 for about $40. 1 oz. copper would be $14 for 5 or $20 for 10, but there'll be more losses in the copper. (If you don't drive it to the limit set by the fuses (for instance, you use external MOSFETs and/or SSRs to switch heaters), you can probably get away with it...but at a per-board difference of $2 (qty 5), why skimp?
Edited 1 time(s). Last edit at 03/27/2019 11:58PM by salfter.
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