At the moment, the Farfadet collection is composed of the following boards :

The main Farfadet board

It is based on Trinamic's TMC5130A and can drive a single stepper motor with up to 1.5A / phase.

This is a very complete chip that integrates a hardware ramp generator : it only needs a power supply (12 - 45V) and a serial data bus to operate. No need to generate a Step/Dir signal from a microcontroller with a library such as AccelStepper, it will always operate jitter-free and with 256 microsteps.

Additionally, this chip can run in a silent mode called stealthChop and integrates advanced features from Trinamic like stall detection (useful for sensorless homing).

It has a NEMA17 form factor and can be mounted directly on the back of a stepper motor.

Farfadet TMC5130 - v1.0 (red) vs v1.1 (green)

The magnetic encoder board

This board supports a magnetic absolute encoder IC from AMS : the AS5132. It has a theoretical 1° resolution and can be used to control the stepper operation and correct position in case of missed steps. Unfortunately the TMC5130 doesn't support closed loop operation so this is only for failure detection.

This board can be mounted on NEMA17 and NEMA23 motors.

The XLR connector board

Adds XLR connectors (rugged and standard in the entertainment industry) for the Farfadet data bus instead of the standard Picoblade connectors.

The 3 main Farfadet boards : XLR (background left), TMC5130 driver (background right), AS5132 magnetic encoder (foreground)

The differential transceiver board

It is used to generate the data bus for the Farfadet modules from a microcontroller. It is designed to plug on a Teensy 3.x board but could be used with any 3.3V / 5V device with a serial port.

The Farfadet data bus is a differential RS485-like bus, referenced to 3.3V. With correct cable impedance and shielding, long cable distances can be used without altering the signal.

Project Logs

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Magnetic encoder and XLR boards - First tests
Tom Magnier • 02/20/2018 at 21:10 • 0 comments

I finally took some time to solder the magnetic encoder and XLR PCBs.
Here they are :
XLR, encoder, TMC5130 boards
The encoder boards has a AMS AS5132 chip, which should be capable of a 1° resolution.
It has a NEMA23 form factor and can double as a mounting support for the TMC5130 board.
Fixing the magnet on the motor shaft
The encoder board in place with 3mm standoffs
Encoder board and TMC5130 driver stacked
I haven't had the time to test it with the TMC5130 but the encoder IC seems to work :
The yellow LED is connected to the PWM output of the encoder IC, that encodes the angular position into the duty cycle. On each turn of the motor a ramp followed by a step is clearly visible, which means that the encoder works !
I will still have to experiment with the precision, but I think that the magnet placement is not ideal : too far away from the chip (the datasheet suggests a 1~2mm distance, here it is at least at 4mm) and stuck directly on the shaft which weakens further the magnetic field.
TMC5130 Rev1.1 - Soldering and tests
Tom Magnier • 02/06/2018 at 13:30 • 0 comments
Placing components on the bottom side

Ready for bottom side reflow

Top side reflow

Some of the connections didn't reflow well... (look at the bottom of the image). Maybe because the board was on standoffs to preserve the bottom side components ? I've never had this happen before.

After top side reflow

Following steps :
- hot-air rework
- de-panelization (a bit harsh on the PCBs, I will have to rework the panel connections for the future revisions)
- through hole soldering
- heat sink fixed with thermal adhesive
And....

It's alive !

v1.0 (red) vs v1.1 (green) comparison

As expected, v1.1 boards have better thermal performances (they are 4-layer instead of 2-layer). Heat spreads into the whole PCB including the mounting holes and I was able to pull a bit more current without the TMC5130 overtemp protection kicking in.

However these new boards still can't use the max 1.68A / phase current in this configuration. I will have to test with some fans that I have laying around if the full current can be achieved.

Anyway with the recent announcement of the TMC5160 by Trinamic a higher current Farfadet with external power stage will probably join the party :)

Next steps : soldering and trying the magnetic encoder and XLR extension boards... And a lot of software and documentation work !
New PCBs have arrived !
Tom Magnier • 02/01/2018 at 16:39 • 0 comments
Fresh PCBs and stencil from the factory !
We have here :
- a new version of Farfadet main board (stepper motor driver), hopefully with better thermal performances than the previous
- an extension board with XLR connectors
- an extension board with a magnetic encoder for feedback
- a transceiver board designed to fit on a Teensy, with XLR or picoBlade connectivity to the Farfadets
Testing the magnetic encoder PCB fit on NEMA17 & NEMA23 :
First time ordering with ALLPCB : the quality looks excellent and that was definitely the fastest PCB order I've ever seen (less than 1 week, shipping included, for an order with 2-layer / 4-layer boards and a stencil).