[mcm_xyz]

Hello dear machinists!

A long time ago I tried to build my own servo drive (and I almost did), based on ELM CHAN Servo drive schematics and code.
I am now building an AC servo drive from scratch. I have my own program, and my own schematic.
After a couple of weeks of hard working, reading, soldering and programming this is what I obtained:

A cheap servo drive, based on ATMEGA644 (lower versions can also be used as compiled program hardly occupies 15% of MCU flash).
The whole boar wont cost you more than 30$!!!
The features so far:

Works with AC motors without using any Hall sensors.
Step / Dir inputs
UART connection for tuning and debuging

I can tell you that I am really happy with the performance obtained so far. My own build servo (a cdrom motor and an optic encoder from an old mouse) works really fine. I was able to obtain about 1200 RPM with this 6 poles motor and 90 PPR encoder.

Little software / hardware description.
MCU must have 6 pwm outputs and 3 external inputs.
3 x IR2101 are used for driving the final stage mosfets.
1 x 74hc14 is used to buffer my encoder inputs.
16 Mhz clock on MCU (can be raised to 20 Mhz)
PID process for controlling movement.

I will make the schematic and source code available for anyone here. Please feel free to modify them as you need (they are not under any kind of licensing)

Here are some pictures and video of my very beta board and servo!

VID 20141215 013443 - YouTube

Mihai

[mcm_xyz]

Here is the firmware and schematic as promised.
Program is compiled with Mikropascal Pro for AVR.
Schematic and board are done in Eagle 5.8.0.

I am a software engineer so please forgive my mistakes in the schematic.

I am open to any suggestion or remark!

Mihai.