Re: [CAD_CAM_EDM_DRO] Interesting Gecko project

> Sven Peter wrote:
>
> > Hello Jon,
> > As I understand
> > Nicolas made a kind of mathcoprocesor for taking load from the PC and
> > dosition backfeed.

That's another project. I built a stand-alone CNC controller that has
its own microprocessor and takes G-code as input (via RS232) and
generates step/dir pulses for up to 5 axes as output.

Jon Elson wrote:

> Well, the GeckoFilter seems to be mostly an output filter (throttle came
> out, when he must have said "choke" in the original, meaning inductor.
> Also, engine comes out, when he meant motor.

Yes, the translation is a bit flaky but amazingly good compared to some
manuals I got for japaneese products...

> It also seems to have some filtering and optoisolation for the encoder
> signals. It took me a while to realize the board on top with the SMT chips
> and discrete components is the Gecko Servo board without the case.

No, it is not the gecko board, it's my own. I think I should come up
with a real translation of the whole page, but for now, let me explain
in a few words what the "GeckoFilter" does:

1. It does some filtering of the supply and motor lines (additional
decoupling capacitor on the supply line, differential choke on the motor
line to filter HF common mode noise plus some snubber RC networks). This
is the board on the bottom.

2. The sensitivity of the encoder signals to noise problems is greatly
reduced by transmitting them differentialy (twisted pair instead of a
single wire for each phase A and B). This feature is implemeted with a
small driver board which is directly mounted on the encoder (last
picture) and a differential amplifier/receiver (left half of the top SMD
PCB).

3. Easier driving and polling of the ERR/RES pin. Instead of one
tristate bidirectional signal, the ERR/RES signal is split into two
seperate ENABLE (to gecko) and STATUS (from gecko) signals.

4. The resolution and accuracy of a limit/reference switch is enhanced
by logically combining the reference switch signal with the index output
(one pulse per rev) of the encoder.

5. ENABLE, STATUS and REFSWITCH signals are optoisolated, so the PC or
CNC-controller unit can be completely isolated from the motor/power
circuit. (step and dir signals are already optooisolated by the geckos).
Features 3-5 are on the right half of the SMD PCB.

> Wow, a pond sounds like a big project!

Huh? What do you mean with that?

Ciao
Bene

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