G220 (G201BP)

Hi,

Here's a progress update on the "bullet-proof" G201 project.

A lot of things have happened since I got input from everyone here on
what they wanted regarding a "clean sheet" redesign of the G201. Some
of them are pretty exciting, (to me anyway).

There has been a breakthrough in the design that gets around some of
the contradictory goals of a good drive design. That simply means
different objectives that before caused each other trouble now work
together helpfully.

I'll list the features now:

1) A new switching metod that keeps the motor temperature cool even
with very high overdrive ratios at while stopped or turning at a low
speed. This eliminates the need for current reduction (and torque
reduction) when the motor is stopped. Even with an 80VDC supply, the
motor "sees" only an 16VDC supply when it is stopped; it stays cold.

2) No need for an external "helper" capacitor across the power supply
inputs. No more 470uF caps above 3A phase current settings.

3) Short circuit protection. You can short the motor leads any way
you want, (including bad, shorted-turn motors) without hurting the
drive. The DISABLE input will now function like the G320 ERR/RES
terminal to notify the PC a drive fault has occurred. I'm still
working on a reliable motor stall detect to include on this terminal
as well, which would be very cool. The present POWER indicator
becomes a FAULT indicator.

4) Integrates the G210's full-step, half-step, 5 microstep and 10
microstep features into the G220.

5) Works with either a common ground or common +5VDC STEP and
DIRECTION interface automatically. A Schottkey diode bride across the
opto-isolator LEDs means the COMMON terminal can be at either
potential without having to set jumpers.

6) Return energy dump circuit on-board. No matter how rapidly motors
are decelerated, returned energy (kinetic energy from the load) will
be shorted to ground. No more mysterious "the drive smoked when I
turned it on" failures.

7) Overvoltage protection. Any power supply voltage in excess of
82VDC will be shorted to ground. This works in conjunction with (6)
and absolutely requires the use of a 5A or less fuse in series with
the power supply. No fuse, a burned board, no warrantee. A fuse will
be an absoulte must.

8) Over-temperature protection. If the drive temperature exceeds 85C,
the drive shuts down.

9) Top cover adjustments. This means the ADJUST trimpot, the option
header and the jumpers to set drive resolution will be available from
and through the top of the cover. No more need to remove the can to
make changes.

10) Two-board construction. This a biggie, just after the new
switching topology in importance. The bottom (main) board will
contain the power section. All parts will be uncovered which will
make it ameanable to easy repair so long as the board isn't charred,
(no fuse operation).

The top board ( a much bigger version of the plug-in pulse multiplier
in the G210) will contain the low-level circuitry. No matter what
gets done to the power section, this board will survive and still be
usable, keeping 40% of the value of the drive.

The G220 will not have reverse voltage protection (too big of a power
loss to cover this rare miss-use) and will be destroyed if someone
applies an over-voltage power supply (>82VDC) without a fuse. Even in
this case, 40% of the drive value will be preserved.

The idea here is to build a drive that is impervious to accidental
destruction. It cannot prevent the best efforts of the truly
ingenious user but luckily they comprise less than 1% of all people.

All this is expensive and will make the G240 cost out at just below
$200 per unit, single quantity.

I would advise not to wait wait in immediate expectation for tis
drive. The proof of concept prototype printed circuit boards go out
next week. On return the new switching topolgy, the drive will be
tested for functionality. Then (if everything works as designed),
there will be a very long test period of it being subjected to every
possibe abuse for hundreds of thousands of cycles.

When it comes out to market, it will be the very best I can do.

Mariss