Re: [CAD_CAM_EDM_DRO] Re: 2 Fried G210's in a single day :-(

> > So always add al _large_ capacitor to the DC supply. I even add a
> > seperate "energy absorber" (large Zener diode or
> > Zener-transistor-resistor combination) to my setups because I don't
> > trust the capacitor alone.

RC wrote:

>
> Can you tell us more about the zenor diode, how it is connected, a good
> souce for them, and the specs?

Yes, of course. If you have small motors and low inertia then a single
zener diode may be sufficient, but make sure it is rated at least 10W
and has a metal case. Do not connect zener diodes in parallel because
only one of them will carry all the current. You can connect them in
series. For higher power the following circuit is better:

-----------o---------+
+ | |
| |
| | |
R1 | | |
| | |
| |
| |
| |
\___ |
/_\ |C
| |
| B |/
o-------|\
| | V
| |E
| | |
R2 | | |
| | |
| |
GND | |
-----------o---------+

R1 = 100 Ohms
R2 = 1kOhm
Zener Voltage = max supply Voltage + 5V
Transistor = any type that can withstand at least 20A
for example TIP35C (plastic case, 100V, 25A) or 2N6287 (metal case,
100V, 20A)

If you use a darlington type transistor the zener can be low power (1W),
otherwise it should have >=5W. You don't need a big heatsink since the
transistor is conducting only for very short periods of time. If you
have to dissipate really high energy pulses (large motors, high mass
inertia, 4 or more axes) you should add a big resistor (1 Ohm, >100W) in
the collector path of the transistor.

Ciao
Bene

--
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