Re: Over voltage crowbar - (for Mariss really )

Andrew,

Good afternoon! That certainly works but it is at the expense of a
fuse that must die then. I have a more elegant solution posted for a
while now in the "files" section called POWER SUPPLY.pdf

1) The power supply voltage is kept from rising above the supply no-
load value (returned energy dump).

2) The circuit discharges the supply cap in about 0.25 second when
the mains are switched off.

3) The circuit dynamically brakes the motors to a stop very rapidly,
so the mains switch functions as an e-stop as well.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Andrew Mawson" <andrew@m...>
wrote:

> Mariss,
>
> I understand from one of your very informative posts, overvoltage

is

> a large cause of failure with Gecko stepper drivers.
>
> Many years ago in the early days of semiconductors, the lab I

worked

> in developed a simple 'overvoltage crowbar' circuit that was

desgined

> to blow fuses if the rail went over a certain limit. Simplicity
> itself, it consisted of a thyristor accross the supply, with a

drive

> circuit based on a zener diode, that turned the thyrisor on at a
> certain voltage.
>
> The theory was that fuses were not fast enough to protect the
> semiconductors in the circuit, but the thyristor would drop the

volts

> and hold on long enough for the fuse to blow thus saving the day.
>
> At the time we were protecting vastly expensive yttrium iron

garnate

> infra red multielement array detectors used to watch the Russians
> from space, but could not a similar concept be incorporated to
> protect Gecko 201 & 210's ?
>
> Andrew Mawson
> Bromley,
> Kent,
> UK