A Simple, Valve Curve Plotter

[Mark Hennessy]

Power supply choice  aside, would this be ok for over voltage crowbar protection:

http://www.ti.com/lit/ds/symlink/lm431.pdf

Lawrence.

The TL431 is a great little chip - used in just about every PC power supply, and second-sourced by many manufacturers. Think of it as an adjustable Zener diode. 2.5 volts up to 36. Lovely

Of course, for this to fire a crow-bar, you have to add the 0.6V of the SCR. So ~3.1V would be the lowest firing voltage. Now, I've no experience of battery valves, but presumably the filament would tolerate an over-voltage situation *very* briefly? The crowbar could fire in a matter of milliseconds.

A rotary switch that selects different resistors for different voltages from the chosen regulator could also choose different values around the TL431.

Anyway, not necessarily the best solution for Nick right now, but might well be worth looking at separately...

Cheers,

Mark