[balou]

Hi,
I always thought that just shutting off the LED completely at a certain voltage is a suboptimal solution, you may not know if the amp is still running by having a quick glance at it, leading to possible deep discharge of the rechargables.

So, I came up with this circuit:

The green LED should light up if the voltage is above the reverse voltage of the zener, and the voltage of the zener in turn steps on the garden hose inside the JFET (hey, I'm new at transistor circuits

), letting no current through.

So my questions are: will this circuit work? And at the moment, the current through the LED is just regulated by a resistor, not by a CRD. If I'd substitute the resistors with CRDs, I'd end up with 3 JFETs for the LED. Is this whole thing also possible with just two or one JFET?

there are also duo leds with just two connections, they change color according to polarity. would there be an easy low battery circuit for them?

 

[threepointone]

i wouldn't bother trying anything that requires reverse polarity. I'd been trying to figure something simple out to drive a latching relay with one coil before, and I couldn't help but end up with an h-bridge (4 transistors, probably way too complicated) or something that had way too much idle power consumption
i'm not saying that it's impossible, but I think it's probably not worth trying

 

[balou]

ok, then I'll stay with the 3-lead leds.
As I see it, the JFET and RLED2 should act as a CCS (dunno exactly where the feedback goes through and it's maybe not such a stable CCS, but who cares it's just a LED). Then I'd only have to exchange RLED1 with a JFET+Resistor in a feedback loop to get a CCS on the other side.
This would reduce parts to a Zener, 2 resistors, 2 JFETs and 1 duo LED.

But I still do not know... would this really work or have I made a mistake in my circuit somehwere?

 

[balou]

bump.. anyone? I actually ordered a prototype amp board with this circuit on it, now it would at least be nice to know if this circuit will short/blow things/etc