AMB Laboratories DIY Audio

[amb]

The protection chip does have pins to flag low-power, under-voltage and over-voltage condition, but we don't have the board/interior/panel space for all these as LEDs and we need to be compatible with the existing Mini³ board and case.

The JP1 jumper is for initializing the protection chip after connecting the batteries -- the chip comes up in disabled state. You just need to install the jumper and then remove it to get it enabled.

[amb]

I updated the first post of this thread with the latest 3D rendering, plus the PCB layout, schematic diagram, and a short description of the components used. Have a look.

[MisterX]

The protection chip does have pins to flag low-power, under-voltage and over-voltage condition, but we don't have the board/interior/panel space for all these as LEDs and we need to be compatible with the existing Mini³ board and case.

How about a "Piezo bender" and oscillator then?
I bet there is enough room on the bottom for them.

Hehe... could you imagine the response a 90dB low power warning buzzer would create?

[dougigs]

Yes, the logic of a "battery's dead" siren would be interesting....

Seriously, though: If it's a 2-colour LED on the back, wouldn't undervoltage (rather than "fault") be a more useful function for the second colour? I have no idea if this would be as easy to implement, if it would entail a microgate, or if it would be impossible. But it's worth asking.

[amb]

Yes, the logic of a "battery's dead" siren would be interesting...

So that the siren would draw down the battery even faster?

Seriously, though: If it's a 2-colour LED on the back, wouldn't undervoltage (rather than "fault") be a more useful function for the second colour? I have no idea if this would be as easy to implement, if it would entail a microgate, or if it would be impossible. But it's worth asking.

As shown in the schematic diagram (see first post), the bi-color LED shows the STAT1 and STAT2 states of the charge controller's pins. To do what you ask would indeed require extra logic, but the board is full! The empty areas are unusable -- they must be there to clear the pot, jacks, and capacitors on the Mini³ board. Also, since there are three more status pins on the protection chip: low-power, under-voltage and over-voltage; which one(s) would we display? In fact, the protection chip provides information with a combination of those statu bits (see UCC3911 datasheet). There are only two LED colors, so we' could only display two bits of info, and the LED is closest to the charge controller...

[MisterX]

You could string together a zener diode + resistor (in place of R6) to make LED2 turn off when the battery voltage drops below the reverse bias "curve" of the zener.
Very simple but questionably effective?

[amb]

There is no R6?

[MisterX]

On the Mini3 board.

[amb]

Ah, ok. That might work, but I'm not sure it makes functional sense to turn off the main power LED when the power is still on.

[MisterX]

Yeah, that is the questionable effectiveness part.
Much the same as an LED that remains on when the amplifier is switched off?