9v battery check/monitor w. bi-colour led (common ground)

[any]

Hi,

After wanting a simple battery health monitor for my Active bass (Bartolini NTBT) I had a look for what I could find on the net
but nothing quite did what i wanted (minimum parts count, and a bi-colour led with common ground but separate anodes) and an easy way
to set a fairly accurate voltage where it would go from green to orange to red.

So here's my take on a circuit I found and converted to common cathode, as well as fairly good adjustability with the 10k trimpot.
(I needed to set it around 8.5v and it was no problem, can go down to 7 I think without issue)

with my settings 9.5v/8.75v(approx) is green, 8.5v starts to get orange, and 8v red

Could be a nice addition to pedals as well that need a certain supply voltage to sound good and takes up nearly no space on a board.
(10 holes x5 strips vero)

[niektb]

Just a question as food for thought, how much does the circuit drain in terms of current? (as I see a fairly low-impedance resistor divider that's always on)

[iainpunk]

i build a similar thing for a 12v system for a school project once, it was designed for way lower currents tho, and it had 3 lights, all 3 on was full 12v, only 2 was 11v and one was 10v, if all were off, it was running on less than 10v. this saves power when the batterey was nearly empty.
i used a quad opamp and some zener diode and resistor magic

cheers

[duck_arse]

no circuit diagram? no CLR on the orange led?

[davent]

A couple ideas from Paul in the lab...

https://paulinthelab.blogspot.com/2014/07/simple-dual-led-battery-monitor.html

I've built this one, gets lots of use, so much stuff with 9v batteries in them.

https://paulinthelab.blogspot.com/2013/02/self-powered-9-volt-bar-led-battery.html
dave

[any]

Just a question as food for thought, how much does the circuit drain in terms of current? (as I see a fairly low-impedance resistor divider that's always on)

Fair, need to check that. As it's for my active Bass that would be good to know. Thanks
(edit) Just found out my Ma setting on the multimeter is not working... so TBC 

[any]

no circuit diagram? no CLR on the orange led?

I'll post a circuit diagram but went straight from breadboard to vero  . Orange is when green is on and red starts to light up as well,
so there's no 'orange led' just green and red bi-colour)

[any]

A couple ideas from Paul in the lab...

https://paulinthelab.blogspot.com/2014/07/simple-dual-led-battery-monitor.html

I've built this one, gets lots of use, so much stuff with 9v batteries in them.

Yeah tried that initially, but a pain for me with the zeners and setting the transition from green to red precisely with a trimpot.
I'll check the current drain on this though that was a fair comment. not really considered that but obviously important to know... ha!

[any]

Just a question as food for thought, how much does the circuit drain in terms of current? (as I see a fairly low-impedance resistor divider that's always on)

Well, just checked and current drain for the circuit is 3.75Ma ;-)
I think that falls into 'acceptable' compared to a 'dumb' status led?

[stallik]

Just knocked one together but used 2 separate led's as I'm out of pi-polar. Works fine, hardly as accurate as a meter but useful if I ever need one in a pedal. Used a vertical trim pot to get the board size down to 7x5

[any]

Just knocked one together but used 2 separate led's as I'm out of pi-polar. Works fine, hardly as accurate as a meter but useful if I ever need one in a pedal. Used a vertical trim pot to get the board size down to 7x5

Cool, What I ended up doing is measure a battery with the multimeter to a voltage that was still good and then adjust the trimpot to show red. Found it easier than zeners as it's easier to adjust 'on the fly'.

[amptramp]

There is always the analog option.  Just grab the meter out of one of these:



A lot of old cassette recorders had meters of this type or smaller circular ones that could easily be pressed into service.  You can make up a voltage divider for it.  This is the mojo solution.

[Phend]

When all else fails (do not attempt on wall sockets)

[stallik]

I replaced the face of such a meter so it had "Blatty/Mojo/Clean on the scale. Intended to put it in a fuzz but couldn't find one I liked. Now I have, I can't find the meter