Low voltage audio indication- HHd1

[GT Blocker]

Hey all,
I'm looking at using a flasher LED in place of LED1 (the low voltage indicator), routed to the audio feed at pin 3 IC9 (with appropriate signal buffering). Seems to me that this would superimpose an intermittent (and probably irritating) noise in the audio output once the battery voltage reached the LV threshold set point.
Any thoughts on implementation of the idea?
Would there be a better point to inject the LED signal?
My final HH version is destined for fresh water U/W work, and I don't have time to look at lights. Audio LV works, and this seemed simple.
Am I on the right track?
Thanks, GTB

[GT Blocker]

Hello?

I really could use a bit of input here...
Dumb idea? Possible? Thoughts?
THX

[Carl-NC]

Injecting at the output of IC9 will will result in clicking noises that might be hard to distinguish, especially if you're using Scuba. I would try injecting at the collector of Q6, which would make the VCO start beeping. It might be as easy as connecting the cathode of D5 to Q6-C, and maybe increasing the value of R54 to reduce the injected current.

- Carl

[GT Blocker]

Thanks for the help, Carl!

Howdy,
I am nearly done with my first HHd1 build, so I wanted to test an audio LV alert with it before moving to those SMD boards.
Nice boards BTW! I've gotta keep thinking, relax, don't rush it....(Though I couldn't resist starting on one of 'em).
Since the old standby 3909 LED flasher IC is getting so hard to find, I figured that a cheap flasher LED would substitute.
I had wondered if injecting the signal should be done earlier as you suggested or not, but I had no idea what the audio output would be.
You are right in mentioning that headphone clicking sounds while SCUBA diving might be hidden by the regulator sounds, as it would depend on the loudness of the clicks and when one was breathing in relationship to those clicks.
An annoying true 'beep' tone would be harder to miss no matter what the above conditions. Sounds more like what I was thinking of.
I'll let ya all know how it works out when I get to try it in a working circuit.
Thanks again, GTB

[GT Blocker]

Change of plan...

Hey Folks,
The LED flasher rate is too fast to have time to listen between pulses/flashes.
I'm going to try an NE555 switched on by the LV output with the pulse width at about .5sec and and freq of about once every 30sec. The audio LV signal that I want should indicate 'get ready to quit', not 'you're done'.
Thoughts?
GTB