## Re: "fuel gauge"

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• I have found a way of using an LM311N as a voltage comparator to drive a piezo buzzer. The idea is that as soon as the battery voltage drops to to a certain
Message 1 of 7 , May 1, 2008
I have found a way of using an LM311N as a voltage comparator to drive
a piezo buzzer.

The idea is that as soon as the battery voltage drops to to a certain
voltage the buzzer will sound.

The main problem is that the voltage curve of the typical Li-on and
NiMH batteries is fairly flat, and then takes a fairly steep curve
towards the end. So it would need a bit of experimentation to find the
best "trigger voltage" that still leaves enough capacity to get you
home, but doesn't trigger so soon that you don't get the most out of
the battery.

Take a look at http://www.electronics-
lab.com/projects/models/004/index.html
and us.sanyo.com/batteries/pdfs/lion_E.pdf
• Here is another possible alternative. I drive a relay with small back- up batteries using the DCC output from the rcvr. To explain further - I did several
Message 2 of 7 , May 1, 2008
Here is another possible alternative. I drive a relay with small
back-
up batteries using the DCC output from the rcvr. To explain further -
I did several tests with Alkaline, Ni-Cad, NiMH, and Li-Ion. As you
stated, with anything but the Li-Ion the battery dimishes quite
rapidly
at the end but there are clues the battery is getting low and I have
always been able to get home.
What forced the back-up battery idea was because the Li-Ion reaches
the
low power cut-off and it suddenly dies. But, because no power is
being
drawn from the battery the voltage will rise enough to cause the
consist to suddenly start up, then immediately die again.

To solve it I put a relay from a set of AA batteries to power the
consist long enought to get home. AA batteries are not suitable to
run
the consist (Dash-9 and 25 cars) but it will allow me to limp home,
although very slowly because the battery voltage drops a bunch with a
allowing
the locomotive to move my itself without an external power source.

I function the relay with F12 so I won't accidently punch it without
paying attendtion.

Bill
• Just a note to thank my fellow readers for their great suggestions. Much appreciated. Thanks, B2
Message 3 of 7 , May 5, 2008
Just a note to thank my fellow readers for their great suggestions.
Much appreciated. Thanks,

B2

--- In AirWire@yahoogroups.com, "Bruce K. Bates" <birdwater@...> wrote:
>
> Do any of you have any experience with battery indicators? I love
> using my Airwire equiped engines with on board batteries, but get
> perturbed wien they take on a mind of their own, due to a low battery.
> It would b enice to be able to have a visual indicaiton of the "Fuel"
> remaiining so that I cold get the engine back to a serviceing area
> before it dies.
>
> Any suggestions?
>
> Bruce
>
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