[ARC5] adventures in battery ops

[Bill Cromwell]

Hi Neil,

The Arduino, or any computer at all really *is* overkill for this 
particular job. That is the first thing that occurred to me. Next thing 
that occurred to me about a half second later is having to deal with the 
digital noise it might add. Have you listened to LF and low MF lately. 
What's a little more noise <evil grin>. It might not be too difficult to 
suppress.

The real reason to use the Arduino is to gain more experience using it. 
The next step will be using the computers to monitor and help control 
battery charges - with data logging. The data logging part will help 
track battery health. I'm still doing that with paper and as I get more 
batteries it consumes more time. I also want to use the data logging in 
other, non radio investigations. It's time to trade in the clipboard. So 
this is really a stepping stone to bigger projects. And..I get to point 
at the cool Arduino and the pretty blinking LEDs.

I am NOT going to drag all that to the park with me for field 
operations!! An op-amp comparator with an LED will do nicely. That is 
even smaller than a dedicated voltmeter. Umm...how much are they getting 
for those Harbor Freight DMMs?

73,

Bill  KU8H


On 04/06/2015 02:54 AM, AKLDGUY . wrote:
> Arduino seems a bit overkill for battery level warning.
> Why not configure a $2 op-amp in a window comparator circuit?
>
> I set one up years ago to monitor the falling voltage of my cellphone's
> NiCad battery, when discharging in my homebrew discharger
> (remember how we had to ensure NiCads were fully discharged before
> charging?). The window comparator's output operated a high-pitched
> buzzer via a cheap transistor of the BC108 class.
>
> For those who don't know, a window comparator makes use of the
> way the op-amp's output rapidly switches from ground to + rail (or vice
> versa) when one of its input voltages crosses the threshhold voltage on
> the other input.
>
> With a voltage divider or pot, you set the desired battery minimum
> voltage (eg. 11.5 volts) on the appropriate input of the op-amp and
> connect the battery to the other input. Nothing happens 'till the battery
> discharges to the preset voltage, when the op-amp abruptly turns on
> (or off), triggering the buzzer.
>
> 73 de Neil ZL1ANM
>