[NSRCA-discussion] E-power

[J.Oddino]

I have a little more complicated setup.  An Eagle Tree flight recorder with a telemetry down link.  Before taking off I run up the motor and read the voltage, current and rpm from the handheld receiver.  If everything looks good,away I go.
Recently I removed the system to use it on my test stand.  One day I was out putting in a flight every half hour.  When I went to charge one pack after my fifth flight I noticed it wouldn't switch out of initial charge.  After I read the TP charger manual I found out it was supposed to stay in initial charge until it reached 37 volts and it was definitely below.  I started looking at my charge data and noticed I had only put in 3200 mAh before that flight.  At the time I hadn't looked at the voltage and assumed I had just used less power on that flight as I was doing a lot of horizontal stuff instead of the usual pattern.  Bad.
I think you folks have convinced me to put the Eagle Tree back in the plane.

Jim O
  ----- Original Message ----- 
  From: Bob Richards 
  To: NSRCA Mailing List 
  Sent: Wednesday, April 18, 2007 3:31 PM
  Subject: Re: [NSRCA-discussion] E-power


  A little more complicated, but for one of the 3S type planes that I fly, I have an eLogger from Eagle Tree, with the optional LCD display. I see the voltage when I plug up, check the current/watts when I run the motor up, and see the max current, min voltage and consumed power (mah) when I land. If I had an epower pattern plane, I would install one without thinking twice about it. Besides the visual parameter display, it can also log info for the whole flight so you can see the current that each maneuver requires.

  The 3914 is a bargraph display driver. It can be wired as an expanded scale meter which would work well for what we are doing. However, if a simple "green light" type of voltage indicator was all I needed, I would probably just use a simple op-amp or comparator set to just under the fully charged battery voltage.

  Bob R.


  Jay Marshall <lightfoot at sc.rr.com> wrote:
    I'm sure most of us are familiar with the VoltWatch battery monitor. It uses a simple LM3914 integrated circuit from National Semiconductor. A nice visual indicator just before takeoff. Seems to me that it could be easily modified, or even re-designed, for the higher voltage packs the E-power guys are using. Any of you EEs want to make a few bucks?




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