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Re: [Paparazzi-devel] IR resister swap, power supply, and video teleme t

From: address@hidden
Subject: Re: [Paparazzi-devel] IR resister swap, power supply, and video teleme try
Date: Wed, 21 Feb 2007 16:29:10 GMT


Glad to hear things are progressing for you.  The FMA sensor is 
calibrated for 5V operation and the effect of running it at 3V is that 
the amplifier gain nearly doubles.  To prevent sensor saturation in 
high contrast environments we reduce the opamp gain by 50% by changing 
one of the resistors.  This is done once per channel, so a total of 3 
resistors are changed for a full xyz sensor setup.  This procedure is 
not documented and I have never done it myself so I cannot tell you 
what resistors or what values to change.  Hopefully one of the other 
members will add instructions to the wiki.

A single battery is recommended for maximum reliability.  The 
autopilot monitors the main battery voltage and warns the operator, or 
even returns home to land when it gets dangerously low.  It will also 
turn off the motor to preserve servo power and all of this behavior is 
fully customizable.  You can certainly create a second voltage monitor 
with one of the many available adc channels and add this data to your 
telemetry downlink and GCS but I see no advantage.  Also, be warned 
that stabilized flight results in a nearly constant movement of all 
servos which can easily overheat the linear regulator in your esc.  
This is the reason the Tiny is equipped with a robust switching 
regulator that will not overheat even under maximum load with no 
cooling.  Note: the Tiny has only been tested with 6-13V input and the 
input caps C5 and C8 are only rated for 16V, so if your power system 
is over 13V you will need to use a separate flight battery.  Tiny 2.0 
will have an 18V maximum input.

The audio channel downlink is an alternative to the modem and is not 
supported in Tiny 1.1 and later.  This is useful in extremely weight 
critical systems as it eliminates the need for an onboard modem.  If 
you intend to use a modem, which you should, none of this affects you 
and you can use any video system you like, so long as it does not 
share the same radio frequency as your modem.

Good luck!

We are moving along on our project, but I have some questions.
1.  I purchased the ready made FMA Direct IR Sensor.  Before I go opening up the case, the website ( indicates that a "simple resister swap" is all that is required to make this device workable.  I assume you are talking about the sensor board.  Could you elaborate please.
2.  The general diagram showing the Tiny 13 v1.1 board (  indicates that the flight battery is split between the board and the ESC.  I assume you are talking about a y connection and not two separate batteries so that you can monitor voltage as part of your system operations.  Is this correct?  Is there a reason that I couldn't use two batteries and keep the motor systems separate?  Are there any advantages to this solution?  I realize that we are talking more weight now.
3.  I am confused regarding the need for modem and/or video transmitter.  It sounds like if you can live without a video camera, you can install a modem for data telemetry.  But if you want a video camera, you need to find a video transmitter that handles audio so that you can send telemetry down that side of the system.  I suppose you could have a separate video system with flight telemetry going through the Auto Pilot using both a modem and a video transmitter, but I don't think that is what is intended.  Like I said, I am a little confused and I just need some clarification before I start the development of my ground station.
Thanks in advance for your help.

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