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Oct 05, 2017, 02:25 PM
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telemetry: worth the weight?

Yeah, telemetry is addictive, I know. In addition to helping you get the absolute most out of your battery before having to land, you can get the core data a pilot would need, enriching the fantasy. When many of you buy batteries, you are mindful of their weight relative to their capacity. You do this because every gram counts, particularly when you're flying planes that weigh less than, oh, 2kg. The more weight, the faster the stall speed, the worse the climb rate, the more momentum and less agility, you may lose unlimited vertical and hovering, you may throw off your CG if you're not careful and your flight times could suffer if the extra weight is significant.

So to squeeze out the last drop of your battery before landing, you drop $50 on Spektrum's TM1000 (or similar of another brand) to beam down telemetry data including voltage, and, even though it's the voltage that matters, you also lay down $80 for Spektrum's current sensor that keeps a tally of milliamp hours of your 180g 2200mAh 3S 35C that you burned.

While in your Spektrum telemetry buying spree you also grab the variometer, the GPS module, the airspeed sensor and, why not, the Gforce sensor. Well before you slap all of that into your Valiant, Timber or Tundra, check this out: I grabbed my scale to weigh some of this stuff to see if it weighed anything. The answer is yes: If you add the aforementioned Spektrum gear inside your plane, it will weigh 75g more, almost three ounces, and it will consume additional power from your battery while you fly, albeit a small amount.

Instead of spending that weight on relatively useless information, wouldn't you prefer to save money while flying with this 3650mAh instead of the 2200mAh? If you are worried about the low voltage cutoff, use one of those three dollar on-board voltage alarms which weigh nine grams. Or get this device, the voltage sensor and transmitter adds only 4.3g to the plane.

Or just stick to the 2200mAh and enjoy flying a much lighter version of your plane using a timer. Not knowing when that LVC is gonna kick your butt keeps the adrenaline pumping.

Now as for you sailplane guys who need voltage and a variometer, and not necessarily a flight controller, and you like your Spektrum transmitter (yes I'm aware Frsky is better at everything especially telemetry and prices), Lemon-RX should soon release an inexpensive seven channel receiver with telemetry built-in (like the AR7350) that will weigh maybe ten grams and give you voltage, a thermometer, voltage and a good variometer, the LM0052. Its predecessor, which doesn't have vario but does have an altimeter, can be had for $36, not bad.

Cheers, Doug
Last edited by Doug Simmons; Oct 05, 2017 at 03:19 PM.
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