Equipment for indoor electric scale models

[Jmk89]

Cost would be around 85 UKP / Euro. To be confirmed. A website with full instructions, Youtube links, etc is under construction.

Dave and Allan

Just wondering if the website for this is up and running yet, and if it is still coming, when do you think it might be available?

[lincoln]

- snipToday, we have thankfully a big variety of LiPo-Batteries at hand, which in it's nature are the lightest possible electric power sources available today, and thankfully also in very small sizes. With a proximate flight time of just a couple seconds to a few minutes

For short enough durations, supercaps will be lighter especially if they enable you to omit the timer. For instance, let's say you have a 40 gram model and you want a minute of duration. Looking at Sam's* supercap information, and at Digikey, maybe you'd use a 20 F supercap that weighed 4.8 grams. If I'm not mistaken, that cap is rated for around 20 amps! I'm assuming that the current is 2amps. With a lipo, maybe you'd use a 100 mAh battery from Nick Leichty that weighs 2.7 grams**. However, if you didn't want it to fly away, you'd need a timer which would probably weigh at least a gram. So, 3.7 grams instead of 4.8. on the other hand, for a 30 second flight with a capacitor, you'd only need 10 F, weighing as little as 2.8 grams. The lipo with timer would still weigh 3.7 grams.

*See the free flight section in RC Groups. At the moment, two of these discussions are "sticky" and appear at the top. Free flight, unfortunately, is a subforum of one that is called exotic, or something like that.

**Oops, maybe the lipo weighs 2 grams. However, the 10 F cap is lighter than that lipo with a 1 gram timer.

[lincoln]

Let's look at what you might need for one of those Comet 54" models. I'm guessing we need on the order of 10 amps. A 100 F cap, which we'll assume is good for a 1 minute flight, would weigh maybe 22 grams, and a 50 F might be 13. If we go by the ratings, which I'm a bit skeptical of, a lipo capable of that much current might be only 5 g without the connector. Let's add 2 g for more robust timer. If we look at hybrid caps, a 300 F rated for 10 amps might weigh 9 or 10 grams. (It seems to me that the hybrid caps now have lower resistances than I remember.) We'd still need a timer. So, for a 30 second flight, it's 13 grams for a regular 50 F supercap, 11 or 12 g for a hybrid supercap plus timer, and maybe 7 g for the battery plus timer. For a 1 minute flight, the regular 100 F supercap would be 22 g. These are all SWAGs*. YMMV, especially in another year or two. To get a more accurate comparison, it would take more time than I want to spend. However, at most we're only talking about a 15 gram penalty on a 200 gram model, with more convenience and less complexity.

For a short motor run, perhaps 8 seconds as you might use in an E20 model, I think the supercap probably comes out lighter. But maybe not in open E20, where your power system has to be capable of 3 motor runs. At least according to the PMFC rules.

[g_kandylakis]

Hi lincoln,

you have a point in your calculations comparing Lipos and capacitors. Indeed a lighter solution could be achieved with a supercap.

But the use of a cap without a timer is not the best solution for the F4E indoor class.

The aim here is to dublicate a realistic flight with a minimum of 15 seconds in order to be a qualifying flight. A flight of 30-50 seconds is usually enough for a good score by the judges. Less is not going to sore well, more is dangerous (walls-ceiling) and unnecessary.

For realism you need to be able to adjust the motor speed, not just go full power and this is where the timer becomes necessary. In order to have climb, cruise and descend. It can be achieved maybe without a timer, much like a CO2 powered model where the power also gradually decreases, but there are too many variables for that to work.

I do not know if a timer would work with a cap, I imagine it would but haven't tried it.

The complexity is not with the battery but with setting up the power/flight profile as required.

George

[Matze]

If the voltage is always above 3V then it should work.

[DaveL]

Apologies for not getting back sooner - got carried away working on yet another version of this!

The website is now up and running, link below.  At the moment, we have only the 2s version on offer, whilst Allan is wrapping up the 1s version:

Check out:   https://www.dva-controls.com/

[DaveL]

I did have a play around with the WiFi side of things - an html form is held on the ESP and, when you connect to its own wifi, this form downloads to the device (Iphone or android), and here you can enter flight values before returning them to the widget.  However, it did not have the flexibility of an app and, crucially, the power consumption when running wifi on the ESP was prohibitive.

But then, I thought about the BLE link and how to do away with it - which led me to build a device that appears to be very similar to the one described here by Matze - I use the popular 'Cheap Yellow Display' as a configurator - and the flight params are transferred to the much smaller widget (uses an ATtiny85) via an infra red link. 

Amazing how things change...it took me the best part of 2 years part time pootling to create the first version, but just a few hours to create this one - with the help of AI for the coding.  I'm just now waiting for draft pcb's to come, before trying it out.

cheers, Dave