So how much current DO servos use in flight ?

[Bladerunner]

Posted by Mal Quelch on 16/06/2008 11:18:00:

Hi again Timbo.

So your figures are for 'realistic'  current draw and that is amazing, 0.5A Peakcurrent !

 it was the place of measurement that would have helped initially.

As for I/C flying   I guess the word motor must have confused me! I know I should have checked but everything seems to be electric these days  !! And as you were using A123's in your WOT4 a separate rx battery is a must,  unless you use very well timed flights due to the low discharge voltage possible from these cells and the abrupt cut off associated with them.

Once again-truly amazed!

Mal

On the Ripmax 4-Cell monitor I have, its 4.3V-4.4V for lowest Red LED and 2nd Red LED and 4.7V - 4.8V for 2nd Green LED and 1st Green LED.

[Tony Smith 7]

Hope its OK adding to this old thread, but I just wondered what resolution that graph has.  Would it have picked up peaks of only one or two milliseconds, or would these have been averaged over a longer period?

 

I'm still puzzling over my servos that won't work on a Y lead, but work on two channels slaved together, and I have a theory that their current draw is maybe very heavy just at the moment they receive their PWM pulse - putting them on separate channels would then offset those pulses.   I'm trying to work out how to test for that.

[Tim Mackey]

According to the manufacturer, the servo current logger has a resolution of .01 A ( 1 x 100th of an Amp ) which is pretty good I think.

[Lee Smalley]

Again we are in danger of giving Nimh cells a bad name everyone seems to think lipo and reg is the way to go, im sorry but that's just not the case Timbo has done some excellent work and it shows as i have always suspected that's current draw for a typical flight is in the milliamp s NOT amps region and modern cells can do that with their eyes shut there is absolutely no need to replace all your cells for lipos, if you already have them that's fine  so lets dispell some myths and rumours

 

Modern Nimh do not loose charge overnight stick to eneloops or vapatex instants and all is well the charge you stick in them will last for months 

 

Modern nimh do not struggle to deliver the currents that we need for powering our radios and servos 

 

I have used Vapatex instants for 2 years now and i have only had to throw one pack in that time they charge well store well and can easily deliver the current required in my biggest planes they cost about £8 for a five cell pack eneloops are slightly dearer but even better quality! i use an old hitec battery monitor that applies a 650mah load on the battery when testing so a quick plug in and wait for 30 seconds is enough to tell you if the battery is on the wane

Lipo and regulator is fine but lets not pan nimh cells based on outdated results 

 

Edited By Lee Smalley on 26/11/2010 11:14:45

[Peter Beeney]

   I think I first started to realise just how much current the airborne pack didn’t use was when I first started serious proportional control. In those days, all the batteries were generally 500 mAh, nicads, both tx and rx. It seemed to be the only size available. When we had occasion to fly all day, giving training lessons, we found that the rx pack would easily last for this time, but the tx would only last around for around 3 - 4 hours. The pack was hard wired in, you couldn’t change the battery, and of course there were no fast chargers then. In fact, I had the only field charger that I remember, Skyleader, this ran from a mains or 12V source, but was still only a very basic ten hour rate device. I just calculated (guessed!) from this that the servos, and in turn the control surfaces, were indeed a very light load on the rx pack! I did overcome the tx problem, but that’s another story! In fact, the Skyleader transmitter charging system was a slightly different animal and thus was of some interest in itself anyway. The clue is in what I’ve already said!
   Once upon a time a noticed a man running with his electric model from the pits to to the strip. When I queried why he did this he replied. “I want to start flying before my nihms go flat.” This started me thinking about all the stories that abound about this loss of capacity, so six years ago I started a little experiment, which has been running ever since. This is only one battery, and a very basic set up, but this has never indicated that even standard Ni-MH’s lose their capacity at a great rate of knots. I’ve always charged my kit on the way to the flying field, anyway.
   I would very much agree with Lee, I still use nickel-metal hydrides, I have remarked before, the tx pack is now well over 10 years old and still going strong! Provided that you check the capacity carefully regularly, you can then keep using them until they show signs of starting to deteriorate; and as I’ve said before, unfortunately, on the odd occasion, they can be like this from new.
   I bought some Eneloop AAs, £7 from Amazon, free delivery, this is a 4 cell bunch, there is an 8 cell for £14 option, if you wanted to make a 5 cell pile. I presume that the ‘Instants’ come as a ready made up rx pack? I was going to play with these, but I’ve been using them them in a camera so far.
   I’ve also copped some Maplins Hybrid AAs, more expensive, these are advertised to have have the advantages of the long-lasting, high-capacity Ni-MHs, but with good low temperature performance. So a couple of cycles in the freezer will be in order, I just haven’t gotten round to it yet. Sounds familiar! This is unlikely to make any difference to our little gang, though, they are tending toward the point where the blood starts to thin, (in a couple of comparisons, I’m sure Oliver Twist’s gruel bowl would look like old porridge!) and thus they think that cold is anything less than mid-summers day; so they are unlikely to be operating in sub zero temperatures, at least not for long periods of time.

   I’m sure the nickel cell will be around for a long time to come, is it not simply a case of personal choice?

   PB