BECS and regulator info ( beginners )

[Roy Gallagher]

Sorry Timbo what i ment was given the information that i have given, how would you do the math to check it was suitable on paper, or given the C47 what size brushless motors and battery combination and ESC's would do the job at the given all up weight of plane with the 59g motors, my line of attack was i had a buzz lightning and knew what the motor could do so assumed motors would be ok in C47, if over powered some what, i also knew it would be ok with lipo as i had previously flown it with stock motors on same battery, so i just got two motors and two 30amp esc the only differance being the extra ESC weight which was not much and as i had saved a little weight with motors i thought it would not make a great deal of differance guessed it really. Hope that is a little bit clearer and enjoy your session up the Orm.

[Stephen Grigg]

Timbo,If I may go back abit,my pioneer sqeeling motor.I carried out a test last night.Iset the timing at high as suggested by scott at BRC.the motor is 500w and the motor,esc and batttery supplied as1 set by BRC.With the battery not fully charged, a4s 3700 20c watt test 540w 37amp,esc 40 amp.Battery fully charged 16.8v  test showed640watt,41amp rechecked timing its put itself back to low. Reset timing at high retest same reading, check timing back to  low.So for some reason the esc appears not to be retaining the timing setting.I am using one of those very good programme cards and its helped alot at the field.Some of the Glider fraternity had rotating folding props they felt were causing drag,with my program card at the ready I was able to eliminate there problem,and gained some very useful browny points in the progress.there are different cards so 1 card doesnt work on every make of esc.

[Tim Mackey]

We are getting way off topic here guys - please post these new questions in another thread  - feel free to start a new one with suitable title in this same forum topic section.

[Stephen Grigg]

OK timbo

[Fats Flyer]

Hiya Timbo,

Can i ask you a quickie question(for you that is).

I have a HK450 heli and im going to use a hobby city turnigy e500 6t 4000kv motor.

It says in the ratings at hobby city  that a 20amp plus esc is to be used.

People i have spoken to say that it can use upto around 33 amps.

the speed controller i bought for it has a rating of 30 amps...,now, .....(im getting there)if i disable the bec on the speed controller and use a seperate hextronik ubec to save power from the speed controller, will it be ok to use or will it still have the possability of burning out or am i barking up the wrong tree again..

thanks

vince

[Tim Mackey]

If you expect to be using 20Amp in the rig, then any ESC of 25A  or more is fine.

preferably use one of at least 30% more capacity than likely to be needed, so for instance if 20A is the consumption, then 20+30% = 26A, so 25A is near enough. Most motors unload a fair bit in the air ( not sure about helis mind you )  so the current will reduce in flight anyway. The issue of the BEC in the speed conroller is a separate matter really, and whether it is enabled or disabled will have little oir no effect whatsoever on the main function of the ESC.

What governs the use of the ESC BEC is the volts of the battery you are using on it, and tghe number of servos you want to drive.

I think what you are saying is the motor could actualy draw as much as 33A not the 20A claimed by hobby city. This may well be so, and will be likely, if for instance, you used a higher cell count than recommended. If the motor claims 20A on for instance 3s Lipo , and you use a 4s Lipo instead, the current will increase, quite possibly up to the 30A mentioned.

As ever with these "calculations" the safest way to be sure is to run it up using a wattmeter to check power consumption - difficult I guess with a heli

In summary.... you can use as large a speeed conttoller as you can fit in - and headroom is a good thing.

 

[Fats Flyer]

Cheers Timbo,

Ive just been reading some of the write ups about this motor and alot of people seem to think that hobby king has all the information wrong.a few recon that this motor is so powerful that a 40 amp esc at a minimum should be used and a couple say that they measure it to be well over a 500w motor which is better suited to a 500 class heli.................well one things for sure , it's gonna fly and fly very quick as well..

cheers

vince

 

 

oh p.s

 

i am going to use a 50 amp esc

Edited By Timbo - Moderator on 06/05/2009 19:26:23

[stuey]

Hi, just want to confirm this idea. I have an EDF model that I want to upgrade to a 4s pack. I am looking at a 60A controller, and it has a 5V/3A switching mode bec. It will be powering four 9gram servos. Am I correct in thinking this should be ok? I know that I wouldnt do this with a linear bec.

[Romeo Whisky]

I have just fitted a 3A UBEC into a model, and to be honest, although it works OK I'm not really sure what I've achieved - ie. is there really any benefit?

 

The model is an Overlander 1.2m Tucano, with a big 1500Kv inrunner, 10x5 prop, Mtroniks Genesis 60A ESC with 3A BEC (presumably linear) and all powered from a 2200mAh 8-cell NiMh.  (Model needs a ton of weight up front to balance).  I have "cut" the red lead from the ESC and fitted the UBEC as per instructions.  Servos are 2 HS81 (ailerons) and 2 SD200 (R/E).

 

My reason for fitting the UBEC is that this set up takes a lot out of the battery pack, and I've also noticed the ESC gets hot and I'm afraid of thermal cut-out (although it has a massive heatsink).  Having just changed the RX to a Spektrum AR6200 I wanted to be sure of avoiding brown-outs, and although I had previously fitted a separate 4-cell RX pack I felt very uncertain of the reliability of this with Spektrum hi-voltage requirement compared to 35MHz and of course it is heavy and space up front for it is a problem too.

 

Will the UBEC give me a more reliable power source for the RX and servos when close to or at LVC - that's really the main issue?

 

 

Edited By Romeo Whisky on 29/10/2009 08:28:26

[Tim Mackey]

Yes ....and no. One main reason for using a UBEC V the ESC bec, is that many ESC becs cannot handle higher voltage inputs ( such as more than 3s Lipo for instance ). Not the case in your scenario. secondly, the ESC BEC are often limited in how many servos they can power, often only 3 as a mximum...the UBEC usually handles more, due to a higher current rating. You ESC unit is rated 3A anywya, so no difference there. Your point about ESC overheating is fair, and if it did fry, then assuming it dint cause a dead short across the battery, the separate UBEC will still power your radio.

As for LVC...makes no odds - the ESC unit will still supply power via the BEC when LVC is reached ( which you shouldnt be letting happen anyway really ) as will the UBEC.

Avoiding brown outs is best accomplished by using a 6V supply, which most UBECs are capable of doing, however ESC bECs are nornally only 5V

[Romeo Whisky]

Thanks Timbo - much appreciated.  So it doesn't sound as though I'm gaining much, but not losing anything.  it's all helpful in learning about new things.  UBECs are new territory to me.

 

There are some related points which perhaps you could clear up for me:-

 

1.   Some servos (eg. SD200) only refer to 4.8V as their operating voltage.  Are all servos OK with 6V or will some fry?

 

2.   I have ESCs with BECs rated from 1.5A upwards, and they all mention how many STANDARD servos they will drive depending on input voltage, but as I only use minis and micros I have no idea how much less (or more?) power they consume.

 

3.   Spektrum RXs are said to need 3.8V minimum so why is 6V better than 5V input - is it just a matter of headroom?

 

4.  Never bought an OPTO ESC but earlier on in this thread you mention that OPTO EScs and UBECs are really incompatible.  Not sure of difference between an OPTO and a standard ESC with the red wire cut.  Friends also seem to think they're virtually the same animal.

 

5.  When you cut the red wire on a standard (BEC) ESC, what is the internal effect of this?  Since a linear BEC generates heat, will the ESC run cooler with a UBEC fitted?

 

Some of these queries might seems obvious to you, but believe me, when a bunch of model flyers with different experiences start talking about these things you get as many opinions as there are people, and some definitive info is worth a great many guesses and opinions!

[Tim Mackey]

1) Some ( very few these days ) will fry.

2) Minis take more juice than standards...usually.

3) Yes..and of course higher voltage gives more torque and speed to the servos

4) They are not rhe same at all - OPTO uses fibre optic technique to transmit the signal...not copper wires. This gives complete isolation from the battery  common connection point and should eliminate interference

5) Some....as the linear BEC inside the ESC is still receiving a power input but not actually supplying any out.