BECS and regulator info ( beginners )

[Tim Mackey]

ESC BECS and REGULATORS.

The two things are really the same. There are however basically two different types of regulator, LINEAR or SWITCMODE.  Most ESCs use a simple linear regulator, which is fine for  low powered devices and utilizing lowish voltage inputs. They are easy to make, cheap and therefore very popular BEC devices found in the cheaper ESCs.  BUT due to the way they work, they are extremely inefficient. They simply take the difference between the input and output voltages, and just burn it up as heat. The bigger the difference between the input and output voltage, the more wasted heat is produced. In many cases, they waste more power stepping down the voltage than they actually end up delivering to the target device! With typical efficiencies of  a very  poor 40%, and sometimes as low as a pathetic14%,  linear voltage regulation generates a lot of waste heat which has to be dissipated with bulky,  heavy heat-sinks. Even better designed “low drop-out” regulators are still inefficient - all they really do is just give you more flexibility with regard to input voltage.

The equation for all that wasted power in a linear regulator is as follows….

( Input voltage – output voltage ) * Load current = Power wasted

So with a 3s LiPo input of 11V, regulated down to 5V for the radio gear, multiplied by the typical current drawn by that gear of say 2A this gives ….

(11 - 5) X 2 = 12. That’s 12 watts of wasted power !!  Even with a generous heatsink, 12 Watts is a lot of life to pull out of your battery just to warm the inside of your aeroplane!  Driving loads over about 300ma with these simple and cheap linear regulators when the input voltage is quite high ( and therefore a lot of wasted heat is generated ) is a bit dodgy, as is driving high servo counts with heavy current demands, so most people use a separate battery pack for their radios in these situations. Of course, this means you have twice the batteries to remember to charge.

A switching regulator however works by taking little bits of all the input power, bit by bit, from the source battery, and moving them in a controlled or “switched” manner to the output stage - hence the term “switching regulator”. In many ways it works like a sort of speed controller! The losses involved in switching the energy in this way are quite small, and the result is that a switching regulator can typically have as much as 80% efficiency. There is a theory that these switching regulators are prone to creating electrical “noise” which could interfere with the radio and there is some truth in that. However, when considered against the potential for such noise from the ESC itself this potential is pretty small, and in a well designed and constructed switch-mode regulator it is of no real concern. The switching regulator such as the UBEC and others, can therefore more easily and safely power heavier loads from a higher voltage, PLUS save you the weight and trouble  of additional battery packs.  Since it is so much more efficient than a linear regulator, it is great coupled with  lithium batteries to power your radio because you will get much more useable energy from the lithium battery pack to power your receiver than if you used a linear regulator.  Remember also that the higher your input voltage....the more efficient it will be.  For instance, when using a 3-cell LiPo  pack the current drawn from the battery pack will be around half of what a 4-cell nickel pack would be required to deliver.   How is this?   Read on….
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[Tim Mackey]

Part 2 as it were......

Let’s say your radio and servos draw 4 amps - at 5 volts that equals 20 watts of power ( 4 X 5 ). This means that the old 4-cell nickel pack ( at roughly 5V ) will have to drain at 4 amps. However, the 3-cell lithium pack at about 10V ( under load ) would only have to supply about 2 amps through the regulator to deliver the same 20 watts power! This is simple Ohms law at work folks!

As an added bonus it also means that a relatively small 3-cell lithium pack at 850 mah in capacity could power your radio gear for about the same amount of time as a 1500 mah 4-cell nickel pack. Now calculate the running time for a 2000m/a LiPo pack! No contest really .

I should also point out here that although I am a fan of standalone switchmode regulators even these, when used in conjunction with an OPTO style ESC will compromise the OPTO isolation feature of the ESC. The only sure way to retain its feature of radio isolation is to use a seperate battery completely. Using a standalone BEC merely restores the common battery positive and negative rails being tied back to the ESC and defeats the object. BEC and OPTO are as it were.... mutually exclusive.

[Alan Scarlett]

 Hi Timbo

   Some off the ESC can take up to 3-cell but some can take up to 6-cell for the BEC can you let me know how this all works

[Tim Mackey]

Hi Alan and welcome to the forum on this bright sunny Christmas day...just back from a quick fly down the park

It depends on the quality, construction and design of the regulator used. Some of the later models of ESC are now deploying "switching" BEC regulators, and these are capable of handling higher input voltages such as those from 4, 5 or even 6 cell LiPos.

[Lew Weaver]

Just to add my personal experience of switching regulators - I found that all of them gave reduced range when using 35mHZ - something it might be advisable to check if fitting one.

Problem disappears when using 2.4 GHz 

[Alan Scarlett]

Hi Timbo

 thank for let me know as some of the ESC are for 6 LiPos or 18 Cells but but 3LiPos or 10 Cell only for the BEC which i did not know how worked

[Piper Cub]

Hello, its me again!

OK, BEC's are very popular in rc cars and boats, mainly because it means there's less weight to lug around. If a nimh or nicad powered car \ boat's battery gets low, you lose steering and power but, this isnt really a problem as you're already at ground level.

But in a plane...........!

So, is it advisable to use a BEC ESC in a plane? When is it best to have a non BEC ESC and is this relevant to the size of plane \ motor size etc? I guess what Im getting at is why would you ever have a BEC ESC in a plane?

EDIT. Sorry also what does OPTO mean with regard to an ESC? What does it do if anything and can you get an OPTO BEC ESC as well as a non BEC ESC?

Finally whats a program card and how do you use these?

Er, thanks!!

[Tim Mackey]

The BEC that is part of an aeroplane ESC is special, and it supplies the radio gear EVEN AFTER the LVC has cut in. This stops the motor and tells the pilot the battery is low, and you then land immediately, with full power still supplied to the radio gear. I use a BEC in all my electric aeroplanes, some are built in to the ESC, some stand alone. I use a stand alone when the BEC in the ESC is not man enough to work the number or size of servos used, most ESC becs are only happy on up to 4 servos, or with a Flight battery of 4 LiPos maximum, in these cases, use a standalone BEC or seperate small battery.

OPTO means opto isolation which in turn means the ESC is optically isolated from the radio receiver, so pretty much eliminating any glitching from the ESC. You dont get OPTO and BEC both together in an ESC as they are mutually incompatible....the BEC would null the effect of the OPTO, as stated in the opening posts

A program card is for people too lazy or dumb to work out how to program the ESC with the tr stick and the ESC silly music beeping and so on. They are handy I believe, but personally have never found I needed one.

Er,,, your welcome.

[Myron Beaumont]

Timbo    I at last have all my bits ready to fire up/connect but would you please clear up a few points before I do .

1   Should I use 1/2 throttle setting on my Tx in case it needs reversing(like a servo )My Hitec gear mentions this but the Futaba does not !)

2   How do I know the COP of the BEC is not going to let each Lipo cell drop below 3V Folks talk of 70% of fully charged voltage But that is 2.59 V  in my book .80% is 2.96 near enough I think But how do I prepare for this .&/or avoid a mistake ?

3   Is the voltage provided by the BEC automatically OK for my Rx & servos (4.8 withmy Nicads) Servos are Futaba S3003's HitecHS325HB's & E-SKY 8 gm jobs

Computer is going funny somust stop here Myron

[Tim Mackey]

1. No - otherwise you will not achieve full power to measure things properly - just ensure you have "trained" the ESC to recognize the tr throttle high and low positions - futaba normally have throttle direction set to reverse. THEN connect everything up, open throttle a tiny bit, and confirm that fan /prop is spinning in correct direction...if not, reverse any TWO wires to motor. Then go for it !!
2. ESC should have instrucions for setting the LVC. 3v is only for cell voltage OFF LOAD. it is quite usual for the voltage to drop to around 2.8V per cell or so when in actual use. Despite this....just observe and listen carefully for the slowing down of the motor - it wil be obvious...thats the time to stop flying /testing and head for the strip / teapot.
3. Yes - most are 5v output same as a 4 cell pack....you could just confirm if you want with a M/M across the pos neg pins on the throttle lead to rcvr. ... telephone me if you want before blast off pm first

[Former Member]

[This posting has been removed]

[Myron Beaumont]

Thanks for replies Timbo & Eric  .I might seem to be a real thicko but how do I "train" the ESC to recognise throttle high & low settings & if they are the wrong way round can I do the reversing after the test run & still have throttle trim operable ?  As you can tell I'm extremely worried about the whole business I always am if not 100% confident.  There were no destructions with the Hifie ESC either .It's spec is ESC-45A-G-SE       2-6  lipo4ASwitching BEC 

[Tim Mackey]

will reply later this morning......or as I say....ring me if you want after 10am

[Tim Mackey]

Myron. Most ESCs are trained by the following procedure. ( Doesnt Scott have the instruction for this one ? )

Disconnect flight battery. Switch on tr , move throttle stick to FULL HIGH. Connect flight battery, ESC beeps a couple of times - move throttle stick to LOW...more tunes..... then silence. Disconnect flight pack. Job done.

Normal start up procedure is then....

Throttle LOW, tr ON. Flight pack connect...

ESC does self check routine, probably plays "shine on you crazy diamond" , followed by long beep....all is armed and ready for lift off.

PS 45A ESC ?? - thought it was a big 'un you needed / were having ??

PPS heres a link I found after a google around..

ESC instructions

[Erfolg]

Timbo

• Who makes switching ESC
• Is it normal practice for the manufacturer, to tell you what type of BEC is incorporated

To be honest I have never noticed my ESC getting warm, or my motors or my batteries. Have I asbestos fingers, or does it matter how you operate "your Drive Train".

Erfolg.

PS are you now the controller of the universe, as I have noticed you sometimes tell us you are the moderator

[Tim Mackey]

Loads of peeps make switching regulators, and SOME escs have them, others have cheaper less efficient linear.

Yes - did you look at the link I gave ?

PS NO..... and yes

[Erfolg]

Timbo

Most if not all my ESC give beeps when initially connected, before often breaking into some sort of tune/melody. As most of my speed controllers are low cost, I assume that they are linear.

I have missed something in the link, as it seems very similar to most of my instructions, except one plug and play. Gives us a clue Timbo. It is the first to give some guidance on timing or soft start issues, so that is informative. It may also give so insight as to why I have shed some blades on start up (one brand new), with folders. Although I do tend to start initially on low power, till seconds before launch. 

Erfolg

[Tim Mackey]

A clue to what ??

Incidentally, for a fast revving inrunner such as on your EDF timing should be set to low. I use soft start for all my stuff. 

[Former Member]

[This posting has been removed]

[Erfolg]

When I said "Gives us a clue Timbo", I was referring to where it tells you about if it is a Linear or a Switching ESC.

A bit tired at the moment, I have been stripping roofs this afternoon. No, not the Lead of the local church, but Bitchimun and felt. Pity no one wants old felt though, just does not pack the nose of any model efficiently.

Erfolg

[Tim Mackey]

well looking at their home page...this clue tells me they are using linear, so I suggest you may want to use a UBEC.

Pz = (V1 - V2) × I.

PM me if you want a decent quality and capable UBEC, I have loads here - dead cheap. 

PS google is your friend Erfolg

[Former Member]

[This posting has been removed]

[Tim Mackey]

Jetsome is absolutely right....ESC BECs for instance are often wildly out on their real capability. I have now taken to using UBECs for all but the smallest and lightest of models. Several UBEC devices are now available for a few pounds which utilize decent efficient switching regulators with decent current capacity. I have just purchased one from my fav HK supplier which is 5A constant capable and 6V output too if required ( which I now adopt on all my Spekky gear where servo limits permit ) PLUS it will take up to 10s LiPo battery as input, all for just about a tenner!..

here

I have tested this device on the bench, using a load which pulled 5.5A and it was rock steady at 5.98V all the way, and was barely warm at the end. I actually have removed both the switch and the suppression coil unit from it as they added weight, and I find the supprression unit un-necessary with 2.4Ghz. They also do an 8A constant (15A burst)  version for the really heavy demand user, but this is only for max 3S lipo input.

Great for 2s LiPo receiver packs though in large IC models !

I also have several other UBECS from this stable, including the one I used in the article about using LiPos to power radio gear - this 4A capable unit has a built in low voltage warning alarm for use with 2x lipo cell receiver packs. I use these in my IC models, and my slope soarers too - around a fiver at todays exchanges !!

4A alarm ubec

As for dealers and their supply, I am afraid that many or most of my goods are now sourced abroad, my "local" shop is a 2 hour drive return, and one of my favourite UK specialists has been unable to supply my needs on the last 2 phone calls. Competition is good for consumers....but I am afraid the UK guys are in for a real fight.

[Tim Mackey]

They call 'emselves hobby city these days John.

try this

[Tim Mackey]

Ah well the old debate about twin ESCs and BECs. It is generally not recommended to use both BECs. I would think that a single 5A constant version like that highlighted would be plenty man enough for most scenarios. In all the tests I have done with stalling several digital servos etc, I have never managed to pull more than 2A on a 6V supply. The larger UBEC just gives plenty of nice headroom.