Jun 01, 2015, 05:40 PM
Expert Heli Crasher
Joined Jan 2014
2,636 Posts
Discussion
Governors in ESC's

A few people here at RCG over in the KBAR thread talked me into (or I talked myself into) fiddling with governors. My ESC has one. I'm not sure if it's any good or not, and I'm not sure if it will do me any good or not, but I figured I'd fiddle with it anyway.

I think I have most of it straight based on research. Correct what is wrong with the following so I have a better idea of what I am doing before I start tinkering:

450 heli
3S LiPo
3400 Kv motor (6 pole not 8 pole)
12T pinion
150T main gear
HobbyWing 40A Platinum Pro ESC

Step 1: Determine whether to use governor Low or High on the ESC:

Gov Low = 0 min to 45,000 motor RPM max
Gov High = 46,000 min to 200,000 motor RPM max

ESC RPM/(poles/2)*pinion T/Main T

45000/(6/2)*12/150 = 1200 RPM headspeed = too low to use Gov Low! Must use Gov High.

Step 2: Determine what flat throttle curve to program and above what stick position (I'm not using the ESC soft start to spool up automatically, I do it manually).

Note: I read that you can use no more than 75% throttle MAX to give enough headroom to governor to work properly. 70% throttle max is "supposed to be ideal."

Then I came across this:

Quote:
 Look at the curve on the ESC data sheet, and you see that GOV HIGH with a throttle of 70% gives 70,000 rpm for 2 pole motor, so for the stock 8 pole motor you get 70,000/4*16/120=2333 rpm head speed.
From graph in my HobbyWing ESC manual, 70% = 70,000 RPM in governor high mode. I have a 6 pole motor.

70000/(6/3)*12/150 = 2800 RPM

So, at 70% throttle on the TX I will have 2800 RPM head speed. My motor can not sustain this head speed throughout the flight on 3S with a 12T pinion according to my calculations. So I did more math (I hate math).

50000/2*12/150 = 2000 RPM
60000/2*12/150 = 2400 RPM
70000/2*12/150 = 2800 RPM

2400 RPM should be sustainable from the beginning of the flight to the end. So I use the graph for Governor High from the ESC manual to find that 60,000 RPM corresponds to a throttle of 68.5% in governor high mode. That's pretty close to 70% that is supposed to be "ideal." Now I have to translate that to Walkera/Deviation values, which range from -100 to +100.

This is the part that confuses me most. The manual for the ESC says that the governor is only active at 60% throttle and above. So it's active at 68.5% right? What happens between 60% and 68.5%? Something does not make sense to me here.

-Florida Heli-
Last edited by Florida Heli; Jun 01, 2015 at 06:54 PM.
 Jun 01, 2015, 07:49 PM Registered User Denver, CO Joined Dec 2005 6,871 Posts Just remember its a Chinese translation. So you have to interpret, or ignore most of the manual. The formula, and chart in the manual is about the maximum, and minimum abilities of the ESC. Not the actual rpm your motor will turn. So you have the 3400kv times the battery voltage of 11.1volts to determine the motor rpm, 3400 x 11.1 = 37740 motor rpm. Now figure from the gearing 37740 / (150/12)= 3019, in reality its likely to only get about 90% of that so about 2717 rpm. Throttle at 70% is the minimum for most esc's, as they tend to overheat if much lower. Around 90% is likely to be the most efficient as to power, to current draw. What is ideal for one person may not be ideal for you. Lets say you want to run at 70% governor. The system must be able to also run at 100%. So you might have to compromise with a lower maximum rpm from the lower gearing. That is why some more serious flyers have way oversized motors, and ESC's, so they can run crazy head speeds at lower throttle, and have the capacity to go to 100% throttle without smoke. They are taking advantage of the big motors torque, and using the governor to prevent over speed. Your gearing is conservative, so should be fine for 100% throttle, with a reasonable amount of blade pitch. I would just up the throttle until the head speed is where you want, then check to make sure its over 70%. The maximum really is not that important. I like around 90% on most of mine. Once you get up high you lose some of the governors ability to compensate for bogging, but with your gearing that should not be much of an issue.
 Jun 01, 2015, 09:11 PM Expert Heli Crasher Joined Jan 2014 2,636 Posts Ah, yes, the Chinese translation isn't the best. I don't think I'll have any problem with over speed with a 12T pinion on it. So I should start with a flat throttle curve of 80% to 90% then? The plan is to use slow start (roughly 8 seconds) on the ESC to spool up when I remove TH. If I program in a 90% flat throttle curve, then it should spool up and stay at 90% power and the governor should apply the additional 10% power to hold head speed constant if I do something like apply full collective? Am I getting this right? Now what happens if I want to spool up manually? Do I set a throttle curve to something like 0,33,66,90,90? -Florida Heli-
 Jun 01, 2015, 10:07 PM Where's the swimming pool Joined Jul 2011 1,449 Posts Having varying throttle values like what you describe has no real benefit, for the whole point of the governor is to attempt to give you constant rpm throughout. However, for a 'normal mode' where one might want full low stick to be zero for reasons of an extra safety or personal preference, whatever, this is generally how it is done: 0, X,X... X where X is the throttle signal you want to send to your gov. That will give you a 0 throttle signal at full low stick and I am assuming kick in the governor to whatever setpoint value is indicated by the non-zero throttle. Some governors will just lock onto a stable arbitrary throttle signal, others have predetermined setpoint values depending the exact throttle signal and the governor programming. But I don't know how HW governors behave. There should be a support subforum on Helifreak. I know I keep referring to that site, that info may well exist here but it is just much easier to find things on HF. This may help you get rough calculations done. http://heli.dacsa.net/calcv3/Default.aspx I would caution you however, to check the re-spool times of your esc. If you suddenly decide to peg the stick to low and are NOT in a full flat throttle (thus you send a ZERO throttle), I dunno, say you're doing a pogo or aggressive pitch pumps or something, some esc's may cut the throttle and re-spool very slowly and if you do not have enough blade momentum, you could bleed out a lot of head speed. If your re-spool time is too slow, there is a risk of a crash. Last edited by spykez; Jun 01, 2015 at 10:16 PM.
 Jun 02, 2015, 11:44 AM Expert Heli Crasher Joined Jan 2014 2,636 Posts Yes, the ESC doesn't re-activate slow startup until after the stick has been at zero for roughly 3 seconds. The reason I asked about normal mode is b/c that's the way I have been flying until now. I'm going to try using TH and soft start to spool up the heli automatically, but for 25 years my brain has been programmed that left stick down = motor off. So, if I can't adjust, I may have to go back to a normal mode. -Florida Heli- Last edited by Florida Heli; Jun 09, 2015 at 08:02 PM.
 Jun 02, 2015, 11:53 AM Registered User Denver, CO Joined Dec 2005 6,871 Posts For safety it is best to have Zero throttle in normal mode, at low stick.
 Jun 02, 2015, 12:04 PM Registered User United States, NY, New York Joined Sep 2013 489 Posts I agree, that way you have to either flip two switches (TH and flight mode), or flip TH and move the throttle stick up. That's exactly why I keep it that way - I spool up "somewhat" in normal mode for a few seconds, and then I switch to idle up, finish the spool-up, and fly. Of course I could just flip both switches right away to begin with, but this is how I do it - for no particular reason.
 Jun 02, 2015, 01:19 PM Registered User United Kingdom, England, Slough Joined Dec 2012 1,635 Posts Hi mate I used to be like you and have normal set from zero up, I run governor on my 500s one has the Hobby king Yap this is set up that throttle hold is motor off, normal can be set to a low throttle so as motor spins up flick to idle 1 to give you the head speed you want to fly on, its hard to start off, but once you fly the heli a few times it will start to fall in place, to just use throttle hold to shut down motor after you land I think at the end of the day you do it how you feel comfortable with it, there is no golden rule it has to be done by
 Jun 02, 2015, 09:36 PM Expert Heli Crasher Joined Jan 2014 2,636 Posts There are really two separate topics here. I have been posting over in the Beginner forum about using a little negative pitch to hold the heli firmly on the ground. I fly -2 to +8. One suggestion from a few folks was to simply leave the stick down and use TH and slow start on the ESC to spool up. This way, the heli spools up while maintaining the full -2 at all times. That I can do (and tried yesterday) with ordinary curve programming. Yes, it sort of freaks me out to turn off TH and have the heli "get a mind of its own" and spool itself up. It is sort of cool though. Of course, don't try this with a heli that has more than about -2. Your results will not be pretty. Full head speed with -12 on the ground? I predict kaboom! Then comes the second issue, which is the governor. Taking the above approach a step further, turning off TH not only spools up the heli, but it does so to a constant head speed regardless of the position of the left stick, leaving it solely responsible for pitch (and rudder). There is no more throttle at that point. I'm not sure which combination of approaches I will ultimately use, but I have a feeling that I will end up using 0, X, X ... X where X is my throttle, say 90% yet I still have the extra safety/bad habit reinforcing of the left stick being down shutting off the motor. Anything just above low stick would still serve the purpose of letting the ESC do the spool up and holding -2 pitch and the governor holding the head speed at every point except right at low stick. Even if I hit low stick by mistake midair, via panic or whatever, it takes 3 seconds for the ESC to go back to slow start, so it would not take a slow spool up mid air to recover. IU1 and IU2 can still be programmed for a flat curve even if Normal isn't. I'm still at a point where I don't remember to hit TH until after a crash, but I've decided that's not such a bad thing since the past few times I have been able to maintain just enough control to fly the heli down to a rough landing instead of just giving up and shutting off the motor midair with TH. I don't know how my ESC would behave if I plugged in the heli with 90% throttle on the governor, left stick above low, and forget to the have TH on. I know that if it's at 100% the ESC enters programming mode. Not sure about 80% to 100%. I predict that it would begin slow spool up, whacking my arm and leg in the process as I run like h^ll. Interesting stuff. I don't think the governor is really going to do anything for me, but I always like to tinker with stuff. It's there, so I'll try it. -Florida Heli-
 Jun 02, 2015, 11:28 PM Where's the swimming pool Joined Jul 2011 1,449 Posts Most heli esc will not arm if they see a high throttle signal on boot up. The operative word here is most. A blade 450 stock esc will spool! Lol
Jun 02, 2015, 11:46 PM
Expert Heli Crasher
Joined Jan 2014
2,636 Posts
Quote:
 Originally Posted by spykez The operative word here is most.
And that's the ONLY one that matters to my arms and legs! Yes, I would survive a 450 whacking me on an unexpected spool up when I plug it in before I could run away, but I'd really prefer not to go down that road.