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Old 08-19-2017, 09:23 PM   #1 (permalink)
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Default Flyfun V5 RPM signal problems (was Grounding RPM port?)

My ESC (Flyfun V5) has an RPM signal output which has only one wire (signal wire only). Would it harm the 3DIGI to ground the RPM port to the negative of the receiver battery (2S lipo)? I'm having issues with governor stability and I want to eliminate this as a possible cause. I can hear the motor going up and down in RPM slightly with an accompanying tail twitch.

Last edited by Atomic Skull; 08-22-2017 at 05:07 PM..
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Old 08-21-2017, 12:47 AM   #2 (permalink)
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The GND pins of the 3digi are all connected anyway.
So I think that would not bring any advantage.
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Old 08-21-2017, 01:06 AM   #3 (permalink)
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I think I'm closer to fixing the unstable RPM, I had to lower the gains a lot more with the Flyfun V5 than I did with the YGE. Not sure if it's the new ESC or if some change was made with the governor in version 2 of the firmware.

Is there a difference between lowering the I. and P. gains separately and lowering the overall gain? e.g. if I lower P. gain and I. gain by 20 does that have the same effect as lowering the overall gain by 20?
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Old 08-21-2017, 04:09 AM   #4 (permalink)
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Quote:
Originally Posted by Atomic Skull View Post
Is there a difference between lowering the I. and P. gains separately and lowering the overall gain? e.g. if I lower P. gain and I. gain by 20 does that have the same effect as lowering the overall gain by 20?
Overall gain effects both I and P.
But itīs more a percent thing. If you for example decrease the overall gain by 10 percent then both P and I are decreased by 10 percent.

Example: overall from 60 to 54 (-10%) would be the same as P from 30 to 27 (-10%) and I from 40 to 36 (-10%).
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Old 08-22-2017, 05:22 PM   #5 (permalink)
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Today I tried using a Hobbywing external RPM sensor and it made a dramatic difference. There is something about the Flyfun V5's RPM signal output that the 3DIGI does not like. It's not the dropouts that the Platinum V4 has but seems to be a problem with RPM stability.

Can you take a look at this and see if you can give me any ideas?



This is the internal RPM signal output from the Hobbywing Flyfun V5 160A HV



And this is with a Hobbywing RPM sensor (btw it works fine with 3.3v so you don't actually have to power it from a separate servo port). Notice how the RPM and throttle output is smoother with the external sensor and as well the P-gain part of the governor has a smoother response to disturbances in the RPM. With the internal RPM signal the tail twitches constantly but with the external sensor it does not.

The "governor active" messages are just me changing parameter sets btw.

Governor settings were 50 for I gain 30 for p gain and 30 for overall gain.
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File Type: txt hobbywing_external_RPM_sensor.4DF.txt (1.28 MB, 206 views)
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Old 08-23-2017, 02:54 AM   #6 (permalink)
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Hi
Quote:
Originally Posted by Atomic Skull View Post
Today I tried using a Hobbywing external RPM sensor and it made a dramatic difference.
I think you exaggerate here a little.
I canīt see a "dramatic" difference here.

The sensors both seem to work OK.
With the internal sensor, the RPM varies with about +-20RPM, with the external sensor with about +-15RPM.
That is both not much and little the difference may also be a result of for example different weather conditions (wind?).

When I take a look into the logs I can see the tail moving a little, but not in combination with the RPM changes.

I donīt think itīs a sensor problem, but maybe there are possibilities for some gov parameter optimizations.
Quote:
Governor settings were 50 for I gain 30 for p gain and 30 for overall gain.
If the +-20RPM are too much for you can try to optimize the gov settings. Put the overall gov gain on a knob or slider of your transmitter and try find the optimal setting.
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Old 08-23-2017, 04:38 PM   #7 (permalink)
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Quote:
Originally Posted by DirkS View Post
Hi

I think you exaggerate here a little.
I canīt see a "dramatic" difference here.
I mean how noisy the RPM graph is with the internal sensor vs with the external sensor. Additionally the P part response is noisier with the internal sensor, I'm assuming because of the noisier RPM signal input.

I tried for a couple days to get rid of the tail twitch, even with the overall gain turned down to 10 the tail twitch was still there. However, with the external sensor the twitch is gone even with the gain turned up to 40.
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Old 08-24-2017, 05:23 PM   #8 (permalink)
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One thing I forgot to mention is that the Hobbywing Flyfun ESCs are meant primarily for planes and EDFs and have a very fast throttle response compared to e.g. a YGE or Scorpion ESC. So a noisy RPM signal might not cause problems with those ESCs but the Flyfun ESC might be fast enough to respond to the noise in the throttle output that results from the noisy RPM input signal.

What if there was the option of a filter value on the RPM signal input similar to how the gyro sensor signals are filtered. It would smooth out the noisy RPM signal that some ESCs seem to have and make the governor better behaved in those situations.
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Old 08-26-2017, 12:07 PM   #9 (permalink)
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The RPM signal is already filtered. Mainly because of the bad signal quality of some HW ESCs.

Problem with the P-part? Did you actually look at the governor P-part in the flight data? Itīs nearly nearly all the time at 0 in your flight logs. Even with the noisy Funfly signal.
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Old 08-27-2017, 11:31 PM   #10 (permalink)
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Quote:
Originally Posted by DirkS View Post
The RPM signal is already filtered. Mainly because of the bad signal quality of some HW ESCs.

Problem with the P-part? Did you actually look at the governor P-part in the flight data? Itīs nearly nearly all the time at 0 in your flight logs. Even with the noisy Funfly signal.
I'll experiment with raising the p-gain then. Also I tried a scorpion opto cable and it seemed to improve things somewhat. At the very least it ensures that the signal output to the FBL unit is at 3.3v.

Also, this is what the the soldering on the opto cable looks like, it's pretty horrifying.



I wasn't sure if I could get the glue off to solder on new leads so what I ended up doing is putting a blob of Dow Corning #748 on each end of the board to support the wires and recovered it in shrink tubing after it had set.
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Last edited by Atomic Skull; 08-28-2017 at 11:46 AM..
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Old 08-30-2017, 01:40 AM   #11 (permalink)
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Found something interesting in another thread, I'm going on the assumption that the Flyfun V5 has something similar going on. This is the Hobbywing Platinum V4 RPM signal. Notice how the low part of the signal is around 1.2v or so. It looks like Hobbywing really screwed up the design on this.



This is the signal with a transistor and resistor added to the input:



This is the schematic he used:



I'm going to try that next, I'm pretty sure a 2N2222A should work in place of the BC547.
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