Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[Luqman Khan]

Thanks crxmanpat ... so I am well within limits at 5.3v (good to know).

GG,
In my case increasing the voltage increase (from 5.1 to 5.3v) fixed the servo chatter & automatic deflection of control surfaces that I was experiencing. I do have a choke on Bec cable but it seems my issue might not be related to interference else increasing output voltage from BEC (going to receiver and blue box) won't have fixed it (everything else being equal).

I found this article / additional information.

https://www.promodeler.com/caseSTUDY...reewing-Mig-29

FYI..I am using two MKS HV69 in my MiG-29 to drive the FFSs. The downside is that MKS doesn't offer a reverse version (or they didn't at the time I ordered). Rather than open one up and rewire it, I decided to install a servo reverser. The Futaba SR-10 was ordered. It has performed flawlessly for several thousand flights** and is very stable to ambient temperature changes. Some folks shy away from reversers, but the SR-10 has served me well.

For the hardware: heavy duty DUBRO connectors and a threaded 4-40 rod cut to length.

Also, you may wish to search the forum for RF chokes or ferrite chokes or just chokes. Read and learn. I use several of these on all my high-current ESC EDF birds. The MiG has 7 of them. Overkill? Maybe. But how many individual MiGs are flying that have several thousand flights logged w/o a single radio glitch? Here are the locations:

One small choke near each FFS servo (as close to the MKS HV69 as possible). There's a nice pocket ahead of each servo.
One larger choke on each ESC mounted as close to the ESC as possible on the battery side.
The green ferrite ring that comes stock.
I added another small one near the green ring.
The SR-10 came with its own.

Yep...that's a total of 7 chokes. Like I said...probably overkill, but the set-up is extremely flight proven.**

I'm gun shy after crashing an A-10 twice and an F-4 twice from loss of control events which a HAM Radio friend said was likely due to the noise generated by the high-current ESCs. Zero loss of control events since I started using the extra RF chokes on my high-current ESC EDFs.

-GG

**Estimated somewhat more than 2500 flights.

[Evan D]

The MCBe (blue box) isn't the issue with voltage, it's the items connected to the MCBe. The stock servos are okay up to 6 volts easy. The retracts are good to about 5.5. There is a sequencer in the MCBe and it's probably okay to over 5.5 but it doesn't matter because the retracts aren't. Last is the LED output slots. The LEDs themselves are 3-3.3V and there is a tiny resistor on each LED output that cuts the voltage the BEC supplies down a fraction. If you increase the input voltage the resistors reduction may not be down to the 3-3.3V the LED can handle and you may blow a LED. All that said 5.5 is the max you want to supply to the MCBe but it's because of the retracts.

[Luqman Khan]

Thanks Evan - makes sense that its the individual components connecting to MCBe that have different tolerances for voltage.

Any idea about why my control surfaces attached to blue box (rudder, flaps, ailerons) would start automatic deflections (minor deflections but visible) when I switched from stock BEC to Castle BEC - here're my observations:

1. Stock BEC - no issues.
2. Switched to Castle 10amp BEC set at 5.1v: started getting servo chatter + surface deflections for anything connected to MCBe. Stock elevator servos were direct to receiver and no problems there. I also checked the telemetry data and receiver was outputting 5v to 4.9v (it kept oscillating between this range).
3. I changed Castle output to 5v and then 4.9v and 4.8v: with each drop the chatter and servo movements became more pronounced.
4. Finally I changed to 5.2v and everything went to normal and then for peace of mind I changed to 5.3v output at Castle BEC -- and no issues since then. I checked the telemetry and I get readings of 5.2 to 5.3v for receiver output.

The MCBe (blue box) isn't the issue with voltage, it's the items connected to the MCBe. The stock servos are okay up to 6 volts easy. The retracts are good to about 5.5. There is a sequencer in the MCBe and it's probably okay to over 5.5 but it doesn't matter because the retracts aren't. Last is the LED output slots. The LEDs themselves are 3-3.3V and there is a tiny resistor on each LED output that cuts the voltage the BEC supplies down a fraction. If you increase the input voltage the resistors reduction may not be down to the 3-3.3V the LED can handle and you may blow a LED. All that said 5.5 is the max you want to supply to the MCBe but it's because of the retracts.

[GliderGuy]

Hi crxpatman,

Sorry for the confusion whereby I mixed in a different topic as an FYI. The RF chokes are not meant to address your chattering servo issue...which I gather was happening without the EDF fans running.

The info on the RF chokes was presented for your edification regarding RF noise generated by the ESCs when the fans are running. This "may' cause a complete loss of control as the noise may upset the pointer in the look-up table that the TX and RX are using when the binding/linking process takes place.

So to make things absolutely clear: (1) I don't have any inputs or suggestions for your chattering servo issue. (2) The RF choke info is to potentially prevent you from having a loss of control event due to the RF noise generated by ESCs during flight.

Hope that clears it up.

-GG

[Evan D]

In MY experience what you are describing is normally caused by feedback in the servo leads caused by resistance. Normally a bad connection at an extension connection or something similar. Remember the MCBe is basically a bunch of Y connectors. I think when you increase the supply voltage it’s pushing through this extra resistance causing the feed back.

What you need to do is track down the source of the resistance and correct or eliminate it. It may be dirty connections, bad solder joints in the MCBe, servo wires that are close to other wires (the chokes are a great fix if this is the cause but also twisting the servo wires can help if this is the issue ), or what ever.

The thing is that you still have an issue even though you are reducing the symptoms by increasing the voltage. If it was me I would bypass the MCBe with standard extensions and Y’s as a first step.

[Luqman Khan]

Many thanks for sharing your experience - i guess I'll have to start with process of elimination as you suggested.

Its good that i'm able to easily reproduce the issue on bench so I'll know for sure when it works.

In MY experience what you are describing is normally caused by feedback in the servo leads caused by resistance. Normally a bad connection at an extension connection or something similar. Remember the MCBe is basically a bunch of Y connectors. I think when you increase the supply voltage it’s pushing through this extra resistance causing the feed back.

What you need to do is track down the source of the resistance and correct or eliminate it. It may be dirty connections, bad solder joints in the MCBe, servo wires that are close to other wires (the chokes are a great fix if this is the cause but also twisting the servo wires can help if this is the issue ), or what ever.

The thing is that you still have an issue even though you are reducing the symptoms by increasing the voltage. If it was me I would bypass the MCBe with standard extensions and Y’s as a first step.

[Ironside]

Anyone know the total thrust (in newtons and/or lbs) the Mig 29 is pushing on two 6S batteries?

[Evan D]

Pretty sure people have posted it before in both this and the RCG thread.

[kallend]

To those (GG?) who have put ferrite rings on the long servo leads, do you have a link to a source?

[jasmith41]

To those (GG?) who have put ferrite rings on the long servo leads, do you have a link to a source?

Amazon.com: Ceedmon 20 Pieces Clip-on Ferrite Ring Core RFI EMI Noise Suppressor Cable Clip for 3mm/5mm/7mm/9mm/13mm Diameter Cable, Black : Industrial & Scientific

[kallend]

Amazon.com: Ceedmon 20 Pieces Clip-on Ferrite Ring Core RFI EMI Noise Suppressor Cable Clip for 3mm/5mm/7mm/9mm/13mm Diameter Cable, Black : Industrial & Scientific

Thanks, but I was hoping for something more specific than a range from 3mm to 13mm, most of which would be redundant.

[kallend]

Amazon.com: Ceedmon 20 Pieces Clip-on Ferrite Ring Core RFI EMI Noise Suppressor Cable Clip for 3mm/5mm/7mm/9mm/13mm Diameter Cable, Black : Industrial & Scientific

EDIT: Site (or my browser) went berserk and posted same thing 3 times.

[GliderGuy]

Thanks, but I was hoping for something more specific than a range from 3mm to 13mm, most of which would be redundant.

You will use 2 of the 13 mm near the ESC body. Then I added a 3 or 5 mm by each FFS servo…not much room back there.

I ordered a multi-pak and have dipped into it on several occasions…and will again when my PJ50 gets here. Handy to have redundantly on hand.

-GG

[xviper]

I have had several Eflite planes and I recall that on a couple of them, rather than using those green rings (like wedding rings), they use those "chokes" on the throttle lead. Even when using those chokes, they wrapped the lead in and out of the choke several times just like on the green rings.

[kallend]

OK, thanks, guys. Chokes on order.


Incidentally, it's not for a MiG. I'm using the PWM feature of an Arduino to drive a high power LED and want to avoid noise on the power line feeding back into the Rx.

[Luqman Khan]

Problem solved: it was the castle creations 10amp bec … moving back to stock bec solved the issue.

Thank you Evan & GG for your suggestions.

Many thanks for sharing your experience - i guess I'll have to start with process of elimination as you suggested.

Its good that i'm able to easily reproduce the issue on bench so I'll know for sure when it works.

[kallend]

Problem solved: it was the castle creations 10amp bec … moving back to stock bec solved the issue.

Thank you Evan & GG for your suggestions.

I've been building electric airplanes and helis since before it was fashionable (1980s) and have not had the greatest luck with Castle's creations. Not as bad as Detrum, mind you, 100% failure rate with those. I've never had a Hobbywing give any trouble.

[jasmith41]

I have had several Eflite planes and I recall that on a couple of them, rather than using those green rings (like wedding rings), they use those "chokes" on the throttle lead. Even when using those chokes, they wrapped the lead in and out of the choke several times just like on the green rings.

since i'm out of the bigger chokes, is there any reason i can't put one smaller one on each battery line...?

[jasmith41]

Thanks, but I was hoping for something more specific than a range from 3mm to 13mm, most of which would be redundant.

the next size down from the 11mm seems to work perfectly on the battery line in my 6s planes... not sure what wire gauge they are - sorry...

[GliderGuy]

since i'm out of the bigger chokes, is there any reason i can't put one smaller one on each battery line...?

That works, too. Of course, maybe not quite as effective, but in my opinion you are still ahead of the game just by using them.

-GG