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Old Mar 25, 2012, 07:11 PM
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United Kingdom, England, London
Joined Nov 2006
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Help!
help diagnosing what seems to be interference with 2.4GHz radio

Yesterday was the first time i have experienced loss of control of a model. This is a model that i have been flying for 3 seasons. Radio is a Futaba 7C and receiver is a 617. Receiver is powered by a Western Robotics Hercules Super Mini BEC and model has 7 analogue HS325 HB servos. ESC is Hobbywing 60A pentium, battery is 5s 4000mAh 25C. Motor draws 42A@18.5V.

Here is what happened. First flight of the day; low power range check done everything is working fine. Take-off and climb out no problem but just after turning down wind plane rolls either left or right and I correct it but something does not feel right. I carry on down wind for a bit, turn up wind and head towards location where first down wind turn was made. This time i can clearly see that i am losing control of the plane and then regaining contol as it is happening frequently now. Turn left, lose cotrol, regain control, turn right, lose control, plane loses altitude, regain control etc.. Scary to say the least. Anyway, manage to keep it in the air, trave a bit down wind and go to turn up wind to land; pretty much a same location wher i made first up wind turn. Same thing hapenns, but worse. The Time between loss and regain of control seems to have increased. I honestly thought i was going to lose the model. At this point i am shouting that i have lost it. Some how i manage to make turn, level wings and land sefely.

Since then i havent flown and wont be for a while as i havent got a clue as to what happened. On landing did another range check and every thing was fine. I havent taken anything out of the plane yet but what i intend to do as suggest by someone at the field is to remove the receiver and fit it to a cheaper model and see what happens. The only other explanation i can thing of is that our field is next to a hospital and maybe they were using some equipment that affect the signal; but this has never happened in the 3 years i have been using this radio with this model at this field.
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Old Mar 25, 2012, 07:45 PM
Balsa addiction since age 3
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Upstate NY
Joined May 2005
1,253 Posts
More info needed...

Does the Hobbywing 60A ESC include a BEC? If so, is it disconnected since you have a Mini BEC?

Can you measure the current being drawn by the servos? That Western Robotics Hercules Super Mini BEC seems like it could easily handle the load you are placing on it.

Do you have a way to range check with full RF power? (I know you did a range check at low power) Just to double/triple check the RF link? I am fortunate enough to have a large field (over 800') to walk and verify my connection with various aircraft orientations along the way... Is it possible you have a loose antenna connection or battery blocking receiver antenna?

Scott
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Old Mar 25, 2012, 08:06 PM
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The ESC is OPTO and doesnt have a BEC.

I dont know what current is being drawn by the servos, but most of the time only 4 servo are being used (3 for flaps and retracts) and like you said the Super mini BEC is good for 10A; but i will try and measure they individual currents starting with the rudder servo since i notice recently that sometimes it doesnt move as smoothly as it use to. I have been meaning to change it but thought it would be ok for now.

When i landed i did check on low and full power at about 150m (450ft) and everything was fine.

The antenna connections look ok and i run both antennae outside on either side of the fuselage.
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Old Mar 25, 2012, 08:24 PM
Balsa addiction since age 3
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Upstate NY
Joined May 2005
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Quote:
Originally Posted by bajinuk View Post
The ESC is OPTO and doesnt have a BEC.

I dont know what current is being drawn by the servos, but most of the time only 4 servo are being used (3 for flaps and retracts) and like you said the Super mini BEC is good for 10A; but i will try and measure they individual currents starting with the rudder servo since i notice recently that sometimes it doesnt move as smoothly as it use to. I have been meaning to change it but thought it would be ok for now.

When i landed i did check on low and full power at about 150m (450ft) and everything was fine.

The antenna connections look ok and i run both antennae outside on either side of the fuselage.
I just wonder if you have a binding gear (internal to servo - especially rudder since they can take a beating if it is a tail dragger) or other binding issue - hence the "current' check suggestion.
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Old Mar 25, 2012, 08:26 PM
If it flies - I want one!
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Werribee, Victoria, Australia
Joined Jul 2008
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All channels?

Bajinuk,
Were you losing complete control - ie throttle failsafing to neutral, pitch changes etc - or was the aircraft failing to respond to aileron corrections?
If the problem was only in one axis, a servo might be suspect.
If the lot went off-air, logical suspects are Tx, Rx or power source.
External interference is possible, I guess, but beyond my expertise to diagnose.
Well done getting it down safe!
PeteM
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Old Mar 25, 2012, 10:12 PM
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Measured rudder servo current and current is between 0.1A and 0.2A (resolution of meter is 0.1A) so that servo is ok. Will check the others tomorrow but i believe they will be ok as well. Voltage supplied is 6V, drops to 5.98V when servo is moved. Watts is 1.1W so actual current is 184mA.

I believe complete control was loss.

Tx voltage was 10.4V so that should be ok as well.

I check the soldering on the input wires on the BEC and there are two outputs to the receiver. Everything looks good.

Which leaves the radio or interference; but radio check is fine on ground.
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Old Mar 25, 2012, 10:23 PM
Life-abstract=conformity
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Joined Aug 2002
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I'm interested to see what you find.
So far it sounds like a brown out or an antennae orientation problem.
What kind of model? Is there carbon?
Skies
Jay.
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Old Mar 25, 2012, 10:30 PM
iva
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Vancouver Harbour Sp, Canada
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If you have a spare Tx antennae, that could be another area to check. You may have intermittent contact that is not showing during the range check.
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Old Mar 26, 2012, 08:04 AM
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Joined Nov 2006
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Model is hangar 9 p-51 mustang sport so no carbon; receiver antennae are routed to the outside on either side of the fuselage so shouldnt be an orientation problem.

Bear in mind this model has been flown at this site with the exact setup without any problems.

Gonna test the current draw in the remaining servos now then remove receiver and mount in cheaper, smaller and lighter model and possibly fly this afternoon and see what happens.
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Old Mar 29, 2012, 04:09 PM
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I have now tested all of the servos and none of them are binding. I have also removed the receiver, mounted it a cheap model and flown with the same radio at the same site with no problem. Could be that the interference that i experienced was now gone. I have also open the battery to check the soldering on the leads and that looks fine. Also checked the soldering of the ESC and BEC to the deans connector and that looks good too.

I am now suspicious of the deans connector. After 3 years of use, batteries included (same two batteries), you can imagine the two flat now oxidised contacts held together with a spring, combined with the high frequency vibration form the motor causing intermittent contact.

What i am going to do next is remove the deans connector from the 5-s battery and put it onto a 3-s so that i can test that connector along with the ESC and BEC in the cheap model and see what happens then. Just came to me as i was writing as a way of testing the deans connector.
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Last edited by bajinuk; Mar 29, 2012 at 04:26 PM.
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Old Mar 29, 2012, 06:37 PM
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Mcminnville, Or USA
Joined Jul 2009
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I have experienced interference on 2.4 myself. I was flying by myself in a open field. I have flown at this field before with 72 mhz equipment. I would get glitches periodically with 72mhz.
So I thought 2.4 wouldn't have the same problem. I was wrong as soon as I went up I started getting random short glitches.
I packed up and haven't been back to this location since. And I haven't had any glitches since.
I think some locations can be problematic for whatever unknown reason.
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