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Dec 21, 2016, 05:02 PM
Once in a lifetime
danielphantom's Avatar
Discussion

Yellow light on my tattle tale


I recently bought one and tried it out on two planes that I've been flying for the last few months. Ive never had any issues with controllability but hooking up the TT shows that my voltage is dropping below 4v, yellow light.

Both planes are running with lipos, one 3s and the other 5s. I also noticed on the 5s plane that after a few left right aileron deflections, the receiver green light turns orange. I don't usually have visual access to the receiver. It's back in the fuselage.

The 5s plane only has elevons, nose gear servo. Elevons are digital and I don't see any binding.

Any advice?

Thanks,

Daniel
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Dec 21, 2016, 07:27 PM
Xtreme Power Systems
What are you powering the receiver/servos with? You can't be using the Lipos directly because the voltage would be way too high. So you either have a separate receiver pack or you are using a BEC, maybe one built into an ESC?
Dec 21, 2016, 07:34 PM
Once in a lifetime
danielphantom's Avatar
Yes an esc in both cases. One about 70amp the other 18amp.

I'm not sure if there is a bec in the escs. So it might be an esc problem? I picked up a supplemental battery pack from scorpion that I think is designed to be installed along side the lipo. As a backup.
Dec 21, 2016, 08:14 PM
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FlyingW's Avatar
Daniel,

I suspect that your ESC's built-in BECs are not up to the job. Even two servos can require a lot of power. The Tattle-Tale sees what your receiver and servos see and it does not lie.

I recommend installing a good stand-alone BEC like the Castle BEC instead of relying on the ESC's internal BEC.

It is a good thing you checked with the Tattle-Tale - you may have saved your airplanes from a future crash due to insufficient power to the airborne electronics.

After converting to the stand-alone BECs, you can still add the Scorpion backup device for extra insurance.

Good luck,

Paul
Last edited by FlyingW; Dec 21, 2016 at 08:21 PM.
Dec 21, 2016, 08:23 PM
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danielphantom's Avatar
thank you guys--I'll take the corrective action--

Daniel
Dec 22, 2016, 10:54 AM
Xtreme Power Systems
If the plane is large enough, I would use a 2S LiFe pack to power your receiver/servos. Even things like my Habu32 have a separate receiver battery pack. I don't trust BECs at all. We don't make one for a good reason - you can't beat a dedicated battery pack for power.
Jan 07, 2017, 07:55 AM
Once in a lifetime
danielphantom's Avatar
How do I use a 2s LiFe pack that runs 6.6Vdc into my "regular servos, digital or analog" not designed for hi voltage? I know you're not a fan of regulators. Do I need to switch over to hi-voltage servos to be "extra safe?"

Is it as simple as plugging the LiFe pack directly to the receiver and the esc to the receiver?

Would a nimh battery be damaged if I used it instead of the LiFe? The nimh is the right voltage for my servos.

thanks,

Daniel
Jan 07, 2017, 09:40 AM
CRS and CDS Certified
thebluemax's Avatar
Quote:
Originally Posted by danielphantom
How do I use a 2s LiFe pack that runs 6.6Vdc into my "regular servos, digital or analog" not designed for hi voltage? I know you're not a fan of regulators. Do I need to switch over to hi-voltage servos to be "extra safe?"

Is it as simple as plugging the LiFe pack directly to the receiver and the esc to the receiver?

Would a nimh battery be damaged if I used it instead of the LiFe? The nimh is the right voltage for my servos.

thanks,

Daniel

Personally I would replace the servos to handle the 6.6 volts and I have changed all mine out to do so. Sell them and use the money towards the right servos.

Don't use a regulator from the battery to the receiver but I think you probably could use a regulator from the receiver just to the servo itself. If you need a regulator for every servo it could be costly and cheaper to just replace the servos.

I don't think the NiMh would be damaged but it surely does not have enough power for everything and you would be browning out big time. Jim can answer for sure.
Jan 07, 2017, 10:24 AM
Once in a lifetime
danielphantom's Avatar
I was reading somewhere else, that people often times remove the red wire from the esc when they use a second battery to power the receiver/servos.

lm7805 Regulators usually need a greater difference than a couple volts between the source and the load.
Jan 07, 2017, 10:34 AM
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FlyingW's Avatar
Daniel,

Yes, you remove the red (+power) lead from the ESC if you are using another source of power for the receiver and servos. Another source of power can be a battery pack or a stand-alone BEC.

I use LiFe (A123) receiver packs in some of my planes. The servos are rated for 4.8v to 6v. I have often worried that the 6.6v of the A123 pack pushes the servo a little too hard, however, I have not yet any obvious servo burn-outs from the higher voltage. Regrettably, "high-voltage" servos often specify their voltage range from 6v to 7.2v or 8.4v - and that minimum of 6 scares me. I wouldn't want to have a servo reboot if the power dips below 6v.

I wish servo manufacturers would release servos intended for A123 receiver power - with a voltage range from 4.8v to 7v.

Other than the voltage being a little high, the LiFe packs are really good for powering the receiver and servos. They can handle large loads and are lighter than the equivalent NIMH pack.

Paul
Jan 07, 2017, 10:36 AM
CRS and CDS Certified
thebluemax's Avatar
I was using regulators by Radio South before switching everything over to XPS. So I sold them all and I haven't used a regulator in years and have not kept up with them. Anyway see what Jim says. Good luck...

I have been using A123 batteries with analog and digital servos rated for 4.8 to 6 volts since switching to XPS and I have not had any problems with them at all. Knock on wood.....
Jan 07, 2017, 01:03 PM
Xtreme Power Systems
A "6 volt capable" servo is designed to handle a 5 cell Nimh pack. A 5 cell Nimh pack peaks at 1.45v per cell, which is 7.25v. The voltage drops to around 6.5v, but it does start out at well above 7v. So, a 2S A123 is 6.6v and safe.
Jan 22, 2017, 05:29 PM
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danielphantom's Avatar
Well my LiFe pack has arrived, but my hi voltage servos have been delayed. In the meantime, I remembered a 2s lipo backup pack from Scorpion that I received in a lot deal. It has a regulator on it to run the servos and receiver

I put that in on the receiver, removed the red wire from the esc connector and hooked it up--Wallah, no yellow light on the tattletale and my receiver (old school 8-channel) doesn't go to orange during servo actuation.

So when my servos get here, will be changing out the elevon servos and will be in business with the LiFe pack.

I'll probably put that scorpion pack on one of my other planes.

thanks again for the advice,

Daniel
Jan 27, 2017, 09:09 PM
Once in a lifetime
danielphantom's Avatar
Have everything installed as of last night--kst hv servos, and my trusty LiFe pack along with my tattletale. We took to the blue sky today and it was a complete success. No issues with voltage drop, and I like the fact that i can test out programming/servo movement with just the receiver pack--no worries about the prop jumping to life.

Daniel
Jan 27, 2017, 10:15 PM
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FlyingW's Avatar
Glad you had a successful flying session Dan. Yes, being able to turn on the radio without yet plugging in the motor battery just feels safer. After the airborne electronics check out ok, plug in the motor battery and go. Writing about it here makes me want to go flying. Paul