Spektrum receiver voltage cutoffs

[Quax]

Hello flyers,

I recently lost a model out of straight and level flight with medium speed.

I first thought I had a signal problem or did a mistake while flying level. But, I was lucky and got the spare parts of the totally destroyed model from my local hobby store for free (they had the parts and could not sell them anymore - thanks again). So I was able to do some testing with the stock setup that led to the crash.

I was able to confirm that when quickly moving several rudders (elevator and aileron only) the receiver, in this case an Spektrum AR7350, cuts off after about 25 seconds and fails to initialize again afterwards. Of course, I did check all servos for free movement and also checked the servo wires. Obviously the BEC rating is not good enough but I could not confirm that with telemetry (voltage stays around 5V), so it must be short spikes leading to the cutoff. I will confirm that with some more measurements.

When adding a capacitor or using an external BEC everything works normal as far as I could test this until now.

Therefore I contacted the Horizon Hobby support. First they were quite interested in the info but then declared that this could not happen to one of their receivers and also stated that this wouldn't be a warranty case (however, I did not ask for replacement) as I had bought the receiver from second-hand in their opinion (which is not the case).

Despite I am totally unhappy about how Horizon treats feedback of their customers, I do not want to blame them (I was quite happy with their products in the last year) but wanted to share my experience with that receiver and that extra actions should be taken when using such a receiver in stock model setups.

Best regards

[Valkpilot]

Hello flyers,

I recently lost a model out of straight and level flight with medium speed.

I first thought I had a signal problem or did a mistake while flying level. But, I was lucky and got the spare parts of the totally destroyed model from my local hobby store for free (they had the parts and could not sell them anymore - thanks again). So I was able to do some testing with the stock setup that led to the crash.

I was able to confirm that when quickly moving several rudders (elevator and aileron only) the receiver, in this case an Spektrum AR7350, cuts off after about 25 seconds and fails to initialize again afterwards. Of course, I did check all servos for free movement and also checked the servo wires. Obviously the BEC rating is not good enough but I could not confirm that with telemetry (voltage stays around 5V), so it must be short spikes leading to the cutoff. I will confirm that with some more measurements.

When adding a capacitor or using an external BEC everything works normal as far as I could test this until now.

Therefore I contacted the Horizon Hobby support. First they were quite interested in the info but then declared that this could not happen to one of their receivers and also stated that this wouldn't be a warranty case (however, I did not ask for replacement) as I had bought the receiver from second-hand in their opinion (which is not the case).

Despite I am totally unhappy about how Horizon treats feedback of their customers, I do not want to blame them (I was quite happy with their products in the last year) but wanted to share my experience with that receiver and that extra actions should be taken when using such a receiver in stock model setups.

Best regards

Right now I'm going round and round with them over one of the products of their Tower subsidiary. And then they made the mistake of asking me to review the product. I gave a review, based on my experience, and they rejected it. As for the RX, my personal opinion is that AS3X is great for UMX aircraft, but not for anything larger. And they keep on linking it and SAFE, and I've had nothing but trouble with those models. I'm currently looking at the HobbyZone Scout, since it's similar to my Esky Eagle, but since they only offer RTF and BNF, if I get the BNF I WILL replace the RX.

[Quax]

I am thinking of leaving Spektrum entirely and switching to Jeti. I had a pretty long email "conversation" with them but that was not helpful at all. In fact they just told me it could not be caused by their receiver and to get the receiver out of the model and test without any connection to any rudder (so basically without any resistance on the servos). Of course, this is not even close a valid test for an inflight situation.

[RLZ]

I've been using Spectrum equipment for over 9 years. If the voltage falls below 4.8 volts the receiver will brown out. Spectrums receivers and servos will work flawlessly at 5 - 6 volts. Most of their Receivers and Servos will operate at 7.2 volts. ( 2 cell LiPo or LiFe)

[tab28682]

I've been using Spectrum equipment for over 9 years. If the voltage falls below 4.8 volts the receiver will brown out. Spectrums receivers and servos will work flawlessly at 5 - 6 volts. Most of their Receivers and Servos will operate at 7.2 volts. ( 2 cell LiPo or LiFe)

That is actually inaccurate. Current Spektrum RX designs work down to 3.5 volts.

Link to Spektrum AR620 RX manual. Works at 3.5 volts.

https://www.horizonhobby.com/pdf/SPMAR620-Manual-EN.pdf

The older AR8000 RX also works down to 3.5 volts:

https://www.spektrumrc.com/ProdInfo/Files/SPMAR8000-Manual.pdf

And the AR7350 under discussion also works down to 3.5 volts.

https://www.spektrumrc.com/ProdInfo/Files/SPMAR8000-Manual.pdf

Basically, the RX is still working when the voltage is basically too low for the servos to move any more (moot point, but the truth). I have a feeling that this is what the customer service people were trying to express. Highly unlikely to be a RX issue. It is highly likely to be a power issue.

I actually fly some very lightweight gliders with the radio powered with a single lipo cell of 4.2 volts on AR400 RX units and and similar RX units. I have found that the RX and servos are still working well at 3.8 volts, after a number of short flights without recharging. (The servos are starting to slow down just a touch at that voltage)

However, in general, it is best to have radio power that always delivers at least 5 volts, regardless of how many servos are in use on the aircraft.

[Quax]

Sorry, I did not see the latest replies to this post.

To cut a long story short: I was able to reproduce a receiver cutout by simply moving ailerons and elevators continuously for about 20 seconds. Given that there could be a voltage spike the Spektrum manual states that a receiver will rebind within about 1.5 seconds (if I remember correctly). However, it does not and stays in booting mode - this is what makes me angry. I could accept that my power supply wasn't properly sized (stock setup of the model). I checked the voltage readings and there were some changes +/- 0.1V on the receiver so the spike must have been very short. So clearly a quality problem at Spektrum where receivers do not recover and small voltage drops can cause problems.

However, I did switch to Jeti and I am totally happy now.

[Alan 3D]

That is how I got my spektrum equipment for free at the beginning. I was reluctant to try it because of the problems that some spektrum RC pilots specifically electric planes were having but I tried it and yes I had issues too but I learned from those issues and I solved them.

The link below talks more about radio interference which is usually the least amount of problems that RC pilots have with any system. If you check my posts from Alan 3D, the second or third post explains how I learned about brownouts and loss of control which is the result of poor receiver power from bec/esc to the receiver. Planes using receiver batteries did not have that problem. Quads don't have servos to Brownout the receiver in most cases so it's not a problem for them.

https://www.hobbysquawk.com/forum/el...oss-of-control