Western Robotics BEC noise?

[BruceW]

Went range testing my RX today and yesterday and noticed it was severely cut down when using the WR 5A BEC. With just a battery, the JR R790 (FM, no 2.4GHz yet) was able to go more than a 1/4 mile (walked to end of street) but with the BEC I could only get about 50-75 yards!!!

Has anybody else experienced this with an FM system and what did you do? I put ferrite ring on the line to the RX and got a little more range but I'm still perplexed and nervous.

[BruceW]

Looks like I'm not the only person with this problem...

http://www.helifreak.com/showthread.php?p=427819&postcount=16

I put more wraps on the ring last night and will try this again today. Is it possible I got a bum BEC?

[BruceW]

Tried it again with many wraps on the ferrite ring and still only 50 yards. :bawl Looks like I'll be looking for a new BEC or flying with a battery since I'm not changing my PCM radio.

[zguy]

Bruce,
Maybe try calling WR and see what they have to say about it? I'm using it w/ 2.4 GHz and have not had an issue, but would be curious to hear what they think.

[alvinchai]

Bruce, I will talk to WR about your issues and get back to you asap.

Alvin

[BruceW]

alvinchai, thanks for offering to pass on the issue. I sent an email today and got a reply asking for my rx type but haven't heard back since then.

Other things I've done since then:
1. Moved BEC as far away (25cm) from rx as possible (added an extension) with several wraps on a ferrite ring and no change.

2. Switched to 5V and no change.

3. Tomorrow I'll put it on an oscilloscope and check the signal. I'm guessing there is a lot of noise. Maybe I'll check the caps but I don't want to take anything apart and void the warranty at this stage.

This is starting to look like a voltage problem more than RF interference since my range is still limited to the same distance even with the BEC moved farther away. I would have expected a 1/r^2 affect if this was an interference problem.

Also, I ordered a CC BEC but found out that you need the Castle link USB kit to change the voltage from the default of 5.1V up to 6V. When it rains it pours.:Slap

[3secondsToImpact]

I found that the mosfet on the WR bec was getting extremely hot just testing servo throws.
I may have got a defective 1 though, but try it yourself.

[BruceW]

Just put the BEC on the scope and the signal is very clean at both 5V and 6V. Now I'm back to thinking this is an RF problem so I'll build an antenna and put that on the scope and see if it can detect a signal.

After that, I'll switch to the R790 from my T450.

[BruceW]

Sorry for the constant bumps but I found the problem.

It looks like the BEC is generating a 0.2V AC spikes (ringing) on top of the 6V line in sync with the servos when they are moving (even have a ferrite ring). The ringing is about 10ms in length. I also ran the rx with a battery and placed the powered up BEC next to it and there was no RF noise causing interference. At this point it looks like the BEC is bad and cannot handle any load. Could be a bad capacitor or MOSFET.

Sent an email to WR and will wait for a response.

[zguy]

Thanks for the updates Bruce!
Please keep us posted as anyone using this product should be aware of a potential problem.

[alvinchai]

Hi Bruce, WR told me they spoke to you and everything is sorted :) Good to hear

Apparently the Hercules 5A BEC will cause range problems with some 72MHz receivers, WR is currently aware of this and is working on a solution. Right now they recommend using the 5A BEC with 2.4GHz only until they work out a solution.

Also just a heads up on guys running two Hercules 5A BEC in parallel, make sure to power both BEC at the same time and make sure both units are set to the same voltage (5V/6V) or the BEC will go up in smoke :smokin:

Alvin

[zguy]

Interesting. Can you explain in more detail what is happening?

[BruceW]

Hi alvinchai,

Yes, I had a few emails with them today about the situation and as you stated, they mentioned there seems to be a problem using the 5A BEC with FM radios and they recommend 2.4GHz only. The solution they proposed is to to take two 3A and hook them in parallel which I will do. There is another 5A BEC coming in from from where I purchased the original as an RMA exchange so I want to run it and see if the situation is the same.

Today when I put the BEC on the scope I could see lots of AC ringing on the leading edge of the pull down signal generated from the servo (yes, on the DC line supply to the Rx). When I ran on battery, the pull down from the servo is a clean square notch . I also compared this to the BEC on the Jazz 80 (4A @ 4.9V) which was fairly clean but I need to go back and do more measurements for accuracy. Also I could see the high frequency AC signal generated from the switching but didn't look at the time division (guessing around 20kHz but will remeasure tomorrow) since I was in a hurry at the end of the day.

More to come...

Overall, WR tech support is very responsive and seems to right on top of things.

EDIT - I will be using the BEC on my Jazz 80 in the meantime even though its rated at 5V.

[zguy]

I'm happy to hear that WR is being responsive.

Still would like to know how this is effecting 72mhz and why 2.4ghz is OK?

[Klinger]

Also had similar problems with 36 mhz and gave up trying to fix it. Went to a duralite setup and this fixed everything. I think their suggesting of running two in parallel is a poor solution. If they have known issues with certain systems they should make it clear on there site instead of saying these things are the best bec around! Never WR again for me!

[alvinchai]

In WR's defence, they only just found out about this issue with certain FM/PCM receivers and are working on a solution. The website has already been updated recommending the 5A BEC for use with 2.4GHz only. This problem is only with the 5A BEC, the 3A and HV BECs does not cause any problems.

The paralleling of two 3A BECs is just a temporary solution if you want to continue running 5A with FM/PCM receivers.

[BruceW]

I got the second WR 5A BEC in today and it has the same issue as the first so it looks like I will be switching over to running the 3A version in parallel. In the meantime, the BEC on the Jazz 80 is working fine but I might try out the CC BEC temporarily.