Spectrum Capacitor mod

[moyesboy]

Two parts to this.

First:
Who has done the capacitor mod, putting a 4700 uF capacitor on the power line to make sure you don't get any brief dips below 3.5v that will cause the receiver to reboot?
I am going to do this myself and solder it in the switch harness, rather than buy the plug in to a spare channel capacitor from spectrum (available from als Hobbies).

Second
Anyone with the relatively new AR9000 receivers should read this:
http://www.horizonhobby.com/Articles...ArticleId=1709
There is a large capacitor inside the case (perhaps doing the job above?) which is not well supported and vibration is making it snap off.

[robgt]

Are you running a regulator and LiPo Gordon?
I'm not sure if this issue can affect a regulated system if 6 volts is being pumped in continuously... but I'd like to know for sure

Cheers,
Rob

[moyesboy]

I'm on a 4 cell nimh sub C pack (My collective servo won't take 6v, neither will the tail - so there isn't much to gain).
My voltspy LEDS flash about when I waggle the sticks, but it is quite sensitive, and the bottom LED is 4.8v (Its only the top three leds that flash). Of course it may not be that responsive, and could be very innaccurate.

We had a large fixed wing go in at our field, running a lipo and regulator with lots of big digital servos. Testing the remains after, they could get the regulator voltage to dip by loading up the control surfaces - ie the regulator was not up to the job. The model had flown successfully quite a lot, but the charge level of the lipo was also under suspicion. The owner is going to go for a larger ampage 6v ragulator I think. This guy lives at our field (retired) with his van load of models. He has over 50% of the our club crashes, but that's because he does 95% of the flying!

A regulator, like a crap trex450 ESC BEC, will have a voltage collapse when it overheats through too much current draw. It may come back slow or quick (or not) but the rx then takes 2-3 seconds to reboot. The lipo should be well up to supplying the current.

I'm going to see what volts and current are coming out of my rx pack using my wattsup by loading up the servos. My raptor is in bits waiting for some bearings anyway. It didn't crash, but it might have on 35Mhz!

[robgt]

I think I'll have a test in a similar way on my 600n - plug a volt meter in to the receiver and give the sticks some grief

It will be interesting to see what happens.
I'm using a 2 in 1 regulator and a Revolution 2S2P 3000 mah 20C pack - not that it needs 20C capability of course
Cheers,
Rob

[jiberjaber]

This is definatly something I was looking into, not so much a problem with my trex as the Jazz BEC has been fine so far - but my worry is with the Raptor as it is on a seperate battery. Has anyone actualy calculated the capacitor value and amount of time it needs to cover the dip for?

[moyesboy]

I already tested my battery setup with the wattmeter here:
http://www.rcheliaddict.co.uk/showthread.php?t=5825
that was before I went spectrum. The aR7000 will draw a little more amps.

[Ashley Davis]

this is why my heli has a Powerforce VRLI2 regulator in it, it can supply 23 servos so my piddly 4 servos shouldn't worry it.

[Fixxxer]

I've done the mod with a glue gun on 2 9ch rx's.

[marktigere1]

this is why my heli has a Powerforce VRLI2 regulator in it, it can supply 23 servos so my piddly 4 servos shouldn't worry it.

Blimey, is it fan cooled as well?

[Ade_Law]

how big is your nimh pack and how discharged was it when you did the test?

Ade

[Ashley Davis]

Blimey, is it fan cooled as well?

yep, bloody great big one on top of my heli

[moyesboy]

so Aide, Rob, these are my results.

The 4300 Vapextech NuMh pack has done three flights yesterday plus this messing about and has not been recharged.
It is showing 5.1-5.0v on the voltspy and 5.06 on the wattsup and at rest with everything connected, when it draws 200-250mA (variation from tail servo and gyro)

waggling everything (including the gyro which is loose and results in faster movement of the tail servo than moving the stick) will pull up to 1.09A and pulls the wattsup down to 4.8v, and makes the red bottom light on the voltspy (4.6v) flicker.

Loading everything up I can get the amps up to 2.0, but I've run out of hands to load all the servos. Then the volts can get down to 4.7.

But the capacitor (4700uF) doesn't make a lot of differnce, I thought it might make the flickery voltspy less flickery. I thought it might produce a discernable delay as the power switch is switched off, but it didn't.

Maybe I need to do some sums to see how long 4700uf takes to discharge at 250mA!

anyhow it doesn't look like thereis a risk of my system gwetting near 4.0V under load, so I'll just continue to top up the flight pack regularly.

[trvo]

Anyone with the relatively new AR9000 receivers should read this:
http://www.horizonhobby.com/Articles...ArticleId=1709
There is a large capacitor inside the case (perhaps doing the job above?) which is not well supported and vibration is making it snap off.

I didnt know about this problem till it was too late, caused my 600n to deck itself, not a happy chappy

Trev

[robgt]

but I've run out of hands

I hate it when that happens
Thanks for the update Gordon!

Trev, did you not see this a couple of weeks back?


Cheers,
Rob

[trvo]

It happened to me about 3-4 weeks back before this post was started...

Trev