T-Rex 500 Info

[robgt]

The receiver isn't really at fault though - it is being supplied too low voltage and the reset occures because of that - cure the failing part upstream (BEC) and it becomes a non-issue... hopefully

Cheers,
Rob

[barney]

Speaking of the low voltage re-sets Paul. My DC-Up has picked it up twice now..one was 3.5v the other 3.3v.

Both instances of this have occured whilst running the 4200 packs..I think you were possibly on the 42 as well???? These packs are definitly packing a bigger punch than the smaller packs + the heli is pulling a bit of weight. The 42 does have a noticably higher headspeed than any other packs we have tried to date.

Could it be the BEC is struggling to cope with the oommpphhh these big packs are capable of and shutting down?.

How long does a BEC/Speed take to re-set? as we know the DC-up holds a residual V to run the heli for a few seconds by itself.

cheers

[Ashley Davis]

The BEC is a separate component to the speed control part. As you load the pack the voltage of the pack reduces and the job of the BEC gets EASIER not harder.
The BEC has it's hardest time when the pack is sat at full voltage waiting for you to spool up as it has to step down a much higher voltage.

[Ashley Davis]

It's possible the ESC is overheating and for some reason the BEC is cutting out as a result.....but that's all I've come up with so far as to a possible reason.

[raptorheli2]

barney, i can't mind tbh what packs it was. if it was when you flew it that was with the 4200's. but i can't remember to be honest.

i can't see bigger batteries causing this but i'll tell you this, if you seen 3.3v on your dcup that is VERY worrying and your VERY lucky. the spektrum shutsdown at 3.4v on mine.

i wonder if the dcup is measuring the voltage when it's switched on and thats going to be lower while it charges up???

that said i have not seen less than 4.9v other than this once. perhaps the bigger packs are all but stalling the servos at times?? i dunno lads, guessing here but something is amiss.

cheers

p.s i got a 15t pinion coming, found one in usa. it shipped yesterday.

[LipolyGone]

the reset problems are probably a lot less likely to happen than a glitch with 35mhz, i wouldn't let that alone stop you from changing. i wouldn't fly ANY and i mean ANY electric heli on 35mhz anymore.

cheers

I think to get a heli glitching so bad that it would cause it to crash as has the BEC done in Ash's case you may have to pair that BEC up with an equaly dodgy component made by Align, an Align RX
Why not go the whole hog & put expensive Align servos in it as well, I hear they are very good also

Align do not make good electronics, end of!
Their Speed controllers have been known to leak magic smoke.
Their RX's are just plain nasty.
And they make Motors that fall apart.

I've yet to ever have any problems that I couldnt sort out on my electric helis, & I mean, EVER
But then again I only use a top spec TX & RX setup on them.
The Rx is always a Shultz 835 S or W & my trusty very high powered Multiplex Royal Evo Nine Synthed Transmitter.
You cant go wrong in electrics with those two paired together & a senceable layout of the components.
Martin

[barney]

Heres a pic of the Revo 3200 Install to get the Canopy to fit properly..It is very very tight. Placement has to be within a couple MM's or the canopy will not fit. You can only use a small bit of velcro on the battery, It's that close.

Unfortunately they wont fit between the frames widthways like the 4200's or when doubled on edge either.

It would be easy enough to move the canopy posts forward about 1/2" and extend the lower tray allowing for more space which will let you have the packs doubled properly as in the above configuration it is a tad nose heavy.

Another option which I really don't see a problem with is to have the battery doubled (or very close to that) for C&G reasons on the upper tray.
Use the current Canopy posts but just use the battery nose end to locate the front of the canopy as the cells are long and flat fit snuggly into the nose of the canopy. Like this It sits about 1/4" above the retaining slot and is certainly not going anywhere in a hurry

[raptorheli2]

martin, my own experience is 35mhz can and does glitch in electric models even using a sep power source. my old x400 glitched no matter what i did, esc bec, sep bec, sep rx pack etc. i wouldn't chance it if i had option, which i do.

others might find it ok but i'll stick to 2.4 for now.

i'm just going to move the canopy posts a little, solve this prob nicely.

cheers

[Ashley Davis]

I'm wondering if the 3.5 and 3.3V measured on DCUP is slightly unsuccessful connections trying to plug in the deans. Really we should be holding the button in on the DCUP after connection and then flying. That way we get a true reading rather than a power up reading.

[Edders]

yep I noticed this I was getting low voltage before the flight and realised it was due to a dodgy dean connector which meant for a second the dcup was running the heli (during initial switch on) once I realised this I removed the DCUP until the deans where plugged in then plugged the DCUp in and went and flew voltage was set to 5.5v for initial testing and the lowest it went was 5.3v which is still not perfect but my fromeco Arizona reg and battery running at 6v on the 600n would drop to 5.8v during a hard 3d flight with a DCUP fitted will be doing some more testing soon without the DCUP to see what the “real” lowest voltage it could be….

Edders

[moyesboy]

Two things effect the loading of the BEC.
The voltage in (more power to dissipate in the steppng down of voltage)
The current drawn out (more current when the servos are loaded harder).

If the big pack is holding a higher head speed through a heavy manoevre when the servos are moving fast and loaded hard, then the BEC will be at its most heavily loaded then. The effect of the extra current into the servos probably outweighs the drop in input volts.

With a weedy pack the input volts would drop, the head speed would drop, the load on the servos will get less as a result and the BEC wold have it easier.
So a bigger better pack will load the BEC more - but at the same time the adjacent ESC will get hotter too.

If the BEC is browning out for long enough the DC up will eventually run out of juice.
Better to decouple the power to the Rx from the servos and run a separate BEC like a medusa for only the rx, or a little 2 cell lipo or nicad. The current for the rx only is tiny -30mA or so so - a little indoor rx pack would do it for 10 hours.

It would be nice if there was a commercially available unit for doing that, or if the rx was constructed so the power to the rx wasn't ganged with the servos.

Alternatively, Just doing away with the BEC and running the rx and servos of an AA 4.8v pack might be more reliable, cheaper and there is plenty of time to top it up while the flight packs are charging. The servos shouldn't pull that down below 4 volts for a few flights.

[F.arch]

2.4 and waiting

Out of interest, is anyone flying the 500 on 35MHz ?

Hearing about these reset problems with the Spektrum receivers doesn't really make me want to switch over just yet.

Cheers

Kevin

Reading this lot 2.4 has got a little way to go before I change! I'm with RCslopesurfer Multiplex Evo 9 synth and a multiplex PPM synth receiver. Never had a glitch on my electric heli nor anything else.
I admirer all you guys for doing someone else’s research & development.
I’m going wait until all the pioneering is over, give it a another 6 months and I’ll buy a 500.

[Ashley Davis]

If the big pack is holding a higher head speed through a heavy manoevre when the servos are moving fast and loaded hard, then the BEC will be at its most heavily loaded then. The effect of the extra current into the servos probably outweighs the drop in input volts.

Differences in current drawn would be really minimal though, we have tried stalling all the servos totally on the heli and the current drawn is not very large compared to the output ability of the ESC BEC. Certainly 9650s draw very little current in comparison to what a big standard digital is capable of pulling.

[Ashley Davis]

Reading this lot 2.4 has got a little way to go before I change!

This has got nothing to do with 2.4 at all. I can assure you that if the ESC BEC cutout you would also crash on 35mhz.....period.
The issue here is the ESC BEC not providing voltage to the rx, which is not the rx's fault at all.

[barney]

Good Call Edders..I think you may well have a reasonable explanation for the low DC-UP readings as it does seem more common than we thought.

As the DC-UP is still live after initial connection and you un-plugged it briefly and re-plugged, It may well give a false reading..