Spectrum reset?

[mattie-lodge]

Hi,

I've been doing a few tests on my AR7000 rx as there is growing concerns of these spectrum resets. Today I received my DCUP from the very very trusty Andy at Real Raptors <plug plug>. Whist this is fitted to my model it will make me feel better of any impending voltage drops whist flying. However there has been talk about the spectrum reset time being around three seconds. I can't get it no way near this. If I turn my rx off with the DCUP in or out it takes about 1/4 second to come back on line when the power is reapplied. This happens ever time. Actually the DCUP keeps it fully functioning for about 2sec after power down.

I'm I missing anything here?

If power fails to these rx I can only see a momentary pause of around 1/4 second before you would regain control. Pretty much like a conventional 35mHz rx, maybe a slight pause.

Now this leads me to my next concern. I've only heard of these rx failures or power failures within the last couple of weeks. Whist we have had this real cold spell of weather. What about LiPo failure?

Interested in your views

Cheers

Matt

[raptorheli2]

yes you are missing something, with the dcup you will, in theory, never get a reset as the voltage won't get that low in first place as the dcup will top it up should the bec crap out briefly. my own dx7 when it loses the signal takes maybe 2-3 seconds to come back.

cheers

[mattie-lodge]

As I said the rx only takes 1/4 to reset with it in or out

[raptorheli2]

mines takes far longer than the 1/4 second yours takes. however, even at that, it is 1/4 second more of a glitch than i want. as i said my own reset takes WAY more than 1/4 second.

the main difference is you will likely never get a glitch on 35mhz due to a power problem, you are more likely to see this on spektrum due to low power. the dcup won't prevent a glitch, it will prevent power loss however for a couple of seconds which obviously reduces the chance of the spektrum crapping out.

cheers

[mattie-lodge]

At what voltage does a 35 mHz rx drop out at compared to a spectrum?

Cheers

Matt

[raptorheli2]

i have no idea tbh, i could probably test it if i could be bothered digging out my 14mz, perhaps someone else will know. i've never heard of low voltage on 35mhz cuasing this. infact i have seen a gv1 and a 601 shutdown due to low voltage before the radio went.

cheers

[Ade_Law]

most regs need about 1v more volts going in than going out to function. below this the output voltage will drop at the same rate.

i have just done a test on the knight with bls351s.

measuring the current at the battery,
voltage at input to reg (power pole connector)
voltage at reg
voltage at rx

with ccpm and tail servo stalled its pulling around 9amps OUCH!!
model switched on but doing nothing pulls about 300ma
" " " battery voltage is 8.1v
wiggling ccpm battery voltage drops to 7.8v
ccpm stalled battery voltage drops to 7.1v
voltage at the reg stays at 6v no matter what
voltage at rx drops to around 5.8 when wiggling ccpm servos
voltage at rx drops to 5.6v when CCPM servos stalled.

this is a freshly charged pack hence the 8.1 at rest so when your down at 7.2ish near the end of the charge the onload voltage could well be down near 6v take a volt off that for the drop accross the reg take 0.5v off of that due to the drop accross the rx...

thats 4.5v

add cold weather to that... its gotta be getting close to 4.8

as a bare minimum im going to buy 3 extention leads and solder the reg into the +VE so the CCPM servos get the full volts and rx only sees current for tail (1.3amps) throttle and carb smart (bugger all)

this will gain 0.5v at full load.

i would be interested to know what voltage others are getting out of their regs. Fromeco have a very good reputation for holding their voltage which certainly is justified!

i have been told that the JR900s rx is reged internally to 3.3v which would mean it would need around 4.0v to maintain this.

Ade

[Arky]

very good thread will be following this one, and am thinking of taking the load away from the rx aswell

jason

[mattie-lodge]

Ade,

I've tried my Fromco on a pack which has had three flights on it. I've set the voltage at 5.6v. With the DCUP in, I stalled the servo's as much as I dare and the most it dropped to was 5.4v.

Next question what does everybodies 2s2p lipo read after about three flights with a 1 amp load applied? Tested mine and it reads 7.6volts

Matt

[Ade_Law]

sounds about right matt 8 flights drops it to about 7.3

this is an old and abused 4600 fromeco li-ion

Ade

[Bunter]

Interesting thread this. Should a beginner worry about these transient voltage drops or are they only associated with more extreme flying. Does the DCUP just plug into a spare socket in the RX (bind/battery is spare in my AR6200).

Thanks in advance.

Bill

[Ade_Law]

yes it really is just when your throwing the model around. if somebody has a wattmeter they could put in the battery feed to the reg and get some inflight current/voltage readings it would be cool.

Ade

[mattie-lodge]

Intially I think there will be nothing for a beginner to worry about.

I've elected to fit one to my 90 size heli for redunancey protection due to the higher current draw being a larger model. It's fitted to a spare socket on my reciever.

I'm still skeptical as to the reason why this is happening. Especially at this time of year.

Matt

[Ade_Law]

i think its a combination of factors... the volt drop through the RX the load we are pulling is way higher than these systems were orriginally designed for.

however i think there might be a basic design flaw in how the spectrum RX handles low voltage. It should go to the fail safe position during power up

or are you saying that these lockouts arent low voltage?

Ade

[ChrisB]

I will watch this develop with interest but to date in over a year i have had zero problems using 4.8nicads or now the Align regulators.

I am suspicious of the cold weather playing a part so will keep my onboard Lipos topped up and not consider extra protection for drop outs

If and when i do get a lockout and crash and i suspect it is voltage related i will rethink then,but to sum it up many hundreds of totally trouble free Spektrum flights under my belt

If you are getting servos binding then that needs to be sorted as a separate issue