AR7000 up to 9v

[moyesboy]

Given that the AR7000 (spectrum) rx is liable to reboot if its input voltage dips too far - it would seem useful to take advantage of its capability of running up to 9v.

So it can run directly off a 2 cell lipo. (7.4v nominal, 8.4v max).

I propose to isoltate the power to the servos etc and run them off a regulator, but run the receiver directly from the cell lipo.

Does anyone have experience of running the reciver at this higher voltage? Because when you get close to the limits of manufactureres specs you often find they exaggerated a little and things can blow up!

[flatspins]

You don`t need to run the Rx at that high voltage and regulate it afterwards.

Just use the regulator before the Rx as it will maintain the voltage, and will certainly be a lot easier to do than regulating each servo after the Rx

[Bubblefish777]

Actually, I always make the assumption that a manufacturer tends to understate performance... so if they say 'X' volts they tend to make it 'X' + 15-20%. electrical components tend to be like this as anything <5% tolerance winds the price up. Also it means that if they do get electrical failure they don't get warranty claims as they can be sure you're running at 10v+
I think you'll be safe at 9V to be honest IF that's what the tolerance claim is ...

[moyesboy]

Flatspins:
whgat I'm worries about is my digital servos drawing over 6A due to stalling etc and pullin gthe regulator voltage down below the reboot trigger of the Rx.
I would separate the power wires on the servos etc and add an extra plug so each servo has a plug with the + and - on and a plug with only the signal. all the signal wires go in the rx, all the power wires go into a common power rail connected to the regulator.
with the rx power independent of the servo power the rx isn't supject to the instataneous dips in voltage due to the momentary high curent demands of digital servos - or one of them demanding 3A+ because it stalled.
(see ashleys account of his 600e crash).


Bubblefish
With model electronics I think you will be tempting fate assuming there is headroom in the electronics specs. If you run a 30A ESC at 30A then it will blow after a short while - you need 20-30% headroom above what your wattmeter reads if you want a reliable installation. I would not trust any R/C model electronics to have any "headroom" in the spec as many of them are exaggerating the performance ("30C" lipos for example ).

[Bubblefish777]

MoyesBoy.... I bow to your experience in this arena. I was going on purely what I knew from my days in the R.N.

[moyesboy]

My only personal experience (so far, touch wood) was that my align 25A ESC could not manage to hold 2800 rpm on my x400 spnning 290mm zoom 400 blades (in the hover - the current was a lot less than 25A). It went into slow shutdown.
The claimed rating of align ESC is more like the peak rating. I replaced that with a Quark 33A that is rated at a true 33A continuous and 55A max short duration.

Generally the better quality stuff they are less likely to be lying about the ratng.
However in regard of the voltage rating of the AR7000, I would be suprised if they said 9v and it were not true, because the spectrum stuff does seem to be good quality and what would be the point of saying 9v if that were not what it would take?
Some day soon we will all get servos etc that run on 2 cell lipos directly, which no doubt is the reason for the 9v rating on this receiver. We need more power than can be supplied through the wiring and plugs we use and the most cost effective and weight efficient solution is to run all the rx system on a higher voltage such as directly off a 7.4v lipo.

[robgt]

We need more power than can be supplied through the wiring and plugs we use and the most cost effective and weight efficient solution is to run all the rx system on a higher voltage such as directly off a 7.4v lipo.

Agreed - just make sure the servos (and other electronics being used) can handle the voltage

No good trying to run a 4.8v servo on 7.2 volts
Cheers,
Rob

[moyesboy]

I thought I said that Rob!

Some day soon we will all get servos etc that run on 2 cell lipos directly

[robgt]

Yes, you did
I'm thinking in terms of what's available today, being that this is being discussed today
You never know - someone out there might think this is a great idea, and then go try it on their raptor powered with 3152 servos

Cheers,
Rob

[moyesboy]

I met a guy who was wondering why his mini pred weasn't working. He though the problam was ESC BEC and he found that the Tx pack from his spare walkera had the right plug on it to fit straight into the receiver...(12+v into the receiver,servos,gyro etc.)
After that nothing was working...

Hopefully the techno-babble in this post is enough to discourage anyone who doesn't know enough about electrics from undue experimentation!

[robgt]

You've heard the saying, a little information is deadly

LOL
Cheers,
Rob

[SRH990]

Spektrum have servos in testing (Alan Szabo and others I think) that will run direct from a 2 cell lipo pack so you only need a regulator for the tail servo, they're supposed to be very fast & high torque too, the way of the future