|Oct 24, 2010, 10:54 AM|
Joined Oct 2009
How much current can flow through my Ar700?
Need some expert advice please. Can't seem to find any answers in this blog.
Here is my case.
I have just ordered an 88 inch Yak54 which will be powered by a 6000W brushless motor, a 120 Amp Esc and hence separate 12s Lipo battery.
I intend to install a dual Ubec (2x8 Amp) with two Lipos to provide power for my receiver (Spektrum AR700) and to the servos.
The plane requires 5 high power servos and I intend to install 5 Power HD, HD-9110MG (10.5 kg at 6 Volts).
My problem is that I am unsure if I can put all the current that is required by the servos and the receiver directly through the AR700. Do I risk buning up the circuits?
There are different opinions at my club and I cannot decide whether or not it is necessary to separate power to the receiver from power to the servos.
Can anyone please provide some expert insight.
Many thanks in advance
|Oct 24, 2010, 12:55 PM|
I would assume the common rail on the receiver is dimensioned to handle full current drawn through each connector, so I tried to find the max amp rating for servo-type connectors, but had no luck.
Here is a product that is meant for high-current use, which shows that it may be a problem (why else make this special one, well maybe except to get more money ): http://www.spektrumrc.com/Products/D...odID=SPMAR9100
Here is a post I found that references your question: http://www.rcuniverse.com/forum/m_92...tm.htm#9267260
Maybe try to send that guy a mail!
|Oct 25, 2010, 10:22 AM|
Well that would be what is normally referred to as a 50cc size bird and there are GS guys who use the AR-7000 rx. I use the JR R-921 in my 50cc size bird and the power buss on that rx (same as the Spektrum AR-9000 bye the way) can take a continous 35 amps so that's not an issue. Like you, I've not been able to track down a specific amperage rating for the AR-7000 rx's so I can't tell you what that might be but the bigger issue is the servo connector power input.
I'd say a dual current path is mandatory as those little connectors won't take a lot of current. High quality 20g wire leads with gold plated pins can handle 4 amps and only get slightly warm, depending on whose research you believe they can spike to between 6 and 8 amps. Lower quality leads without the gold plated pins can only be expected to take about 3 amps.
For purposes of trying to figure out the approximate current load, you can use a rule of thumb which says that every 100 oz. of servo torque requires 1 amp of current and if you check the servo specs that is usually pretty close. Sorry but you'll have to do the SAE/Metric conversion on those torque ratings.
Whether or not you should separate the servo power from the rx as opposed to running everything through the rx is the subject of much debate and has a lot to do with the size of the model. In general, most folks running gas engines don't think there is any reason to use a PE on a 50cc size bird so you're 'gonna have to take what you've learned and make a decision as I doubt you'll get a concensus of opinion....
Hope that helps?
|Oct 25, 2010, 10:59 AM|
OK, I'll throw my 2 cents in.
As Zeeb mentioned, as long as you split the current input to the receiver, with a dual feed, as us gas/glow types do with dual battery and switch setups, you should be fine.
I know of no 50cc class planes in our area using any type of power expanders, and at our field, we do have one 50cc powered model using an AR7000 and 5 very high torque servos, plus the throttle servo you don't have to deal with.
If you do feel the need to isolate the current from receivers power bus. Servo City makes a very simple and cost effective power expander setup that has heavy duty inputs for the power input.
Best of luck,
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