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HelicopterMain Discussion › Servo Max Current Draw and Torque
12-04-2005 09:17 PM  12 years agoPost 1
ESWLFSE

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Liberty Hill, TX

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An interesting question came up in this thread here. So I picked up a Watts Up on Al Magaloff's recommendation and added some connectors and pigtails to measure servo load.

At 5.66 V I almost stalled a Futaba 9202 and a 9252. The 9202 peaked at .26A and the 9252 pulled 1.21A.

Now I'd like to do a full throttle climb-out with this meter on my 9252 to see how close it actually gets to those numbers.

Or someone could measure servo X on collective during hard 3D on a 90 and get a peak value. Then reproduce that value at home with weights and a lever so we can actually determine what kind of a load hard 3D collective inputs actually impose on a servo.

I wonder if we actually need as much torque as we sometimes have or not. Maybe a 9252 is plenty for anything and more servo is a waste of money.

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12-05-2005 12:38 AM  12 years agoPost 2
Al Magaloff

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Ray Stacy and I hooked some servos, and Gyro together with receiver, on the bench, with our WattsUps. We pulled some pretty high numbers. You can easily see why the Futaba gyros re-set in flight. I really couldn't answer the torque question, but I think the DuraLite battery regulator set-up puts a lot of cushion in the equation.

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12-05-2005 12:48 AM  12 years agoPost 3
wolfdad

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Southern Maryland

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Al,
Do you happen to remember or, by any chance, did you record those numbers. I would be very interested in hearing what they were. I also wonder what factor you might add in for inflight loading on the servos....or, at maximum torque, what the current draw is/was.

wolfdad sends...

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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12-05-2005 01:09 AM  12 years agoPost 4
Al Magaloff

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I think we saw over 2amps at the spike, no stalling, but don't quote me on this. These are the things we should be doing this winter. Testing, evaluating, etc. After the "testing" Ray and I agreed that we were moving beyond our current NiCads. The flight loads are another question we need to answer. A nice feature in the WattsUp, is that it records the spikes. You place it between the receiver and battery, and go fly.

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12-05-2005 02:35 AM  12 years agoPost 5
wolfdad

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Southern Maryland

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Al,
And, you know what really sucks buttermilk??? Immediately after reading this thread, I drifted over to Heliproz, looked up the Watt's Up and, they are out of stock....I would wager for good. The item description mentioned they were on close-out, so I guess that's the end of that, unless you know of somewhere else that has them.

This is an extremely important side of the hobby that either hasn't been touched on much or hasn't gotten much publicity to my knowledge, other than a spike in the noise level like we saw with the 401 resets.

I would also concur with the opinion that says our helicopter electrical demands are out-pacing the capacities of both Nicd and Nimh batteries. The LiPo's are probably going to be the long-term solution, however we have a long way to go in our understanding and handling of these batteries. So, I guess the way to go is to test and document the electrical demands, then try to "stay within bounds" with equipment to battery matching.

wolfdad sends....

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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12-05-2005 03:00 AM  12 years agoPost 6
Al Magaloff

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There is another unit made, similar to the WattsUp, that I saw at the LHS. I don't remember the manufacturer.

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12-05-2005 03:53 AM  12 years agoPost 7
ESWLFSE

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Liberty Hill, TX

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Well I'd like to say where I bought mine, but I better not. It came in the second and last order I'll ever place with them after reading some reviews here. If you dare risk placing an order with them they may send you one if they have some left.

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12-05-2005 06:30 AM  12 years agoPost 8
Ace Dude

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USA

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Take a look at the Medusa Research watt meters. I have one and I'm quite happy with it. I have a Power Analyzer Pro and I'm quite happy with it. And, they're made in the USA!


http://www.medusaresearch.com/

http://www.medusaproducts.com/Other...ers/PA-Main.htm

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12-05-2005 10:11 AM  12 years agoPost 9
wolfdad

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Southern Maryland

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The MedUSA products appear to be good products and the watt meter/power analyzer looks the same as the Watt's Up...that is, until you slide all the way to the right and see the price WOW! Quite a jump from the $29.95 price tag at Heliproz. In all fairness, MedUSA is marketing an entire data-capture system and that might not be a bad deal.

wolfdad sends...

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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12-05-2005 03:29 PM  12 years agoPost 10
Ace Dude

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USA

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Yes, the Medusa has a genuine USB interface (not an RS-232 converter) and upgradeable firmware so it's probably fair to say the the Medusa and Watt's Up really aren't in the same league.

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12-06-2005 12:24 AM  12 years agoPost 11
neophyte

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California

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A low tech (but very informative) tool is an Amp meter from any electronics store or Radioshack. Just hook up the Amp meter using a servo wire extension.

Plug it in to an individual servo that you may want to measure, or plug it in between your battery and switch to find total system draw.

The analog Amp meter will let you see all spikes, even the spike the gyro makes when it initializes, their duration and intensity. Also the Amp meter does not cost an arm and a leg.

Works for me. Ron

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12-06-2005 12:30 AM  12 years agoPost 12
Al Magaloff

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Ron, the WattsUp records the spikes during the flight. It's current draw under flight load I'm worried about. I never crashed a heli that was sitting on the bench!

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12-06-2005 12:59 AM  12 years agoPost 13
Ace Dude

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USA

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Al, correct me if I'm wrong, but the Watt's Up only measures average and max values for certain functions.

Now, if you want to see how long those spikes last and how many occur, you'll need a recording device.

The Medusa Pro Model does have a recording module.

However, this looks like it would a bit more suitable for in-flight measurements because of its size and capabilities.

http://www.bnbproducts.com/

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12-06-2005 01:02 AM  12 years agoPost 14
Ace Dude

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USA

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Here's a thread on the DPR.

I may have to order one myself....

http://www.rcgroups.com/forums/showthread.php?t=375953

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12-06-2005 01:02 AM  12 years agoPost 15
Al Magaloff

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Ace, you're correct. The Medusa looks like a very, versatile and usefull tool.

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