Is there an easy way to test the power draw of your servos?

[Show871]

I was wondering if there was a simple way to test the power draw of each individual servo on your plane? I have a new 35%, and it seems to be using up alot of battery. I set up my plane with arms to use the full travel of my servos to get maximum resolution....also on my T servo. I have a simple power s/u, a ar9100 with two 2300 A123, and a pin flag switch in replacement of the soft switch. I guess I just wanted to confirm I did not have a servo problem in any way, sucking up power. THANKS! 871

[dmichael]

I use this:

http://www.hangar-9.com/Products/Def...?ProdID=HAN172

[1bwana1]

The best way I know is to put a digital volt meter between the RX and the servo. This will show how much each servo is drawing, and will let you know if you have a binding problem. This is especially useful on surfaces with multiple servos. Here is a Link to the one I use.

http://www.airwildpilotshop.com/more...uct&sku=HAN172

[dmcquinn]

Yes. Take a servo extension and cut the red wire in the middle and strip off 1/4 inch of insulation from both ends. Leave the brown and orange wires uncut. Put this extension betwen the receiver and the servo. Connect an ammeter across the ends of the red wire. Operate your servo and watch the current draw on the ammeter. Do this for all the servos and see if they are all about the same. When the servos are at idle, they should draw very little (50mA?). Two servos on the same surface sometimes are fighting and may draw more. In the air the surfaces are working harder and will draw more than on the ground. Hold one of the surfaces so it can't move. Then move the transmitter stick full throw. If you hold the surface (stalling the servo) it will draw a lot - probably over one amp.

My 35% plane draws about 2 amps on average. So my A123 pack (2 cell 2300) only goes about one hour of flying. I field recharge after every two or three flights. sometimes every flight if I'm doing something else. I have 10 servos - all JR DS 8411 or HiTec 7955 TG.

[Tired Old Man]

The H-9 volt and amp meter is very easy to use. Keep in mind that digital servos connected to a surface at idle draw a bit more amperage than analogs because they work harder to hold the surface against gravity. That buzzing noise you hear is from that.

Check your linkages to assure they are not binding against the wing or flight surface itself at high deflection angles. A lot of people set up their stuff and don't notice when a linkage rod is making contact with the surface, or when a ball link is binding becaue of angular issues.

[Show871]

Thanks alot for the help! I just picked up the H9 meter. Is there any bench mark readings for 7955's I should be looking for? 871

[Tired Old Man]

Not really. Check all the servos while disconnected from the linkage to develop the baseline.

[Show871]

Thanks again... this H9 trinket is great! I found all surfaces were around .05-.07 A @ Idle. I had one wing a bit off....it was .85 on full deflection. Got things tweaked, and both wings are in the .25 range at full up deflection, that was the best I could get. Aileron down was .07-.1. Rudder was .15 at full deflection, throttle all good..........871

[Tired Old Man]

Most people use tailwheel springs which tend to add some to the rudder servo current if the t/w linkage is connected to the rudder. Sounds like you have her in line. You probably already noted that the initial amperage required to start the surface moving is a lot less that it takes to hold it in position. A quick initial peak then falls off.

[MikeC3D]

	Quote: Originally Posted by dmcquinn
	My 35% plane draws about 2 amps on average. So my A123 pack (2 cell 2300) only goes about one hour of flying. I field recharge after every two or three flights. sometimes every flight if I'm doing something else. I have 10 servos - all JR DS 8411 or HiTec 7955 TG.

If thats all you get, either those batts have a problem or you have major linkage binding prob's. Something is drawing those batts down bad.
We use flight power 2500mah li-po's and we can fly 8-10 times and still have plenty of power left for more. We never have to charge at the field. 2 of us use 8- 9156's with a Smart fly turbo reg and 3050 on thr. w/ 6014 rx... The other 2 use the new JR rx and use the same batts with all 8611 A's and no regs. No matchboxes, proper linkage geometry, and never have a problem.

[wylieruneyjr]

The H-9 is what I use. I try to get Zero,s at center and full deflections at each direction. At least get it down to .ox such as .o5, .07, .03 . A trick I use on main wing is to check the ailerons with the wing not installed flat, but on the wing tube and the trailing edge straight up, so that the servos don,t have to hold up the ailerons. truer reading. The H-9 can beused anywhere inline as between BATT a RX to check total cumsumption as well.

[rcgood]

This is very interesting as I always wondered myself. Is there a way you can find the draw while flying though? That's what I'm most curious about. I want to get batteries for my 35% and the Li-Ions 2400 can only put out about 4amps which would give me about 8 amps to work with on 2 batts. I saw an article in a magazine that tested different servos and this is what they had for the HS 5945:

At 25% of max load (45.25 oz of weight) it was drawing 444 mA
At 50% (90.5oz) - 670mA
At 75% (135.75oz) - 1.1 A
At 100% (181oz) - 1.6 A

Now on a 35% plane you have 8 servos (2 on rudder and not counting throttle). If you use just 75% of their max load you consume 8.8 A which is too much for the batts. What if you use 100% though (which I kinda doubt, but I guess it could be possible in multiple snaps) then you'd draw 12.8 amps. I want to have enough current to handle snaps and so on...I guess it's all a mistery???

[MikeC3D]

L I - P O ' S

[wylieruneyjr]

Not really a mystery, Spectrum did some work in this area. A professional yak set -up with two 4000 mah lipo,s 2 cell batts , and no regs used. Drew 17.8 amps at peak and was at an average current of 2.62 amps durning a hard 3D flight. Milliamps used durning 10 minute flight was 435mah. Two 5200,s 4 cell LITHUM ION,S will supply 20 amps in burst 10 amps each. and 123,s batt much more. The airplane was a 40% yak with 9 -JR 8711,s and 1 -JR 8317 on throttle. Another set-up they ran was a 33% Sukhoi 7 -JR 8611,s and 1- JR 8317 on throttle 1- 7.4 Lipo 2-cell and 6 volt reg , Moderate 3D Average current drain was .82 amps and peak was 6.92 amps. Milliamps used durning a 10 minute flight was 137 mah . Note this was with lipo,s I use lithum ion,s myself with 6 volt regs. Andy "RutnBuc" Runey All Info was from the AR9100 PowerSafe User Guide SPEKTRUM

[zoomer260]

	Quote: Originally Posted by 1bwana1
	The best way I know is to put a digital volt meter between the RX and the servo. This will show how much each servo is drawing, and will let you know if you have a binding problem. This is especially useful on surfaces with multiple servos. Here is a Link to the one I use. http://www.airwildpilotshop.com/more...uct&sku=HAN172

Volt meter ? I think maybe a meter that measures Amps.