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Old Mar 14, 2013, 01:45 PM
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tacx's Avatar
United States, MI, Macomb
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Question
servo tester to control motor

Can a servo tester be used in lieu of a RX to control a brushless outrunner?

The reason I ask is that I picked up a Astro Whattmeter 101 at a swap meet. Searched the net for instructions and came up with the attached instruction sheet.

On page 2 you will see a diagram showing a servo tester being used to operate a motor. It shows being plugged into the ESC.

Normally, one would plug in a battery to the servo tester then a servo into the servo ports. The diagram does not indicate which port is to be used, but I am assuming it would be the servo port.

Here is the instruction sheets with the diagram on page 2.

Thanks

Tom
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Old Mar 14, 2013, 05:12 PM
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Staffs, UK
Joined Nov 2003
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Yes many of have been doing it for years. Almost everyone who does any motor testing uses something like that instead of messing about with a TX and RX.

Note: that diagram assumes that the ESC has a BEC function to power the servo tester via the ESC lead. If it doesn't then the servo tester will need connecting to the receiver battery too.

Steve
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Old Mar 14, 2013, 06:56 PM
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USA, CA, Oxnard
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Will it work with a car ESC to run the motor both forward and backward?
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Old Mar 14, 2013, 07:20 PM
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Moab, Utah, USA
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Yes. Just be aware that the servo tester must be in the center position for the motor to be stopped. The motor will run in opposite directions as the servo tester is moved away from the center position in each direction.

Larry
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Old Mar 14, 2013, 07:36 PM
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Chattanooga, Tennessee, United States
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Here is my test stand with the servo tester (from Gobrushless.com) in place.
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Old Mar 14, 2013, 09:04 PM
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United States, MI, Macomb
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Great thanks,

Will save the hassel of hooking up to a rx and using the TX.

But I have one more question. When testing a power setup you usually check the amp draw at WOT. A ESC has to be clibrated to the TXs high and low throttle parameters.

If checking amp draw with a servo tester how does one know if the motor is at WOT?

In other words, does the ESC have to be calibrated to the servo testers high low parameters?

Thanks

Tom
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Last edited by tacx; Mar 14, 2013 at 09:11 PM.
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Old Mar 14, 2013, 10:59 PM
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Moab, Utah, USA
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The servo tester would be calibrated to the ESC the same way as a transmitter throttle control is. The only difference is that you would be using the servo tester's knob instead of the transmitter's throttle stick.

Larry
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Old Mar 17, 2013, 09:06 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by tacx View Post
Great thanks,

Will save the hassel of hooking up to a rx and using the TX.

But I have one more question. When testing a power setup you usually check the amp draw at WOT. A ESC has to be clibrated to the TXs high and low throttle parameters.

If checking amp draw with a servo tester how does one know if the motor is at WOT?

In other words, does the ESC have to be calibrated to the servo testers high low parameters?

Thanks

Tom
Are you using a Castle Creations ESC (Phoenix, Thunderbird, etc.)? If so those can be calibrated quickly each time they are powered up. And it might be worth trying the same process on other ESCs too:

1 - Set the servo tester to about 3/4 of it's rotation clockwise (that would be about 3/4 throttle)

2 - Connect the ESC to the battery, wait a few seconds (CC ESC will count cells and stop on the partial throttle error and make some tones)

3 - Turn servo tester to full throttle and wait for more tones (CC ESC will set that as full throttle and play the happy tones)

4 - Slowly turn the servo tester CCW until you hear another set of happy tones and then the arming tones (that is zero throttle).

Then I am calibrated and ready to test. CC ESCs will not run the motor backwards (as is suggested above) if you go below zero throttle. In fact I've never seen any ESC that will do that. But I don't have any reversing capable ESCs either. Maybe that is the difference.

Jack
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