Do you know this ESC? What to do with extra leads

[TimWescott]

A friend asked me to figure out this ESC.  It's a small ESC, comes with a note that it's from "flyflyhobby.com".  It has an extra lead -- it's got the usual battery, RX and motor leads, but it also has a JR-style female connector.  I'm assuming it's for an arming switch, but I don't know.

If anyone knows for sure it'd be nice to have some data before I go blindly playing with things.

Thanks.

[Maxout]

I honestly couldn't tell you...if you can't get an answer here, ask on the Flite Test forums.

Flyfly has a pretty decent reputation from what I've heard.

[PeeTee]

Tim

Arming switches are normally in one of the ESC leads to the Receiver. This connector could possibly be for a 'sensored' brushless motor. When brushless motors were first introduced  10-15 years ago, sensors in the motor 'told' the ESC the direction of rotation and the position of the rotor - or something like that, I'm going from memory  . Now, clever software in the ESC senses certain parameters in the three motor leads and derives the information, and thus sensors aren't needed.

This all well above my labour grade and you can surely find more info with an internet search. I would say that fairly recently I've seen comments to the effect that 'sensored' motors are making a return - for what reason I don't know although I'm sure you'll find answers on the RCGroups forum.

Hope this helps

Peter

[TimWescott]

This spare connector only has two wires.

The sensored brushless motors that I know (from industry, not RC) have five wires to the sensors -- power, ground, and one wire to each of the sensors.  The sensors themselves are used for commutation.  I think the RC motors are the same.

Sensored motors have always been used for RC cars -- you can't generate any significant torque at low speeds with a sensorless motor (at least not without wasting a lot of power and generating a lot of heat).  Low torque at startup is fine if you're pushing against the air with a propeller, but it isn't fine at all if you're trying to start a car up hill or similar.

[PeeTee]

Well, you obviously know more about this than me, so good luck.

[TimWescott]

Well, you obviously know more about this than me, so good luck.

More theoretical, maybe, but not necessarily more practical.

Among other things, I build motor control boards for brushed and brushless motors -- for industry so far, but if someone has six man-months of engineers wages lying around and they want to start producing ESCs, I can help! 

That doesn't mean that I know what some designer other than me was thinking when they populated a board with connectors, and since I mostly fly slime, I haven't had a lot of 'lectric equipment pass through my hands.  So I can only make educated guesses where someone who's got real experience with a lot of real ESCs may have actually seen what I've got in front of me, and know.

[Pops]

Tim,

I do not have one of these exact regulators but some of my ESCs have the same arrangement. There the two-wire connector is used for a jumper, setting the ESC's cut-off voltage. Then it determines what kind of battery you're using, chosing between <8.9V (6-7 cellsNiMh/2S LIPO) when put on and between 9V and 13.3V (8-12 cells NiMh/3S LIPO) when taken off. If you're not familiar with the term "cut-off", this function monitors the battery voltage, stopping the motor when battery voltage drops below the set value. This ensures that when your "go-juice" gets low, you will be warned (motor stops) and still have enough power to turn around and head for a glidepath home. It also protects the cells from discharging too far, which can destroy them.

Hope this helps.

Brg

Pops

[TimWescott]

Argh!  I never followed up!  It turns out that it was to arm the ESC -- unplugged, the ESC did nothing.  With a jumper installed (or, presumably, a switch), the motor was enabled.

[Pops]

Ah, then it's solved!

I tried to find info regarding that ESC on the Net but came up short - guess you've done the same earlier.

- I trust that you tried this with both 2S and 3S battery packs?

Brg

Pops