RC ESC throttle signal

[John in CR]

I can't find anywhere an explanation (for a non-RC guy) for how these things work and what signal the ESC expects. This first usage will be turning a prop for only a few seconds of full thrust, so I need only a throttle that acts like an on off switch, though I would like to be able to modify that short thrust later if it turns out to be stronger than necessary. I see just under 5v coming up the 3 wire cable for the throttle, but what is the ESC expecting back on the sense wire?

I would also like to know for future ebike reference too, because my approach to solving the startup issue in our use will be to just put a centrifugal clutch on the output shaft (why isn't anyone doing this?). I just got an HXT outrunner, but not one of the biggest ones, so I'll need to use a geared hub to get what I want, and I think the soft start of a clutch will be key to longevity of my Nexus3 hub.

John

 

[nieles]

hi,

you need a servo tester to control the esc. something like this:
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6554

the signal to an esc is an 20ms pulsed signal the duty cycle is ajusted for control. 1ms high signal is lowest position(0% throttle) and 2ms high signal is highest postion (100% throttle)

as far as i know there isnt anything simple like a switch you can use.

Niels

 

[gwhy!]

I would also like to know for future ebike reference too, because my approach to solving the startup issue in our use will be to just put a centrifugal clutch on the output shaft (why isn't anyone doing this?). I just got an HXT outrunner, but not one of the biggest ones, so I'll need to use a geared hub to get what I want, and I think the soft start of a clutch will be key to longevity of my Nexus3 hub.

John

The cf clutch works very well on my gas scoot conversion :wink: .

 

[John in CR]

The cf clutch works very well on my gas scoot conversion :wink: .

Thanks gwhy, I forgot all about you running one. Now to find one that is sufficient and doesn't weigh more than the motor itself. Am I understanding correctly that allowing the motor to spin up some should be good for the ESC as well as my geared hub?

John

 

[kartopla]

I can't find anywhere an explanation (for a non-RC guy) for how these things work and what signal the ESC expects. This first usage will be turning a prop for only a few seconds of full thrust, so I need only a throttle that acts like an on off switch, though I would like to be able to modify that short thrust later if it turns out to be stronger than necessary. I see just under 5v coming up the 3 wire cable for the throttle, but what is the ESC expecting back on the sense wire?

I would also like to know for future ebike reference too, because my approach to solving the startup issue in our use will be to just put a centrifugal clutch on the output shaft (why isn't anyone doing this?). I just got an HXT outrunner, but not one of the biggest ones, so I'll need to use a geared hub to get what I want, and I think the soft start of a clutch will be key to longevity of my Nexus3 hub.

John

I just built a simple servo tester a few days ago using a 555 timer. I have a 20 year old novak controller and I wanted to use it on an ebike. It doesn't get too warm. I'm not sure if anyone here remembers the orange colored rc car novaks. They were actually made in the USA. A little pricy though. There is a pdf file of it on this forum somewhere. Just search for servo tester.

 

[evblazer]

I have a novak racing controller I used on my bolink(?) and one with reverse that I used on my old jrxt you know back when a 6S nicad pack was the bomb!
I actually pulled out an old novak receiver with the radio taped to my road bars to test drive my friction drive around before I got me a servo tester.

 

[katou]

The reason that I chose not to use one is that it is not *strictly* necessary for an electric motor.

An IC motor needs one because it must not slow down it's RPM below a certain threshold. If it does, it stalls. (I assume all this you know, this is for the other readers)

An electric motor, especially a DC motor, has full torque at all RPM's (at least in theory) and will not stall. So, you don't NEED a centrifugal clutch, the electric motor will start and run, even at 1 rpm.

That being said, I understand why you are thinking of using one. It cushions the drivetrain, and avoids massive spikes of amperage as the motor struggles. It is interesting that the RPM for full engagement of an IC centrifugal clutch, and the normal operating range of our DC motors are so similar.

As Gwhy aptly showed, all that was required was changing the weighting of the clutch rollers, and off you go.

I think that the centrifugal clutch would be especially useful in a geared setup, driving through the gears, or driving an internal hub as a mid-drive transmission.

But I'm with you. If it's such a good idea, why aren't more people using them? They are ubiquitous on Karts, and their needs are similar to ours, so we know that they work, and are tough...

Katou

 

[gwhy!]

The cf clutch works very well on my gas scoot conversion :wink: .

Thanks gwhy, I forgot all about you running one. Now to find one that is sufficient and doesn't weigh more than the motor itself. Am I understanding correctly that allowing the motor to spin up some should be good for the ESC as well as my geared hub?

John

From what I have read about all the failures of rc esc I think its the initial load at 0 rpm placed on them so a cf clutch will over come this and allow the motor to get up to a fully rotating speed before it starts to engage and takes up the load. So with a cf clutch you should be able to gear the bike very tall without fear of bogging the motor down. As you say John to find a small light clutch for e-bike use maybe the real problem though.

 

[John in CR]

I'm thinking commercial size weedeater type clutch might work, assuming they have one.

Yes, cushioning the drive train is one aspect, but I also like the idea of having my motor spinning up to decent rpms for a split second before the load is introduced. O rpm may have the same torque, but its also zero efficiency, so I'd get to skip right past the range of my motor's lowest efficiency. That means it's likely to increase overall efficiency with my stop and go type riding. It sure seems worth a shot, and may even make the cheap ESC's useful to us. I have a hard time getting past the expense of the RC rigs with those cheap motors just a teaser to hook you. Unless the required FETs are expensive, I'm sorry but this stuff should be dirt cheap because it requires so much less in materials.

John