Author Topic: Esc brake and throttle curves etc. Help!  (Read 3052 times)

Offline Alan Williams

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Esc brake and throttle curves etc. Help!
« on: 16, May 2017, 06:13:08 PM »
i have been trying to sort out my throttle settings as i am having lots of trouble with throttle and speed management. I know this is due to lack of experience and practise but i would like to at least understand the theory. I am using a 99 opto/c50-13xl combination. So question 1, when does the esc brake come on? Does it operate when the motor stops, or when it is retarded down to the arming point. The way my throttle channel is set up, in order to arm the esc, my trim level is down to -200 (futaba  mz) but i usually fly with the trim at about -89 and for a slow idle is is on + 60. So will the brake work at -89?
Question 2, I have tried adjusting the throttel curve using both expo 2 and spline but cannot sort out what I need to do. If left linear, the aircraft is quite fast at mid stick. I tried dropping the mid point power down but this gives me a negative expo type curve which means the top end power comes in late. So if anyone can give a clue as to how to go about changing and testing to get the correct sort of throttle response, it would save me floundering around and making little or no progress.


Many thanks
Al

Offline Adrian Mansell

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Re: Esc brake and throttle curves etc. Help!
« Reply #1 on: 16, May 2017, 08:33:58 PM »
Hi Alan,


I haven't set-up a spin 99 for a couple of years so my memory is a bit cloudy, but here are a few points.


1. I always used fixed start and end point settings on the ESC (from recollection 1.1ms and 1.9ms).  The auto end points I found just confused things too much.  Set them on the ESC and then set your Tx channel endpoints to match.
2. Set-up a throttle lock switch which takes the throttle down below 1.1ms to the arming point.  This means you never have to touch the trim once it is set.  The switch doubles as a throttle off lock and an arming switch.
3. You can only get a slow idle on the spin 99 by setting it to exponential throttle curve
4. Run the spin 99 with the Jetibox connected, it'll tell you what it thinks the throttle setting is and exactly when the brake activates
5. I often have 5-point or 7-point throttle curves in order to get the response I want.  No substitute for spending time flying and progressively changing the curve as you identify behaviours you don't like.


Cheers, A.

Offline Alan Wild

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Re: Esc brake and throttle curves etc. Help!
« Reply #2 on: 16, May 2017, 08:48:01 PM »
OR:
(What I wrote on another site)
Look in the spin box settings to find the lowest setting for low throttle--it will probably be 1.00 msec.[/size]Then,use the spin box connected to the Rx throttle channel. to set the low throttle travel adjust (orATV or whatever your Tx calls it) to read 1.00 msec---on my JR Tx it's around 130%.(You're OK with 100% high throttle on the Tx,and that will be around your 1.92 msec.)Now switch on the Tx, and Rx, and connect up the motor battery with the throttle stick at its lowest point, and no trim.The ESC will not arm yet(no beep).Go to travel adjust on the throttle channel, and increase the downward travel, one unit at a time, until the beep.This will be your low (est) throttle position--and the point at which any brake setting you have dialled in, will commence.Leave the ESC curve as linear, and use the throttle curve function on the TX to adjust the motor's throttle response.Most people find that the curve needs to be steeply upward at first (so that 50% at the Tx is around 70% output), and then sloping more gradually to 100% at the top.The spin 99 usually has a small dead band at the very bottom of its travel,which may or may not bother you----one of my pattern friends prefers the OS ESC for that reason.


I believe that, for Futaba Txs(I use JR), you can get a similar curve by leaving the esc as a linear one, and,using the Futaba spline curve function with minus 40% expo.
[/color]

Offline Alan Wild

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Re: Esc brake and throttle curves etc. Help!
« Reply #3 on: 16, May 2017, 08:50:29 PM »
I left the previous post on in the hope that a more savvy person can make the copied text a more sensible size...

Offline Peter Jenkins

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Re: Esc brake and throttle curves etc. Help!
« Reply #4 on: 16, May 2017, 09:00:49 PM »
Just highlighting the first row of what looks like just a line and then right clicking and selecting search comes up with the goods.

Offline Phil Lewis

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Re: Esc brake and throttle curves etc. Help!
« Reply #5 on: 16, May 2017, 09:01:02 PM »
Savvy person speaking then, here you are:

Look in the spin box settings to find the lowest setting for low throttle it will probably be 1.00 msec. Then use the spin box connected to the Rx throttle channel. To set the low throttle travel adjust (or ATV or whatever your Tx calls it) to read 1.00 msec on my JR Tx it's around 130%.(You're OK with 100% high throttle on the Tx, and that will be around your 1.92 msec.)Now switch on the Tx, and Rx, and connect up the motor battery with the throttle stick at its lowest point, and no trim.

The ESC will not arm yet (no beep). Go to travel adjust on the throttle channel, and increase the downward travel, one unit at a time, until the beep. This will be your low (est) throttle position--and the point at which any brake setting you have dialled in, will commence. Leave the ESC curve as linear, and use the throttle curve function on the TX to adjust the motor's throttle response.[

Most people find that the curve needs to be steeply upward at first (so that 50% at the Tx is around 70% output), and then sloping more gradually to 100% at the top. The spin 99 usually has a small dead band at the very bottom of its travel, which may or may not bother you one of my pattern friends prefers the OS ESC for that reason.
 
 
 I believe that, for Futaba Txs(I use JR), you can get a similar curve by leaving the esc as a linear one, and, using the Futaba spline curve function with minus 40% expo.
« Last Edit: 16, May 2017, 09:04:08 PM by Phil Lewis »

Offline Alan Wild

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Re: Esc brake and throttle curves etc. Help!
« Reply #6 on: 16, May 2017, 09:07:09 PM »
Thanks chaps!
Just to add---use the manual brake settings part of the esc programming notes for use with the jeti box.

Offline Alan Wild

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Re: Esc brake and throttle curves etc. Help!
« Reply #7 on: 17, May 2017, 07:21:14 AM »
Just a further point----from what I've seen/heard over the years, many seem to struggle with the programming on the otherwise estimable jeti spin 99.
I have no connection with either jeti or OS, but the OS esc equivalent (is it the 1100HV?) is undoubtedly much easier to set up(using the OS programming box)---particularly in the setting of the high and low end points.
« Last Edit: 17, May 2017, 07:26:40 AM by Alan Wild »

Offline Alan Williams

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Re: Esc brake and throttle curves etc. Help!
« Reply #8 on: 17, May 2017, 09:40:36 AM »
Thanks Gentlemen,
I do have the esc set up with fixed endpoints and I have a switch set to drop the trim below the arming point. I never touch the trim switch as I have a flight condition which sets the trim below idle and another condition ( for landing) which runs a bit higher and also gets rid of the throttle to elevator mix. I am guessing from the replies that if I want the brake on I may need to set the normal condition as low as the esc arming point but I will take up , suggestion and connect the jeti box and see if I can determine when it detects 0 throttle.
I remain confused about the Futaba throttle curve, Negative expo means that at mid stick I am getting less than 50% power, positive expo would give more than 50% power, yet negative expo seems to be the recommendation, including from Futaba. Using the spline curve does not allow the use of expo but does meanI can set an huge number of points across the curve.
So next flights will be to start again with no curve and then try yet again to sort it out.  I will try to add pictures of the expo curves. then maybe someone can give a clue as to a strategy to follow,


Thanks again

Offline Alan Williams

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Re: Esc brake and throttle curves etc. Help!
« Reply #9 on: 17, May 2017, 09:53:16 AM »
Ok so with negative expo set to 35% I would have 25% less than half power at stick midpoint. this equates to a reasonable straight and level speed

Offline Alan Williams

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Re: Esc brake and throttle curves etc. Help!
« Reply #10 on: 17, May 2017, 09:58:02 AM »
sorry about individual posts but having trouble posting,
this is positive expo on the transmitter, where mid stick gives about 75% power, this would be quite fast in straight and level flight, but maybe that is what I need. Next time out,  try both!!

Offline Alan Wild

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Re: Esc brake and throttle curves etc. Help!
« Reply #11 on: 17, May 2017, 11:38:22 AM »
Sorry about the neg or pos expo confusion.
If you go to RC Universe Electric Pattern Flying, there's a recent thread byBem titled something like mid-stick plateau on throttle curve, which itself includes a very clear article by Scotland's own Mr Malcolm Harris,which I think you'll find very helpful(and from where I pinched the info re Futaba throttle curves.)
JR, Futaba, or whatever, the curve which gives the linear feel to the throttle, is the one you'll see in fig 4 in Malcolm's article.

Offline Malcolm Harris

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Re: Esc brake and throttle curves etc. Help!
« Reply #12 on: 17, May 2017, 01:04:29 PM »
Ha this is great!

Saves me jumping in when somebody else quotes me ;D

Reminds me of a film called Broadcast News in which William Hurt is a TV news reporter and he's off duty but watching one of his colleagues make a mess of reporting a story. So he phones the newsroom and tells them to patch him through to the colleague and starts telling him what to say straight into the guy's earpiece. The guy all of a sudden appears to know what he's talking about. Once he's finished Hurt says: "I say it here and it comes out there!"

M

Offline Alan Wild

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Re: Esc brake and throttle curves etc. Help!
« Reply #13 on: 17, May 2017, 03:09:47 PM »
Here's the curve I Use:
PointL is the lowest setting available on the esc/jetibox at 1msec nominal---the point at which any braking dialled in will initiate.
Incidentally, if I switch to the lowest point above L where an idle will hold, (in my case 9 points above L), I get exactly 600rpm,so quite a slow idle I think.

Offline Alan Williams

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Re: Esc brake and throttle curves etc. Help!
« Reply #14 on: 17, May 2017, 05:19:40 PM »
well many thanks and the article really helps as I did not understand the relationship between RPM and power delivered.EXCEPT (here it comes) I am still confused on this positive v negative expo. On my xmitter (futaba 18mz) to increase the rpm at mid stick I have to use positive expo, as in my photos above, negative expo pulls the curve lower so output drops  I can use a spline function and manually input the points but it makes no use of expo in that scenario. As it was raining today and I had some time I connected up the jeti box and did some test runs, altering the expo between each run and recording the RPM shown by the jeti box.
I have attached the results, these all with negative expo, so now I can try again with positive. Interestingly with no expo I seem to get 5560 rpm at mid stick which is more than half of full throttle which is 8080 ( variable!)