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Jul 20, 2005, 03:12 PM
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Jazz 40-6-18 Throttle range question


Guys, I love my Jazz !! I plugged it in and turned on mode 4 and 9 for my t-rex mega motor and lipos and haven't had a minute's trouble. I have the same setup on 2 t-rexs and love them both.

Now I'm wondering what the Jazz uses to set the throttle range. for example, on my jr radio the throttle range goes from 0 to 100 percent. In fact, I could go to 150 % I believe although I haven't tried it.

Is there some sort of initial calibration that the jazz uses to calculate what my max throttle corresponds to? I'm trying to understand how it's max throttle corresponds to what my radio thinks is max throttle and when the red light (on the jazz) comes on, which i think corresponds to max throttle but I'm not sure about that.

did i do something to calibrate the jazz for throttle control or is it learning it some other way?

thanks.
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Jul 20, 2005, 04:36 PM
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This has been confusing me for quite some time, too.

I've figured out that on my JR XP662, a little red LED in the Jazz comes on when my throttle stick position causes the throttle *curve* value to pass 73%.

Or - if I reduce the positive axis range on the throttle channel to +43% (from +100%), and leave the negative axis range at -100%, then the red LED comes on at full throttle stick position, when the curve is set to 100 at full stick.

With regards to this "automatic throttle range sensing" phenomenon, the problem is that everything above about 50 on the throttle curve gives me the SAME head speed. Said another way (with a 0-50-100 throttle curve), as I move the stick up from zero, I suddenly get around 1700 rpm at approx. 1/5 full stick travel, increasing to 2800 rpm at half stick, and 2800 rpm constant all the way to full stick?? Again - this is with a 0-50-100 throttle curve in mode 4.

In order to get my head speed to 2400 (desired), I would have *thought* that I should figure 2400/2800 = 85%. Therefore program the idle curve as 85-85-85. Nope. Actually, it looks like I'll have to set the curve to 46-46-46 to get 2400 rpm. I *can* fly this, but I seem to recall that the instructions say not to go below 85... Is this 85% in the throttle curve (exact same head speed as 50% thru 100%), or is this 85% of maximum head speed (corresponding to 46% throttle curve)?

Super confused. Please help, Kontronik!

-Trev
Jul 26, 2005, 08:47 PM
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knock knock...

Any thoughts on this one?
Jul 26, 2005, 10:07 PM
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Huh. Haldor answered all the *other* outstanding threads, and skipped this one...

Maybe it's a tough question?

Maybe we've stumped him/them?

To this day, I still don't know quite what to do with this Jazz. I found a hint at http://logoheli.com/smile.htm, and some people believe that this applies to the Jazz also. I can confirm that something weird happens based on my actions the very first time I power up after choosing Mode 4.

i) If I go to full throttle right away, it seems like I can never get any resolution on the speed, it's either Off or Full Speed for future flights. but,

ii) If I go to minimum throttle, just enough to get the motor to ramp up a little, wait a bit, spool down and unplug the battery - then I can program mid-40s% on my throttle curve (flat across) to get 2400 rpm, out of a maximum 2800 rpm.

Note, that any throttle values chosen above about 50% ALL give me 2800 rpm.

I can't figure it out?!

Soggy: I hope this isn't thread theft! I think we're asking the same question about calibrating the Jazz throttle range. I just ALSO wonder why the throttle curve doesn't have a linear relationship to head speed.

-Trev
Aug 03, 2005, 11:08 AM
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Thread OP
I'm wondering if maybe the jazz learns the 'full throttle' position when the mode is set and the stick is pushed up. if so, then I guess it would be real important to make sure the stick is ALL the way up. but that's just a guess.

tickle, bump, nudge to the top....
Aug 03, 2005, 10:46 PM
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CustomPC's Avatar
Soggy,

I've just been playing with my new Jazz.
The jazz manual says that when in modes 2-6 & 8 it uses a fixed throttle range. I guess that it is programmed so that a certain pulse width from the radio correlates to the throttle percentage.

Different brands of radios emit different pulse width signals so 0% & 100% on a JR is not the same as 0% & 100% on a Futaba.

The Jazz's LED will light up when it sees the pulse widths that it correlates to 0% and 100%.

On my JR PCM 9XII with the throttle endpoints at 100% The led lights up and cuts the motor at 9% and shows full throttle at 91%.
So, there is a dead area in the first 9% of stick travel and anything above 91% won't give me any more power.

If i wanted to keep my throttle curve at the "true" 85%, i need to set it for 85% of 91 which is 77.5%.

I did it a little differently by adjusting the endpoints of my throttle channel until the LED glows at bottom stick and top stick (with a 0-100 throttle curve). On my radio the endpoints are 81% up and 81% down. (I set them at 82% for a little fudge factor.)

This had made my throttle curve numbers in the radio correlate to the true throttle setting. So now 0% on the throttle curve cuts the motor and 85% in the throttle curve equals a true 85%.

Make sure you disconnect your motor wires while you're playing with throttle settings on the radio.
Aug 04, 2005, 07:55 AM
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Thread OP
customPC, thanks for the good info. that all does make sense. I'll so some bench testing and see if I can get my stick endpoints to correspond to the jazz endpoints. My jazz is soldered directly to the mega motor tabs, so I'm not sure if I want to just remove blades or strap it to a ladder or what but I'll rig up some sort of test for it.

Very good info, thanks again.
Aug 04, 2005, 04:55 PM
Registered User
I wanted to have more data before posting such a scanty graph, but the thread caught up to me.

I've been immersed in this little challenge on another forum (can I say that here?! ), and still haven't figured it out.

CustomPC - as you say, I've found my throttle curve setting of 73% lights the LED. I haven't checked the low throttle yet. There is definitely something weird about the setup, and I think your comments are only the beginning of it. Check out the graph here:



It seems that the best anybody can do, is to get their full throttle range (tightened up if you wish, as CustomPC states) to cover approximately the upper HALF of the full head speed range.

I can't even do that well. It seems that the 1st time I power up after programming mode 4, the ESC learns something different depending on how high the throttle is pushed. I need to find the time to do some further bench tests.

I'd REALLY like some feedback from Kontronik on this one...

-Trev
Aug 04, 2005, 06:01 PM
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CustomPC's Avatar
I may have spoken too soon. I did some testing yesterday, only this time with the heli firmly fixed to the floor of my loungeroom, and found some curious results.

When in mode 4 (governor) mode, the motor will spin up to a pretty high speed from only 1% throttle curve. I couldn't tach the head speed indoors.
I was expecting (and based my previous comments on) a direct correlation of radio output to throttle setting but this does not seem to be the case.

The Jazz manual says.
================================================== ============

In Heli-Mode the Jazz operates with active RPM control. This means, that the motor
RPM will be kept constant and changes of the load and the falling battery voltage
will be compensated, as long as the motor and battery capacity allows this. So itís
not necessary to use any mixer in the Tx to stabilize the RPM. This RPM control
works only if the speed controller is mounted in the helicopter. With no load its
possible that the speed controller jerks.
Just plug the receiver cable of the Jazz in a free slot of the Rx which can be
independently operated from the Tx with a slider. Program the Jazz to Heli-Mode
using this slider.
To start the motor push the slider towards full throttle. The Jazz will ramp up the
motor RPM in a few seconds in open mode. When the designated RPM is reached
the Jazz switches over to close loop speed. The more the slider position comes to
full throttle, the higher is the designated motor RPM.
With the slider back in motor-off position the motor will be switched off. Be aware
not to do so in flight, otherwise it would take some long seconds to start the motor
again.
The range of RPM selected by the slider is self adjusted by the Jazz. Its done when
the motor is started for the first time after the battery is connected.
There is a check whether the battery, the motor, the gear ratio and the helicopter
are fitting well together: with the lowest possible RPM which can be selected after
the Jazz has adjusted, it should not be possible to hover the helicopter. If its
possible, the Jazz is operating out of itís limit and can be destroyed! Use a higher
gear ratio or a motor with less RPM and more torque.
================================================== =============

It's pretty vague and not really helpful. I want to know if the "self adjusted range of RPM" happens the first time after you program it to mode 4 OR each time you connect a battery pack.

If it self adjusts each time, how are we supposed to set our throttle curves for a consistent headspeed on every flight. Do we need to ensure that we move the throttle stick in a consistent way whenever we start the motor for the fisrt time?
We might have to switch straight into Idle-up from zero so that the radio output is identical for each flight.

I'm going to set my jazz for mode 3 just to see if my theory about the end points is correct.
Then i'll take the heli outside and run a series of tests in mode 4 with my tach to see what variation in headspeeds i get by starting the heli from different points in the curve. 1%, 50% and 100% for starters.
Aug 04, 2005, 09:12 PM
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aau007's Avatar
You should try the following:

1. Program idleup0 with throttle curve 0% to 100%
2. Program idleup1 with throttle flat throttle curve.
3. At the first power up after plugging in the battery pack, use idleup0 and push throttle stick all the way up. Hold the max throttle position for at least a second and power down to 0. Within those 1 or 2 seconds of max throttle, the jazz should not spin up fast enough to lift the heli. This does the initial calibration and should need to be done only once after plugging the battery. Subsequent power down and up without disconnecting battery does not need to recalibrate.
4. You can now slowly power up the heli and measure rpm at different throttle point.
Aug 04, 2005, 10:35 PM
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CustomPC's Avatar
Thanks aau007, that looks like it may have the desired effect.

I done some more testing.
I programmed in mode 3 (aircraft mode) and the LED lights up at the same endpoints (81% up and down on my JR) so it looks like that part of my theory is correct.
It starts to spool up from about 3% throttle but there is no soft start.

Back to mode 4 and i tried your method. Heli starts to spool up from 11% throttle with a nice soft spool up. Moving the throttle to various points makes a noticable change in head speed.

I also tried your method with the endpoints at 100%. Motor started at 18% throttle so it looks like kontronik program in a 10% deadzone on mode 4.

Later today or tommorrow, i will tach the headspeeds at 10%, 50%, 85% and 100% throttle with 2 different scenarios.
Scenario 1, Plug in & fly.
Scenario 2, Plug in, throttle to100% for 1 second, throttle off, go fly.

I'm curious to see the results.
Aug 05, 2005, 09:24 AM
Registered User
I happen to feel that the idle0 (0%-100%), idle1 (flat) thing as suggested by aau007 is very important to get anything sensible from the Jazz.

There is 1 more permutation, though. As stated in my earliest post, the fellow at logoheli says to power up the first time in Mode 4 with the minimum throttle (on 0%-100% curve) required to turn the head, and wait. Power down, power up, go fly on your flat curve. This is different than going to 100% on the first power up.

Also, if you set a flat pitch curve in idle0 for NO pitch, letting the headspeed spool up to full on that first power up is not a problem. Again, this gives different results for me. I keep forgetting to perform my last tests during daylight hours, so that I can tach it

If you happen to get numbers tached, Custom PC, please share them (and even a couple extra throttle points, once you're at it). I'd like to include them in the plot I'm working up with different folks' curves vs/ headspeed. A detailed explanation of how you did your programming would help, to make it repeatable for others.

Thanks guys, we might figure this ESC out yet!

-Trev
Aug 05, 2005, 04:02 PM
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aau007's Avatar
The way I understand about the logic in Jazz heli mode is the following.

1. When the manual states to put throttle on a slider is to prevent the heli from lifting off during calibration on first battery connect. Pitch is usually mixed with throttle and max throttle stick means max pitch. This is for the Jazz to calibrate max rpm with max throttle. It takes a few seconds according to the manual but I notice that 3 seconds are good enough and the esc really does not require the motor to spin to max rpm to make that determination, only max throttle timing.

2. I don't have a separate slider to do the above but I notice that 3 seconds are long enough for calibration but not long enough for my ECO8's head speed to lift off, even on max. pitch.

3. After the calibration, move the slider just enough to start the motor. Corresponding to the manual, leaving the slider at this position, your heli should not hover even with max. pitch.

4. It is very possible that there are dead zones at the min/max where the last x percent does not make a difference.

5. There is no where I can find any documentation as to how the Jazz determines max rpm other than using a combination of battery (I take it as voltage or # of cells), motor (charateristics) and gear ratio (I take this as the load). For motor charateristics, I bet that during the "open mode", it varies the frequency and advance internally to find the best efficiency under certain load. I think this is also the trade secret that CC has not figured out in their heli programming.
Aug 05, 2005, 04:15 PM
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aau007's Avatar
CustomPC,

During your testing, try to hold the throttle at 100% for as long as you can without the heli lifting off. I tried up to 3 seconds for my own comfort but noticed 1 to 2 seconds also worked. This is to ensure the Jazz finishes its calibration since the manual says "a few seconds" and who knows how long that means.
Aug 06, 2005, 09:05 AM
Registered User
aau007: In your last 2 posts, you mention the heli lifting off during the "calibration" part. It's really quite easy to prevent, by simply (temporarily) programming a flat pitch curve, with the blades at 0 deg pitch. This way, even at full head speed, there is no way the heli will climb.

BTW, I think that the max head speed, with Jazz installed, has very little to do with the ESC. My meaning is - any speed controller would find nearly the exact same max head speed, as you suggest, simply as a combination of the full series battery voltage, motor constant, and gear ratios. Mine comes out very close to my max theoretical speed, calculated in this way.

All supposition, though, on most of our parts, I think. It would be great if we could get some advice from the manufacturer, here in their own forum...

-Trev


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