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Author Topic: New timer  (Read 974 times)

Offline Larry Wong

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New timer
« on: May 30, 2008, 06:25:33 PM »
OK guys I got a new timer from Will Hubin today, this is what happen I plug it in with a full charged battery(14.8 V) started it up and it ran great, for 4min then it started to miss or hunt so I shut it off, the RPM was a steady 9100 rpm with 12x6E .
the battery was warm but not hot, I plug it into my FMA charger and it said 13.1v and 2% my battery is a 14.8 4c 4000 mha. what should I do to get a 6min flight ? the ESC is in Heli high RPM mode.. ??? ???
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Larry

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Alan Hahn

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Re: New timer
« Reply #1 on: May 30, 2008, 08:18:34 PM »
Larry,
This is a Lipo or a A123 pack? I'm too lazy to look!
A freshly charged lipo should be 16.8V (or pretty close to that). When I put my Lipo battery up to charge after a flight, it claims the voltage is just about 15V.
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Alan Hahn

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Re: New timer
« Reply #2 on: May 30, 2008, 08:25:20 PM »
Larry,
I just looked at your other post and I think this is a Lipo pack. If it is read on. If not ignore what I am saying!

On your FMA charger, are you setup to charge "1C Lipo"? It comes from the factory as a default setup for A123, which is a lower voltage per cell. If it is set for A123 and you have a lipo, then you aren't charging it to full capacity.

Again, if I am right, you can change the mode of charging by powering on the FMA chargqe without a battery. Now push AND HOLD the mode button on the right top side of the charger. It will cycle through a lot of options, one of which is 1C Lipo. When that one pops up, release the button, and that will select that charge mode. Now hook up the battery and charge it. When you plug the battery in, it should beep 4 times(I think) to tell you is is a 4s battery.
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Offline Larry Wong

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Re: New timer
« Reply #3 on: May 30, 2008, 09:01:57 PM »
Thanks Alan I changed the mode to 1c and will try it, but whats with the hunting after 4min ? this is new to me , it didn't do it before.  is it a sign of over proping?
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Larry

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Alan Hahn

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Re: New timer
« Reply #4 on: May 30, 2008, 09:15:18 PM »
I think that is the ESC detecting the Low Voltage cutoff of the battery (the voltage is too low).

When the voltage drops less than ~3.0 V/cell---under load, the ESC pulses the motor. That happened to me once on the test stand ---at first I thought the motor was shorting out or something under load. Then I realized the test had gone on so long, that the battery was seriously depleted.

I experienced  the LVC again last weekend at the Windy City Classic Contest. I accidentally put the uncharged battery from the first flight back in for the second flight. Right after the reverse wingover, the motor began to stutter. Once that happened I knew what I had done  HB~>. The ESC kept lowering the power (and stuttering) and finally I landed the plane under partial very low power. Unfortunately, the prop caught the grass and the motor twisted the mount off the plane again. This time at least, it really didn't do any serious damage like the last time (during full power on takeoff a few weeks ago).

I think getting a full charge will solve your problems. I thought it was strange that FMA ships the charger in A123 mode---it isn't the most common battery people are using (I would venture "1C Lipo" is the most used setting). You are the second person (not including me!) who was surprised when the charger didn't quite work as planned.
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Offline Larry Wong

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Re: New timer
« Reply #5 on: May 30, 2008, 09:21:51 PM »
OK that is good to know , now I think I will get a full pattern in this week end,I hope all the bugs are over, and I can do some flying.  Thanks for all the help from the guys on this site.  H^^ H^^
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Offline Larry Wong

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Re: New timer
« Reply #6 on: June 01, 2008, 03:59:17 PM »
Sunday flying.  First flight was fast 3.7 lap times on 60 ft lines and 12x8E prop , ended with a signal o0f low voltage.
2nd flight I switch to a 12x6E prop and lower the RPM to 9100K and got lap times 4.7 still to fast will try changing props or lowering RPM, I did get to do some wing overs and loops at 4.7 lap times. just have to tweak some, (I think)   #^ #^ both flight I did not hear beep from plane before shut down. ( Why ?) ???
« Last Edit: June 01, 2008, 04:42:35 PM by Larry Wong »
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Offline bfrog

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Re: New timer
« Reply #7 on: June 01, 2008, 05:14:08 PM »

I think you ran out of battery on both flights. When we measured the current on the ground (for the second flight) it was 38 amps. The charger said we took about 600 mah out in the testing. Now if you assume a 10% drop in current in the air that means you were probably drawing about 34 amps during flight. If you calculate that out, I'll try and do that here in words, you flew about 5 min 45 seconds by my watch. So: 34 amps times 345 seconds (convert to seconds, its easier) divide by 3600 sec/hr equals 3258mah. If you started with 4000 as the battery capacity, take out 600mah for the test we did on the ground before that flight, then you end up with 3400mah left. Depending on where the low voltage cutoff is set on the ESC you probably hit that. After the flight your charger said 18% left in the battery which would be .18X4000 = 720. That probably means that you were acutally drawing less in the air than the 10% drop I guessed at the start. So, all in all it's in the ballpark for the low voltage cut off to kick in before your 6 minutes of flying time was completed.

As we talked about I think you can use a smaller prop and lower the current even more to get your 5 sec plus lap times and bring the power consumption down to a level that the battery will be more than sufficient to handle. You may have to experiment with a couple of different prop sizes to get the one that is just right, but you are close.

Let me know what happens with the different props.
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Alan Hahn

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Re: New timer
« Reply #8 on: June 01, 2008, 05:54:20 PM »
I would drop the rpm another notch or two. I will also say I have input a flying time on 5m10s. This time includes ~5-8 s it takes for the motor to spool up (due to the governor mode on the CC ESC) and the plane is released. I end up with ~5 laps after the clover before my timer signals its two bleeps followed by another 2 laps or so before landing.
I am flying 5.0 s laps, and running 8100 rpm with an APC 12-6 prop on my Nobler. I think your plane is larger than mine, so with that same prop you will need more rpm.
It does take some time to get things adjusted correctly, so take your time and don't put your plane in peril until you know it is running close to where you want it to be.
What I do at first is to run 2 minute flights to get the speed nominally where I want it. That gives me about 2 flights per battery to adjust rpms, and I'll do a few simple maneuvers like inside and outside loops, maybe one square loop to see if I like what is going on.
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Offline Larry Wong

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Re: New timer
« Reply #9 on: June 01, 2008, 05:59:13 PM »
I picked up a (Watt's Up ) is a watt meter and power analizer  this should help me set up things. and some props
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Larry

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