APM 2.5

[R_Lefebvre]

Yes, that's the exact Tx I'm using as well.

I've also built a Tx in a Pelican case, from scratching using my own program running on an Arduino Mega. This is intended to be an industrial use system. It isn't as nice to fly as a good hobby radio, but that's not the point. I'm actually using a sprung-center throttle stick since it's primarily going to be used in auto modes.

I built it using the FrSky DHT module. Forget about prices, there's really nothing else available that offers the same performance.

[jolyboy]

Originally Posted by salience

I guess not enough coffee yet this A.M. What's VP & FP?
My direct for the 450 is a HK Parkfly, a bit too fast but have an extra channel to control the 2nd ESC. But only 25gm.

VP = variable pitch
FP = fixed pitch
I see yours is VP, nice. Mines FP so performs not as well but is really simple to balance and hook up.

These are exciting times. As more members here get their APMs flying and see how well it flies it's only gonna get better for the community More users = more support = more users again

[sixback]

I have a APM2.0.
Are you going to separate out your signal lines and power your standard servos via a separate or dual regulator?
I do that with my HV FBL controller setups using a Gryphon dual regulator, running 7.4v to the servos, 5v to the controllers and tail.
It's rather easy to inadvertently fry a APM, know this firsthand.

[jolyboy]

It's a good idea to power your servos by a separate BEC, yes.

I don't know of anybody powering their servos by apm, but most 450 helis do use the 5v rails to power the servos from an external BEC. Bigger helis need a separate distro board to prevent burning the apm tracks.

Joly

[salience]

Originally Posted by jolyboy

It's a good idea to power your servos by a separate BEC, yes.
Joly

Salut joly and all,
Made the plunge and ordered my unit <Beavis and Butthead giggle>. It will be awhile before I start the project to install on a Trex600DFC, but amid this discussion of power supply I thought I'd ask about my intended setup. I'll be using a direct drive tail, having got addicted to this kind of setup with a 450 and now a 500 (Quiet!! Low vibes!! 6 pesky fragile gears eliminated!!!). So my tail motor will be driven by a YEP45A on a 4S, which conveniently has a 5.5V BEC I could use for the FrSky Rx and APM (only). Main motor on 12S with either a YEPHV or a K-Force HV120 which I already have, so may try it first. And a CCBEC Pro @6V off the 4S for the servos. How's that sound?

The question relating to the APM: can I connect the +6V from the CCBEC to the + output rail of the APM with the jumper off (or on, I forget at the moment which it is supposed to be), OR is it best to connect only the signal wires to the APM and supply the +6V to the servos directly from the CCBEC?

[salience]

Originally Posted by jolyboy

VP = variable pitch
FP = fixed pitch
I see yours is VP, nice. Mines FP so performs not as well but is really simple to balance and hook up.<snip>

About 30 seconds after I hit the reply button the coffee hit me and I discovered I had VP...
Yesterday I installed a very tiny and lightweight ESC for my 450 tail motor, and unlike most small ESCs it has a great governor.
http://mgm-controllers.com/index.php...rs-1210-3-heli
A bit pricey, true, but the governor works fine, and keeps the tail at constant rpm as you vary the pitch. The MGM ESC settings allow you to set a max rpm. And a mere 9 grams weight. A slight drawback of the DD Tail, you have to jury rig a way to make Throttle Hold suitable for landing. I did this with a mix from pitch to aux2 that operates only when TH is set so at least I continue to get some tail motor after hitting TH. aux2 is controlled via a mix from THR operating on normal and stunt, so tail starts up and achieves its fixed rpm along with the main. I have to shoot the breeze about it since it snowed again last night so no flight test today of the new ESC...

[R_Lefebvre]

Originally Posted by salience

Salut joly and all,
Made the plunge and ordered my unit <Beavis and Butthead giggle>. It will be awhile before I start the project to install on a Trex600DFC, but amid this discussion of power supply I thought I'd ask about my intended setup. I'll be using a direct drive tail, having got addicted to this kind of setup with a 450 and now a 500 (Quiet!! Low vibes!! 6 pesky fragile gears eliminated!!!). So my tail motor will be driven by a YEP45A on a 4S, which conveniently has a 5.5V BEC I could use for the FrSky Rx and APM (only). Main motor on 12S with either a YEPHV or a K-Force HV120 which I already have, so may try it first. And a CCBEC Pro @6V off the 4S for the servos. How's that sound?

I'm looking at a very similar setup. I've built a 550 stretched to 600, maybe 700 in the future. I have both a K-force 120A HV, and the YEP 120A HV. I'll try the K-Force first. I intend to use the YEP when in the future because I want the active free-wheeling so I can slow the headspeed down safely while in a hover, speed it up for FFF.

I'll be running with a mechanically driven tail at first, but have plans to try motor-tail.

I also have a K-force 40A which is currently on my 450. And a new YEP 45A. Either one of these I planned to use on my motor-driven tail. I have not decided yet. The only thing is, I'm still a little unsure about the this part. I know I need about 6-7000 RPM on the tail rotor. I bought this motor for the job:

http://www.hobbyking.com/hobbyking/s...dProduct=17230

Running on 2S, this motor would do about 7140rpm max, less under load. Ideally, it should run on 3S, goverened to 70%, which would be nice so it holds a constant speed as the battery drains and the load goes up. However, I really don't want another 3S battery on the heli! I'm already going to have a 2S for the Avionics. and 2x4S5000 in Series for an 8S motor system. Maybe even two sets in parallel for duration. If I put another 3S on there, it'll look like a battery delivery service! Maybe this one would be better on 2S:

http://www.hobbyking.com/hobbyking/s...ter_Motor.html

Whatever I use needs a 5mm shaft.

Maybe this would be better:

http://www.hobbyking.com/hobbyking/s...00kv_640w.html

But I'm also worried about the wattage rating. The tail can draw a LOT of power sometimes. I'm not even sure if the 45A ESC will be enough. I should test all this before I go blindly buying anything else.

The question relating to the APM: can I connect the +6V from the CCBEC to the + output rail of the APM with the jumper off (or on, I forget at the moment which it is supposed to be), OR is it best to connect only the signal wires to the APM and supply the +6V to the servos directly from the CCBEC?

Yes, you can connect 6V to the APM output rail if the jumper is disconnected. However, I wouldn't do this for anything bigger than 450. The circuit traces are just not made for that. However, there's a fairly easy fix. You can simply solder a bridge across the power and ground pins of the output rail to beef it up. I've done this, it's easy if you're good at soldering. You could bring in your battery power wire, strip a length equal to the length of the rail. Tin it, then solder it to pins sticking out the underside of the board.

You just have to be careful not to short out the lines when doing this. Squeazing the positive in there can be tight.

Personally, I just find it more convenient to build a separate servo power breakout board. Or just buy one.

[R_Lefebvre]

Originally Posted by salience

A slight drawback of the DD Tail, you have to jury rig a way to make Throttle Hold suitable for landing. I did this with a mix from pitch to aux2 that operates only when TH is set so at least I continue to get some tail motor after hitting TH. aux2 is controlled via a mix from THR operating on normal and stunt, so tail starts up and achieves its fixed rpm along with the main. I have to shoot the breeze about it since it snowed again last night so no flight test today of the new ESC...

Yeah, I plan to fix the code so that it's easy to use a motor driven tail. The beauty of open source. I believe motor driven tails are the future, at least for UAV applications.

So I already figured out how to do this when winding up, and am preparing to do something so Joly can test it. I'm just waiting until he confirms he's figured out how to compile and upload.

But, I didn't consider what to do when landing, using "throttle hold", or when you want to disarm. And to be clear, when I say "throttle hold" I mean setting Ch8 high, with RSC_Mode set to 2, which is meant to run a governor ESC. Setting Ch8 high tells the APM to start the main motor. Setting it low switches it off.

Clearly, we don't want to shut down the tail motor every time we hit TH. You guys might want to practice auto-gyros, or whatever. So how do we do this?

How about this? Currently, the main motor switches on as soon as APM sees Ch8 go 100 PWM above the min of that channel. I can change that to 800 above for all cases. This should not be a big deal for anybody. I bet most already have the Ch8 going full when the switch is up.

Then, for tail motor rotor guys, I can make it so that when the signal is 400 above min, the tail motor will start. So now, you put Ch8 on a 3-position switch. Down is TH, all off. Put it in the middle, the tail motor will start. Put it up, and the main rotor starts. This allows you to start the tail rotor first, then the main motor. You can also shut off the main motor, wait for it to stop, shut off the tail motor, and disarm.

What do you think? I think it's perfect.

Please, if you see any holes in the logic, let me know.

[salience]

Hi Rob,
Joly will have to help you on this for now - I havent even received my unit yet, much less started to install, much much less started to configure. But so far with my 450 FBLDFCTTL (torque-tubeless!) the tail motor control has worked well using mixes in the Tx as described above. Using a DX7S for the moment but I intend to use a Turnigy with the er9x software and FrSky units and telemetry for future helis, so I'll have plenty of options for mixes, switches, et al.

By noon the sun was out and by 3 the helipad was free of snow so I did get a test flight today, just a shorty to see how the new ESC with gov would work. Went well, even TH was OK, but could be improved. When Mix1 (THR>AUX2 for tail ESC, THR curve flat above 25%, on nor and 1) stops signalling AUX2 when hitting TH, then Mix2 does PIT>AUX2, and even though the signaled rate to the tail ESC is then way less than what it just was previously before hitting TH, the tail merely blips a bit CCW as the rpm suddenly slows, and then stabilizes until landing. Since one is only landing with TH, there might not be too much necessity to keep the tail rpm's up to gov speed at all, if this requires tricky programming or whatever. Of course, for a scale flyer, that little tail blip would be a sacrilege and a contest-loser!

Also I did a power test on the tail motor, this is a 1600Kv mini
http://www.hobbyking.com/hobbyking/s...er_1600kv.html
chosen for light weight mostly. It's governed at just below 10,000rpm - plenty I think for my conservative flying. So, when the motor was at speed and pitch centered, the total battery draw was just below 1A. Picking up the heli and rotating it to get the tail servo to give max pitch, the total battery draw went 9.5A max and the new 12A ESC barely warmed.

My first estimate of main-to-tail power consumption - and this should scale up I think - is that in casual flight the tail might not consume more than 10-15% of the main. With 6 minutes of fast pirouette, I would no longer speculate! The tail motors you refer to for a 600-650 are about in the range I was looking at, but I was going to use a 4S motor rather than 6S. Not much chance of anything being much below 150-200 grams. By the way - I took a quick look and it seems you could use a 450 mainshaft as a direct drive tail shaft, with the ring in the middle as in my setup for the 450. For 3 and 4mm shafts, I had to buy special:
https://sdp-si.com/eStore/Direct.asp?GroupID=466

In all, for the 450, I thought that 1600Kv would be too high, but my test today showed you could run it at 10krpm on the gov ESC, and apparently get plenty of power and no overheating when needed. When I was rotating the heli by hand to get max pitch, there was an impressive thrust. I should measure it, I built a rotating table to do this when I wanted to test how much thrust a TT unit delivered in the 500. Again, for 3D fans your DD tail is going to be a whole 'nother affair than for scale, AP, or casual flight. I guess they will be stuck with TTs until warp drive motors are finally on sale...

[jolyboy]

Stand by dudes, reading all this haha

Joly

[jolyboy]

Hey rob I'm almost ready to compile, gimme 1 more week
Your idea is great, only we need to include the option to pass thru throttle signal like in mode 1. That way we can keep running variable gov modes etc.

Obviously the tail switch would he set so it merely 'switches' output from the motor channel and for FP tails it switches ch4 output. That way we won't need to clear the I term after arming (or will we? In either case VP or FP we don't want sudden spinning after switching on the tail)

Salience, congrats on getting involved you are gonna love it Rob is the go-to guy for helis bigger than 450 as you can see.

Joly

[R_Lefebvre]

Hey, I've got a 450 too!

You want to be able to pass through a throttle signal on the tail for variable gov speed? This is starting to get a bit complicated. I would have thought you'd want the tail speed pretty constant?

However... this may be possible... Can you explain EXACTLY what you want to do?

[jolyboy]

No.. Sorry I said that all wrong. We want fixed tail speed for VP tail. I mean we want variable main rotor speed as an option like we already have. So aside from additional tail support we want the main motor setup left as is.

Ok, so we have two more tail types that we want to add APM support for: DDVP and DDFP. These explanations are largely repeating what you already said So, ignoring the main motor, here is how I imagine our ideal tail code:

DDVP:
Fixed motor signal with variable servo signal. While disarmed, servo signal is active, tail motor is disabled. While armed, servo signal is still active and tail motor is enabled. Then you have a 3 pos switch - 0: kill all motors, 1: tail motor on, 2: both motors on.

DDFP:
Variable motor signal (same as servo signal). While disarmed, motor signal is disabled. While armed, motor signal is enabled. Then the 3 pos switch - 0: kill all motors, 1: tail motor enabled, 2: main motor on with tail motor enabled.

Now comes an important point: if we hold full right rudder to arm there is a large rate yaw I term built up meaning that if we suddenly enable our tail motor (3 pos 1) the heli will spin or at least kick. We need to clear the rate yaw I term either when we click from 3 pos 0 to 3 pos 1, or about 2 seconds after we arm as there is time to center the rudder stick after arming. Currently I have to hold full left stick for a while to get I zeroed.

Joly

[R_Lefebvre]

Ok, I concur with the control system, I can do that.

As for the I-term stuff, I need to look at that carefully. What I know right now is that after arming, then when I spin up and lift off, I don't have a problem with the heli rotating. At least it's not something I have noticed. I'll try to have a look.

One issue it that I'm currently working on old code. I just can't afford to test fly the latest stuff anymore because the crashes are killing my wallet, so I hold back on the last stable release. That's what I'm developing on. At some point, I have to merge my changes into the latest code, which can get ugly.

For most of what I'm doing, it's OK. But for like this I-term reset thing, that's a general type of thing that may have changed.

Also, I just realized, I may be able to generate Hex files, which you can easily upload through mission planner. I'll look into that.

[jolyboy]

I think the difference is that for FP systems the Imax value is larger.. I use like 5000

Maybe you could just force Imax to be 1 until the tail motor is powered on, then revert to rate_yaw_Imax. Then you effectively have zero I from the get-go


Joly

[R_Lefebvre]

I'll have a look. I can probably do a couple things. When you turn on the motor, reset I, and set the heading hold at the current location.

These are the types of things that you can do when the system is aware of the motor state, and why I push running the ESC through the APM.

[jolyboy]

Sounds good to me. Yeah if you can send me hex files that would be ideal

Joly

[salience]

Originally Posted by jolyboy

DDVP:
Fixed motor signal with variable servo signal. While disarmed, servo signal is active, tail motor is disabled. While armed, servo signal is still active and tail motor is enabled. Then you have a 3 pos switch - 0: kill all motors, 1: tail motor on, 2: both motors on.

3-way replacing TH, a sort of dual-throttle hold, sounds good. We are having, of course, the throttle stick control both motors simultaneously with a Tx mix, with 2 ESCs on gov mode and a throttle curve flat @70-100% from 25% of stick travel? That's what I've got for the 450. HS about 3000 and tail about 9500. A faster tail would be the norm on a TT, but for "stately flying" I deemed the lower rpm better, has less vibration and seems to have plenty of thrust for any less-than-3D manoeuvre.

Here's a little complication, mebbe: Some with limited channels may also want to do this. On my 500 FBLTTL I'm going to try running both motors/ESCs on a single Rx channel, since I only have 8 and I want a camera angle control. I will juggle tail motor Kv and ESC gov settings to get suitable rpms for each. TH will definitely be a non-starter here. (Or maybe that's a non-stopper?)

Rob, Thinking about your motor choice, 6S to run on a 2S battery: I'd test that thoroughly before committing, seems to me it might be problematic, with both ESC and motor trying to give power at their lowest voltage inputs. A 3-4S motor might work better. And according to what I've seen on the 450 with the 1600Kv motor running sweet at 9-10krpm on a 3S using the gov max-rpm setting available on my new ESC, a choice of a higher Kv motor (and thus higher potential W and thrust) than might be at first thought appropriate cd be the way to go. On my 450, with tail at 9500rpm drawing just 1A, then pulling the tail smartly to get the servo to suddenly give max pitch, the motor easily stays at 9500 while the current draw goes to over 9A - the rms voltage at the motor here must be at a max to get the motor to draw its max rated current. Trying something similar with a 6S motor and 2-6S ESC on a mere 2S batt might be a problem, not sure. Just some speculation. I'll try to do some more quantitative tests on my setups as I go along. I did run a test of a 3S motor on a 6S battery, measuring the rms volts at the motor terminals. As long as I kept rms voltage below what the motor was supposed to handle, it ran fine with no overheating. There was another thread here on the subject where some heated discussion ensued, some saying I'd blow the motor straightaway. Not so. The discussion was far more heated than the motor:>) So one might be able to run a 3-4S tail motor and a 6S main, both from the 6S flight battery, on the 500 for example where the 4mm tail shaft limits you to 3-4S motors. A 600 with 12S main might work similarly, but maybe a 6S tail on 12S would be tempting fate. I think on mine I will use 4 - 4S 3300 Zippy compacts. 3 in series for 12S main, the 4th for the tail. I dont particularly like the 600's slide-in battery tray with 2 3300 6S strapped to it. If they ever swelled in flight you'd have a problem, Houston. I'd rather put electronics in there, nice and protected, and mount batteries on rails attached to the outside. This is what I did on my 500. I'll post a photo... sorry this post got to such unsupportable length! At least it hasn't overheated so far...

[jolyboy]

In your case motor rpms will be set in APM, meaning no need for combining channels. Your tx will just be an on/off switch for APM to to see. So your core channels will be:

Ail
Ele
Coll Pit
Rud
Aux 1 - off, tail on, main on

Throttle channel will be optional. And only really needed for throttle mode 1 users.

To re-iterate, your throttle stick only controls collective.

Joly

[salience]

Ah, that sounds simple and elegant. But I think you mean
Aux1 - off, tail on, both on?
what about the gear channel, is this liberated from having to "control" the tail? I'm constantly annoyed that the channel is wasted on sending the exact same signal all the time. If both gear and aux2 are liberated, you have two channels for AP control - brilliant!