I have just bought the ArduPilot Mega 2560 Full Kit... plus the Triple Axis Magnetometer HMC5883L. I should have it built over the weekend.. then i'm off to a my mates machine shop, and i'll make the splitter plate for the lower frame onto which i am going to fit the Ardupilot. the magnetometer i'll put on the tail as suggested. I am going to use my X-cell Razor 600E. For those that dont know its around the 50 size nitro heli.
Do i need to buy any other sensors i.e. the Sonar... i can fly a helicopter all day long but this is my first time flying one with stabilisation so any tips would be gratefully appreciated.
If this works well then i am going to try and use it on my x-cell gasser. i can get up to 20 minute flights with this. But i think for the time being a battery 600 is the way to go.
i'll post some pictures when i have it all together.
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Just received my latest Hobby King order which included the 783,333uF capacitor bank. And I did some power testing with the Power Analyzer. First, I had to disconnect the servo power supply BEC from the APM in order to break a ground-loop that was confusing the power analyzer. Once I did that, I was able to measure the full-boat APM power requirement with the mag, GPS, sonar and Xbee (not active) at only 0.2A. That proves (I think) that the L7805 is more than capable of powering the entire system. Anecdotal is that these things are reliable. I also tested the inrush current to charge the cap bank. It shows a spike up to 1.4A when first plugged in, which quickly decays to about 0.5A. After disconnecting the power supply, the cap bank can power the APM for something like 2 seconds. It then does something... sort of like a brownout, but it's weird. The servos seem to go to some undefined location, even though the APM LED's are still on. After reconnecting the power (even though the LED's never went off) it appears like the APM has to reboot. So, I'd say you have about 2 seconds power protection from a complete blackout, after which, the heli will enter some undefined flight mode which will probably result in a crash. In any case, you've got 2 seconds you didn't have before.
The cap bank is about the size of a D-cell battery, but is very light. Maybe 1 oz or something. Actually, HK shows 26g. I think it's well worth the weight on any heli if you can fit it.
I've had the L7805 powering the system for about 15 minutes now with no airflow, and it's... it's warm. I can touch my bottom lip to it (much more sensitive than a finger) and it's almost painful. Finger temp, barely feel anything. I dunno, maybe 60C.
I should note, these brownout protection times (actually, they're blackout protection) are NOT powering the servos. If you were powering the servos, much less. But still better than nothing. Long enough to get you through an transient servo load spikes, but not a stalled servo.
One thing I'm slightly concerned about is the effect of the cap-bank on powering down the board. Will this prolonged period of being at 1-4V cause any problems for the APM?
My Engine has been paid for, or more correctly, the shipping costs for my engine have now been paid for so as soo as it arrives I can get down to tuning. I am using the Arducopter V1 hardware meaning the AC2 with OILPAN and sonar, mag sensor and GPS so wil report my finding once I get airborne. I have talked to Malc about starting PID values but will most probably talk with randy about where to start with those too seeing as this is a gas powered 90 size helicopter. Good news at any rate. Although the engine I am getting is not the one I desired - I am getting the G260puh and I really wanted the G231puh instead as they have lower vibration - but whatev.
id like to get gps hold on my heli
Yesterday I added the small caps to the L7805. I ran shielded wire for the GPS and Mag on the tail. I believe my APM installation is finally complete. Now I just need to fix the mechanicals. I was hoping to fly yesterday, but it just didn't happen. Winter is here, and I promised my wife I'd paint my daughters room in the winter... she's holding me to it. :( ;)
Might after to wait until the week after Christmas now.
I have taken another slightly different route now. I performed the Jason power hack. And I hooked up an L7805CV 5V voltage regulator to power the APM and receiver. It seems to work perfectly fine. This is rated to provide up to 1A. Previously I measured the APM and receiver drawing 0.2A. So it should be fine? I'm powering the servos separately with 6V from the UBEC.
I tested the setup, and all looks great. In fact, the voltage coming out of the L7805 seems to be more stable than the UBEC.
Am I missing anything? Any reason why it has to be more complicated than this? Anything wrong with the L7805? (reliability?)
I've checked in those changes to fix the slow roll/pitch updating. I haven't updated the version coming out of the ap mission planner yet until I have a chance to check the alt hold again.
I'm pretty sure the sudden climb issues that marianne was seeing (and i also saw recently) were caused by a high I value on the throttle rate. I think what is happening is sudden negative spikes (which happen often if you have a noisy sonar due to an uneven power supply) in altitude from the sonar would cause the I term to build up and these would overpower the P. That's my guess at the moment (more testing this weekend).
It looks like the diydrones store has sold out of trex mounting plates so I'll send some more in. The mounting plates fix the APM2 as well by the way although I have not yet flown a heli with the APM2.
Made some progress on the weekend.
I removed the shielded cable I used for my tail servo, and replaced it with simple twisted servo wire. But instead of running the ground and power direct to the battery, with only the signal wire going to the APM, I put the ground and signal to the APM, and only the power wire directly to the battery. I also added a large 4700uF cap glued directly on the back of the servo. This appears to have fixed the problem! I have no noise at all from the Xbee.
I'm not really sure why this worked, as there really isn't anything, no resistance of voltage drop, between the battery ground and the ground rail of the APM. So it shouldn't matter, but it appears it does make a difference.
I also made my own capacitor bank for the APM. It's 5x4700uF caps soldered together. It helps for sure. I can actually flick the power switch on-off-on very fast and the APM does not reboot. You have to do it FAST, but it works. Also, the servos are drawing on the cap bank as well. I'm sure once I split the servo rail from the APM, it will keep the APM alive even longer.
Hello!
Been out of the loop for a while (though checking in every day) and thought I'd share the progress - still waiting for the enging but that is no longer major hurdle as I have paid for it, all I have to do is pay for shipping and then the magic will be happening (by magic, I mean the tuning and flying of the arducopter will begin)
Ok, I wanted to get to the bottom of this power problem, so I soldered up some connectors and ran my Power Analyser on the radio system to see what I could get.
Interesting.
Ok, first of all, the results for the APM and the receiver, all servo disconnected. APM was running the Xbee and GPS, but not the mag or sonar at this time. I saw a max power draw of only 0.22Amps. That's less than I thought. It's so low, I think I'm going to bring my Fluke meter from work to double check. But lets go with it for now.
Then I checked the same setup with the 3 swashplate servos plugged in. I madly stirred the sticks, and the highest I saw was only 1.57A That surprised me. So, I pushed down on the swashplate as hard as I dared, all 3 servos buzzing away, and I saw only 2.5A. Wow. So, I then decided to see what I could get out of it if I plugged another 958 servo in to the tail channel. Then, again madly stiring the sticks, this time even faster than before, I saw a peak of 3.5A. Still not even close to my advertised 7.5A limit.
But then I saw, min voltage on the display... 4.92V. That's interesting. I wonder how that happens. Maybe whatever circuit is controlling the FETs in the BEC can't respond fast enough to some voltage spikes?
Is that low enough to cause a brownout?
One of my ideas was to avoid a brownout by powering the APM and receiver with the built-in power regulator on the APM. This would ensure that no matter what, the servos can't take out the APM. Unfortunately, it seems like the power regulator on the APM really isn't big enough for the function it is intended for?
http://www.diydrones.com/forum/topics/powering-the-apm-board-separa...
So, I worked with my setup all yesterday, didn't get nearly as much done as I'd like, but I did make progress.
I cleaned up the spagetti mess of wiring I had between the reciever and APM where I'd used extensions on top of the 4 short jumpers provided with the kit. I made all-new custom length wires. I thought I'd get real slick and use only 1 3-wire connector to provide power to the reciever, and then only use signal wires on the other channels. In fact, I turned the connectors sideways so a single 3-wide servo connector picked up 3 signals.
But it got all messed up because of my radio setup since the servo channels are not straight through. Mine goes like this:
Receiver 1:APM 1
Receiver 2:APM 2
Receiver 3:ESC
Receiver 4:APM4
Receiver 5:None
Receiver 6:APM 3
Receiver 7:APM 5
Receiver 8:None
Anyway, no more extensions and jumpers, just jumpers.
I also rewired my 3S tail servo with 3 conductor shielded wire. I put a torroid inductor on the power wire. This helped with the Xbee problem, but not completely.
Then I moved the Xbee up front mounted under the main battery tray. I ran that with 4 conductor shielded wire. I don't know if the shielding was really necessary, but since the cable is passing directly under the motor, why not.
This virtually eliminated the Xbee intereference on the tail servo. I could hear the servo making more noise when the Xbee was connected than when it wasn't, but it wasn't actually moving.
Then, I put a large cap on the power wire going to the tail servo, and it's dead quiet. In fact, it's quieter than it is when the Xbee is not connected at all. Success!
I did have a thought though:
My FrSky reciever is a telemetry model. So it's outputting 2.4ghz signals back to my transmitter model. The antenna for it are very close to the tail servo, but it doesn't seem to cause any interference at all, unlike the Xbee. I wonder why.
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