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.
Yes please put it through the APM as I cant get git to work/ dont understand its operation. :/p>
Ok, I've updated the version coming out of the AP Mission Planner.
I'm still having troubles with alt hold but it may be hardware as my barometer seems to be acting up.
Randy, any comment on the problem with the logs that seems to be prevalent lately? I think I'm still running 2.0.49 or something like that.
Hopefully I might get to fly this weekend and test out the latest code. Probably a bit late to have any hope of generating an entry for the T3 competition.
my logs looks ok.
However I've just noticed that there's a bug in the current trunk code and the sonar doesn't work anymore. I'm working on it now and when I have it fixed I'll update the APMissionPlanner again. sigh...a bit like climbing a mountain of pebbles...scramble up, something shifts in the code and we slip back again.
Ok, sonar bug fixed and pushed again to the AP Mission Planner so might be ok 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 think the reliability of a L7805 should be fine just be carefull not to mixt the circuits.
and mount the L7805 on a heat sink plate if you don't it could get to hot even with low amps.
how do you supply power to the L7805?
could be a good solution.
I've got the L7805 wired direct to the battery. Currently there is no switch. Soon as I plug the battery in, it's live. The servos are still controlled by a switch.
I mounted it with a screw that goes into my aluminum tail boom mount. A huge lump of aluminum. I left it on for about 10-15 minutes and it was just barely warm.
But you did used a capacitor between the input votage and ground and the output voltage and ground.
just like i this data sheet to prevent the regulator from oscillating?
Most of the time they stay stable but just to be sure.
How about just using a small BEC? I think there are two advantages for a BEC:
1. it's a switching regulator instead of linear so it will use less power and heat up less
2. less trouble!
the only tihng about a switching regulator is that I've heard you shouldn't have two switching regulators in parallel providing power to a single circuit as they can interfere with each other..but i think that concern isn't relevant in this case.
Randy, some of the problems with BEC's that I have encountered:
1. Unstable voltage. Actually, I think this is a really big deal. When I was running the whole system off a single BEC, voltage on the bus was fluctuating anywhere between 4.8V and 5.3V, mostly depending on servo load. Not a huge deal for the servos, but the 4.8V is getting a little low for the APM, and in particular this will mess up the analog signal coming from the sonar.
2. Ripple, I don't have an oscilliscope, but I've heard about it talked about a lot with switching BEC's. Does it cause any extra noise?
3. Input. The BEC's that are big enough to supply 5+ amps for the servos typically want 3s (11V+) input. The BEC's small enough for the APM (<3A) typically are driven from 2s (7.4V). I was going to end up needing 2 radio batteries, unless I powered the servo BEC from the main battery pack. Which probably would have worked.
4. Reliability. I have no idea if this is true or not, but the impression that I get is that switching BECs can be unreliable. The FETs can fail and stick open or closed at any time. My impression is a linear regulator is more reliable. True or false?
5. Cost/size/weight. The L7805 is barely bigger than a servo connector. BEC's are bigger, and while I've got plenty of room on the 600, it's still another thing to find a home for. I actually have another 5A BEC coming from HobbyKing and was planning on doing just as you say, but it's not here yet, so I decided to give this a shot, and it works.
I actually picked up a 10A Castle Creations BEC on Friday night at the LHS. I was going to use that for the servos, and the 5A Turnigy BEC for the APM system. But when I got home, I read the instructions and found out I need the CC programmer just to increase the voltage on the CC BEC to 6V! What a PITA. I'm not a fan of CC stuff generally, and this was another blow. I'll probably return the thing.
Now as to your concerns:
1. How big of a deal is this? I have a 3S 2200 pack for the reciever. I have found I can muck about for 2 hours between tuning and flying, and still be at 90% capacity. I think I have way more than enough capacity. This is probably more of a concern on a small aircraft. How much power do they really waste anyway?
2. Less trouble? How so? Are the linear regulators unreliable?
At the end of the day, that is my #1 concern. Reliability. My impression to date, is that linear regulators are more reliable. True or false?
Anyway, I spent most of yesterday making a nice mount for the sonar that I'm finally happy with. And I put the input RC filter on it, and the sensor heating circuit. Took way longer than I wanted, but it's finally done. Part of what took so long is it seems like the Maxbotics sensor is specifically designed to make it as difficult as possible to mount. The silver box on the back. It needs an RC filter, but nowhere to mount the components. Etc. I tried to come up with some scheme to use Moon Gel damping pads, but couldn't make it work, so it's isolated only with rubber servo isolators.
Tested it and it works, but the scale is off, I think because I'm using the MB1260 EZ-LO. I'll have to update the firmware and use a #define in APMConfig according to your latest changes?
I had to laugh when I read the bit about "specially designed to be as difficult as possible to mount". No kidding! I had to take that silver block into account when I designed the mount for the trex. that's why it's got the piece out of it at the bottom.
I checked in a fix just yesterday fix the scaling and tested it under various set-ups and sonars and it looked pretty good to me. When the next version is pushed out (should be this friday) you can pick up the fixed version through the ap mission planner. Then you can just change the SONAR_TYPE to 2 through the configuration screen (or maybe Michael O will have updated the planner by then to add a drop-down to the hardware set-up screen).
If you're happy with the regulator then cool!