Hi All,
I had an APM 2.5 on my plane for a couple of years and after the initial setup it performed reliably for those 2 years and was quite solid. Recently I decided to upgrade to the pixhawk and ended up buying two of them for two different planes. So far my experience with them has sucked. One of them died with the (No PX4IO board found) message which indicates hardware failure. 3DR agreed and replaced it (but it took a month). Now, just today the other one lost it's USB port and it's hardware failure as well. This is devastating to me and has me wondering if I should just give up on Pixhawk and just us the Eagle Tree Vector instead which so far at least has been easier to setup and with no failures ( I have two of them as well).
Though I'm intrigued by some of Pixhawks advanced features and capabilities I really want something rock solid and usable. But I'm upset that I've wasted about $800 and countless hours on this experiment. Did I just have really bad luck with this hardware or is it a poor design and fragile?
Thanks for any insight.
-Paul
Replies
Thanks Andre,
Yes, that's what I thought you meant. So, in practical terms don't run more than one ground wire between devices when the ground is common within each of the devices. To check that we can use a continuity tester or ohm meter.
Thanks,
-Paul
1) I'm not aware of that one. Where did you see it?
2) The standard GPS cable length is fine to avoid magnetic interference (especially if you use the mast on a copter, to raise above batteries and the like). If you need longer cables, DF13s are available from lots of places.
3) Where did you see that warning? (link?). I don't know why you shouldn't connect your gimbal to the Rx
1) Here is where I saw I needed a zener diode
http://plane.ardupilot.com/wiki/common-powering-the-pixhawk/
2) My planes are on the larger side and in trying to place the PH near the center of gravity it should be under the wing. I like on the fuse behind the wing for the GPS to be away from my video TX noise so I need about 12 inches at a minimum. I ended up extending a cable by soldering in Cat5 cable wire as it was the closest I had to that fine cable. It works but it's very kludgy. This was a problem on my APM too as the cable that came with it was less than 2" if I recall. Needless to say the APM wasn't near the center of gravity (It worked so I'm not sure how important that is)
3) The warning is at the top of this page and is very stern.
http://plane.ardupilot.com/wiki/common-pixhawk-wiring-and-quick-start/
1) That's only if you're *not* using the power module that comes in the Pixhawk kit. I assume you are using the PM, so that's not required.
2) The GPS is typically not affected by that kind of RF noise. The only reason to mount it away from electronics is because it also contains the magnetometer, which is affected by the sort of magnetic fields the come from motors and batteries (anything with lots of current). So that's the only thing you need to keep it away from. Again the mast should do the trick.
3) Got it. That's only if you're powering the Rx from Pixhawk. If you want to run servos directly from the Rx, just use a separate BEC to power the Rx.
1) I just thought it was strange to ask the user to do this when over voltage protection could be included internally fairly easily, no? Was I wrong to not get that fine point from the documentation?
2) If you put up a longer GPS cable on your web site for sale and sold 100's of them could I get a cut of the profits? :-) I just imagine many users would appreciate the extra layout options this would provide even if they had to pay extra to get it. When you say the DF13's are available I can't picture how hard it might be to make my own cable with these as they seem so small and delicate. Is it easy? Is a special tool required?
3) So is it safe to connect the same BEC 5V output to a spare Pixhawk PWM output to provide 5v to the PWM rail AND connect it to the RX rail to provide power to the RX and servos connected directly to the RX? If so, couldn't I just connect the BEC to one and then connect a male to male servo wire between the Pixhawk and the RX? Also if so, should I cut the red wire to the RC in port on the Pixhawk? Is that port part of the 5v rail?
You can see this is fairly complex and confusing. I think it would be easier to just keep the PWM 5v rail completely isolated from the Pixhawk internal power. And if a user wanted to tie the two together for redundancy they would need to install an external physical jumper which would be easier to understand. I would also insure it was protected from voltage spikes so users didn't have to purchase and install zener diodes under any circumstances.
Another aspect of this is how controlling the a brushless gimbal would compare to servos. I suspect it would be less power hungry but I really don't know.
Thanks for your responses Chris. I'm very impressed to be getting advice from the president of the company and truly am star struck as I've followed your story for years.
-Paul
Hi Paul,
If I may, I would say it is mandatory to use a zener diode on the servo rail if you have any servo connected to it. The objective is to protect your pixhawk shutting down from voltage spikes generated from external devices on its servo rail.
If you want the ultimate solution to power safely and with redundancy your pixhawk, I designed AirbotPower board. This board is not cheap but I sell it "at cost", produced in very small volume and it is produced in Europe for quality assurance:
http://www.airbotservices.com/airbotpower-pre-ordering-send-us-email
Thes eboards are now available (not anymore in pre-ordering but I did not have time to update the web page yet)
1) The documentation you're referring to is the user-created wiki at ardupilot.com, not the official 3DR user manual. That wiki is not controlled by 3DR, so it can get into more detail than the average user might need.
2) All those cables are on the 3DR store. Here's a 30cm one for example.
1) Yes, I understand with the open source nature of this device there is some duplication of effort and multiple sources of information. As an example, I got confused by the multiple ground station software available, originally thinking that APM Planner was a more modern release of Mission Planner. It looks similar but more modern.
2) Excellent! I feel a bit embarrassed it was there the whole time and I never found it. I swear I tried by posting questions on the forums. The responses I received said none were available that I had to build it myself. I'll order some right away!
3) I guess I got a little wordy with this point. Let me just say that powering all this properly is a confusing but important topic that deserves a prominent place in your official user manual.
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