I bought my APM 2.0 before it was actually available, and spent a long time waiting for it to finally arrive..mounted it on my home brew quad and went into tuning hell...I never got it to where it would fly better than the KK board I had on it previously, so I removed the APM 2.0 and went back to the KK board.
I had some time off around the holidays, so decided I could revisit this a bit. Big code changes, more advise on how to tune properly and now it flies well...still working up to a mission, but I think I'm getting close.
I notice that there is a recommendation for a "power protection kit" that is a zener diode and a fuse that should be soldered in place. I have been searching and I can't find out WHY this kit is required...I can see threads where it's discussed how to install it, that it's available, etc, but I've hit my limit on time for trying to find out WHY it's required...
Can anyone comment?
BTW, finding accurate and up to date information on the APM is my single biggest frustration with the purchase. You find things on the wiki or in the forum. The 2.8.1 tuning guide is by far the best thing I've located to date and it was a link in the wiki that I almost didn't notice.
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As a company, 3DR is in that stage I liken Microsoft to have been in after they got the IBM PC (the dual floppy disc PC - mid 1980's) firmware deal. Tranforming from smallish tech company to a larger customer oriented business can be a tough transition. As the entire thing/product has been open source, I think it makes the job more difficult.
Documentation will always be behind the release until they centralize the process of development. There is an active effort on the part of 3DR to improve the situation. This has been repeated several times by Chris Anderson.
The tuning variables... I don't even want to think about the changes in them. The Code Monkeys (an affectionate term - I love and appreciate the efforts of the development team) have the hardest job in the world. As folk come and go, keeping track of all the various builds and tweaks is a Herculean job. Happy 2013 to the Development Team!
Glad to see another EE trained hobbyist. There were so many questions regarding the power input of the AMP2.x, I felt compelled to massage the schematics for the basic power to help ease some of the questions. Not everyone is comfortable with Eagle or even has access to a PC (if they are running with tablets, netbooks, etc). Thus the simplified power schematic.
3DR is looking to staff some engineers. If you leave in southern California (or want to) and are ready to change positions, give them a shout.
My 1st quad was built from their published 'B' model drawings. I essentially cloned their dimensions with variations in materials. My 2nd will have shorter arms ('C' model has shorter arms) but a larger central body. The motor-to-motor moments will be the same as the 'B' version to flatten the tuning curve.
-=Doug
If you are comfortable with reading schematics, look over the simplified 5V circuit of the APM2.0 and APM2.5.
Instructions for adding the zener and fuse are HERE (Arduplane wiki). The schematic for the fix is HERE.
The 'kit' was never listed in the store that I remember but 3DR would send the parts to you if requested.
In essence, failure analysis was showing that the input voltage was being exceeded by builders. A major problem with this hobby is that a number of people coming in do not understand how fragile and sensitive the components of the APM are to overvoltage. Often they are learning electronics while trying to learn RC also. The pico fuse and zener addition were an attempt to mitigate a overvoltage input mistake. Power reversal is also suspected in some situations. It is that simple.
With APM2.5+ and the introduction of the APM Power Module, these events should eventually fade.
I didn't receive a fuse and zener in my APM2.0 purchase. I use the 3DR PDB with all four ESCs connected and have never had a problem.
I am sorry to hear you had a poor experience with your APM2.0. After I sorted out my radio setup issues, it has been fantastic with only me to blame for any damage due to flying/learning to fly.
-=Doug
I know how it works and I know how to install it...I just haven't been able to locate a discussion on what problem it's trying to solve.
I mean, are people blowing the board up with to much voltage? Voltage spikes taking things down? What motivated the change?
I'm trying to understand the reasons behind the addition to determine if my quad is at risk...and I've been completely unsuccessful.
I'm also not finding the power protection kit on the DIYDrones store, although the instructions do provide part numbers of the devices so I can likely source them another place.
Seems this shipped with the later boards...
The caveat is that both the Zener and fuse have MAX voltages and current that they can carry, so if you exceed that catastrophic failure can still happen. But it's much more robust.