Destroyed my first propeller chip!!!
ypapelis
Posts: 99
Well, after using prop chips for quite a while now, I think I have just destroyed the first one. It was flying on a quadcopter, using a USB protoboard to capture the RC pulses from the RC receiver and echo them to the flight board, while intercepting the throttle channel so I can maintain altitude based on the on-board parallax altimeter. Things were going well up to the point where the quad quit responding to the RC command to disable auto-altitude mode and kept climbing. Given the surroundings (powerlines, roads etc.) I used steep banking to bring it down, which unfortunately lead to a pretty solid knife edge crash into the grass, and I mean deep into the grass. Most screws were sheared, broken mounts etc. The crystal on the USB protoboard was gone and after replacing it it appeard the board was working (I could connect to it and upload firmware) however some of the output pins were just not working any more and some other pins were acting strange (i.e., a 1KHz square wave had a nice steep leading edge but the trailing edge was rounded).
That board had been through so much I am surprised it lasted that long. It had crashed numerous times (mostly onto grass but sometimes on gravel), pins were bent all over, pins were routinely shorted by accident, connectors plugged in the wrong way, etc. I don't know of any piece of hardware that i own that has been through so much abuse, yet up to this final crash, it just kept on ticking!
That board had been through so much I am surprised it lasted that long. It had crashed numerous times (mostly onto grass but sometimes on gravel), pins were bent all over, pins were routinely shorted by accident, connectors plugged in the wrong way, etc. I don't know of any piece of hardware that i own that has been through so much abuse, yet up to this final crash, it just kept on ticking!
Comments
The only possible one I have destroyed - I say possible because I have not tested it - is one I overheated with my IR soldering station. I know I overheated it because it gave off that rather obvious smell, and a raised bubbled blob on the top of the chip. I have shorted pins to both rails, supplied 5v to the chip, etc etc and all have survived.
One comment regarding the plugin xtal. Due to the vibration in the quads, plugin xtals may not be the best choice. I will have to consider this on my pcbs too.
Cluso99,
I very much agree with this. Regarding the crystal, I never realized it was just plugged in the socket; lesson learned. The same goes with connectors on the quads, especially most of the designs I have been working that involve multiple boards spread apart and connected by wires. In fact, I think the root cause of my crash was that one of the wires between the propeller board and the flight board came undone, which is why I could no longer control the throttle but could control pitch and bank. I used simple female crimped terminals with heat shrink around them, which after inserting on a male pin time after time become loose. I also noticed that these terminals are square and sometimes if you insert them in a diagonal orientation they loosen even more. So I am seriously re-thinking the types of connectors I am using as well as using mechanical means of ensuring positive contact.
Been there and done that and mine also survived.
However, I applied 12V to one and that one did bite the dust.
I can't blame Parallax for my stupidity.
Duane
I wish all RC receivers used standard (.1") spacing on their pins. My 7 channel futaba receiver has non-standard spacing across the 7 pins sets. I believe this is to allow side-by-side 'fat' servo cables to fit. I tried to use a single 7 point connector across the 7 signal lines and it just won't fit, the spacing is just off by enough to make it impossible. What I will try next time is use the same crimp terminals but bend them right after the crimp point and tie the 9 wires on the body of the receiver, that way the tie will keep positive pressure on them.
I would love to see what you do with your distribution board. The cabling and wiring is just a mess, I have probably spent 75% of my time on mechanical and wiring issues and 24% on s/w design/coding. The last 1% is flying the quads ...
Could you build unit LESS sturdy, so when it inevitably crashes, there are more "crumple zones" to take the shock?
I hope crashing every other flight is not used for inspiration for anyone!
The approach i am using is to fly cheap, throw-away frames during development and transition to 'better' frames as things stabilize. I have found that for small crashes (such as launch flips, etc.) using out-riggers is a better safety feature than a soft frame. Out-riggers are pieces of wood stuck on the end of the motor arms so as the quad flips, the outriggers touch the ground first as opposed to the propellers; if something goes wrong, the quad just flips over but everything remains intact. On larger crashes, like the one I started this thread about, soft frames tend to bend and make the propellers sheer everything, which causes more damage than the shock.
Interestingly enough, except for the propeller board, this crash "cost" about $45; 3 cheap motors and one ESC; not bad...