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The Raven

09/06/2015

The past month or so has seen tremendous progress on this project. At long last, and after more than eight years of designing, refining, and agonizing over the electronics layout and operation, I ordered the PC boards. That was a huge step toward things coming together on the electronics front. I must say that ExpressPCB does a fantastic job of manufacturing these boards. Every dimension is spot-on and the finish is gorgeous. Solder masking is nearly flawless and protects the copper very well. All of the hole and component locations are within stated tolerance, as well. In short, the board matches my design to a tee.



The first step toward operation was to assemble the regulators and run some tests. Everything performed as expected. The solder work has been tedious (mainly due to the fact that I am so anal about the look of things) but nearly complete now. All four regulators work well and hold their voltage levels nicely even during varying the main input voltage. The layout made sense as I tried to move all external connections to the forward end of the board to allow for pivoting up when necessary. The motors and camera pan/tilt connect to the forward end, as well as the bridge and auxiliary receiver outputs.

One issue seems to be signal quality, and this problem may simply be the receiver. It is more than fifteen years old at this point in time and may have degraded over the years. Three of the channels (2, 3 and 8) behave normally for a period and then exhibit erratic behavior through the servos. A few seconds of such and none of the three channels respond to commands from the transmitter. I have yet to find a solution for this and if replacing the receiver becomes necessary it is honestly just a drop in the bucket. I did put the receiver output from channel 3 on the scope to read the pulse width quality and it shows constant voltage on the signal pin and lower-than-expected voltage on the 6-volt pin. I have yet to comprehensively test the otther channels in question. They will read very similar, I suspect. Of course, the model has functions for all nine channels on the receiver and anything not operating smoothly will cause me to rethink using 72MHz.




As can be seen above, the board matches previous layout images perfectly. Wiring everything is tough with such narrow spacing and has resulted in a bit of a mess near the receiver and main headers. Over time I will shorten and tie the sections to keep them neat. The coloring of the silkscreen layer is bright enough to read all of the font work down to .050", and the detail is clear throughout. Readability is very important for the smaller lettering, especially for such a large layout.



I am so far very pleased with the look and overall function of the big board. Despite trying to cram so many components into as small a space as possible, working within the board has not been as difficult as I had imagined. The headers do not fit next to each other as I had hoped, but using a few unshrouded headers instead has made it possible to work with such a compressed design. Trying to picture things on the board before it is manufactured is quite tough. I even laid out some of the sub-boards to ensure the external connections would work. So far, so good. And the spot servos fit neatly without hindering adjustment of the TFC. I may eventually relocate the spot pan/tilt system onto the camera positioner in order to free up space on the receiver and open up a few more options as to where the board sits within the roll cage. If so, the board height will shrink a bit which will also help with mounting.



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Content Updated: Sunday, September 04, 2016 at 10:25 pdt

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