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The Raven

08/28/2016

After working out some electronics issues and watching still more develop, I decided to at least clean up the wiring at the receiver end of the board. In order to accomplish a streamlined look, it was necessary to rotate the receiver end-to-end. This alleviated the clearance issue between the output jacks and 12-pin header directly in front. Once it was turned around, I was able to adjust the lead length for each channel and clean the whole mess. The look is much nicer and easier to service.




I also mounted the board to a temporary hinge using standoffs. The board is quite heavy so this will not work as a long term idea. Because of the combined weight of the board and roll cage, I will need to employ a piano hinge and allow everything to swing up toward one side of the truck instead of toward one axle. Still, this idea may require stabilization of some sort.

The cage is more than 30 inches long and holds acrylic body panels for a high-tech look. It also holds the camera mount toward the rear of the roof. The weight and height of all of these parts is pushing me to hinge the board and cage in two different directions -- each side will hold weight so the truck can stay on its tires. Just like the race car drivers say... keep the painted side up.

The entire board assembly is much heavier than I had originally anticipated due to the many changes in regulator design over all these years. At the outset of the idea, there were three regulators, one each for 5v, 6v, and 9v. These were very simplistic and likely would have drifted under load. Eventually the 9v regulator went away due to eliminating end point limit switches for the steering block. I then added lighted switches for each function which required a 2v section to power the LEDs. Once the 2v was configured, I realized there would need to be strict control of the voltage as well as current so the LED power would not damage the diodes (the switches in question are expensive and protection became necessary). As my crazy ideas for additional functioning modules expanded, the need for a 3.3v supply arose. Now up to four regulators, I decided to use switching supplies to keep the signals clean. Also, the receiver power (6v) needed to be fairly stout for all of the servos. Since I eventually added traces for servo power and pulse width, everything went into the stratosphere with regard to cleanliness. The resulting board is enormous when compared to the first design.

Plus, the servo pulses running along board traces are not without their own issues. And there are more issues...




Upon first powering up the regulators, I noticed the main power switch was not doing much of anything. The voltage reading on the board's display seemed to fluctuate in the neighborhood of 5-600mV when the main was switched on and off. Extensive testing revealed that the solid state relay which controls the 13.8v rail (from which everything is drawn) was not opening when the main was switched off. Apparently there is some bleeding of voltage on the rail which is below the threshold of the relay (~300mV). Suspecting the relay was defective, I quickly replaced it only to find the same result. At that point I began to systematically cover the board with test probes and even drew a huge flowchart in order to diagnose the issue. In the end, I found nothing. All traces test out fine and everything else is operating as it should. So, the relay sits there and falunts its high price tage in my face day after day. On the upside, there is a thermal breaker upstream of the relay which performs flawlessly.

No complex system is without its headaches, right? Ugh.

The relay was removed for a time and the photo below shows its footprint.




Also visible in the photo with the missing relay is the SparkFun USB Weather board which was very difficult to locate. Once discontinued, I searched the world and finally found one in Singapore. Whatever the effort, the left end of the board was designed around the size and shape of that component and I just would not have it another way. To the weather board's immediate right is the GPS module and below, the infamous current detector which to this day I am still trying to work with. That board is very flexible with regard to output voltage, and I even went as far as making all of the previously-fixed resistors into trimpots for further adjustment capability. Still, and ever after a year of tweaking all of the trimmers, the current display which should represent the draw of the entire system remains below 100uA. This is unlikely, for sure. Fortunately, I can work with it outside of the remaining parameters. It is only for reference, anyway.

I really went to great lengths and costs to make this system look and work exactly the way in which I had envisioned years ago. So far, the entire picture from the axles to the top of the spot positioner is extremely technical, and quite colorful. Of course, this shelf queen will never be dirty. Can you blame me? For chrissakes, it just went out of control.




Several aspects and systems are as of yet unrealized. For instance, the auxiliary 5v micro-USB input has been removed due to issues related to the regulator, the Arduino inputs are not interfaced with the AHRS, and the 12v switching mosfet seems to be putting out 5v at the header ground when signaled from the transmitter. These problems are small, of course, but the whole system would be much more inspiring if everything worked as designed. Over time I will work with each section as the higher priorities are smoothed out.

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

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