Archive Page 3

Progress

Matt here, the last few meetings have been fairly short and not terribly productive. We’ve still been unable to get our home-baked serial shifter prototype to work, however we did track the (previously unmentioned?) problem in our power supply that was causing it to produce 6.5V instead of 5V to a .1uf filtering cap we put on the output line. Everyone seems to use and suggest them, but we breadboarded several permutations with our spare regulator and found that it only produced 5V with no filtering cap. With that cap desoldered our power supply on the main board now works correctly.

Our goal has been to boot up the board as it currently stands and then check our analog connections in software, but since we’ve wasted enough time trying to our serial to work the next meeting we’re planning on it aside and soldering the rest of the board together. Hopefully we’ll finish up the other small things like the EEPROM, micromag, and buzzer. Then I’ll take the board home and in the evenings fiddle with the board and the shifter prototype as well as the working sparkfun version until I can finally get my one click programming to work arduino-style!

Board Progress

Well, the new board is getting there, here are some pictures of it. In the upper left, is the power supply. the center is the arm, and the gyros/accelerometers are below that. To be added:

Serial Shifter circuit, upper right

ESC connections, Lower left

Shift register, lower center

Radio controller, lower left

EEPROM, middle right

and of course, for matt’s enjoyment, the power supply for the buzzer, should be squished in between the power supply already there, and the sensor rows

Empty Board

Empty Board

Halfway assembled board

Halfway assembled board

~Will

Week 4

Matt again! Construction of the new board has begun! Its exciting because after building this the only thing standing between us and a flying quadcopter is the Kalman filter and PID loops, both of which should be pretty interesting since I’ve never coded anything like them before. Unfortunately, its looking like constructing the board could take a while. After a short meeting on saturday ( 1 1/2 hours) and a full length (~5 hours), all we managed to build was the power regulation section of the board. We also learned a few embarrassingly obvious things about board layout we had previous overlooked:

  • Always check the physical sizes of your components! I did large portions of the layout being most familiar with the schematic, but it comes time to solder R1 comes up and Will tells me it simply won’t fit! Doh! I had given resistors only one hole spacing which works for the low wattage ones, but we were only able to dig up resistors of higher wattages in some cases, which really need two holes or more. This prompted a bit of redrawing, although thankfully nothing painful.
  • Always check the datasheets for pinouts! We got three regulators each from a different manufacturer from the electronic goldmine, and were able to avoid needing the more complex adjustable regulators for two of our three voltage supplies (5V, 8V for Camera, and a seperate 7-9 for future autopilot controller XBC). At the last minute, we decided to double check the pinouts for each part, and as it turns out, they were all different! This unfortunately prompted much redrawing, particularly because half the drawing was already soldered on to the board..
  • Keep in mind the scale of the drawing! This is one thing that a computer CAD program would definitely help with, if you took the time to track down and create footprints for everything.. which we didn’t. Our graph paper is roughly twice as big as the holes on the board, so everything gets closer together when you actually create it. In particular, our power supply capacitor ended up blocking nearly twice the radius of holes as predicted, which also necessitated redrawing…

Despite our mistakes, we ended the day with 0 casualties (though we did purchase a spare of every component) with a working circuit on the first try. Unfortunately, I forgot my camera and Will’s has been acting strangely, so I have no pictures :/. I’ll try to get him to take a few for the blog post in the next few days.

In the mean time, week 5 will probably be the construction of the new serial shifter. We’ve worked in some improvements on top of sparkfun’s basic RS232 Shifter (during physics class while learning about amperage, no less :D), namely control of the reset line and the boot0 line of the stm32. With this new circuit, my PC should be able reboot the MCU in bootloader mode, download the code, then reboot again in running mode using some extra control lines in an RS232 cable. We stole the concept from Arduino, but because the stm32’s bootloader can only be activated by a specific boot pin we needed to make it a bit more complex.

Week Two

Hah, and laziness it was. Yes, with school in session there’s increasingly less and less time for work, rest, and sleep, not to mention fun things like the quad. Last weekend did go well though, with full plans drawn up for our newest PCB and our firing up all four motors at once, three with propellers on them. Sadly, due to camera difficulties we do not have any of the many videos we made, but we will get them up with multiple motors spinning soon. Instead we do have a picture of the more exciting part of the meeting:

The PCB Draft!

The PCB Draft!

While it’s probably not too legible in this form, to get an idea for it, the solid lines are traces, and the dotted (and sometimes rather wandering) lines are wires.

As for meetings, Matt ordered the new parts (mostly including the female headers, essential to the new board) from Goldmine as stated earlier, but they are due to be shipped in Monday… the day after we need them, so our meeting will have to be held off an extra week. Meanwhile we are entertaining ourselves with the prospect of it flying.

~Will

Week One

Well, this post is quite a bit belated, thanks to Will’s laziness :P. I’m unofficially deciding that since school is in, we’ll measure time by week rather than by day, since we usually can only meet once on weekends anyway. So this post is going to explain what we did the weekend of the first week of school.

As was evident in the previous post, we fired up an ESC for the first time. After fixing a bug in the timer driver, we were able to control throttle from the vex remote, albeit with some glitches. I learned that the ESC calibrates your arming signal as the “off” position, but the code assumed that 1ms always meant off but sent a .75ms signal to arm. Because of this, as I mentioned briefly in the video we were unable to turn off the motor short of shutting off the signal, which causes the ESC to power off only after a few second delay. Easy fix however, we’ll simply send a 1ms arming signal and also use that to signal motor power off.

We also ordered female headers and a bunch of other goodies from Electronic Goldmine. They have all kinds of random awesome stuff, like this electronic interrupter that should make excellent landing gear, or this really cheap 1×24 character LCD. Since we’re extremely low on IO lines, we’re going to attempt to drive the LCD’s data lines using a shift register. We also picked up 5 super caps for Jeff, for a possible future railgun project. And a bunch of other random stuff, like transistors, and an assortment of voltage regulators for powering various things like XBCs and wireless cameras.

I’ve been working on the final board’s schematic for a bit. Like the previous board, it primarily is just routing power and signal lines to the microcontroller and sensors, but this new board will also contain our EEPROM and altimeter, which finally arrived from Futurlec. It also contains its own power regulator, and provided I can convince Will a built in serial shifter circuit as well. The direct connection to the battery means we can also measure our battery voltage.

Since we’ve got a three day weekend, tomorrow will be our Week two meeting. We should get to construct some sort of harness to keep the copter from flying away during later testing. We’ll also measure our power draw with a watt meter, and if everything looks good fire up all four motors. After that, we should probably try out our the LiPo charger for the first time. And last but not least, work more on our board layout using the schematic. Construction of the final board should begin on Week three provided we finish the layout tomorrow and the parts come sometime this week!

Oh, and here’s my crappy board schematic, made in ExpressSCH. I used Eagle for a while, but its part list was annoyingly slow and massive, while ExpressSCH works much faster and also is more intuitive to work with. Since this schematic will never get fabbed, its also nice that ExpressSCH doesn’t keep making you worry about picking identical parts with different footprints. It looks kinda ugly right now, going to spread components out more once I’ve placed them all. All thats remaining are the boring connectors for a few spare UARTs, and the transistor-driven 12V buzzer I think.

Mainboard WIP Schematic

Mainboard WIP Schematic

Now With a Propellor!

P8300170, originally uploaded by wimbot32259.

Again, but about five minutes later with a prop attached.

~Will

Motor Spinup!

P8300168, originally uploaded by wimbot32259.

So, finally, after many many hours of work, and many many unsuccessful tries to accomplish a single task the quad moves on its own. A combined effect of my being tired, it being night time, and us having this video makes me not feel like blogging the details yet, but they should be up later, for now enjoy the video.

~Will


Project Quadcopter

Welcome to our quadcopter blog! We're a bunch of high school seniors from Florida attempting to create an awesome flying robot before we all have to go our separate ways for college. To learn more, see the about pages!

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