Related pages on www.mikekohn.net: atmel rs232, atmel probe, picarus, msp430 guitar processor, 6581 Sound Chip, FPGA VGA, SX VGA, Atmel VGA, Bitbanging, Motor Control, Linksys Helicopter

Introduction

So using the Atmel Pilot firmware and software around it, I wanted to build something that could fly from it, so I stole my friend Oliver Hillmann's idea of building a quadcopter :(. Sorry Oli :(. Anyway I did deviate from his idea in that I wanted to use a Linksys router instead of a radio kit of some kind or Fonera. Using the Linksys router all the commands to the micro can be done over TCP/IP with the Naken Web webserver. For more information on how this system works, take a look at the Atmel Pilot web page. There is an explanation of the system with a diagram and a video of it working.

Special thanks to my dad for designing the motor driver circuitry so my microcontroller doesn't catch fire :).

Explanation

So basically what this is is 4 DC motors with propellers controlled by the Atmel Pilot system. The throttle control of the joystick will control the speed of all the motors together. When the joystick is tilted the speed of the motors will become uneven causing the device to tilt.

Materials

• 4 SuperSpeed 9-18VDC Hobby motors Model 273-256 from Radio Shack
• MJ4701 Collet Prop Adaptor for 2.3mm Shaft From Hobby-Lobby
• PE06055E 6x5.5E Thin Electric Prop From Hobby-Lobby
• Linksys WRT54GL with OpenWRT Firmware
• Atmel ATMega168
• Electronic parts (read the schematic after it's posted)
• Wood, paint, wood glue, epoxy. Lots of epoxy :(.
• 8 disposable AA batteries for 12V

Weights

• Router 350g
• 1 Motor 50g * 4
• Wood 25g
• Microcontroller circuit 75 gm
• Battery:
  • 8 AA Rechargable or Throw away 200gm
  • 12 cell NiMH R/C airplane batteries (I think 400gm)
  • LiPo ?

Weighing the entire system together, it appears to be just under 1kg.

Possible Problems

My biggest concerns (other than bad solder joints.. which since I suck at soldering is quite possible) are:

• I'm trying to pull possibly up to 7A out of these AA batteries.. is this possible?
• The motors are connected to the circuit board through header pins and the connectors used to hook up a PC case to the motherboard for LED's and power switches. These wires are small and potentially 1.5A could go through them and maybe melt them.
• The Atmel firmware has an echo to the main computer but the main computer doesn't check to make sure it's the same. If some bits are lost the router could be in deep @#!#@
• If the wifi connection is lost the motors will stay in the last position they were told to be in.
• If the webserver drops the connection it's a pretty long delay to re-establish a TCP connection.
• If the web server crashes. Byebye router.
• Delay from the computer to the motors (due to network data transfer, UART speed, and the 20ms update time of the router) may make it hard to control.

Status

So all the circuitry and software is working. I can control all 4 motors on the router with my Logitech joystick. The probablem appears to be the weight and probably the motors. I put the device on a scale (pictures below) and with the motors turned off it appears to weight around 1150g. When i turn the motors on full blast the weight drops to around 700g. So it looks like I'm able to push about 500g with those motors/propellers. So I'm kind of wondering if using motors actually made for R/C airplanes would fix it. The problem is an R/C airplane electric motor can cost between $80 and $200 (while these cheapo radio shack motors I used were $6 each) and I've already sunk quite a bit of money (for me at least) into this thing, so I'm not sure if I really want to try to sink another $320 to $800 into it. If anyone would like to donate 4 identical motors to me, let me know. Also, if anyone has experience with motors/propellers like this, feel free to email me any suggestions

I'm hoping to post a YouTube video of the thing tonight.

Pictures

	A brand new Linksys WRT54GL router with a fresh install of OpenWRTsnapped apart. I think my warranty may be voided.
	A view of the wires I soldered to the UART on the motherboard of the router.
	All put back together with its new dual serial ports out the bottom.
	Here's the first propeller I got and motor mounted to a candle holder sitting on top of a scale. I was trying to use the scale to measure how much thrust this prop/motor combo would give using different power supplies, altho because of the way the motor was shaking, I think it may be a false test. Either way it only seemed to want to push about 25 to 50gm, which isn't enough for what I need.
	Here is the circuit board sitting next to the router and one of the motors while I test to make sure I didn't mess something up. This is one of the most annoying circuits I've ever had to make. So many parts and not enough space the board.
	Here is the final product minus the 8 AA batteries that will go at the bottom. The frame is made out of all wood with lots of wood glue and epoxy to hold it together. Since the router was already mostly blue, it was pretty obvious I needed to paint the structure yellow so I could have my favorite color pattern: blå och gul.
	This shows the router sitting idle on a kitchen scale with the newest propellers I've been trying (bigger than the original). It's hard to tell from this picture, but the whole thing with these R/C airplane batteries (12 NiMH cells instead of the original 8 AA batteries I was using) weighs almost 1200g.
	Here is the router again, zoomed in on the scale with the motors running at full blast. The scale now reads 700g which means I'm only pushing around 500g.

Schematic

Coming soon

Download

Coming Soon