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Showing posts from 2009

Remote Controlled Turret

This is an update and rehosting of a senior design project completed in Spring 2008 at RIT . It is (to date) my favorite robotics project. Myself and two friends collaborated to create a remote controlled turret that was accessible from anywhere on the web. The project makes use of a 5 gallon air tank at ~80 psi to fire foam (Nerf) darts. One servo operates six rotating barrels which are mounted on two more servos that provide pan and tilt movement. There are two ultra bright LEDs providing light in dark conditions for a top mounted web-cam. An Arduino is used to control the turret, while communicating (via serial over USB) with a web server that hosts the custom web page and live video stream. A modified PC power supply was used to provide the power. Here's a video of the finished turret... Full System Test I was in charge of most of the hardware and electrical work, Mike programmed the Arduino (I usually work with other AVR stuff ) to take serial commands from a server

The First

This post is a retrospective look at the first robot I built solely for myself (back in 2008). I had only helped build one robot before this. It's clear I got a very late start into robotics. Although school did prepare me formally to dive right in, I wish I had been more focused on it when I was younger, I would have really flourished in college. This robot was designed mostly on a whim, but has turned out to be a nice solid prototype, and it is very useful for testing sensors and AVR code... The Parts List: Aluminum Chassis, Motor Mounts & Tire hubs - Machined while I was still at RIT when I had access to their machine shop. No original designs are available, I just went in and used what scrap I could find...I'd be embarrassed by providing the true measurements :). Stepper Motors - From Sparkfun ...I may replace these some day with cheaper gear motors so I can use these steppers in a CNC/Drill Press. EasyDriver Stepper Motor Driver - Also from Sparkfun...sim

Hidden Maze Gift

Okay...this doesn't even remotely fit the robotics theme of the site, but it's a weekend project/gift for a family member. The only rule at my family's gift exchange this year is that the gifts have to be "made". For me this is an excuse to kill a weekend with arts and crafts. I started with the idea of duplicating the brain teaser puzzle below. Original Duplicate Well that one was easy enough to make...unfortunately it's not as colorful as the original (couldn't find that kind of rope). While looking online at similar wooden brain teasers I saw a picture of a small wooden box. As it turned out the box had a maze inside with the intended goal of getting a small ball through the invisible maze. I was hooked. So I went back to Lowe's grabbed what I needed and got to work. It has some weird dimensions because I had the guys at Lowe's cut the top and bottom before I really had anything designed (I wish I had a table saw...). I've always loved drawi

The competition that wasn't

Well unfortunately I was the only person to enter the competition officially, so it was canceled . To appease the robot gods' thirst for robotic mayhem Sparkfun morphed the events this weekend into a robot building/hacking/soccer match shindig . Making the 8 hr drive (one-way) was totally worth it even without the competition. I was able to demo "Spin Cycle" to those attending. Most of the day was spent on a class detailing the steps necessary to build an Ardubot for several people who had never made their own robot before. I've been a loyal customer and follower of for at least 3 years. It was great to finally meet some of the people behind the handles . I'm frazzled so no more text. Here is a video of my bot in action, and some pics from the trip. "Spin Cycle" The view from not even a mile away from SparkFun's building. (So...jealous) The fancy sign. Some nifty robot tracking (webcam+IR LEDs+ projector+codes=awesome). Th


Time for the code... The software portion of this robot was fairly straight forward compared to the electrical and hardware designs. I had several previous robots and experiences to pull from when writing the code. As a result the code is very clean and well documented. There are two languages required to understand the code: JAVA and C ( AVR Libc to be precise). JAVA: I used JAVA to create a user interface which would take keyboard input and translate it into serial commands. The UI is very simple. It uses a KeyListener (which is added to all visible components of the UI) to pick up key strokes from the user. When a key is "typed" a string of characters is sent via GiovynetSerialPort1.3 to the XBee Module attached to the PC. The XBee acts a transparent serial cable with the XBee on the robot as the other end of the cable. Any serial data coming from the robot is displayed in the text area... I used Giovynet's serial port library for two reasons; first, Sun (JAVA)

Final Assembly

Well I managed to get all the parts purchased, designed and/or fabricated before the weekend of the event. As is often the case with project like this, my designs changed as I searched for parts. You will see below the final designs created in SketchUp (they really are final, based on the bot I took this weekend). I put a great deal of effort into getting exact dimensions in every place I could. In fact the only blatant differences between the drawings and the real robot are in the purchased parts(drill and batteries) which have too many curves to replicate. SketchUp Model I'm pretty certain no one will want to duplicate this exact design (anyone capable would probably find that boring) ; however, some of the components may be useful. The motors , motor drivers , wheels and hubs are all precisely measured, and could easily be copied into another drawing. I've decided on a name: "Spin Cycle" (a suggestion from my older brother). The name stems directly from the

Best laid plans...

Well it seems that every attempt I make to reduce cost on this robot just comes back to bite me in the end. I think I've learned my new shit and don't try to cut corners. I'm referring to the motors and the motor controller... While investigations into the motor controller resulted in a good design (based on that of the Open Source Motor Controller ) the cost and time needed is prohibitive at least for the motors I'm going to use. So I've ended up purchasing two 9A motor controllers (one for each drive motor). They work very well for these motors (they are way bigger than necessary). One issue came up when I mounted these to the chassis though... Two of the controller's mounting holes are attached to OUT A on the PCB as you can see in the picture. So when I bolted the things to the bot and started using them, a full 15V was applied to the chassis. This burnt out two cheap sensors (fortunately I had enough replacements on hand) and it wouldn't l

Motor Control Circuit

Update: This circuit doesn't work (thanks Sparkfun Forums folks) revised version will be in next post. So I've worked out the motor controller circuit I'll be using. I've ordered the components too. Hopefully when I get them it will work as planned without too much modification. Or the Google Doc The major components: Power MOSFET NPN Switching Transistors Opto-isolator/Photocoupler It's less complicated than the circuit makes it look... It's really 4 identical circuits (which I show in lower part of schematic) attached to the MOSFETs of an H bridge. The optoisolators ( PS2501 ) are also a single package so wiring won't be as complicated either. Please feel free to comment or suggest changes... I've never built a circuit for high voltage/current motors like this before and could really use another set of eyes on this. (Especially if it looks correct, I need positive reinforcement as much as criticism :)

Change of Plans...

I've visited about 15 local hardware/hobby/auto parts/tool stores in the last 3-4 day looking for ideas and ways to turn these drill motors into drive motors for the robot. I've also logged about 8 hours of research into gears, gear types, gear ratios, and speed/torque conversions. I've decided to scrap the idea of using these motors as drive motors. The two main reasons are cost and unknowns. It costs as much to buy geared motors as it does to buy the gears to get these working. These motors are terrible as far as documentation goes. There's no way to find out their intended voltages, current draw, stall current stall torque and on and on... Because of this I don't know how far they need to be geared down. It would take some trial and error at my cost. I don't have the time or funds to do it. The other reason is complexity...It would take a fair amount of machining to create mounts for all the hardware in a custom gearing solution. Don't believe me? Have a

2 Days in and already Over Budget

I did some scouting at local pawn shops for suitable power tools w/ strong motors over the last two days. I ended up finding 2 14.4V Craftsman drills (each of which came with 2 batteries and a charger) and a 14.4 V Black and Decker circular saw (w/ 1 battery). Grand Total $140...Doh! I shopped around with the intention of matching the two drill motors so that they would be balanced in torque/current/dimensions/etc. I made the assumption that being the same voltage and brand would be enough to get evenly matched motors. Unfortunately when I disassembled them later I found that the Larger (red) one had a motor much larger than the other (gray), and the transmission was very different... The circular saw has a motor similar to the larger drill. All three have different drive gears. So the plan at this point is to ditch the transmission from the larger motor and the gear box of the circular saw and find gearing for these two to make them drive motors. Next time I think I'll just bu

2 Upcoming Competitions

Okay so the main reason for this new website/blog (for the time being) is to chronicle the build of a super sumo style robot for Sparkfun's RoboJoust competition on December 6, 2009. As I'm currently at my childhood home in nowhere's-ville Kansas I'm near enough to the competition site (Boulder, CO) to actually participate. I'm looking forward to touring Sparkfun's building and meet other robotics folks. Info on the competition is here . The basic idea is to have two robots start at opposite ends of the track (below) , meet in the middle, undergo epic battle conditions and finally limp to the opponents starting point. First prize for the event is $100 so I'm considering that to be my budget for materials. With that budget in mind I'll be trying to locate old cordless drill motors (for locomotion and weaponization). For now I'm still sketching and brain storming, but due to the budget I'm going to be keeping things very simple: heavy - (battery/