How I built the notswatbot
I started with a military surplus enclosure,sanded and painted it with krylon wrinkle finish. Custom assembled the track system from parts found on Ebay, some lynxmotion tracks. (hubs had to be drilled to match up with actobotics hubs. and actobotics couplers used to line up bearings and shafts, and attach the foreward tracks. I used some planetary gearmotors with just the right torque and speed ( I tried several motors of various ratings and settled on these) 82 rpm, globe motors, the type used to shift a transmission into 4x4, not the quietest but plenty of power to spare. I constructed the robotic arm with a servo gearbox for lift and a servo block to rotate the parallel gripper, all from servo city. The wheels were mounted to the back to keep it from tipping over backwards when going up stairs and a pittman gearmotor with servo city bevel gears and chain/sprockets gives it an extra bit of climbing power as there was very little surface area for the tracks to grip when initially starting the climb. Then added the bottom mount gearbox with spt 400 tilt system (upgraded the servo to a hitec hs7955tg to handle the extra weight of the camera head)
The camera head has three cameras including one foreward facing board camera with ir led array for night vision, a rearview and a hd zoom camera with an rc camera switcher and on screen display module showing operating time and battery voltage. the video signal is transmitted back to the operators position with a Hobby King long range transmitter. Currently it is being operated with a radiolink AT9 and spektrum DX6 transmitter, running a Roboclaw 30a controller as I have not finished assembling/programming the xbee/arduino transmitter. But I couldnt wait any longer to test it out. :)
Step 1: The Enclosure and the Parts List
Choose a suitable enclosure. Bigger is better if you plan on expanding and adding more functions later on.I used a 1953 south korean war era military storage box. it has a hinged top and latches already installed, I thought this would be nice for updating the electronics later on.
Actobotics/Sparkfun parts list:
QtyDescription 1 Sparkfun redboard arduino (robot transmitter) 2 xbee pro (one to recieve and one to transmit serial data) 2 xbee arduino adapters (adapts xbees to redboard and botboarduino for servo control) 132T, 0.250 inch Bore, 32P Bevel Gear (powers the rear wheel axel) 216T Aluminum Hub Sprocket (0.250 in) (transfers power to both sets of rear wheels) 21/4 inch Bore Set Screw Hub (0.770 inch) (holds the chain sprockets) 20.250 inch Plastic Chain (transfers power to both rear axels) 116T, 5mm Bore, 32P Bevel Gear (used to transfer power from motor to axel) 1Aluminum Motor Mount D(rear motor mount) 1Precision Planetary Gearmotor End Cap 1Gearmotor End Cap 41/4 inch Collar (Holds rear axel in place) 2.250 inch ID x .500 inch OD Flanged Ball Bearing (Stainless Steel) 2 pack(axel bearings) 27.70 inch Aluminum Beam (Holds rear tire assembly at the desired angle and also used to stiffen the front track assembly) 19.00 inch Aluminum Channel (used to mount rear motor/axels) 21/4 inch x 6 inch D-Shaft(rear axels, 1.5"cut off one) 22 Function Joystick (ball) (R201BM2)(for rc transmitter) 290 Degree Angle Bracket A( used to adapt robot arm to gearbox) 10Metal Bracket(used to mount some of the aluminum beams) 40.375 inch Mini Channel( still thinking about a use for these :) 31/8 inch ID x 3/8 inch OD Ball Bearing (used to run a shaft thru the tracks to transfer power from one tread to another) 1Aluminum Vertical Servo Mount(future use with servo block for sensor movement) 190 Degree Hub Mount Bracket A(future use) 21/8 inch x7 inch Precision Shaft(track power transfer) 81/8inch Collar(track power transfer) 41/8 inch Bore Set Screw Hub (0.770 inch)(track power transfer) 2Aluminum Hub Spacer (1 in. thick) (mounted between track assemblies) 11/8 inch ID x 3/8 inch OD Ball Bearing (track power transfer) 2Hub Adaptor B(track power transfer) 1Channel Bracket C(camera mount) 1Mount for 2x15A or 2x30A Roboclaw Controller( mounts the roboclaw to a beaminside the enclosure) 61/2 inch Collar(originally part of a counterweight for the arm but changed the design and no room now) 21/2 inch Bore Parallel Tube Clamp(originally part of a counterweight for the arm but changed the design and no room now)( found another use as an led/ camera mount) 11/2 inch x 4 inch Precision Shaft(originally part of a counterweight for the arm but changed the design and no room now) 132T, 32 Pitch Metal Servo Gear (Futaba)( whoops ordered the wrong part, future add on ?) 1Center Hole Adaptors (still thinking about these :) 12.5 x 5.5mm Panel Mount Jack( charge port) 211 Hole Plastic Beam (3.85 inches)( battery holdown) 215 Hole Plastic Beam (5.39 inches)( battery holdown) 126-32x1/2 inch Flat Head Phillip Machine Screw (Stainless Steel) 126-32 Machine Screw Nylock Nuts 190 Degree Hub Mount Bracket A( not used yet) 4Beam Crossover Adaptor A( used as mount for rear tire assembly) 1Channel Mount Servo Power Gearbox - Continuous Rotation( robot arm lift) Ratio is 7:1 Metal Gears 13.75 inch Aluminum Channel( zoom camera mount) 190 Degree Quad Hub Mount E (robot arm) 190 Degree Tube Clamping Hub (.770 inch)(robot arm) 1(17.01.03) 8 inch length x 5/8 inch dia. Aluminum Tubing(robot arm, cut it down to make up for length of added servo block so gripper would park itself in a manner that the main camera could have a clear view)) 15/8 inch Tube Clamping Hub (.770 inch)(robot arm) 145 Degree Single Angle Channel Bracket(robot arm, first design then switched to stronger angle brackets) 1Parallel Gripper Kit A - Standard (robot arm, mounted to servo block for wrist rotation) 212 inch Standard Extension (S/JR/Z)(used to extend the servo wires to reach the controller) 1Beam Attachment Block B (various beam mounting) 14.50 inch Aluminum Channel(inside enclosure electronics mounting) 1.1875 in L x 6-32 Zinc-Plated Alloy Steel Socket Head Cap Screw (25 pk) 1.250 in L x 6-32 Zinc-Plated Alloy Steel Socket Head Cap Screw (25 pk) 21.54 inch Aluminum Beam (2 pack)(future use) 13.85 inch Aluminum Beam (2 pack)(mount rear tire assembly to enclosure) 22.31 inch Aluminum Beam (2 pack)( future use) 1 SPT 400 TILT SYSTEM (modified with a hitec hs7955tg to easily move the heavy camera head) mounted on: 1 SPG785A-BM bottom mount gearbox
Step 2: The Drive System
I used some tracks that were custom built from lynxmotion treads, I found two different sets of these already put together on ebay. The tracks are simply two pieces of sheet aluminum with lynxmotion sprockets mounted between them and aluminum standoffs holding the assembly together. I used the hub adapters from servo city to mount the sprockets to the motors. You can purchase kits from them if you like the style they sell. They use nylon spacers as rollers for less friction on the tracks.
Motor selection: there are alot of different motors to choose from, the ones I settled on are 82rpm planetary gearmotors 12 volt, the type used to shift a 4x4 transmission.
you have to decide how fast you want your build to go and how much power you want it to have, servo city has good information on the motors they sell, thats a great place to start.
Here is also some good information: http://www.gearseds.com/files/Lesson3_Mathematical...
The sprockets I used are approximately 4 inch so I used that as wheel size.
Servo city also has some great wheels you can use if you want to drive your robot with wheels instead of tracks.
Step 3: The Robots Arm/gripper
How much are you going to lift?
If your going to lift only small items you can get away with just using plain rc servos when building the arm.
If you want to lift heavier objects you can use a good strong servo with a servo city gearbox and lift much heavier items. Servo city has all the information you need on the lifting power of most common servos on the market. and with their gearboxes, you can do some amazing things.
I used my heaviest crescent wrench as a baseline for designing my arm, as I thought it would be fun to use the robot to pick up tools around the shop.
If you want the gripper to rotate then you will have to incorporate that into your build as well, I used a servo block for added strength here. And grip strength is also a factor depending on the type of servo you choose, mine is currently just a cheap metal gear servo but still strong enough to hold a small tool. Im sure you could have a gripper strong enough to crush a can if you wanted that much strength.
I used a continuous rotation servo to raise and lower the arm, I just stop the movement, but it should either have a limit switch or use a potentiometer controlled servo to keep the servo from being damaged by stopping its movement. Be sure to check out Servo Citys website for all the information they have on servos, I learned most of what I know from them.
Step 4: The Camera Turret
The weight of your camera is what you need to look at here, my camera was quite heavy and required some heavy duty servos, and gearboxes to hold it in place especially when driving over rough terrain.
I also put all the video transmitter electronics inside the housing to keep the wiring down to a minimum, one thing I like is the hollow shaft on the gearbox that allows wires to be passed through the gearbox.
If you just want a small lightweight camera you can just use a servo by itself, but for a heavier camera, the gearbox is a great way to go.
Step 5: Electronics to Move the Robot
I used the Roboclaw 30 amp controller, I decided on this when checking the motors, they had 21 amps max so I went a little over to be sure.
The roboclaw also provides 5v power for the servos but it tends to draw too much and shows a fault light if I over do it with moving too many servos at once, so a separate 5v power supply is a good idea.
The roboclaw can by controlled alot of different ways so it left me with options for controlling the robot.
Im using an rc transmitter right now, untill I finish building the arduino/xbee controller which will give me even more options for adding on more motion ideas.
Check out the options at Servo city, they have alot of new electronics newly listed for controlling your robot.
To be continued
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