Introduction: Rocket Brand Studios Little Wheels Robot
The Little Wheels Robot is a great little bot for beginners and experienced robot builders alike. Simple, well designed and cute as a button, it is just a gosh darn good little bot.
More Info Here.
- Laser Cut Acrylic Chassis
- All hardware needed for assembly
- 120:1 geared motors
- Fancy-schmancy wheels
- Arduino Nano and UnderShield Combo
- Sharp distance sensor
- Really awesome head that looks really cool
Step 1: Getting Started
Open up your kit and separate all the pieces/parts. The hardware baggies are divided into chassis, stand-offs and sensor bracket (head). I have found that these little screws have an amazing ability to jump off your desk --I suggest a muffin tin to hold them while you are working.
You will need:
- Soldering Iron and rosin core (flux core) solder
- Little screw drivers
- Needle nose pliers or tweezers
- Wire strippers
- X-acto knife
Step 2: Assembly 1
The acrylic can have a bit of a funky smell that you may notice when you open the package. This is simply what acrylic smells like when laser cut. The good news is the vast majority of the funky goodness is contained by the paper backing, not the acrylic itself. Peel off the protective paper, throw it away outside and the smell will go with it, promise. The tiny bit of odor left over will dissipate in a couple hours.
We will start by prepping the motors.
- Find (4) of the 6" jumper wires --don't use the red and black ones for this, use 4 of the assorted colors
- Cut one end off of each jumper so each wire has a female connector and a bare (cut) end
- Strip back the insulation from these wires about 3/8" (1-2 cm)
- Find the (2) little brown capacitors and bend their legs outward so the are approx. the width of the contacts of each motor
- Twist and solder one of the jumpers you prepared earlier to each leg of the capacitor
- Finally, solder this capacitor/ jumper wires assembly to each motor (as shown in the picture below)
Step 3: Assembly 2
- Affix the (2) motor mount plates to the motors using 2-56 x 1" screws. They will be the longest screws in the kit
- Place the center plate between the two motors as shown in the pictures
- Place this assembly onto the base plate --Note: There is a left and a right to the base plate. If you study the pictures included in this step, you will see one hole (about 1/4" in dia) along one edge. Use this hole as a reference to align your stuff to match the pictures
- Also Note: You are going to have to wiggle-ka-jiggle the motors a bit to be sure they sit flat and flush down into their little recesses
- Fasten this assembly to the base plate with (4) 2-56 x 3/8" screws and nuts using the "T" shaped holes in the parts
The acrylic parts are a little brittle and care should be taken during assembly. Once assembled, each part is supported by the next and thus, a very strong chassis is obtained. That said, I must repeat that you should be careful during assembly. Don't force anything and do not tighten the screws more than snug. Tweezers or needle-nose pliers will be your best friend in terms of holding on to the tiny nuts and getting them in the little "T" shaped holes. Be gentle and patient and you will be all set.
Step 4: Assembly 3
The battery pack will attach to the bottom of the robot obviously but it seems we have some screw heads in our way. To over come this, there is a spacer plate that will go between the chassis and the battery holder itself. In addition, this plate will help us route the wires coming out of the battery pack to where they need to go.
- Place the spacer plate over the bottom of your little bot. Note that the notch in the spacer plate will line up with 2 small holes in the bottom plate of the chassis.
- Route the wires through these holes being sure the two wires are not twisted
- Help these wires through the holes as you lower the battery pack down on to the spacer plate
- Double check that the battery pack is sitting flat and the wires are sitting neatly in their little notch
- Attach the battery pack with the (2) 2-56 flat head screws. These will be the only flat head screws in the pack
- Note: I have a really hard time trying to source a supplier for these little flat head screws. Thus, I am sometimes forced to purchase them slightly longer than what is needed. If the screws included in your kit are overly long, say, more than 1/16" (1mm) past the nut, you will need to trim it down. Once the nut is tightened, you can easily trim off the rest of the screw with some dykes (diagonal cutters)
Step 5: Assembly 4
We need to attach the little rollie thing on the back. I have found this is a lot easier if you pop the ball out first. It will come out easily with a small screwdriver. Beyond that, this is pretty straight forward.
- Place the (2) screws through the mounting ears of the roller ball.
- Add the thick spacer that comes with the roller ball kit --You can take off the paper so it looks sorta pretty if you want
- Screw it on to the robot.
- That's it, no big whoop.
- --Oh yeah, pop the ball back in if you took it out
Step 6: Assembly 5
Note: If you look closely to the pictures of this step, you will notice the servo has a resistor wired into its lead. This is simply because I used a servo from a previous project for these pictures. Your's will not have a resistor and does not need one installed.
- Mount the servo to the top plate using (2) 2-56 x 3/8 screws and nuts
- Route the servo wire between the motor plates and through the hole in the center plate
- Plate the top plate on the bottom plate assembly
- Wiggle it around a bit to be sure the tabs are in the sockets and the motors are sitting in their recesses
- Secure the top plate with (4) 2-56 x 3/8 screws and nuts --Your needle nose pliers or tweezers are needed here to get to the (2) screws tucked in behind the servo
Step 7: Assembly 6
- Find one red jumper wire and one black jumper wire
- Cut one end off of the red jumper
- Cut the black jumper roughly in 1/2
- Strip back the insulation on the cut ends
- Solder the black wire to the black wire coming from the battery pack. Insulate with a bit of tape or shrink tube
- Solder the red jumper you prepared earlier to the center pin of the switch
- Solder the red wire from the battery pack to one of the outside pins on the switch
- Mount the switch to the bottom plate using the (2) nuts supplied with the switch. One nut will be on each side of the acrylic
Step 8: Assembly 7
- Install (2) 10mm standoffs next to the roller wheel assembly using (2) M3 screws
- Install (3) 5mm standoffs to the electronics plate using (3) M3 nuts
- Install the electronics plate to the 10mm stand offs using (2) M3 screws Note: the notch in the plate is to allow for the switch
Step 9: Assembly 8
Assemble the Nano Undershield.
Please follow the instructions found on the Undershield Instructables page and assemble the Undershield.
When finished, you may install the Undershield on the robot. Note: The undershield is mounted to the 5mm standoff using the shorter M3 screws
Step 10: Assembly 9
This would be a good time to take a moment and familiarize yourself with the Undershield Instruction Manual. It includes pin-outs, information on where power must be connected, etc.
The labels for the pins mentioned in this step are on the underside of the Undershield board. Please use these markings and/or the instruction manual to confirm you are plugging things in where they should go.
- Connect the black and red jumpers (coming from the battery and switch) to the power-in connection on the SIDE of the Undershield.
- Install the small jumper block (right next to the power-in pins you just connected to)
- Connect your servo to D11
- Connect the (2) wires from the left motor to the (2) Motor A pins
- Connect the (2) wires from the right motor to the (2) Motor B pins
- Find the red and black jumpers (the ones that still have both ends still attached)
- Connect the black wire from the Gnd pin of "ping" to the gnd pin of "Mot. in"
- Connect the red wire from the + pin of "Ping" to the + pin of "Mot. in"
Step 11: Assembly 10
Stick the wheels on.
That's it! Stick 'em on. Be gentle and try to support the motor when you press them on.
Step 12: Assembly 11
- Find the small baggie of parts that came with the servo and find one of the "double ended" horns. You can use either one.
- We need to enlarge the holes a bit to allow our 2-56 screws to fit through. Feel free to use a drill, but personally, I don't care to drill such a small part with my fingers so close. Instead, I have found it is super easy and quick to simply insert an X-acto knife into the holes and spin it gently to enlarge the holes. Work from both sides, a little at a time until you can just barely fit a screw through.
- Install this horn on to the head base plate using (2) 2-56 x 1/4" screws and nuts
- Install the (4) 15mm stand offs with (4) M3 nuts
- Intstall the Sharp distance sensor to its mounting plate using (2) M3 screws and nuts
- Place the Sharp mounting plate on to the head base plate
- Install this assembly to the servo on the robot. Secure with the small screw included with the servo parts
- Install the top plate with (4) M3 screws
- Find the wiring harness for the sharp sensor. Included in this package is a small, black connector housing.
- Insert the (3) wires on the Sharp wiring harness into this black connector. If you do it right, they will give you a very small "click" and they won't pull back out. They must go in this order: White, Red, Black (see pictures)
- Plug the small, white JST connector into the Sharp
- Plug the small black connector into A7 (should be right next to where we stole power for the motors ("ping"))
Step 13: Done
Here are a few things to be aware of before you get moving too fast...
- Be sure you are using rechargeable batteries
- Be sure you checked all your solder joints when putting together the Undershield
- ALWAYS remove batteries when you are not working with your bot
- Things getting hot means things are wrong
You can find an example sketch to help you get going here.
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