RVR Assembly
Last updated
Last updated
In preparation for Phase II, we need to modify a Sphero RVR with some littleBits, and program it to avoid obstacles. This section will guide you through the process.
First, let's take a look at the finished product.
To assemble this, you will need to gather the following:
littleBits components:
micro:bit adapter
USB split cable
p3 usb power bit
i7 remote trigger
(2) i8 proximity sensor bit
(5) w1 wire in bit
(5) w1 wire out bit
(4) w19 split bit (single connector)
(2) w19 split bit (dual connector)
9 wires
micro:bit
Sphero RVR
3D printed RVR topper (STL's for printing available here. Please note, these files were exported in inches, not millimeters)
zip ties
tape
drill (optional)
.250" drill bit (optional)
hot glue gun (optional)
To assemble the vehicle, we'll install all the individual bits into the RVR topper, then connect the wires between them.
Obviously the first thing you need to do is print the RVR topper! Again, the files can be found on Github here. The file is modeled in inches, so make sure it's the correct size when you print it. For reference, the overall length is ~11 inches. Be careful when removing the support as you don't want to break off the mounting tabs that interface with the RVR.
Your 3D printer may not be large enough to print the entire RVR Topper at one time. In that case, you should print the three individual sections (front, mid, and rear) and glue them together (super glue typically works well!) In addition, if you'd like to split the file differently for printing, the .stp file is also available here so you can split it as needed.
The mounting holes for the littleBits and the grid pattern on top are 0.250" diameter holes. 3D printers often will ovalize holes. If that's the case, you can use a .250" drill bit to clean up the holes.
The pictures and documentation below were created with an earlier iteration of the RVR topper. Accordingly, the RVR topper you have will be slightly different. They are similar enough, however, that this shouldn't cause any confusion.
OK now that we have the RVR topper printed, lets start putting all the pieces together. We'll start by installing the two proximity sensors on the front bumper. Grab the two i8 proximity sensor bits, 2 w1 wire in bits, and two w1 wire out bits and snap the wire bits onto the proximity sensors. Next, push the mounting posts into the holes on the RVR topper. Be sure the w1 wire out bits are on top! Your assembly should now look like this:
Now we'll install a splitter inside the front of the bumper. Snap together a w19 split bit (single connector) and a w19 split bit (dual connector) and push them into the mounting holes on the inside of the front bumper. Make sure the dual connector bit is on top. Your assembly should look like this:
Now we'll turn our attention to the rear of the RVR topper. Snap a w1 wire in and a w1 wire out onto the sides of the i7 remote trigger bit. This is installed onto the lower surface inside the rear bumper. The w1 wire in should be on the right-hand side of the assembly and the w1 wire out should be on the left-hand side of the assembly. Make sure the sensor is facing the RVR when installed! See the image below for reference.
Next up is the p3 usb power bit. Attach a w19 split bit (dual connector) to the p3 usb power bit and install them onto the mounting boss inside the rear bumper. The USB connector should be on the left-hand side of the assembly. Now your assembly should look like this:
Now we'll install two inline connectors. Grab two w1 wire in bits and two w1 wire out bits and connect them together. They are installed upside down inside the rear bumper. The w1 wire in bits should be facing outward like in the picture below.
Now it's time to install the brains of the operation - the micro:bit! Slide the micro:bit into the micro-bit adapter bit. It can physically be installed in both orientations, so look at the picture below to make sure you've got it right! Then connect three of the w19 split (single connector) bits to ports P0, P1, and P2. The micro-bit assembly should be installed onto the rear bumper. Your assembly should look like the picture below.
Now that all the littleBits are installed, it's time to install the wires. Some of the bits are easy to plug wires into, but some of them you may have to temporarily remove from the RVR topper for better access. Just be sure to re-install them in the same orientation! The first one we will wire is the i7 remote trigger bit. Install a wire from the lower connector of the p3 usb power bit assembly down to the i7 remote trigger assembly. Coil up the loose wire and use a ziptie to secure it. Then route another wire from the other side of the i7 remote trigger assembly through the slot in the bumper and plug it into the P2 port of the micro-bit assembly. Make sure your assembly matches the pictures below.
Now we'll wire up the proximity sensors. Plug wires into the w1 wire out bits of the proximity sensor assemblies and route them towards the back of the RVR topper, underneath the sides, and plug them in to the w1 wire in bits of the inline connectors.
Now connect a wire to the right-hand inline connector and pass it through the slot, and plug it in to port P1 on the micro:bit adapter.
We'll do the same thing with the other inline connector, except this time it will be plugged in to port P0.
You can use a zip tie to tidy up these wires.
To finish wiring the proximity sensors, connect two wires from the front splitter assembly to the lower connectors on the proximity sensor assemblies. It doesn't matter which connector of the dual connector is connected to each proximity sensor assembly. Again, secure the wires with a zip tie.
You probably noticed that the front splitter still has an empty connector. That will be the last connection made, after the RVR topper is installed on the RVR. But in the meantime, we can connect the other end of that wire to the splitter in the rear. One end will be connected to the splitter and the other end will be free for now.
Now it's time to connect the USB split cable. The large USB-A connector goes in the rectangular cutout on the top of the RVR topper. The other end is split. The connector with the white stripe is plugged into the micro-bit, and the connector without the white strip is plugged into the p3 usb power bit. Use a couple of zip ties to secure the wires along the edge of the RVR topper.
The assembled RVR topper is ready to be installed to the RVR itself. There's a plastic cover over the USB plug on the rover. Be sure to rotate this out of the way before installing the RVR topper.
To install the RVR topper, insert the rear mounting tabs into the slots on the RVR, then lower the front of the RVR topper into place. The front mounting tabs will lock into the front slots. Plug the USB-A connector into the RVR. To remove the RVR topper, push the blue button on the RVR and then rotate and lift the RVR topper off.
Last but not least, remember that free wire from earlier? It's time to route it. It runs along the bottom of the RVR and plugs in to the front splitter.
We recommend securing this wire with some tape on the bottom of the RVR as shown below.
Congrats! You have a fully assembled RVR. Now it's time to program it!
In the meantime, here are a few things we recommend:
Double check all wires are secure and clear of the RVR tracks.
Paint it! Phase II is a search and rescue mission. We hope you'll be inspired to give your RVR a cool paint job - maybe some camouflage, or a medical theme, or even your school's mascot and colors!
All the littleBits are press-fit into the plastic. Once you've confirmed it's working correctly, you can use some hot glue on the mounting pegs to make sure nothing comes loose during operation. We recommend waiting until after the RVR is programmed and tested before doing this.
