PR2 Wiring Setup
This tutorial will show you how to wire the PR2 for the DARPA BOLT project. There are several sensors needed for the project.
|ASUS Vision-Xtion (x1)||USB Microphones (x2)||Syntouch BioTac Sensors (x2)|
For instructions on how to mount each of these sensors, please refer to the other wiki pages under Hardware. They will each outline how to get the sensor physically mounted onto the PR2. This page will outline how to wire up all of the components once they have been mounted. Please follow each step carefully as some steps deal with modifying the PR2 electrical wiring.
We recommend also watching this safety video if you have not worked with the PR2 before: http://pr2support.willowgarage.com/wiki/Safety/Video
As well as the other items on this page: http://pr2support.willowgarage.com/wiki/Safety
- Double Sided Velcro Strips (cable wrap Velcro) - We recommend these: link
- These are the Velcro strips we are using to hold the USB and AWG cabling together
- 1/2 Sticky, 1/2 Velcro Strips - we recommend these: link
- These are used to mount items onto the PR2
- Double Sided Sticky Tape
- We recommend using something strong
- 1/8" acrylic + laser cutter
- This piece is used to mount the Multi-BioTac Board to the PR2's hand
For Syntouch BioTac Cables
- 25’ of 10 strand, 28 AWG cabling (roughly 9 feet needed) – MD10R-25-ND: link
- Header Socket - HKC10H-ND: link
- You only need one, but we suggest buying 2 or 3 as backup because it is easy to make mistakes during the installation.
- Header Receptacle - HPA10H-ND: link
- Same as the header, you only need one, but buy 2 or 3
For PR2 Hub integration
- 7-port Self Powered USB Hub: link
- This hub will power each USB device the full 500mA and can connect directly into the PR2's 12V plug in the body.
- High Speed USB 2.0 Cable: link
- You do not need this exact cable, but if you do not have one, this is one example that can be purchased
- 18 Gauge AWG Speaker Wire: link
- You don't need this exact wire, but it does need to be 18 gauge. We recommend a black and wire combo. This wire is nice because it is spliced together for easier cable management.
- Female Molex Headers - WM1021-ND link
- You only need 1, but we recommend buying 5
- Molex Crimp Pins - WM18518CT-ND link
- Need 2, we recommend buying 10 (they are difficult to crimp!)
Opening the Robot's Back Casing
First and foremost: Shut down the PR2 and turn OFF its breaker. You are about to perform electrical surgery on the robot. This procedure is not difficult when performed correctly, but care must be taken not to damage your electromechanical friend.
Second: Open the back casing of the robot. You can find an in-depth tutorial from Willow Garage here - http://www.scribd.com/doc/34939615/PR2-Top-and-Rear-Spine-Cover-Removal-and-Replacement
Mounting the 7-port USB Hub to the PR2
The PR2 only has one USB port on the outside of the head. To extend this, we installed a 7-port USB hub that is externally powered. This allows each port the full 500mA power supply that many devices need.
- (This step is optional.) Take the 7-port hub and remove the relatively sharp side plates (a band saw would be the best option). The plates are not needed because we will be mounting the hub with tape instead. To avoid metal shavings inside the hub itself, unscrew and remove the back/bottom pannel before sawing. Then afterward, wipe out the case with a damp then dry paper towel to remove all debris and moisture.
- Take double sided tape and attach two long strips to the bottom of the hub.
- Place the hub on the left shoulder of the PR2 with the power ports facing the back of the PR2. Please refer to the image below for exact placement:
Internal Wiring in PR2 for USB Hub
In order to connect the HUB to the PR2, the back of the body needs to be opened. The 12V line and USB line needs to be connected to spline of the PR2. Please refer to this link for an in-depth description of the internal components of the head: http://pr2support.willowgarage.com/wiki/PR2%20Modularity/Specs#A12V_SYS_Bus_Expansion
You will notice that there are multiple points to insert the 12V line. We will be using the body power breakout board on top of the spine.
For our purposes, we will only be dealing with the 12V power line and USB Bus expansion board. Please be careful when performing this part of the tutorial. There are many high powered electric components. The robot must be powered down completely, unplugged from the wall and the DC breaker must be off. Furthermore, please be sure to be grounded with the wrist strap provided by Willow Garage.
- First make the power cables that will be connected to the PR2. Take 18 gauge red and black wire and strip the insulation off the ends. Then crimp the wires with the Molex Crimp Pins listed above. Finally insert the two ends into the Female Molex Headers. Please pay attention to which side ground is connected to
- Next pop open the cover to the back of the PR2 body. Please follow the instructions in these slides from Willow Garage on how to remove the rear spine cover. The instructions cover how to remove both the front and the rear. Remove only the rear cover:
Once the cover is removed, you should see something similar to this (back and side view):
- You should have noticed in the above picture, there is a small red square highlighted. This is where the high speed USB 2.0 cable needs to be attached. The excess cable is wrapped and zip-tied in bright yellow. Below is a closer picture with the cable attached:
- Now we will connect the power cord that was constructed in the first step. Find any open connection the system board to the left of where the USB cable was connected. An example of where we connected our power cable is shown below:
- Clean up the cables and route them out of the left side of the robot. The picture below has both cables securely attached and cleanly routed through the back. The red colored line shows how the USB cable is routed and the yellow shows how the power line is routed.
Also below is a picture of the USB and power cable zip tied and coming out of the side of the PR2:
- Close the back cover. Be careful to let the USB and power cables to come out of the allotted slot on the left side of the PR2. Pay attention to the right length of cabling needed to connect to the port. The USB cable should be looped inside the spine to avoid excess wire outside of the PR2. The power cable should be trimmed to the right length once outside of the PR2:
- Measure the appropriate length for the cable to reach the hub and cut the excess power cable. For reference, here is the length of wire we have from the PR2 to the hub:
- Then strip the two wires at the ends and connect it to the green connector that attaches to the hub for power. Please pay attention to which side is ground
- Connect two cables to the hub. The final product should look like step 7.
Mounting the Cheetah
The Cheetah is mounted on the left shoulder of the PR2. It is attached to the 7-port hub by Velcro.
- Place Tape Velcro on the Cheetah:
- Take a long strip and mount it to the hub. Be sure to measure the location of where the Cheetah will sit on the shoulder. Please ignore the small piece near the top of the hub. That is no longer needed.
- When you place the cheetah on the shoulder it should look like this:
Multi-BioTac Board Mounting Plate (MBTB)
- Attached to the bottom of this page you will find a Solidworks part (.SLDPRT) and the associated print file (.DWG) Use the given files to cut the part out of 1/8" acrylic. The piece should look like the image below:
- Apply some double sided sticky tape to the Multi-BioTac Board:
- Attach the Multi-BioTac Board to the 1/8" acrylic mounting board:
- On the bottom of the acrylic mount, attach a piece of the half sticky/half Velcro tape.
- Put the opposite piece of Velcro on the PR2's aluminum wrist case:
Cheetah to Multi-BioTac Board SPI Cable
The existing SPI cable is far to short to travel down the PR2's arm. The next steps will create an extension cord for the SPI connector.
- Hold one end of the SPI cable, blue stripe to your right. Orient the cable receptaclein such a way that the pin furthest on the right lines up with the blue stripe and is also in the row closest to the incoming cable. The receptacle’s notch needs to be facing the rest of the cable. Basically, the Cheetah’s red stripe needs to line up with the new cable’s blue stripe.
- Seat the cable inside of the receptacle:
- Place the receptacle cap on top of the cable. Squeeze down with your fingers initially and then use pliers to squeeze down harder:
Routing the SPI and USB cables from Cheetah to the MBTB
Now that both the cheetah and the MBTB are mounted, we will route the cable. We will finish making the SPI cable after we measure the appropriate length.
- Connect your new half cable to the Cheetah SPI module. The tabs are incredibly handy for popping the cable off later on during disassembly:
- Connect the USB micro power cable to the hub (6'). Then to hold the USB cable to the SPI cable, wrap the two cables together. This can be done using the double sided velcro straps that you should have purchased from here: link. The results should look similar to below. Be mindful that the USB cable is consistently on one size of the SPI cable.
- Continue combining the USB and SPI cables down the robot’s arm, adding a new Velcro-wire-tie every 4 or so inches. Affix pieces of fluffy Velcro/Tape to the backside of the SPI cable (since it’s flat), and attach to pieces of pokey Velcro/Tape at these two new arm locations:
- Now that you’ve reached the end of the arm, cut off your excess wire and attach the header to the SPI cable near the MBTB:
- Next, cut very thin pieces of Velcro/tape to place in between the screw holes near the finger tip. Places the other side of the Velcro/tape on the BioTac Fingerboards. Also connect the micro USB cable to the MBTB:
- Finally connect the Cheetah to the USB hub:
- At this point everything should be fully wired. You can also connect the ASUS Xtion and USB ears to the USB hub at this time.