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Things we learned and other useful info / Don't twist cables...
« Last post by Louis L on June 13, 2019, 08:09:19 PM »
... except cables that come that way (twisted pair for instance).
Regular cables, single or multi-conductor, should not be twisted. It's easy to inadvertently twist them when winding a cable. For example the power cord on a typical laptop power supply is usually put away by winding the cord along the brick. With each winding, the cable twists onto itself.

Just today I caught sight of the xbox controller in the driver station. It was so badly twisted that the cable's exterior sheathing was in danger of breaking and with it some wires. Yes this can happen (been there, done that).

So please keep an eye out on your cables. Don't twist them.
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Arcadia / Building your own arcade console
« Last post by Louis L on March 21, 2019, 12:52:34 PM »
If you enjoy old arcade games and would like to play these games as close as possible to their original form, you'll be happy to know it's not all that hard to do. Here are some options:
  • Many games are already available on the internet, playable inside your favorite web browser. If this level of play is all you want, just search for your favorite game and play.
  • If playing with a keyboard is not your cup of tea, many games can use USB game controllers.
  • If you want to run the original code for these games, you'll want MAME.
The rest of this post is about option #3 above.
MAME is an open source emulator capable of taking original games in the forms of ROMs and translating them for modern computing platforms. It handles user inputs, sound and video. Along with user interfaces and setup packages, there is a rich set of options out there -  it's up to you to decide which is best for you. I've found that the world of MAME is a moving target so it's not really possible to recommend any one installation. Your best bet is to do some online research.
All that said, you still need to make some decisions.
  • Are you building a dedicated arcade console? Ours has gone through many iterations over the years.
  • What computing resources will you be using? MAME can run on a cheap Raspberry Pi all the way to expensive laptop/desktop. We've run on both a Pi (original model B) and a Windows laptop.
  • What's your budget?
  • Do you have a space or power limitation?
  • What type of user interface do you want? We have an interchangeable console that houses joysticks and a trackball. We use Ultimarc adapters to convert input hardware into keyboard codes delivered to the Pi/laptop over USB.
  • What type of screen do you want? Most old arcade machines used a large, heavy CRT over 20 inches wide. We used a 19 inch 4:3 LCD monitor with HDMI input - these were not easy to find on the used market. 4:3 monitors are old compared to today's widescreen formats and HDMI is a relatively new interface. So the overlap between the two is pretty small. Most old games are made for 4:3. Most new compute platforms use HDMI.
  • What games do you like to play? Make sure the game(s) of your choice are available for download. You'll have to experiment to see if they run properly on your platform. I found that most games run on Windows MAME but not all run on the Pi MAME. It could be user error on my part too!
  • What about sound? Our console uses an old PC speaker driven by the raspberry Pi. A Laptop can do the same thing.
That's about it. Take some time and learn more about MAME, then see what implementation makes the most sense to you. The keys to all this is MAME and the ROMs.
Good luck!
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These sensors do a good job and are relatively inexpensive. But their housing is made of a conductive resin plastic and is shorted to ground by the internal PCB mounting screw. For FRC use, this means you'll see on the order of 100-200 ohms between battery V- and a metal chassis unless the mounting isolates them properly. Refer to the competition checklist for the minimum allowed resistance between battery V+, V- and chassis.
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Things we learned and other useful info / Volume of pneumatic cylinders
« Last post by Louis L on January 25, 2019, 12:51:15 PM »
I've calculated the volume of the cylinders we have in our inventory. This is useful when you want to look at how much air is used vs. how much air you have in your accumulators. Volume is in cubic inches and milliliters.

The Clippard accumulators are 574 mL in volume.
The high pressure side is 120 psi max.
The low (operating) pressure side is 60 psi max.

Length (in) Bore (in) volume (cu in) volume (mL)
2 3/4 0.88 14.42
4 3/4 1.76 28.84
5 3/4 2.21 36.22
6 3/4 2.65 43.43
12 3/4 5.30 86.85
6 1 1/16 5.32 87.18
8 1 1/16 7.09 116.18
2.5 1 1/2 4.22 69.15
8 1 1/2 13.5 221.23
4 2 12.57 205.99
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Things we learned and other useful info / Useful info from Bimba for using pneumatics
« Last post by Louis L on January 11, 2019, 01:43:06 PM »
I pulled two Technical Tips from the Bimba web site (bimba.com). Bimba is a sponsor of FIRST. These are useful for anyone starting out with using pneumatics.




(1) How to Determine the Right-sized Cylinder for Your Job

"Specifying the right cylinder for the right job results in better and longer cylinder performance. And that means lower overall operating costs. Proper cylinder size selection begins by calculating 1) the weight of the load, 2) the required velocity, and 3) the air pressure used. Let’s take a closer look at each of these three factors.
Weight of the load:
This is set by the machine design. In order to move the load, you’ll obviously need a cylinder that pro-vides force
greater than the load. We recommend allowing an additional factor of 25% force over the load to compensate for friction.
Velocity:Velocity is also usually set by machine design, but there’s usually some latitude within a range. Low speeds (up to 4 in/sec) require 25% more force than the load, moderate speeds (4 to 16 in/sec) about 50% more and high speeds (greater than 16 in/sec) about twice as much.
Air pressure:You need consistent air flow at the minimum effective pressure to maintain the desired velocity. Operating the cylinder at too high a pressure accelerates seal wear and creates stress on the cylinder. Inconsistent pressure can cause system malfunction or failure.

Next you’ll need to determine bore size. Let’s look at an example assuming a maximum load of 100 lbs, a minimum velocity of 8 in/sec and a minimum pressure of 60 psi. The velocity is moderate, but the force should be about 50% greater than the load, or 150 lbs. Dividing the force (150) by the pressure (60) gives you a power factor of 2.5. A 2” bore cylinder, with a power factor of 3.1, provides the needed force.
You’ll also have to consider stroke length, spring force and overall dimensions of the space. But this is only the start."



(2) Power Factors
Rather than copying and pasting the contents of the table in their Technical Tips, I'm attaching the entire PDF file. Please refer to its contents.
  • For our uses, look at the first set of columns under "ORIGINAL LINE".
  • The Bore Size is the left-most column. This is the diameter of the cylinder bore in inches.
  • The Power Factor is a multiplier you use to determine what you need. Do the math and you'll see that it's really just the surface area of the bore in square inches. Extend and Retract are asymmetric because the piston rod takes up space and reduces the surface area of the bore.
  • We'll most likely be operating at 60 PSI so use the FORCE(#) values in that column. Do more math and you'll see that this is just 60 times the POWER FACTOR. If we end up using less than 60 PSI, it's easy to calculate the new numbers.
The numbers in this table apply not just to Bimba. We have and will order from other manufacturers as well and all of this still applies. As the PDF notes, this is just for reference but it'll get you close. The rest is up to you :)

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Wiring needs to be controlled. Sometimes the priorities can be confusing as they seem to contradict each other.
  • Keep wiring neat. The more the mess, the greater chance of problems.
  • Have service loops, slack in the cables. This allows plugging and unplugging of cables.
  • Strain relief at connections prevents cables from coming off when a cable gets pulled.
  • Hot glue on connector can be used if the connector feels loose - be careful how it's used.
  • Route cable such that it does not pop off. This usually means folding the cable over 180 degrees and zip tying it down.
  • Check for pinch points.
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Robot Software / Re: User Interface
« Last post by Louis L on October 17, 2018, 01:04:45 PM »
Updated to reflect climber function UI
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Imagery / PacMan costume
« Last post by Louis L on August 20, 2018, 09:42:22 PM »
Ran across this drawing Michele made; thought we could archive it here!
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General Topics / Planet naming contest
« Last post by Louis L on July 22, 2018, 10:09:54 PM »
Use this thread to suggest names for the planet. Rules are below. We'll collect names until Monday Aug 6. Here are the rules:

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DESTINATION: DEEP SPACE Presented By The Boeing Company brings us to a planet in deep space that is as mysterious as it is inhospitable. This lifeless planet presents many challenges: Its atmosphere is toxic, its ever-changing landscape is dangerous and unpredictable, and…it has no name. Would you like to name it? Now is your team's chance to influence our story and be forever known as the team that gave our planet its name!
 
The FIRST Robotics Competition 2019 “Name the Planet" Contest is open to all past FIRST Robotics Competition teams with plans on returning during the 2019 FIRST Robotics Competition season, as well as all rookie teams for the 2019 FIRST Robotics Competition season. Only ONE submission is allowed per team, and must be submitted by the Lead Coach/Mentor 1 or 2 as designated within the Team Dashboard. If your team does not yet have a permanent team number, please use your assigned temporary team number. Submissions must be complete by 11:59PM EDT on Wednesday, August 15, 2018 to be considered.

 
Name the Planet Contest rules:

(1) No submissions may contain material protected by intellectual property laws, including, by way of example, and not as limitation, copyright or trademark laws (or by rights of privacy or publicity) unless you own or control the rights thereto or have received all necessary consents to do the same. For example, “Disneyland” is not an appropriate name.

(2) The Planet Name will represent your team and FIRST, and it must be designed in the spirit of FIRST Core Values.

(3) The Planet Name should be written using characters in the modern Latin alphabet not exceeding 50 characters (including spaces).

(4) It is important that we know the correct pronunciation of your planet name. Although the pronunciation of many names is obvious, some require special attention. The pronunciation guide is a way to help us pronounce your planet name correctly. The pronunciation guide should be written for English language speakers. For example, “Raul Gonzalez” would have a pronunciation guide similar to “rah-OOL gon-SAH-les”. It’s recommended to use a pronunciation resource such as the following document in creating your pronunciation guide:  https://www.tntech.edu/assets/userfiles/resourcefiles/8487/1450475497_Name%20Pronunciation%20Instructions.pdf

By submitting your entry into this survey, you irrevocably grant to FIRST and its assigns, licensees, and successors the right to use your submitted Planet Name in all forms and media including composite or modified representations for all purposes, including advertising, trade, or any commercial purpose throughout the universe and in perpetuity. You also waive the right to inspect or approve the use of the Planet Name for publication or other written copy used in connection with the Planet Name.

Please note, we are collecting the name and email address of the Lead Coach/Mentor 1 or 2 who fills out the contest entry in order to ensure only ONE contest entry per team is received, to follow up with your team if needed, and to notify you if your entry is selected.
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Robot Software / dev laptop holder inside cabinet
« Last post by Louis L on June 24, 2018, 08:59:18 PM »
I made a "holder" for the dev laptops in the tall cabinet. We'll use this Fall (2018).

Up until now, the dev laptops were either stored vertically (where they can fall down) or stacked one atop another. Stacking is not a good idea since each weighs 6 to 7 pounds so the bottom on gets crushed (good thing these have a strong magnesium chassis but the LCD is still a weak point). So I made a box with slats. Each laptop gets its own place to sit vertically without leaning on another laptop or falling over. Each slot is labeled 1, 3, 4, 5, 6, 7. There is no "2" since that laptop has been retired and used for parts. Everyone using a laptop is expected to put it back in the correct slot.

Above this unit, there is space for the chargers so they no longer will clump up on the shelf.
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