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Homebuilt Robotic Platform AKA Retrobot

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  • ercoerco Posts: 20,157
    edited 2010-01-16 18:43
    Good test run on carpet with some "singularities": http://www.youtube.com/watch?v=7K9he0ddc2Q

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    ·"If you build it, they will come."
  • Roy ElthamRoy Eltham Posts: 2,995
    edited 2010-01-16 19:10
    That's really good considering the rugs and bumps. I'm going to be working on odometry with my Stingray this weekend. If I get it working well I post a video also.

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    Check out the Propeller Wiki·and contribute if you can.
  • BocephusBocephus Posts: 58
    edited 2010-01-16 19:10
    That's great erco! Very good accuracy over multiple carpets.
  • Beau SchwabeBeau Schwabe Posts: 6,487
    edited 2010-01-17 23:17
    Here is another idea for a robot frame with the Parallax Motor Mount and Wheel Kit and a few items from your local hardware store.

    This sturdy design allowed my 7 year old and 4 year old to sit on the frame while I manually applied power. It had no problem moving them around even through the grass.


    I later confirmed by borrowing a torque wrench, but I measured the torque of these motors the old fashion way (See Measuring Torque.JPG)


    torque approx 2.0 ft/lbs ( 2.7Nm) at 3.7V
    torque approx 9.5 ft/lbs (12.9Nm) at 12.9V
    torque approx 11.1 ft/lbs (15.0Nm) at 14.5V


    CAUTION: (Using this method to measure torque with a 12V supply (with plenty of current) will have no problem launching 4 pounds of dead weight in the air at a respectable velocity) – speaking from experience [noparse]:o[/noparse])

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.

    Post Edited (Beau Schwabe (Parallax)) : 1/17/2010 11:22:17 PM GMT
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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,318
    edited 2010-01-17 23:53
    erco,

    I'm amazed that, with all the "singularities", you were able to get spot on like that. Great work! (Regarding the wall ding: you could always take a Skil saw and knock those corners off! smile.gif )

    -Phil
  • WhitWhit Posts: 4,191
    edited 2010-01-20 22:03
    Phil Pilgrim (PhiPi) said...
    erco,

    (Regarding the wall ding: you could always take a Skil saw and knock those corners off! smile.gif )

    -Phil
    You could also wallpaper the room with some 60 grit sand paper and slo-o-o-o-o-owly round them off. smilewinkgrin.gif

    @Beau - thanks for the poor-boy torque test! Loved the caution too!

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

    Post Edited (Whit) : 1/20/2010 10:11:23 PM GMT
  • LuckyLucky Posts: 98
    edited 2010-01-21 00:20
    erco,

    did you buy those encoder wheels or did you make them using some online program? If you did use an online program, can you give me the site?

    -Thanks

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    "You do not really understand something unless you can explain it to your grandmother."


    -Lucky[size=-1][/size]
  • ercoerco Posts: 20,157
    edited 2010-01-21 00:33
    Here's a site to get you started: http://groups.csail.mit.edu/mac/users/pmitros/encoder/

    The specific disks I used? I just had those designed and printed those out on paper. I can upload them later if that site doesn't·help you.

    As I said several times, I'm sold on those Hamamatsu optical sensors. Nothing else is that cheap and easy.

    $3.25 at http://www.junun.org/MarkIII/Info.jsp?item=48.

    Circuit at http://www.acroname.com/robotics/parts/R64-P5587.html

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    ·"If you build it, they will come."
  • LuckyLucky Posts: 98
    edited 2010-01-21 01:03
    Thank you, that really helps. (I was planning on making two manually, each having 120 steps; would have taken forever)

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    "You do not really understand something unless you can explain it to your grandmother."


    -Lucky[size=-1][/size]
  • ercoerco Posts: 20,157
    edited 2010-01-21 01:23
    I'll upload 2 files later, one with 36 steps (10 degrees) and one with 72 steps (5 degrees).·My bot is using 36 for now, I'll try 72 soon.

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    ·"If you build it, they will come."
  • ZootZoot Posts: 2,227
    edited 2010-01-21 03:31
    Here's a URL to a postscript file which can be used to generate however many stripes you want, at whatever inner and outer diameters, without drawing by hand or cloning/rotating stripes, etc. You can edit the postscript (.ps) file in any text editor to change the numbers, then open in a vector program such as Freehand or Illustrator or CorelDraw, or it can be imported into a PDF file for printing. You can also dump it right to any PostScript ready printer.

    mitros.org/p/projects/encoder/opt2.ps

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    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • ercoerco Posts: 20,157
    edited 2010-01-21 04:15
    New thread on encoders started at Make Your Own Encoders .

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    ·"If you build it, they will come."
  • ercoerco Posts: 20,157
    edited 2010-01-23 04:35
    My Friday evening has been wildly productive. I fed, burped & diapered the twins, programmed my robot to drive in a circle, and YouTubed it. Video at http://www.youtube.com/watch?v=mMru-ZA3yvQ·, again surprisingly good accuracy for this simple fellow. Inside wheel turns half as fast as the outside wheel.

    I was inspired by this genius, who carved perfect circles with his Propeller robot: http://www.youtube.com/watch?v=iLzyLy_zgew·WOW, that's incredible.

    Before you ask, Jax, code attached!

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    ·"If you build it, they will come."
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,318
    edited 2010-01-23 08:15
    erco said...
    I was inspired by this genius, ...
    I think his pencil lead broke after the first pass! smile.gif Seriously, though, that's pretty amazing. Of course, super skinny wheels and a hard, flat surface help to make such a feat possible.

    -Phil
  • ercoerco Posts: 20,157
    edited 2010-01-30 05:42
    I've started Poor Cousin 2, which will have minor upgrades from the original PC1. It has a rakish·bit of·taper on the front, and the two front ribs are spaced a bit wider to avoid fouling on the front caster safety brake, which had to be cut down a bit on PC1. Also the wider ribs extend back slightly to form a pocket to hold the 12V battery. Two photos provided.

    Same gearmotors, but these·have·different wheels. Thinner & probably weaker than the older ones on PC1, which had a broad flat area·on which to easily glue·(Scotch 77 spray-on adhesive) the paper encoder disks. The new wheels have four ribs on each side, which complicates adding the encoder disks. Additionally, the new wheels are polyethylene, whereas the older ones were nylon. That means you can't easily glue to the new wheels. I affixed·the paper encoder disks to thin sheet styrene with Scotch 77. I used a compass-style cutter to cut them to 4" OD and a 1" ID, then attached them·properly centered on the polyethylene wheels·using thick double-sided foam tape. Two photos provided.

    I am using the higher-resolution 72-stripe disks on PC2 (5 degrees). PC1 achieved excellent results using only 36 stripes (10 degrees).

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    ·"If you build it, they will come."
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  • HighlandtinkerHighlandtinker Posts: 50
    edited 2010-02-01 00:31
    Here is my attempt at a larger Rover Bot. It is absolutly inspired by erco's Postings and every one else who has contributed to the post. My Rover hopfully will be able to hold it's own against my other Living rover ( see Picture "Roverbot" as well as two large members of the feline types.·Still need back wheels and to finish the controller and code. Should have running by next weekend. Keep posting ideas because I love· trying new things and have high hopes for this project. P.S. Dates on photos are wrong. Pics taken today.
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  • WhitWhit Posts: 4,191
    edited 2010-02-01 02:50
    @erco,

    Very impressive! Thanks for posting the code too! I like the looks of PC2.

    @Highlandtinker,

    Looks great!

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • ercoerco Posts: 20,157
    edited 2010-02-01 03:33
    @Whit: Thanks Pal! I'm trying to make PC2 a little classier than PC1. You know, fewer splinters...

    @Highlandtinker: Excellent! I thought I recognized those motors. I'm knee deep in writing all-new code for Poor Cousin to program a path using an IR remote. My brain needed a break and now I'm glad I checked in here! From the looks of your batteries & HB-25s, I would agree that it looks like you have big plans for your bot. You going Stamp or Propeller?

    Those heavy batteries are pretty far from your drive wheels, you may want to relocate them closer to your axle centerline for traction. If your chassis flexes, consider adding a crossbar across the top of your motors, along the lines of what Ken did with his CNC bot.

    Press forward and keep those updates coming. Good luck!

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    ·"If you build it, they will come."
  • HighlandtinkerHighlandtinker Posts: 50
    edited 2010-02-01 03:57
    @erco: You are probably right about the batteries being to far from the motors. This is my first Try at building a robot from scratch so I have a lot to learn. That is why I found this post so great for me at this time. You are right about the motors, I saw them on your post and as I already us AllElectronics for some of my stuff I ordered some. As for Stamp or Prop. I am going to start with Stamp and hope to transistion to Prop some time in the future. I do hope some day to get the wheel set and encoders that Parallax sells but right now don't have that much to spend and better get a grasp on less powerfull Robot first. Thanks for your feed back and insperation.smile.gif

    @Whit: Thanks

    Post Edited (Highlandtinker) : 2/1/2010 4:25:11 AM GMT
  • Roy ElthamRoy Eltham Posts: 2,995
    edited 2010-02-01 04:11
    erco,

    Where is a good place to buy those SLA batteries you use? I need to get some along with a charger. I have done a little searching on the net, but the prices are all over the place and the sites are sometimes questionable. So I'd like a recommendation.

    Thanks,
    Roy

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    Check out the Propeller Wiki·and contribute if you can.
  • HighlandtinkerHighlandtinker Posts: 50
    edited 2010-02-01 04:20
    Roy: I found my batteries and charger at http://www.allelectronics.com/make-a-store/category/160/Batteries-Rechargeable/1.html. The chargers are in the charger section.

    Hope this helps some.··· Highlandtinker

    ·
  • ercoerco Posts: 20,157
    edited 2010-02-01 06:21
    @HLT: Nice! I gotta learn Prop one day soon, too. But I'm having excellent results on this bot with a plain old Stamp!

    @Roy: Per HLT, lots of batteries on the web.· Batterymart·has great prices before shiping. Lead-acid batteries are heavy. Try to find them locally. 12V, 7 AH and 6V, 4.5 AH batteries are cheap because they are commonly used in UPS and alarm systems. Try alarm & hobby shops near you to avoid shipping.

    I buy my batteries & chargers from a great local source, Torrance Electronics. They have a wall-wart charger for ~$15 that does 6 and 12V, selectable charge rate, and automatically switched to float charge when done. I recommend that type. Don't use a car battery charger on small SLAs.

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    ·"If you build it, they will come."
  • Roy ElthamRoy Eltham Posts: 2,995
    edited 2010-02-01 08:37
    Thanks for the tips guys. I guess I'm going to go on a tour of the areas hobby stores.

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    Check out the Propeller Wiki·and contribute if you can.
  • ercoerco Posts: 20,157
    edited 2010-02-01 15:37
    FYI, the hobby shop crowd uses those SLAs to electric-start the gas·engines on model airplanes.

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    ·"If you build it, they will come."
  • ercoerco Posts: 20,157
    edited 2010-02-02 03:55
    I bought 3 SLA battery chargers tonight, Whit was interested in one and I got a bit of a discount on 3 ($14 each). Two are up for grabs if anybody wants them. I can priority ship for $5, so the total is $19. Paypal works for me. 6V and 12V, charges at selectable rate of 20, 400 or 800 mA, then switches to trickle/float mode. Pics attached. PM me if you're interested in one. I've been using this same unit for several years, works fine. I will test each unit before shipping.

    Edit: Maybe I should charge more... Same unit at ·http://www.rpelectronics.com/Default.asp?Main=/English/OnlineCat.asp?Menu=/English/Content/Categories/CatM_68.asp%26Detail=/English/Content/Items/FC-612C.asp

    tongue.gif

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    ·"If you build it, they will come."

    Post Edited (erco) : 2/2/2010 4:08:17 AM GMT
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  • WhitWhit Posts: 4,191
    edited 2010-02-02 15:43
    Looks neat. Can't wait!

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • HighlandtinkerHighlandtinker Posts: 50
    edited 2010-02-03 01:30
    Hi All

    Here is an updated·picture of my new Bot. I moved the 5AH battery closer to the wheels as per erco's suggestion and have added rear caster, control voltage regulators (9V and 5V) and a perfboard where the BS2 board will be. I am going to use a OEM BS2. I realize the HB-25s are overkill but want to learn how to use them so when I build a Bigger Robot I have that figured out. Also know a Propeller would be the way to go but have a lot still to figure out with spin. I learned Basic , Cobal and RPG 25 years ago but never used it so now am trying to get back up to speed. Also only powering these motors with 12V but they work well on 12V.
    I am going to do some wiring tonite and hope to start running some test code tomorrow night.

    @erco: Thank you for your suggestions, I need any help I can get. I have spent 25 +·years as an electronics tech but am fairly new to robots and all that goes with themsmilewinkgrin.gif
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  • ercoerco Posts: 20,157
    edited 2010-02-03 06:50
    Sweet progress, HT. Let's roll!

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    ·"If you build it, they will come."
  • WhitWhit Posts: 4,191
    edited 2010-02-03 12:42
    Highlandtinker,

    Looks good. I like the plan of learning the HB 25's for a future bot.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Tony B.Tony B. Posts: 356
    edited 2010-02-05 23:16
    Highlandtinker,

    Great looking Bot!

    I have a bot in which I am using 2 HB-25s on and still have a couple of control issues to work out. 1. getting them to work with a single pluse to set motor speed 2. getting the Communication Timeout Mode shut off. They work great if I continue to update them like servos, but not with a single pulse.

    I will be following your progress and wish you great success on your first run this weekend.

    Tony
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