From the "if it's good it's wood" department

Martin_H · 2012-03-31 11:37

On a happier note than the death of my new to me, but old BS2e board. After two particle board prototypes I decided to commit the 4x4 design to plywood and varnish. Here's the robot the BS2e was destined to control (its loss as the CBA is epvc). I'd say it came out pretty fine looking and any robot controller I pair it up with will produce a nice bot.

The future goal for this bot is the big outdoors and finding its way around the local park. I'm going to pair it a compass and accelerometer and possible a GPS. A tip of the hat to Gordon's Rigel design which was the genesis of my design.

Matt Gilliland · 2012-03-31 12:08

Martin-
That's beautiful.
(yes, I do appreciate the beauty of wood - just don't tell erco!)
-MattG

erco · 2012-03-31 12:16

+1: As Newman said, "Yea, it's the wood that makes it good."

http://www.imsdb.com/transcripts/Seinfeld-The-Chicken-Roaster.html

GordonMcComb · 2012-03-31 15:43

Let me know if those Tamiya wheels will do the trick over varied surfaces. Last week I spent some time reburbishing things and brought back the chassis (minus wheels or motors) but without cooperative wheels it's more a frustration than anything else.

-- Gordon

GordonMcComb · 2012-03-31 15:51

erco wrote: »

+1: As Newman said, "Yea, it's the wood that makes it good."

Alfred E. Neuman never said that. However he did say:

"A teacher is someone who talks in our sleep!"
"Most people are so lazy, they don't even exercise good judgement!"
"Who says nothing is impossible? Some people do it every day!"

-- Gordon

codyspraker · 2012-03-31 16:33

Very impressive design, I do have a question and a request:
Question: Do you have to unscrew those 4 screws in order to install batteries?
Request: Someone said this already but please post how the design works in varying terrain.
I am looking to a very similar design but I am questionable about the performance of wheels and other factors that might hinder performance. Best of luck on continuing your design and great job!

Martin_H · 2012-03-31 19:27

Thanks for the feedback. I will definitely post more about the performance of the wheels on different terrain. So far they work well on cement and tile. I imagine grass and carpet will be tests for turning performance.

codyspraker wrote: »

Question: Do you have to unscrew those 4 screws in order to install batteries?

Yes that's a minor downside as the top comes off quickly. But I wanted ground clearance and that required the servos under the bottom deck. A rechargeable battery pack and charging jack would solve this problem.

Matt Gilliland · 2012-03-31 20:13

Welcome to the Forums codyspraker :thumb:

Question: Do you have to unscrew those 4 screws in order to install batteries?

Martin_H:
I'm having a tough time judging scale here; what size are those battery holders, and what voltage are you running?
-MattG

Martin_H · 2012-04-01 03:46

Matt Gilliland wrote: »

I'm having a tough time judging scale here; what size are those battery holders, and what voltage are you running?
-MattG

The robot's top deck is 7" long by 5.25" wide. It stands about 3.5" off the ground. So it's not that big, but won't get hung up on uneven surfaces like a Boe-bot or CBA. I don't plan to go crazy, but I am getting tired of the kitchen floor and basement.

Those are six AA cells and I use nickel metal hydride. With the CBA robot I use the 7.2 volt output directly to the GWS servos which can handle up to eight volts. This bot has four used Parallax CR servos I got from ebay, which are rated for 6 volts, so I will initially use the voltage regulator. But I know that you over volted them with the lithium battery, so if I get brave I may run them off 7.2 like I do my GWS servos.

My challenge of doom video includes prototype number two going over my uneven ground simulation.

[video=youtube_share;4BfwvPFvyPw]

GordonMcComb · 2012-04-01 09:37

Martin, thanks for the vid. Nice comparison. On the Tankbot is that it's full speed, or have you slowed it down some?

-- Gordon

Martin_H · 2012-04-01 10:43

GordonMcComb wrote: »

Martin, thanks for the vid. Nice comparison. On the Tankbot is that it's full speed, or have you slowed it down some?

It should be close to top speed. The TankBot is my Arduino bot and I am using the following to control the speed

  servoLeft.write(180) ;
  servoRight.write(0) ;

The batteries are 4 AA's and a bit on the older side, so that could slow it down a bit. But the sprocket on the TankBot is close to half the radius of the wheels. So it's never going to be as fast.

Ttailspin · 2012-04-07 08:10

How did I miss this? My powers of observation are decreasing with age, I guess.

Anyways, that is a very substantial robot platform, How is the skid steer working out for you Martin?

I think I will try to build one of these after UPEW is over, But who knows what kind of Ideas I will get from UPEW...

Thanks for posting, sorry I was late to the party...:)

-Tommy

Martin_H · 2012-04-07 10:06

Ttailspin wrote: »

How did I miss this? My powers of observation are decreasing with age, I guess.

Anyways, that is a very substantial robot platform, How is the skid steer working out for you Martin?

I'm glad you liked it. I figured it would be up your alley because there are no casters. So far the skid steering works fine, but I haven't put it through its paces yet. Life (work, taxes, visits to family, scouting, honey do list) will consume most of my spare time until the end of next weekend. When I get a chance I will post a video of it doing stuff.

smithdavidp · 2012-04-09 07:33

Kinda makes me wonder how you calibrate all four servos. If you could figure that out then you would be able to make it spin like the scribbler for turning. Would the scribbler sensors work with this configuration? Forgive me if it is a stupid question/observation but I am just starting out here. I am still reading the XBee tutorial and haven't even made it to the Navigation phase of my project yet but your base may be the kind of platform I could use on my project.

Martin_H · 2012-04-09 17:25

smithdavidp wrote: »

Kinda makes me wonder how you calibrate all four servos. If you could figure that out then you would be able to make it spin like the scribbler for turning. Would the scribbler sensors work with this configuration?

I send all servos the centering pulse and adjust their trim pot until they are still. At that point there are several options for driving four servo. You can give each one its own control pin which is useful if you want to smooth out the current demand over time. But I just connect pin 12 to both right servos and pin 13 to both left servos. This makes the robot handle like an overgrown Boe-bot which is good for me because I have a ton of programs which will run on it will some tweaking.

Martin_H · 2012-04-23 19:05

I decided to take the 4x4 BS2e robot out for a spin using Bluetooth to remote control it from a PC. Here's a video:

Now I need to be able to write my own PC control program using Python. I plan to have some sensor data processed locally and others relayed to the PC. For example the whiskers will override any commands sent from the PC, but other lower priority sensors will get relayed.

GordonMcComb · 2012-04-24 11:23

Very nice! How does it work on carpet? On smooth linoleum or Formica tabletop?

-- Gordon

Martin_H · 2012-04-24 12:06

GordonMcComb wrote: »

Very nice! How does it work on carpet? On smooth linoleum or Formica tabletop?

Thanks. It works fine on tile, hardwood, and the dining room table (don't tell my wife). We don't have any linoleum so I can't test that. I haven't tried it on carpet, but can do that tonight. I imagine the increased traction could make turning a challenge, but I'm hoping those tire spikes will provide enough lateral skidding.

Martin_H · 2012-04-24 17:50

Good news. Performance on carpet is the same as on hardwood floors or tile. So it looks like the rubber spikes provide the necessary amount skid for skid steering.

Ttailspin · 2012-04-25 13:18

Thanks for the update Martin,
That thing zooms around nicely. :thumb:

-Tommy

erco · 2012-04-25 13:27

Figure 8's 'round dinner plates! Do it! Don't let that thread die!

GordonMcComb · 2012-04-25 16:10

Martin_H wrote: »

Good news. Performance on carpet is the same as on hardwood floors or tile. So it looks like the rubber spikes provide the necessary amount skid for skid steering.

In that case, time to bring back the Rigel!

-- Gordon

erco · 2012-04-26 10:54

Another wood & electronics fan: http://www.galacticstudios.org/page/3/

From the "if it's good it's wood" department

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