Boe-Bot questions for a first time builder

jonez

Hi, very excited to build my first robot! I've ordered the following items off Parallax's store and I'm waiting for them to arrive:

Robotics Shield Kit (for Arduino)
Ping))) Mounting Bracket Kit

The other item's I'm interested in are:

ActivityBot Encoder Kit + ActivityBot Encoder Wheel and Tire x2
Gripper Kit for the Boe-Bot Robot

Q: If I buy the encoder kit and two new wheels will they work with the Boe-Bot chassis? Are there any other parts I need and should order at the same time?
Q: Can you attach both the Ping))) Mounting Bracket and the Gripper Kit at the same time? Will the included screws fit or should I buy longer screws and spacers?

I'm a software developer who's always been interested in robotics. For Christmas I got the Arduino Starter Kit (uno r3) and I own a Lego Mindstorms (r2 not the newest one) and had a blast building and programming a castor rover with it. Mindstorms is a great platform for development but it gets expensive quickly when you want to add more sensors. I still have a lot to learn about building electronics so I figured the shield kit would make my first steps easier.

Initial goal: rebuild my castor rover using my Uno, Boe-Bot kit and Ping sensor. Add a gripper, use waypoint navigation to move items around my house.
Final goal: build an outdoor model that can find garbage on the street and move it to a pile in my garage. Lofty but doable I think!

Thanks!

jonez

Received and built my kit! I placed another order for the encoder kit, wheels, and a compass module. I don't think the gripper will attach without moving some parts around so that will be a future addition.

I can't find one on the store, does Parallax sell a bumper kit (similar to the Sumo-Bot) for the Boe-Bot chassis? If not can anyone recommend one? I'd like to add a bumper with (ideally 2) push sensors that covers the Ping servo. Since the Ping bracket doesn't tilt I'll miss low lying objects that are out of it's line of sight.

Martin_H

Both the gripper kit and the Ping))) mounting kit attach to the chassis and interfere with each other, unless you mount the Ping))) higher. I've done it by using a smaller servo.

The Activity bot wheels and encoder should work fine with your Boe-bot chassis. The Arduino should be a good match for them as well.

I think you'll have a blast with your robot because it's a great little bot.

Mike Green

Some people have mounted the Ping))) on the front of the chassis and the gripper kit on the back of the chassis and it seems to work. Keep in mind that you don't want too much weight in front of the wheels or the Boe-Bot will tend to tip forward. You need some counterweight over the rear skid-ball.

ajward

Martin_H wrote: »

I think you'll have a blast with your robot because it's a great little bot.

I agree! Bob had the Ping kit installed and I'd start him up and just let him roam around just to see how long he could go without getting into some predicament. Then I added an Xbee module for remote control and later a small video camera to document his travels. Still my favorite 'bot!!!

Amanda

GordonMcComb

For bumper switches these work pretty well:

http://www.allelectronics.com/make-a-store/item/SMS-196/SPDT-SNAP-ACTION-SWITCH-W/LEVER/1.html

(Not sure why you need the switches to "cover" the Ping. The Ping shouldn't have anything in front of it, and metallic parts should ideally be kept away from the sound cone it produces.)

Parallax sells some nifty straight and angle all-purpose brackets that make it easier to mount switches like these. As you're using an Arduino, you can wire two switches to pins D2 and D3, which also have external interrupt circuitry, allowing for better capture of any bump. I've written a number of articles for SERVO Magazine explaining how to wire and code these. Check the issues going back a few months. Though the bot isn't on a BOE base, and doesn't use the BOE Shield, the concepts are the same. (The same robot is shown in "dumbed down" form in the February 2012 issue of Popular Mechanics.)

Martin_H

Mike Green wrote: »

Keep in mind that you don't want too much weight in front of the wheels or the Boe-Bot will tend to tip forward. You need some counterweight over the rear skid-ball.

I mounted the servos rotated 180 degrees so the spline was forward, rather than in the middle of the chassis. This makes the Boe-bot much more stable with the gripper and a load.

jonez

GordonMcComb wrote: »

For bumper switches these work pretty well:

http://www.allelectronics.com/make-a-store/item/SMS-196/SPDT-SNAP-ACTION-SWITCH-W/LEVER/1.html

(Not sure why you need the switches to "cover" the Ping. The Ping shouldn't have anything in front of it, and metallic parts should ideally be kept away from the sound cone it produces.)

Parallax sells some nifty straight and angle all-purpose brackets that make it easier to mount switches like these. As you're using an Arduino, you can wire two switches to pins D2 and D3, which also have external interrupt circuitry, allowing for better capture of any bump. I've written a number of articles for SERVO Magazine explaining how to wire and code these. Check the issues going back a few months. Though the bot isn't on a BOE base, and doesn't use the BOE Shield, the concepts are the same. (The same robot is shown in "dumbed down" form in the February 2012 issue of Popular Mechanics.)

Thanks that helps a lot I'll check them out! By cover the Ping I don't mean the sensor just the servo that hangs off the front of the chassis. I'd like to build a bumper (or plow) that detects hits that are under the Ping's LOS and above the wheels ground clearance. That way if he runs into an obstacle that he can't see or drive over I can back up and spin to look for a new direction to drive in.

I just realized I ordered the ActivityBot encoder kit not the Boe-Bot encoder kit. I ordered the matching ActivityBot wheels (more spokes and better treads) and I have lots of spare parts so the extra wires/resistors that come with the Boe-Bot encoder kit won't be an issue. From the description of the two products the encoders look identical but each kit comes with different resistors? The Boe-Bot kit comes with 10k and the ActivityBot kit comes with 20k. When I go to build the kit which resistors should I use 10k? I wasn't sure if that had to do with the board, encoders, or both? I will be connecting the encoders to the breadboard since the 4 servo ports are full (12/13 are wheel servos, 11 is ping servo, 10 is ping sensor).

Well then, cheerio ol' chap!

banjo

jonez wrote: »

I wasn't sure if that had to do with the board, encoders, or both? I will be connecting the encoders to the breadboard since the 4 servo ports are full (12/13 are wheel servos, 11 is ping servo, 10 is ping sensor).

Others need to answer about the resistors. I have also used up all servo ports, but I just wire them on the breadboard instead (using a three-pin male to male adapter), so you might want to look into that as well.

-Thomas

Martin_H

jonez wrote: »

I just realized I ordered the ActivityBot encoder kit not the Boe-Bot encoder kit. I ordered the matching ActivityBot wheels (more spokes and better treads) and I have lots of spare parts so the extra wires/resistors that come with the Boe-Bot encoder kit won't be an issue. From the description of the two products the encoders look identical but each kit comes with different resistors? The Boe-Bot kit comes with 10k and the ActivityBot kit comes with 20k. When I go to build the kit which resistors should I use 10k? I wasn't sure if that had to do with the board, encoders, or both? I will be connecting the encoders to the breadboard since the 4 servo ports are full (12/13 are wheel servos, 11 is ping servo, 10 is ping sensor).

I read the page on the Activity Bot encoders http://www.parallax.com/product/32501 and they are five volt devices. I would guess that they are the same encoders used by the Boe-bot and only the resistors are different. The Propeller chip is a 3.3 volt device and the Arduino and BS2 are 5 volt devices, so the higher resistance value is likely to protect the Propeller's input pin. I would think you can go with the 10 k resistors for an Arduino.

jonez

banjo wrote: »

Others need to answer about the resistors. I have also used up all servo ports, but I just wire them on the breadboard instead (using a three-pin male to male adapter), so you might want to look into that as well.

-Thomas

I also ordered 3pin headers & cables for the compass (and some spares) so I should have everything I need. Sorry I forgot to mention that!

Martin_H wrote: »

I read the page on the Activity Bot encoders http://www.parallax.com/product/32501 and they are five volt devices. I would guess that they are the same encoders used by the Boe-bot and only the resistors are different. The Propeller chip is a 3.3 volt device and the Arduino and BS2 are 5 volt devices, so the higher resistance value is likely to protect the Propeller's input pin. I would think you can go with the 10 k resistors for an Arduino.

Makes sense thanks!

Martin_H

Here are two help document links:

This is the product document for the Boe-bot encoders: http://www.parallax.com/sites/default/files/downloads/28107-Boe-Bot-Digital-Encoder-Product-Doc-v2.0_0.pdf A similar schematic should work with an Arduino as the 10K resistors look like pull ups.

This is Phil Pilgrim's document on how to use digital encoders: http://www.parallax.com/sites/default/files/downloads/28107-ApplyingEncoders-v1.0.pdf While it contains code for the Basic Stamp, the theory applies to any microcontroller. I found it took more than one read to truly understand it all.