Ever since we purchased our Arduino and tinkered around with a few simple electronics projects, we been itching to make a real robot. Well the time has come where we had a few extra dollars to spend and we splurged and purchased the following to help us along:
- DFRobot 2WD Chasis
- Parallax Ping Sensor and Sensor mounting kit
- Wheel encoders designed for use with the chasis/motors
- Screwshield for the arduino to help stack the motor driver we have and have access to the pins
We already had a few things that we needed since we've been taking apart a few things around the house. Here's the important stuff that we had already. I'm sure we're going to need some more sensors and things, but this is a start.
- Arduino Duemilanove (http://arduino.cc/en/Main/ArduinoBoardDuemilanove)
- Old Motor Shield (http://arduino.cc/en/Main/ArduinoMotorShield)
Parallax Ping and Mounting Assembly
I choose the Ping sensor because I can usually find one locally, even in our small town, and there is plenty of examples at the Arduino website. The mounting bracket, servo and cables were purchased to make mounting the sensor easy. General assembly of the parts went smoothly. The instructions suggest using a 3/32" drill to make the mounting holes a little wider for the screws. I could see that without making the holes bigger, the little 'X' bracket on the servo would snap. It also helped to take off the 'X' bracket to attach the nuts and bolts for the Ping. Hopefully mounting and routing the wires will provide just as easy.
We popped open the chasis box and looked at all the stuff. One concern was that the wires for the motors were not pre-assembled. I worried about which was the ground and which was the power. Screw it and I soldered the provided wires to the terminals on the motors making sure they were both attached the same way. Little did I know this would be the first of my issues with this kit.
I had ordered the encoder kit, so I started to assemble the encoders onto each motor mount. Here's a quick bullet list of the issues with the encoder kit:
- One of the provided bolts did not like to take any of the provided nuts very easily. This lead to having to use more force that I thought necessary to attach all the hardware we were looking at.
- The provided encoder wheels had the center hole too small for the screws provided. I had to use more effort than I thought would be needed to get the screw inside the mounting hole. I constantly worried that I was going to bend or break the encoder wheel trying to mount the thing.
- The provided encoder board spacers where too short. When I tried putting the encoders onto the bolts with the spacers, the encoder would hit the encoder wheel and not allow a mounting to take place. Once I put on one of the spare nuts below the spacer, then I was able to get the encoder to line up with what I thought it should look like. The first assembly took me longer that I expected because of the bolt issue and the tiny parts.
Arduino 2WD Chasis
With the motors and encoders finally mounted, I felt some sense of accomplishment. The roller ball and battery case went on without issue. Thinking I was in the clear, I reached for one of the wheels....
I can not for the life of me figure out how to get the wheels to mount. I see the logic of the wheel assembly. Basically you put the tab in the slot and call it a day. Too bad the "tab" of the motor is too large for the wheel "slot". Frustrated after 10 minutes of trying to get the wheels mounted, I send off an inquiry to the place where I bought the kit, hoping for some solution to my problem.
I now start looking at the top plate and how to mount the various other parts. Luckily the on/off switch is too big to fit into the proper hole in the top plate, so it looks like I'll have to make a trip to Radio Shack or something to find a replacement part. The other little plug adapter is not needed since I have no clue how I'd hook anything like that up. Off to the parts bin with that piece.
Well, day 1 started out with some hope but was left with frustration. I don't see how to mount the top plate how I want so that the Ping sensor is place at what I think is the "front" of the robot. I tried figuring out how to mount the Arduino to the top plate as well with no luck. Pieces do not fit like they should and I'm completely frustrated with what I thought would be a fun "kit" for me and the boys to put together.
Maybe day 2 will be better.
P.S. Sorry for the fuzzy pictures, my camera is just no good.