Piezo Film Vibra Tab Mass as Encoder

Another experiment in the Scribbler wheel encoder project that erco and I are working on.

This slightly dark video is a proof of concept video using the Piezo Film Vibra Tab Mass Sensor as a possible wheel encoder on the Parallax Scribbler. It uses the Scribbler's wheel spokes to trip the Vibra Tab as the wheel rotates. It is like a playing card in the spokes of a bicycle wheel.

The Scribbler's wheel has 8 spokes on each side, actually 8 high spots and 8 low spots. That is 16 positions for one turn of the wheel. The wheels are 3-1/8" in diameter (approximately). The circumference is computed with the formula, circumference = pi times diameter, or C= π d. The circumferece is 9.82" or 9-13/16". For each 16th a turn, the wheel has travelled 0.614" or 5/8".

An issue might be the time the Vibra Tab is bent during contact with each spoke. I don't know yet if it sends one message when it bent or continuous messages.

But, as the video shows it does work (at least in concept).

Parallax Scribbler Encoder Project

A friend of mine, erco, from the Parallax Forums and I are working on an encoder project for the Parallax Scribbler. A wheel encoder keeps up with the turns of a wheel. It "counts" the rotation speed by reading teeth (like a gear), notches, or black and white stripes with an optical or mechanical reader. By doing this, you can tell how fast a wheel is turning and how far it has turned (for example, if the wheel turned once and you know its circumference - you know how far you have traveled). This lets you measure the distance the robot has traveled and lets you correctly keep it running in a straight or curved direction. The thread of our discussion on the forum for this project is here.

As a benchmark, my buddy, erco, wrote a simple test program to show how the Scribbler runs forward and backward through a range of speeds. This is a video of my Scribbler running the test program. This shows the difficulty of the Scribbler running straight consistanly through its speed range. Prior to the test, I reset the Scribber with its original program. There is no correction via the Scribbler Program Maker GUI by the calibration routine. The calibration routine lets you make a single correction to one motor to equalize its speed to match the other motor.

As you can see, the Scribbler does not run very straight without some sort of correction.

Merry Christmas

Ho! Ho! Ho! Here's hoping that we all find some fun robot stuff under our trees this year.

Have a very Merry Christmas and a safe and Happy New Year!

I am looking for few fun projects this year and may try to rack up on a few after Christmas sales too!

Robotics Club at Louisiana Tech

Under the leadership of Louisiana Tech professor, Dr. Ben Choi, student leader, Okoye Chuka and with the help of Dr. David Hall; Louisiana Tech is getting its Robotics Club up and running again. The attached image is a flyer for the upcoming meeting. They are including others, like me, who are outside the university, but interested in robotics. I really hope this becomes an ongoing group. It will be great to have some others locally to learn from and talk to.

Propeller Professional Development Board

My Dad used to always say, "When you have some spare money to play with - you don't have any time and when you have some time to play - you don't have any money." That's kind of where I am right now.

I have been really busy with work lately doing some extra work at my children's school, so I have some money, but no time to play. But, I just ordered a new toy. I hope I can find some time to play when it comes in. It is the Propeller Professional Development Board (PPDB) from Parallax and their website describes it as "a high-quality, fully-integrated development platform for the Propeller microcontroller. A wide variety of typical I/O (LEDs, Buttons, etc.) devices and circuitry are built into the PPDB, providing the developer with an ideal platform for rapid Propeller project development." They had a special on some slightly blemished models and are selling them at a discount. Take a look here. They were about 25% off.

This will be lots of fun! It will give me a great way to prototype ideas and check them out (other wise known as playing). Can't wait till it gets here.

Too Busy!

Just a quick post to say that work is seriously impinging on my play time. I only get a bit of time here and there, but I am making a plan...

I am also working with a few folks on getting a robotics club going in the area. That could be very fun!

More news as it developes.

Improved RCA Audio/Video Connection

Just wanted to show some pics of a homemade RCA Audio/Video Connection I made to use with my PEKit. I used info from OBC's Propeller Cookbook and the pdf for the RCA to Breadboard Adapter. The RCA board was one I scavengeed from an old VCR and I made a set of pins to stand in up in the far left ground bus. Video is tied (through resistors) to the standard pins - 12, 13 and 14. Audio is tied (through capicitors and resistors) to pins 10 and 11.

I attached them to a broken DVD player (as mentioned previously). I have a 12 volt power supply and the display and speakers work great. So all the parts and display are junk I had in my junk box.

I have tested the Graphic_ Demo, TV_Text_Demo, the SingingDemo and the SingingDemoSeven from the library in the Propeller Tool. They work great!

Now that it is working and tested, I may consider tight-wiring it, so it takes up less space. I'm really enjoying playing with Labs and learning my way around the Prop.