Jay's Robotic Journal

2009-08-09T21:37:00.002-05:00

Hall sensor board take 2. here is how it turned out on the second go around. Tested it with a neodymium magnet and it works perfectly.

Also, I got a lot better result on the soldermask using thinner for the Vitrea 160 paint.

2009-08-09T21:29:00.004-05:00

Wart Zapper! Here is a circuit I found on the web. I claimed to zap warts (something I wanted to do. Long story short,

IT WORKS :D

I followed the directions here using SMD parts and adjusting the layout to fit on one side.

Jay

2009-08-01T21:50:00.000-05:00

Hall sensor break out board results:

Well, 1.1mm was just too small :) Never got it to work. Oh well, it was a long shot by hand for sure.

So I redid it for a "bigger " sensor device. Also, I am playing with a soldermask technique I found at www.diyaudio.com. It uses a glass paint called Vitrea 160. The image above I painted it with a narrow drush and avoided the pads. Then let it dry for a day and baked it to fuse the paint.

It's a work in progress as I'm not fomd of the "blobiness" of the paint. Trying to get the glass paint smooth is proving a challenge. I want the paint to flow and level out, but it doesn't. I may have to buy some of the thinner to see how that goes.

This last image shows a test I did using Press-N-Peel blue to mask the pads. I then painted over everything, baked it, and then used acetone to remove the mask (and paint on top. Worked really well, just need to improve my PNP blue techie as the mask smeared (due to too high heat and pressure I'm sure).

Jay

2009-07-26T22:36:00.001-05:00

I new milled circuit. Helping out a guy I met on the web that wanted a circuit milled. This is just a test to see if I can do the SMD pads. With the Widgetmaster and Wolfgang ... yep :) The smallest pads are .254mm wide. This is right off the mill with no "cleaning" of the whiskers of copper. I'm impressed.

Removed by request.

2009-07-24T18:19:00.000-05:00

Milled an illuminame for me :D

1/4" Lexan. I bought some ball nose endmills. The rouging pass was with a 1/8" 2-flute end mill. The finish pass was a 1/16" ballnose. The max depth is 1/10". The sign is roughly 8 x 3.5"

I plan to light it from underneath.

2009-07-23T15:47:00.000-05:00

I added a more precise spindle to my CNC router.

I broke down and bought a mount for my Wolfgang spindle to mount it to the Widgetmaster router. Was it worth it? You tell me...

Ran a test circuit to compare...

2009-07-07T23:01:00.000-05:00

I know, I know ... It's been a long time since my last update. However I wanted to share this one. I was contacted by my alma mater to help them mount a SMD hall effect device. Rather than ask me what would be best, they already ordered the part. It's unbelievably small. How small, 1.1mm square!

Yeah, have a look at what I milled out:

Even closer:

The whole board is about 1.5 inches. There are 2 surface mount capacitors in the bottom right. They are size 805 for those that care :D

I'll update when I actually mount the switch and test it. This is a BGA device (4 balls) ... I've never soldered a BGA but plan to use my hot air station. My other option is to buy a skillet from goodwill and do a reflow.

Jay

2009-01-12T15:29:00.000-06:00

As usually happens my attention gets moved from robotics into some subset. IN this case, CNC has my full attention. Most of my adventures are posted at www.cnczone.com versus here. I also have been adding new videos to youtube. I was hoping to get involved with the students at my alma mater to get me back to robotics but it didn't work out.

Jay

2008-09-27T23:10:00.000-05:00

Milling a printed circuit. I have been planning the time when I could mill my own circuits to save the hours of tedious point to point wiring I've done for some of my projects. While it didn't turn out as well as I hoped, I milled my first circuit tonight.

Jay

2008-08-14T02:30:00.000-05:00

Update 8/14/2008

One on my goals is to be able to mill my own circuit boards. I done it using the toner transfer method and etching but I want to use the mill to do it. To do this I know I'll need a faster spindle than the one that is on my mill. So I recently purchased a high speed spindle from Wolfgang Engineering. But, I needed to make a mount for it.

Have a look at the process

Onward,
Jay

2008-07-19T21:54:00.000-05:00

Update 7/19/2008:

Some testing of PCB-gcode on my mill. I added home switches. I mounted the Y axis one but am waiting for my extension kit from CNCFusion before mounting the X.

Anyway here is a short video of a test mill:

Jay

2008-07-16T22:27:00.000-05:00

Updates July 16, 2008

I have posted some pictures of my mill in it's new home.

In addition, I am getting ready to start milling my own prototype PCBs. For this I have found a free ULP for Eagle CAD that converts the board drawing to Gcodes. It's called PCB-Gcode. In my excitement, I also decided to contribute some time to updating some C++ optimization code for PCB-Gcode output. It works very well as you can see in the sample images I uploaded to my Picasa album.

Now I'm working on a GUI interface using Qt. A small learning curve. More about milling PCBs can be found here.

Jay

2008-06-30T10:43:00.000-05:00

A new project.

My son took immediate notice of this month's Nuts&Volts cover. Displayed are 3 LED lit name plates ... one being EVAN. "Daddy will you make Evan for me". I jumped at the chance/reason to get my CNC up and running. So I spent Saturday learning/re-learning how to use CAM, Mach3, and my CNC mini-mill.

I used a bamboo organizer box as the base/case and a piece of PVC for the top (that stuff is too useful IMHO). I am using 6 blue LEDS running off a 5 V 270mAh receiver pack (from my RC stash) drawing 20mA.

Of course this is just the beginning, he already want version 2 with blinking/fading lights and knobs and switches.

Edit, not too long after I decided to make some signs for a buddy's little girls. Rather than mill through, I back engraved the acrylic for a nice effect.

Jay

2008-03-18T22:21:00.000-06:00

Something new:

I leaned something new the other day and decided to give it a go. Charlieplexing is a type of multiplexing for LEDs that allows N pins to control N*(N-1) LEDs. So 5 pins on a Tiny13 can control 20Leds. I used 14 and here is the result:

Update: I tried POV (persistence of vision) but I'm not really clear on what needs to happen for the affect to show up. It was a half-hearted attempt to say the least.

Jay

2008-03-13T21:10:00.000-06:00

Gripper: final version with new video and source code

As promised here is the source code. Also, I hinted at another project I want to tackle .. .that being an electromagnetic levitator. I think the Tiny is up to the task :)

Of course it would behoove me to get my development environment built too. I programmed the Tiny at least 50 times, by removing it from the socket on my circuit. I need to order a ZIF socket, a 6-pin programming cable, and a longer USB cable so I can do ISP and debug wire on future circuits :)

Jay

2008-03-12T15:56:00.000-06:00

Updates: 3/12/2008:

First let me say that if you are an engineer and a father a great "toy" for both you and your kid(s) is the Snap Circuits kits from www.elenco.com (available at Radio Shack for a premium price). We bought the Jr. kit as my son is only 4 and he and I have already made all 101 circuits in one day. I have since ordered the Extreme kit which should offer all kinds of experiments. it just arrived today :D I recommend you get the Extreme first.

Now back to my gripper controller project. I have decided to continue improving the design some more. Most all my friends that have seen the video have commented that the motion looks too jerky and that it's not obvious that my hand is controlling the position of the servo. To address these I am going to modify the code to only update the servo position at 5Hz even though the A2D is being read at 20Hz. Furthermore, the servo position will only move +- 1 each iteration. I may change this based on the actual movement I see of course. As for the second issue, I'll just shoot a better video and maybe add some explaining :) I also plan to add in another sensor to control the gripper opening and closing the same way.

Forward,
Jay

2008-03-10T22:19:00.000-06:00

Update 3/10/2008:

I been MIA working on some paying projects. After I completed that, I got drawn into a new venture with a buddy. I can't say too much about what it'll be, but in order to get ready for it I've been playing with a new chip (to me anyway). The Atmel Tiny13.

Pros:

8-pin dip $1.29
No xtal needed has internal clocks up to 9.6MHz
Supports in-circuit programming
1K flash, .5k EEPROM
6 I/O all of which can be digital or 10-bit A2D
Requires a pull-up on reset
Uses the same GCC compiler as I am used to

Cons:

Internal clocks while they can be calibrated are somewhat inaccurate (thought they work fine for what I want)
1K of flash goes fast :)

In a nutshell I wanted a servo tester/driver. So I surfed the web, found snippets of code here and there, and came up with a little demo. If I were to use this on my robot, I would change it to trigger a "pickup" sequence of servo moves. However, I've never really played with the A2D on an Atmel and I purchased 4 Sharp gp2d12's so I figured why not. The A2D is read about 40Hz which is also how often the servos get a new value (if required). The timer ISR is set to execute every 13us. At the end of every 20ms frame, the servo signals are turned on. Each run of the 13us timer subtracts 1 from the servo count until it reaches 0. Then the servo pin is turned off. I'm only using the upper 8-bits of the A2D conversion (16-bits adds a lot to the program size and I don't think it's needed). The most current reading is compared to the previous reading + or - 7. This is to prevent the servo from "jerking" all over the place, but it results in visible "stops" in the video.

Here is a video of the results. I may add to it, I may not. The important thing is that on a 1" square PCB I can have a multi servo controller that uses analog feedback to position the servos.

I promise to post the source code once I get it cleaned up (this was just quick and dirty) and commented.

Forward,
Jay

2008-01-21T23:03:00.000-06:00

Progress 1/21/2008

While I should be working on a different project I worked on my robotic gripper design today. I have posted video of prototypes 2 and 3.

Jay

2008-01-02T15:12:00.001-06:00

I'm still here, just recovering from the Holidays. My plans to use an RTOS have proved to be too much work and not enough progress so I am going back to my interactive code. At this point my robot is still and R&D tool for me to test my code for a specific purpose so I don't actually need concurrent threads of behaviors.

My next little project is to code to control my 2-DOF gripper. What's that you say, you didn't see any posts about my updated gripper. I'll post some photos soon. The code shouldn't be difficult using the AVRLib library though.

Jay

2007-11-30T12:55:00.000-06:00

One step forward, two steps back:

Well I shot myself in the foot so to speak. I took my code to work to hammer out some of the details. This meant a lot of changes without being able to test them. Somehow I incorporated old code into the new code and contaminated both :(

Long story short, I'm going back to a reliable backup on 11/25/2007 which was before my last two posts. Thus, I'm progressing in the wrong direction. The good news it, I'm incorporating the code optimizations I made recently into the old code prior to me breaking out the functions into their own files. This way I can know they work before I change too many things at once.

On a good note, I've been mocking up a claw mechanism at lunch today. Saw a YouTube video of one I liked and fashioned a working model out of craft sticks.

Jay

2007-11-28T13:55:00.000-06:00

Updates 11/28/2007:

I have successfully added RTOS (real time operating system) to my code. I'm using FreeRTOS (www.freertos.org) and it was relatively painless to incorporate. Some of the details that slowed me down:

The kernel timer uses Output Compare 1A which is the same I was using for the right motor PWM.
The port.c file configures the Timer 1 only for Output Compare 1A which overwrites all my settings for pwm I set in my motorInit code. As such, I changed the code in port.c to use |= when setting it's bits. This is the only kernel change I had to make.
I used to have all my code in one file. This is due to the fact that I just kept adding on to experimental code rather than formalize everything. Prior to the addition of the RTOS, I broke out functions in to separate files based on organization (motors, motion, and eventually sensors).
I was also using a lot of global variables (bad form I know but it's been fixed) in my one file. Rather than declare them extern in my new files (yes I tried that at first), I added functions to "get" and "set" key variables.

The benefits of this rework?

Now I can add a task to the list to execute without other functions having to call it or be aware.
No blocking (well except for serial, but it's the lowest priority) so now pauses (which used to nop for x milliseconds) just yield to other processes.
Now I can build behaviors that can layer on top of each other and turn them on or off via a monitor/command line program.
Sensors will run in their own task loops (like sonar) at set intervals which was more difficult to time with function calls especially when something new was added to the mix.

All in all I'm very pleased with this decision and I know it'll pay bigger dividends as my experimentation increases.

To do:

Wire up the 4 IRPD sensors and 2 bump switches.
Code a wall following behavior
Code a avoid behavior (to drive/navigate) around an obstacle while still trying to get to a target coordinate :)

Other updates:

I ordered a Lipo balancer for my battery. I got a great deal on the battery I use (4S 12C 33oomAH) and the replacement cost would be much more than I paid (thank you www.cheapbatterypacks.com) so I'm going to baby this one.
Through typos I ran my motors full speed using the new RTOS code. The measured speeds were 90 ticks/ 20ms. The movie below shows the motors going 18 ticks/20ms so I plan to increase the max speed a bit. For shorter runs the code will auto slow the bot anyway, but this make longer distance "shorter" ;)

Jay

2007-11-26T09:58:00.000-06:00

Video of new code. Here is a short video of the robot now. The 4 commands I set are:
go 5 5
go -10 3
go 0 0
go 0 1

2007-11-23T23:11:00.000-06:00

Updates for 11/23/2007

My code to command the robot to go x distance or turn x degrees works great .. .the issue is that due to slight differences in the motor speeds, the robot could be off by as much as an inch in a 2 foot span. So I decided to change the system over to a target based one.

The code is inspired/copied from David P Anderson's find_target and odometry code. I did add some tweaks of my own, and I've not yet started on using an RTOS.

I added a function that allows me to specify a target coordinate (x,y). Then I added find_target to my timer loop and call it every 30ms. The function looks at the distance and angle and commands the motors to those speeds. By using he distance left to set the speed I get nice fast and crisp movements. Before I added/fixed the code that your set the speeds proportionally, the robot was all over the map oscillating like crazy. Have a look at tonight's results.

The robot starts at 0,0. I then commanded it to go to 5,5 (that in inches BTW) and then to go to -10, 3. The pink and yellow lines are there for reference. The blue line is the plot of the X and Y coordinates reported by the robot. I have the printout function send data every 40ms (a bit too fast really) so the point markers are really close.

To dos:
1. Add the ability to create a point array from the drive pattern routine. Then have the robot traverse the array.
2. Figure out how to call the print routine every X ms. Because it uses an interrupt, it'll have to be outside the timer routine that I use for the PID and find_target.
3. Find a suitable and ready to go RTOS to port my code to. I'd rather quit fooling with ms timers and just run all the processes concurrently and have a central function call each when it's their turn.

Onward,
Jay

2007-10-13T23:21:00.000-05:00

Lots of discoveries tonight!

Man what a day. I worked with the students today on getting the TIMER basics down, configuring their development platforms (WinAVR, AVR Studio, JTAG ICE), and learning how useful Excel is for calculating TIMER registers.

During all the back and forth, I had an epiphany. I was using code that limited my PID adjustment to +-100 (as in percent). I was using 10-bit PWM, but by limiting myself to (let's just look at forward speed) 100 possible values (out of 1024 (2^10)). Well that's still not totally true either. I'm using locked anti-phase PWM so only values above 512 generate forward motion. But I digress, I'm still only using 1/5 of the total values I could. So I modified my code and changed the limits to +-511. It works, and a lot better. Still need to tune the PID constants, but things are a lot smoother.

On a bad/disappointing note I ran my Lipo to 12.8V. Minimum is 12V (3V per cell) but I decided to check (for the first time since I had it) the individual cell voltages. Bad news:

cell 1 - 2.9V
cell 2 - 3.49V
cell 3 -3.02V
cell 4 - 3.34V

Wow, not good. My charger wouldn't even attempt to charge cell 1. Lipo charges are constant current, constant voltage chargers. I have a pretty sophisticated NiMh/NiCD/Pb charger. I set it for 2 NiMH and the charge current to .1A. I connected my DMM and monitored the voltage until it was 3.2V. Now the Lipo charger is charger that cell first. Only 3 more to go. Oh well, better than having to replace the pack.I'm not drawing huge currents or this could have been a lot worse.

From now on, I'm going to check balance every time.

Jay

2007-10-11T21:50:00.000-05:00

Video

As promised. A short video of my bot in action. The video starts with me showing the pattern function. I told it to drive a pattern with 5 vertices and sides that are 20" long. At this point I fix the speed at a mild rate. After the pattern completes I instruct it to drive 24" at full speed. You can really see the left steer. Then I instruct the bot to turn 360 degrees full speed.

Jay