Putting the Project into an Enclosure – Part 1

For the open Hardware Rallylog device I’ve been working on, I’d based my design around fitting into the handy Sparkfun Project Case and since most of my projects never get to the “enclosure” stage, they are either used bare PCB or thrown into anything that may provide some protection against the elements, such as the widget sensor housing.
(http://blog.strobotics.com.au/2009/06/15/widget-sensor-housings/).
Continue reading “Putting the Project into an Enclosure – Part 1”

Strobit M8 Files

Jans Gentsch has made his compact version of the Strobit Triggr available to the community, his version, the Strobit M08 based on AVR design can be found here.   Please note that there are a couple of things that need doing to the PCB, if you get a chance to implement Jans design, please post back any changes to me so I can make them available.

Hello Stephen,

I’ve attached the Eagle-Design-Data as well as the source code. I haven’t found time to do anything on those since my post, so the are not in the best state. There are a few Problems with the board design:

Transmitter – There is a connection missing between the processor and NIRQ of the transmitter-module (the transmitter module doesn’t have a fifo, so that the nirq-line is needed to clock out the data). I just added a piece of loose wire during assembly.
Receiver – NIRQ isn’t connected as well, so I am constantly polling, not really a power saving design. however I am still running on the first set of batteries so it’s not like they are being drained empty immediatly.
IO-Board – Thr optocoupley was meant to sit on the bottom side but I got confused. It has to sit on top now.

Getting everything into the housing was a major challenge.

The source code has been developed using avr-gcc and the eclipse ide.
As it stands only the most basic function, tiggering, is working. The control flow will have to be reworked in order to add the rest of the functionality. And of course my “magic” trigger id should be changed.

Have fun!

Alle the best
Jan

Files

You will need Eagle PCB to view/edit the schematics and PCB files, found here –http://www.cadsoft.de/

The firmware is written using winavr found here – http://winavr.sourceforge.net/

StrobIt Triggr

Introduction

20/03/09 *UPDATE * This project now has a new home and is actively being developed on Google code project hosting http://code.google.com/p/strobit/

IMPORTANT    This page is no longer being being maintained please go to the new project page.

Welcome to the Strobit Triggr Project, an open source hackable wireless trigger used in photography lighting by using low cost strobe units triggered remotely via RF. This was started while trying to find a cost effective and reliable solution to the commercial alternatives out there. At one end of the market is the Ebay or Cactus Trigger, which is low cost but rather unreliable. At the other end of the market there is the industry standard, Pocket Wizards, very reliable, but very expensive (i.e. way out of my price range).

What I wanted to do was to create an open platform that anyone can easily build for a low cost and then be expand upon by the community. The pair of prototypes I’ve built were a proof of concept that I can get a camera to trigger a strobe unit reliably at a low cost. From early tests it appears that I’ve succeeded in my goal, but further testing is required.

triggr0103

Project Status :

– Prototype successfully working in single master/slave configuration !

– (20/03/2009) Project now has a home at Google Code – http://code.google.com/p/strobit/

Still Todo:

  • Specifications
  • Hardware Design
    • Schematics
    • PCB
  • Software Design
    • Wireless
    • User Interface
    • Protocol
  • Hardware Prototype

License

The strobit hardware design is covered by The TAPR Open Hardware License. Please see http://www.tapr.org/ohl.html for further details.

Schematics:

Strobit Triggr Block Diagram Strobit Triggr Topology StrobIt Triggr Schematic

Prototype Details

Firmware Description

Protocol Description

Downloads – Files associated with the project

Tests – Tests done so Far

In the Wild – Version of this trigger made by others

I’m toying with the idea of putting together a low cost kit for the enthusiast. i.e. PCB, pre-programmed PIC, etc. So we could all benefit with a bulk order of the components. If your interested please email me using the contact form the top menu or use the mailing list signup on the right to give me an indication of numbers interested. Once I finaliaze the design and get some idea of numbers I’ll get a better idea of price. At the moment it will only be available in kit form due to FCC and other Licensing regulations.

Future Improvements:

  • Higher Sync Speed.
  • Frequency Hopping.
  • Forward Error Correction.
  • Power management.
  • UI to change settings, Channel etc.
  • Save settings in Flash memory.

Strobist Trigger

Things seem to have slowed down on the forums qute a bit, I’ve also put a poll up for the project name, based on a few from the marketing topic where a number of people have put forward their suggestions, well, while the poll has been viewed a large number, only 12 people have voted so far, a bit dissapointing, obviously they didn’t like the names I’ve pulled from the forums, Oh well I know you can’t please everyone.

Anyway moving forward….I’ve been busy researching RF modules and coming up with a prototype design.  Currently I have 2 prototypes designs on the go.   One as a drop in board replacement for the Ebay Triggers based on the RFPIC, the other as a Pocket Wizard type trigger, but hackable, based on the Phillips LPC2148 ARM7 Chip.  The designs are not complete by any means.  I’m still in 2 minds about the RFPIC Design I may for go it in favour of a standard pic with an external RF module, that way I could use the same RF module in both designs.

 Ebay Trigger Replacement Preliminary Design (TX)(PDF)

 LPC2148 Based Trigger (PW Replacement) (PDF)

BuzzBot – Initial Testing

I started testing last night after finishing initial motor and wheel sensor hookups to my development board.  Couple of minor issues so far. 

Issues 

I’m using a pic based board from Modtronics. These are great and reasonably priced, along with the prototyping daughterboard.  However I have since found that the onboard RS232 is not on the same pin as the PICAXE28X, so I had to wire in an additional programming circuit, no biggy.  The other issues so far were the wheel sensors.  From my initial design I had used 10K resistors to bias the output of the opto-transistor, this was not tested and when testing the logic probe was picking things up ok, but not the PICAXE, after much stuffing around and not being able to find my multimeter (it was still packed away from shifting house) I ended up prototyping the same circuit, still had some issues, so I went  hunting for my multimeter and of course it was on the bottom box lol.  Luckily thanks to my trusty multimeter I found that the sensor was just dropping down to 3.8v when interrupted, anyway the solution to the problem was a larger resistor, a 22K on the output, this tested AOK, now getting ttl levels when switched, I also noted that the distance of the sensor to the reflective object (paper in this case) was fairly critical.  I modded the breadboard and then found one side was working fine, the other was not being seen.  Checked and found that the sensor was slightly further away than the one that was working.  So out with the hot glue gun and moved the sensor.  Both side are now giving me a reading on the PICAXE.

Motor Tests 

Next I adapted some motor control routines on Hippys PICAXE site to test my motor circuit.  First I tested without my motor control board plugged in, didnt’ want any smoke to escape, and all logic tested aok, then came big crunch of running motors live.  I can gladly say that all tests worked A1 with no issues.  Motor was tested though a range of 3 speeds in FWD, REV, Turn right FWD , Turn Left FWD, Turn Right Rev, Turn Left Rev, Spin Left and finally Spin Right.  While Testing the FWD and REV, I checked the Pulses from the wheel encoders to see how much the same each drive was over 100 counts from the wheel encoders and it looks like the Right side is slightly stronger than the left, no real surprise here as no two motor/gearbox combinations are the same.  I had thought about this a few days ago and knew that with any differential drive system I will encounter this type of problem.

Motor Control Algorithm 

This then leads me onto my motor control algorithm.  Over the last few days I have been researching PID Controller and their application to motor control for robots, as I want Buzzbot to drive in a straight line, also been looking at fuzzy logic, but I think will give that a miss at the moment.  I have been thinking of using and adaptation of the PI Proportional controller from the book “Robots – Inspiration to Implementation”  however so far I’m not 100% happy with the PWM and the way it is from the code I adapted, while it is very simple and works,  I would really like to use the onboard PWMout routines, but as I mentioned in an earlier entry it is only limited to two PWM and to two physical pins on the PICAXE – Bummer!!!!   I also thought I can use the old PWM command.  This command requires it to be refreshed, much like what is happening in  my test code, except with a agreater resolution, unlike the PWMOUT that runs in the background, perfect I thought!, but when I went to test it I found it’s only available on the 08 series…double Bummer!!!!!  So now may have to look at teh PulseOut command.

While the existing configuration does give me three speeds, the lowest is time critical and I notice that when I add a debug routine the slowest speed does start pulsing, also I don’t think it will give me the fine control needed on each of the wheel speed controllers.  I’m going to have to think about this a bit deeper.

Conclusion 

All in all everything is working as expected, with a couple of minor hicups along the way.  Biggest issue will be PWM resolution and time of my routines.  I think I’ll need to come up with another way of doing what I want simply and without too much additional hardware if I want a closed loop control system.  While I ponder on this I’ll test the IR Sensor circuits.  These I’ll prototype first before I hardwire in.  Once I finish these I can then start working on behaviour.  I would like to look at using some sort of subsumption model, but will look at it deeper as I get closer.

buzzbot -  Motor Testingbuzzbot -  Motor TestingBuzzBot - Modtronics PIC Board

Buzzbot – Circuit Design

Last night I did some brain storming asto what the I/O requirements will be.  During this requirements phase I came across a bit of a delima with the PWM requirements for the motor controller.  The motor controller requires two outputs per motor, so this rules out using the onboard PWMout command of the PICAXE, as there are only two dedicated PWM pins on the chip that I’m using.  Although I could do it with some additional glue logic in hardware, I don’t really want to do that (as I’m lazy), so now I will be doing it all within the software, this should free up the servo command within the PICAXE, so I can now use this to drive the servo for the sonar unit.

I’m going to be using the PICAXE 28X. With my I/O current configuration of the 22 available I/O on chip, I have 2 Inputs/Outputs and 4 Analogue Inputs Available for future expansion (or and additional 4 inputs if I don’t want to use the analogue inputs).  It will be interesting to see if the processor will be fast enough process everything in a timely manner, especially with the motor control and encoders.  Well I guess I’m about to find out.

I’m now going to actually get my hands dirty with the PICAXE as I still haven’t plugged the development board into my PC yet 🙂

BuzzBot – I/O Requirements

Buzzbot – PICAXE Circuit

CNC Bug Bites

Over the past number of years, along with my interest in robotics and software development,  I have also had a keen interest in machining and metal work, I suppose ever since I build my first Stuart Turner stationary engine when I was 15 on my fathers Lathe,  BTW my father is also a very keen model engineer/machinist.  So wanting to merge my interests along came CNC.

I don’t own a lather / milling machine, actually I don’t even have a workshop myself (about to change with my new house being built), although I do have access to them when ever I want its still not the same as ducking out to the shed to whip up a part, in general I find making small components and PCBS a bit of a pain, mainly though lack of tools and proper work area.  So Getting back into the robotics/electronics scene after a long break has also re-kindled my interest in the CNC Area, especially for small robotic parts (plastic and aluminium) and one off PCBs (routing and drilling). 

So in my quest for knowledge, I spent the last few nights browsing what’s out there, and was very surprised to see the huge amount of work that people have done.  I must admit it had been a couple of years since I’ve last looked, and there there are some truly amazing machines out there (check out http://www.cnczone.com/).   Anyway I think I want to start off small first with a low cost pcb router/drilling using a 3-axis with a dremal.  Plenty of photos out there with low cost designs and common parts have inspired me to take some steps and begin some design work, so stay tuned.