Strobotics

PCB designs were finally sent off to Gold Phoenix yesterday, a bit of a delay as I had been wanting to complete a couple of other designs to fill up the panel before sending off.  Three different designs, Strobit RFM12B core, Experimental 2.4Ghz core and a prototype personality (think arduino prototype type shield) have now been merged using gerber merge into a 10” x 14.5” panel.  Hopefully they should be back early next week.

Some more components added to the Strobit Eagle3d Library.  Can be found here.

Sparkfun SMA PCB Edge

3.5mm Phone Jack SMD

Ok not quite finished, but almost there!  I’ve had to make a few minor changes.  I’m glad I’ve taken the time to learn and play around with Eagle 3D, it had highlighted some potential clearance problems.  Rather than rush things I’ve decided to take a bit of time modelling than fork out my $$$ and get some prototypes made only to find these problems down the track and could have avoided.  Granted Modelling is not a silver bullet, and I guess I could be here forever, but now I’m a lot happier.

Changes:

• Moved SMA antenna connector back from front edge of the PCB as it was hanging over slightly.  This connector is optional at assembly.  The pad can be used to solder on a wire antenna instead.
• Changed switched power side on the switch, The switched side of the On/Off switch was very close to ground plane coming under the switch so had the potential to short, now is nice and clear.  I’ve also added some more ground plane clearance around the switch contacts just to be on the safe side.
• Added solder jumpers for LEDS, probably don’t want these enabled if a personality board is on, but it gives you the option to use them or not, and re-use the I/O if required.
• Moved vias and tracks away from standoffs.

Todo:

• I think I really need to isolate the 2 power sources from each other, i.e. the Power from the USB and VBAT, so I’m looking at putting in a BAT54C barrier diode.  Just need to research it a bit more.
• Still don’t know what to do with the ICSP connector.  I will probably leave it there with the option of putting it on at assembly.  I’m pretty sure that it will clear any personality board with a bit of care.  Modelling the personality board is my next step.

Strobit Eagle3D Library now available for download….see Eagle3D Page

HopeRF 433Mhz / 915Mhz

Experimental 2.4GHZ

I’ve been playing around with Eagle3D on and off (like most things more off than on lately).  Eagle3D in a nutshell is a bunch of scripts to generates povray files.  Povray is then used to render a realistic representation of the PCB file with all components included. 

The problem I’ve always come up against when using Eagle3D is missing components.  I first looked at this tutorial – http://felixchenier.homelinux.com/doku.php?id=pcb:eagle3dnewpart, however I took one look at how to make library components and thought no way, I don’t really want to generate a 3D component by long hand.

As an example this is the Experimental 2.4GHz version of triggr PCB rendered with default output from Eagle3D, you can see how many components its missing (indicated by the red cylinders), you will also notice that its also picked up the wrong component in the top left of the board, this should be a right angle header, and it’s not correctly aligned.

Well I spent a couple of hours last night playing with Eagle3D to see if I could a) learn to create custom library components using Googles free sketchup program to create a part then export to Eagle3D, and b) to get a better understanding how components are selected and put on the board in the correct orientation.

I finally had success in exporting a sketchup component to use in Eagle3D.  I imported an already existing component for the MRF24J40MA RF module from sketchup and incorporated it into Eagle3D as a part library.  Here is the result.  A lot better wouldn’t you agree?

Here is how I did it in a sparkling new tutorial….Using Google Sketchup to create Eagle3D components

I know I’m a bit slack in updates on the blog.  If you haven’t noticed I now have a twitter account  http://www.twitter.com/madeinoz so you can follow what I’m doing when it’s not getting updated here.

However since the blog is way over due for an update here is what’s been happening in a nutshell.

Strobit Trigger:

I have finally gotten off my butt and done a redesign (hah and you thought the project had died a slow death, it may have stalled slowed, but certainly not dead!)

Features worthy of note in the new design (in no particular order):

• 3V design, will run from x2 AA Alkaline or single CR123A 3V battery.
• Fairly compact board, 30mm x 70mm. (without battery)  slightly lalonger on 2.4ghz design due to antenna.
• Onboard on/off switch to save batteries when not in use.
• FTDI 3.3v breakout cable port for connecting to either RS232 or USB using the FTDI cable.
• Onboard ISCP port for programming.
• Personality daughter boards.  Will allow users to create their own hardware modules, i.e. sound trigger, light trigger, LCD UI, or whatever they like etc
• Atmega168V processor, low cost, low voltage design = longer battery life.
• Can run Arduino bootloader, so developers have access to Arduino development libraries.
• I’ve designed 2 different boards.  One using the RFM12B module at either 433Mhz or 915Mhz.  The second board I’m going to try a 2.4GHZ design using Microchips FCC certified MRF24J40MA 802.15.4 module, this is purely experimental so I don’t have any testing done yet, but I have some of these modules and would like to try them out, also being FCC certified will be an added benefit.  (not to mention I’ll be using these for a mesh sensor network project I have planned around the house)
• RFM12B board design has external SMA antenna.
• Base PCB board designs are done and I’m fairly happy with them so far, I’m just finishing a basic personality modules which I can used for testing and maybe another one so I can make up the  max designs I can have on a single panelized board (may as well get the most designs I can get fabricated when I send it off to GoldPheonix).  I’ve done some initial Eagle3D runs to get an idea of the boards and so I can post them on the blog, but I really need to learn how to create components in Eagle3D as it leaves unknown components blank, i.e. the RF modules and therefore looks incomplete.  (anyone that can help me here please contact me)

Still To Do:

• Panelize boards
• Send to GoldPheonix for PCB fabrication.
• Assemble and test.

I’ve also been playing with learning Alibre, a fantastic 3D design package (they have a free version) so I can get some ideas for building enclosures design for these boards.

RFM12B PCB

MRF24J40MA PCB

Ok I have finally had a little bit of time to work on things (will be short lived as I’ve just bought a house and moving in the next couple of weeks Aghh!!).

Things are getting very close to reality after many design changes, the very nearly final Strobit Trigger base board, aka a modified Ardiuno BT board, with the Bluetooth removed and now fitted with the RFM12B SMD Tranceiver module and an external SMA antenna connector. The Eagle 3D side of things still needs work as some components are not shown and the inductor for the DC-DC converter is incorrect, but you get the basic idea right!

Why have I gone to a non-dedicated trigger board?

Well a couple of reasons, initially to cover myself from any patent issues that might have arrisen had I used a dedicated wireless triggering device, but mainly to allow better expandability. Why have a dedicated trigger with all the fruit and only use half of it, this way dedicated boards can be used, i.e. standard trigger, or sound/light trigger, sequences etc. Another reason is that the Ardruino is very well established and supported in the open source community, especially when it comes to the firmware libraries etc, it’s already been done. also I can use these in my robotics hobby as well, not just for photography.

Ok onto the board features:

• Fairly compact same size as ArduinoBT
• Standard Arduino Pin headers, so should be able to use with existing shields.
• Will operate from as low as 1.2V, so should work from x1 NIMH AA easily enough.
• RFM12 Tranceiver, up to 300m range (as per datasheets, although it does depend on the datarate)
• SMA connector so you can connect an external antenna for better reliability and range, or remove the SMA connector and use a piece of wire as the antenna.

What is left to do?

• Well the design is pretty well done, I want to get some prototypes made so I will be sending it off very shortly for fabrication.
• Different variations of shields need to be done, first one being stock standard strobe type of triggr, input and outputs, then others as needed

What did I say in my last entry about murphys law and my RFM12 header boards?  Guess what arrived in the post today lol…..

I couldn’t get any hands-on hardware development time for the Strobbit open triggr project today, so I designed a breakout board for the Sensirion SHT15 Humidity/Temperature sensor for my weather station I’ve been intending to build.  I have a couple of these sensors at home waiting for something this so I can have a play with them.  PCB uploaded for fabrication today.

As a side note:  While uploading this for fabrication at http://www.batchpcb.com  I noticed that my RFM12 PCBs has been panelized and so should be in production, hopefully they should rock up on the doorstep sometime soon.

The RFM12 module is a pain to prototype with due to the 2mm header (won’t fit into the breadboard), so I’ve whipped up a prototyping board that brings out the pins to a standard header.  It’s been it sent off for fabrication today so I should have back in the next week or so.   I’m trying out www.batchpcb.com for the first time so will be interested in how they turn out. 

In the meantime I’ve soldered on some wires but I don’t really like it.

I’ve put an initial design (both eagle source files and PDF) into SVN that is aimed as a board replacement to the ebay triggers.

http://svn.everythingrobotics.com/strobist/mk1/trunk/design/ebay_trigg.pdf

As i’ve started using Eagle as my electronic design package (protel is fantastic but just too expensive), I’ve created a component library that I’ll be using on the Strobe trigger project.  I’ve put the library in SVN for everyone to use and contribute towards -http://svn.everythingrobotics.com/strobist/eagleLib/