Archive for the ‘Introduction and Background’ Category

An Electronics Hobbyist’s Workspace

December 2, 2006

After several weeks of brainstorming, thinking, researching and cost-prooning, I have finally gotten my electronics workspace up and ready. It has put a couple of weeks of mileage already.

I wanted to make sure I stayed under $100 to setup the workspace (not including the tools of course). So I went to the local hardware store picked up a few boards, railings, support-brackets and vioila!

I wanted to setup the workspace a bit higher from the ground level for couple of reasons, 1) to keep stuff away from kids so they don’t pound on my toys 2) to help support the ergonomics of the working on it and 3) make it comfortable to work on. All three goals were well achieve by this simple layout.

Tools of the Trade:

  1. A good soldering-rework-station. I recently purchased a brand new “AOYUE 968 solder hot-air 2 in 1 Repairing/Rework station” from an online store based off of China. I purchased this one very recently for a very good price – paid USD$95 for the unit and USD$50 for s&h. Pretty good price considering a model lower to AOYUE 968 costs USD$175 w/o s&h at few online stores in the USA.
  2. I have owned a 20mhz Oscilloscope made by GW. I have rarely used it. But, now is the time
  3. Dremel drill press
  4. Vintage Black/White TV to keep me uptodate w/ weekend news
  5. couple of drawers to keep components organized
  6. workspace floroscent light
  7. I bought a towel hanger at the local IKEA – this serves good purpose of hanging my wires spools, tapes, solder spools, etc. And, makes it very easily reachable.
  8. high chair cushioned
  9. digtal multimeter
  10. a trash box (cardboard – nothing fancy)
  11. wireless internet access
  12. laserjet printer (for making PCBs)
  13. and, lastly but not leastly, some quality quite time

Here are a few pics:

1.JPG 2.JPG 3.JPG 4.JPG 5.JPG 6.JPG 7.JPG 8.JPG 9.JPG 10.JPG 11.JPG 

ciao

Nagi

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How To Make Your Own Homebrewed PCBs

December 2, 2006

Over the last few weekends I have been spending some time in learning how to make your own PCBs at home. While there are many online service vendors who do an excellent job for a reasonably good price for bulk quantity, I felt they are a bit of an over kill for single order PCBs – particularly for my project – where the circuits are pretty straight-forward.  For single PCBs, I determined making them myself. Plus this gives me an opportunity to learn this skill without spending too much money.

Tools of the Trade:

  • Press-n-Peel Blue (I bought mine here)
  • Access to a computer
  • Laser Printer (not dot-matrix or ink jet)
  • A board drawing software. I use “Eagle
  • Paper cutter (with a good sharp blade)
  • PCB board panel
  • Ferric Chloride Soln (I bought mine here)
  • Masking Tape
  • Pressing Iron
  • Number 70 Drill bit (I bought mine here)
  • A hand-press drilling tool or a drill machine w/ drill press
  • a plastic tray
  • Steel wool
  • Some Alcohol for washing the PCB (my wife would know – I stole her nail-polish-cleaner-thingy)

Steps:

Circuit Transfer to PCB:

  1. Design your board and print it out on paper using a laser printer
    1. Before printing,
      1. ensure that the “Solid” option is selected on your Eagle software
      2. Also ensure, you pick 300 dpi vs 600 dpi. The 300 dpi ensures the pins alignment is accurate
      3. pcb.jpg
  2. Take your Press-N-Peel paper and cut to fit the printed board drawing – add about 1/2″ extra on all sides
    1. Use a paper cutter to get the square edges on the P-n-P paper.
    2. dsc03781.JPG dsc03782.JPG
  3. With the DULL side of P-n-P cut paper facing UPWARDS, tape it over the printer paper (using thin masking tape) w/ the printed drawing so that the P-n-P covers the drawing on the printer paper.
    1. Make sure you line up the P-n-P paper with the edges.
    2. dsc03783.JPG dsc03784.JPG
  4. Now, place the P-n-P that is over the printed paper facing DOWN into the printer tray (check w/ your printer specs, yours might need it facing up). I’m using HP Laser 6P – which needs it facing down.
  5. Now RE-PRINT the drawing from Eagle software
  6. By now, the Drawing is now printed on the DULL side of the P-n-P paper
    1. While the drawing is being printed, set up your press-iron to either “wool” or “polyester” setting. Let it heat up. Temperature is very CRITICAL
  7. Carefully remove the P-n-P paper from the printer paper making sure your DON’T touch the dull side w/ your fingers. Finger prints can cause issues later on
    1. Carefully remove the masking tape from printer paper and the P-n-P
    2. Carefully set aside the P-n-P in a dust free place. Use a small plastic box to cover over it.
    3. dsc03786.JPG
  8. Now, take the PCB copper panel and using steel wool and some alcohol wipe and wash off the panel.
  9. dsc03787.JPG dsc03788.JPG dsc03789.JPG dsc03791.JPG
    1. make sure you don’t touch the face of the panel board
    2. Repeat the washing 2-3 times to make sure the face is bright and shiny and void of any goo spots
  10. Now, using a clean paper towel, wipe of the PCB panel so that it is completely dry and free of any felt or other remains.
    1. Starting now on, ensure you touch and lift the PCB board ONLY by its corners
  11. Once the PCB is all dry
    1. take the prepared P-n-P w/ the drawing
    2. with the DULL side facing DOWN, line it up over the cleaner face of the PCB panel.
    3. And, using thin masking tape, tape the edges – making sure your are NOT covering up the drawing.
    4. Make sure there are no ripples or air bubbles – we want full contact over the PCB
    5. dsc03792.JPG dsc03793.JPG dsc03794.JPG
  12. While this moment, your pressing-iron must be ready by now.
    1. On a flat surface, lay a paper down (printer paper should work well)
    2. SWITCH OFF the steam setting on your iron – NO STEAM
    3. With the P-n-P side facing UP, place the PCB  over the paper (step 12.2)
    4. Now take another paper and lay it OVER the PCB
    5. dsc03795.JPGdsc03796.JPG
  13. Take your iron and place it over the PCB and press firmly over moving it about over the PCB.
    1. We need to ensure the heat is transfered to the PCB evenly
    2. After abt 3 minutes of firm presses and moving the iron about over the PCB, set the iron over the PCB and leave it alone for about 4 minutes
    3. Now, again, with firm presses move about the iron for another 3 minutes making sure you are running the iron right over the P-n-P side of the PCB
    4. Now take away the printer paper that was place over the PCB
    5. Using your iron, move about the iron with firm presses over the P-n-P DIRECTLY (w/o the paper over it), making sure you’re catching all the corners
    6. dsc03797.JPG dsc03799.JPG dsc03800.JPG dsc03802.JPG
  14. At this time, you can check the status of the transfer of the drawing over to the PCB by briefly lifting the P-n-P from the PCB.
    1. Once all the drawing is transfered to the PC, you can safely remove the P-n-P completely from the PCB
    2. You’re now done w/ transfering the drawing to the PCB
  15. Switch off the iron
  16. Carefully peel off and separate the P-n-P from the PCB.
    1. Make sure again, you are NOT touching the PCB face
    2. dsc03803.JPG dsc03804.JPG dsc03805.JPG
  17. Let the PCB cool off for 2 minutes – be careful PCB will be HOT
  18. Take the PCB and cut to size using the paper cutter- It worked great for me. Making sure you are NOT cutting off the drawing – that would be bad and defeats the purpose.
  19. dsc03806.JPG dsc03807.JPG

 Etching:

  1. In a plastic container – prefereably w/ a deep flat one
    1. Place the PCB, with the drawing facing up
  2. WARNING:
    1. Wear rubber gloves to protect your hands from the Ferric Sulfate
    2. Wear safety glasses
    3. Be at a place where there’s sufficient lighting and ventilation
    4. dsc03808.JPG
  3. Pour the Ferric Chloride just enough to cover the PCB
  4. Now using both your hands, tilt the plastic container to/fro and side-to-side alternating
    1. do this for about 10 minutes
    2. At this time, the copper coating over the PCB should start eroding and eventually should be gone
      1. Leaving alone the drawing portion of the PCB
      2. dsc03811.JPG dsc03812.JPG dsc03813.JPG
  5. Once the drawing side is free of all copper, using your tweazers, turn the PCB bottom side up
    1. Now again using both your hands, tilt the plastic container to/fro and side-to-side alternating
      1. do this for about 10 minutes
      2. At this time, the copper coating over this side of PCB should start eroding and eventually should be gone
      3. dsc03814.JPG dsc03815.JPG dsc03816.JPG dsc03817.JPG
  6. Once all the copper is gone over all the parts of the PCB except the drawing portion, carefully take out the PCB to a sink with running tap water.
  7. Place the PCB under running water making sure the PCB is completely washed free of any left over chemical
  8. dsc03818.JPG dsc03819.JPG
  9. Now with steel wool, firmly rub over the drawing areas of the PCB while letting it run under the running tap.
    1. This removes the laser ink from the board revealing the copper layer.
    2. Wash off until all toner ink is gone
    3. dsc03821.JPG dsc03822.JPG dsc03824.JPG dsc03825.JPG
  10. Wipe off with dry cloth or paper towel
  11. Discard the chemical under running tap water – you don’t want any stains left
  12. dsc03826.JPG

Drilling:

  1. For drilling holes thru the vias, I am using a #70 drill bit and a Dremel drill housed over a workbench
  2. line up each of the PCB hole targets and vias and start drilling away.
  3. dsc03827.JPG dsc03829.JPG dsc03831.JPG dsc03832.JPG dsc03833.JPG dsc03834.JPG dsc03837.JPG dsc03838.JPG 

You’re now a successful PCB Homebrewer!

This was my 2nd attempt to making my own PCBs and this board took me 35 minutes start-finish.

Hope that was useful and helpful in your experiments

BTW, thanks to my dear wife for taking these pictures. Had to sneak that in there!!

ciao

Nagi

Who is A.L.I.B.E.

October 24, 2006

A.L.I.B.E stands for Artificial LIfe BEing – is in the makings of becoming an autonomous land roving robot. The sole purpose of his life is to wander about land terrains in search of his “homebase”. At the skeletal structure, ALIBE is a modified all-wheel drive RC Truck retrofitted with various electronics components to give him the needed sensory and reactionary behaviors. Sensory components essentially help him gather data as he wanders about – such as temperature, light, touch, acceleration, inclination, compass heading, GPS location, object and obstacle range, Vision and other important pieces of data that will help him make the needed decisions to get to his homebase. Reactionary components essentially help him react upon to the data he gathers – such as motion, display and communication to-from him and the homebase.

ALIBE is also equipped with other components such as a communication module (powered by Aerocomm AC4790) that he uses to communicate two-way with the homebase. Essentially, responding to request-of-data and request-to-react. Both of these behaviors are important to ALIBE’s overall behavioral patterns. He needs to be able to send data to the homebase when requested and react to the commands sent by the homebase Command Center – such as overriding behaviors. Think of this as similar to the Command Center at NASA sending data over the air, thru the space to the Mars Rover and back – this one, only on a much shorter range and smaller scale.

ALIBE is equipped with battery packs to fuel all the electronics he runs or decides to run at behavioral time. Which also means, that he knows when to shutdown certain modules as needed or to boot up for use as demand rises.

The brains of ALIBE, are powered by an on-board 32-bit multi-processor based microcontroller chip called, “Propeller” made by Parallax. Propeller is made of a central “Hub” that knows how to control the surrounding 8 multi-processors called, “Cogs“. Each of the cogs can be programmed to take on a task that runs independantly of the others, yet centrally managed by the Hub. It is a very effective way of time-slicing ad processing command cycles. Propeller can be programmed either using Assembly or the proprietary SPIN language. Both of these are very attractive not just from programming structure, But, also from performance and efficiency standpoint.

ALIBE employs Propeller in a way that each of the 8 cogs are designated to handle a certain “wing” of the onboard responsibilities. More details can be found in this blog. From a high level however, a Cog is set to process Communication between ALIBE and the homebase Command Center, another is set to gather sensory data from less intensive sensors such as temperature, accelerometer, compass, CdS, Sonar Range detectors, etc., while another gathers data from the Vision enabling camera; And, another monitors the overall demand-need-status of devices to ensure switching on and off of the devices; another to handle motion; LCD displays, among other behaviors.

A bit more about the communication module in ALIBE; The AC4790 is made by a Aerocomm. It is a Transceiver – very user/developer friendly. AC4790 was chosen among other similar devices for a couple of reasons. One, it is fairly easy to work with compared to other competitive products in the market. It’s Pin layout and Pin characteristics are easy to follow. And, mostly, can be effectively functional just with 3-wires into the microcontroller. It has many featuers. However, for ALIBE, all he needs to do is wait for commands from homebase Command Center and either react to the commands or send data back. A very “Reactive” behavior. For something as simple as this, one is able to make this work with 3-wires. The second reason I chose this was, the range. In a clear Line-Of-Sight, ALIBE is able to keep the communication open for upto 4 mile radius – which is very useful for ALIBE’s behaviors and Thirdly, AC4790 supports not just “Peer-To-Homebase” but, also, “Peer-To-Peer”. So, if in case I were to build another ALIBE, the two will be able to communicate with each other and also with the homebase Command Center effectively. This last feature is very useful for the future of ALIBE.

The ultimate goal of ALIBE is to navigate about the neighborhood, and tackle obstacles and reach the homebase coordinates successfully. The project is on-going for the past 3 months now and I am hoping it will be completed in another 3 to 6 months.

This blog is here to keep and post updates on this project as it happens. You should find a lot of information here 1) background theory 2) electronics details such as parts, circuit diagrams, hardware assembly, etc 3) some level of source code 4) and of course a lot of pictures.

ciao

Nagi