An Electronics Hobbyist’s Workspace

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:

           

ciao

Nagi

How To Make Your Own Homebrewed PCBs

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. 
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.  
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.  
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. 
8. Now, take the PCB copper panel and using steel wool and some alcohol wipe and wash off the panel.
9.    
   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.  
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. 
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.    
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.   
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.  

 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. 
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.   
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.   
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.  
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.    
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. 

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.         

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

Modular Layout and Wiring

Over the last weekend, I received a few mailorder parts for PCB assembly for ALIBE.  For ALIBE, having the layout be modular will help for a few reasons. 1) For extensibility, 2) to be able to isolate a part, replace or fix, 3) easily debug a part in isolation, 4) for “readability” purposes – that is understanding how the parts and circuits are laid out, wired, etc., and 5) for me personally, it helps me think clearly as I build ALIBE.




The approach I took was to build things into modules A) Brain Module (made of Propeller and PropStick), 5V regulator, Main Power Switch, LED indicators, and various PCB connectors for signals and incoming and outgoing powers.

Here’s the picture of the right side up. I am happy with the way it turned out.

However, I am not happy at all how I ended up soldering the underside. I should really be doing this via a well designed and frabricated PCB. (On a side note, I should spend some time next weekend learning some of that stuff).

Now, assembled on ALIBE’s Platform.

The next step was to build a 5v and 3.3v power “outlet” – sort of an onboard “extension chord”. What I did was took a standard RadioShack 1.5″x1.5″ general purpose PCBs and laid out the connectors. One Half of the board supplies 5v and the other half supports 3.3V (Half = the black line marker).

I then basically connected the power supply from the “Brain Module” to the “Extension chord”. Made sure I measure the Voltage. I then took the Parallax LCD 2 line display and hooked it up as in this picture. The power is drawn from the “Extension chord”‘s 5v half and the signal line is hooked up to the “Brain Module”. It is important to note that since this is a 5v device, the signal is treated with a 220R Resistor. Shown in this picture with a heatshrink.

Next in line is hooking up my custom made “Communcation Module” (based on AeroComm AC4790). Here’s the picture. Note that the CB is 3.3V device and connects to the 3.3V half of the “Extension Chord”. ALIBE also needs 3 signal wires from CB to the “Brain Module”. Here’s a picture.

I am planning on getting the other devices done by end of this weekend – I’ll blog more on this soon

ciao

Nagi

Testing the AC4790 and Propeller Interface w/ ALIBE Homebase Command Center

In this post, I wanted to detail how I tested the interface I developed earlier on (described here). The objective is to write the needed code for the Propeller chip (in SPIN language) and make it send and receive data to and from the AC4790 CB. And also, write the startings of the Command Center application in VB.Net that should evolve into a fully functional Command Center that ALIBE will communicate and exchange data with.

The Setup:

1. The homebase command center is made up of one of the AC4790 Dev Boards hooked up to my laptop.
2. The laptop runs the Homebase Command Center (CC) VB.Net app that keeps communication channel w/ ALIBE and exchanges data to/from
3. The ALIBE has my AC4790 on my Carrier Board (CB) that is controlled by the Propeller chip.
   1. ALIBE’s AC4790 is “reactive” – meaning it waits to see data from command center and then responds to it
   2. It does not send any data proactively
4. The Propeller runs the required SPIN code to control the AC4790 – meaning processes incoming data FROM AC4790 and sends data TO AC4790

The Code: 

    NOTE: All links below are intentionally named as “.doc” extensions. Right click on the links and select “Save As…” and save it as “.ZIP” file, and Extract before using

Please note that no commenting yet on my code. But will have something soon

• This SPIN code is fairly standalone and does nothing but the 3 and 4 above.
• This VB.Net Project is the initial makings of the Command Center (CC) that does 2 above.
• This Movie file showcases the above working. Essentially, the follows:
  • CC sends command data as TEXT (for now) over the air TO the CB onboard ALIBE
  • CB onboard ALIBE receives this data
  • Propeller onboard ALIBE receives this data via SerialIn, Simply adds “+” to the end of the text (Process) and sends the data back Over the air to CC.

 Still more work left, this is just one small step ahead in hopefully in the right direction

ciao

Nagi 

Interfacing Aerocomm AC4790 with Propeller Chip – Hardware Perspective

In this post I will attempt to describe how I built a simple carrier board for AC4790 and then interfaced that with my Propeller chip (that is mounted on a Propstick). To get an introduction to what and why of AC4790, please see my earlier post here.

So, as stated in my last posting, AC4790 has 20 pins. Of course, for my application in ALIBE, I will only need for the communication module to be “reactive” vs “proactive” – meaning, the Command Center in homebase will issue a command to ALIBE’s communication module (AC4790) and then will expect ALIBE to either return data back to it or take an action onboard ALIBE. This is what I define as “reactive”. Proactive would be when the communication module would proactively send data to the homebase – ie., without being “asked” for.

In this scenario, I only need to tap into a few pins off the 20 pin lot. Here’s the description of these pins (as I said in my earlier posting).

1 (Session Indicator),
2 (Tx – from Propeller to AC4790 device),
3 (Rx – from AC4790 device to Propeller),
5 (GND),
9 (Rx Indicator),
10 and 11 (both need to be 3.3v VDD). and that’s it. 

I needed pins 1 and 9 for my LEDs (pic below).
My carrier board (very simple one BTW), has soldered LEDs and also exposes the pin 1 and 9 (as pin 1 and 4 carrier board) – if in case I need to further use those pins for future work. I am happy w/ the way it turned out.

Read thru the AC4790 manual especially the Pin characteristics and their meanings. Understanding this will be very helpful – it is only 2 pages long.

I used one of those PCB’s from radioshack and soldered in 7 pin SIP into the board as seen here underside of the PCB: There’s some additional soldering outside of just the 7 SIP pin. We’ll get to that soon.

I found some old connectors from my parts treasure chest and repurposed them to connect the AC4790 with the PCB. The wires are soldered on the underside (above picture) . You can see that here. Take a note of the pin numbers and ensure you are using the right pins and connecting the right pins to the SIP pins. Incorrectly hooking them up WILL for sure fry your AC4790. And, you don’t want that!

I have highlighted the pin layout on AC4790. Pay close attention to the numbering.

This is probably a good time to look at this wiring diagram – it will give you an idea of how simple this is. Also, note that I hooked up my 2 LEDs to the pins 3 and 9 for the Session and Rx indication. They can be very useful to visually see what’s going on onboard ALIBE during communication. Note how pin 10 and 11 are together hooked up to 3.3v Vdd. This is important to know that AC4790 is a 3.3v device and NOT a 5v device.

The completed PCB looks as here. I also added a small piece of foam btwn the AC4790 and the PCB.

I then took my “finished” product to my breadboard and hooked up the AC4790 Carrier Board (CB) to my Propeller pins. As you can tell from this picture, I only need 3 pins on Propeller to make my communication module working. Pretty cool ah!

The best part about this CB design is that I can always unplug the connectors to the AC4790, unscrew the standoffs, and take the AC4790 to my devboard if in case I need to edit its EEPROM settings or do a “dev board to dev board” testing. Very flexible – works well for my project.

Look for the following posting on how I tested this setup.

ciao
Nagi

Aerocomm AC4790 – A short introduction

ALIBE uses AC4790 as its onboard communication module. AC4790 is a Transceiver able to communicate with another AC4790 at varied Baudrates and with a clear line-of-sight, is able to get a range of 4 miles. This clearly was one of the factors that helped me decide to go with it as opposed to other products in the market. There are other benefits of using AC4790 from future scalability standpoint. 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.

So, how did I get started with AC4790?

Well, like many out there, I started asking people and searching web sites for recommendations. I was given a pointer to Aerocomm by a couple of folks in the Parallax forum. I called Aerocomm technical support – BTW, very helpful folks over there. I laid out what I was looking for in my project 1) Range 2) simplicity in interfacing 3) scalability from peer-to-homebase and peer-to-peer and of course 4) cost. Aerocomm has many products under the Transceivers umbrella, however, from the discussions with the Tech support, I determined that AC4790 meets most of my requirements if not all. Cost being one of them that was not that great. But, overall, I felt AC4790 is a good match for what I’m looking to get and do.

I was very new to this long range radio communication field and definitely my handicap was also that I’m not that strong in electronics (always learnign new stuff). So, in order to speed up my learning curve, I decided to buy Aerocomm’s System Development Kit for AC4790. The kit comes with everything you need to get a good handle on things. It comes with two dev boards fully loaded, including AC4790 mounted on each, power adapters, USB cables, Serial cables, manuals, software and even a great carry case.  I thought this was a great deal. I paid, $199 USD to get this kit. Which did not seem too bad at all. BTW, I don’t own any stocks of Aerocomm or any special interest. Just a kicked up hobbyist.

The dev boards can be powered using USB alone – which is what I do everytime I test my stuff up.

To start things out, I hooked up the dev boards via USB to my laptop 2 separate USB ports. Kicked off the app that came with it and voila, I was able to send and receive data back and forth from the two dev boards. The software also allows you to view/edit the EEPROM settings (these settings define the core behavior of the AC4790 chip) very easily. It also shows the address of which setting you’re modifying and the definition of the settings (that is what is does and how it impacts the behavior of the chip). You can also get this information in the manuals.

It is worth noting that the dev boards and the AC4790 can operate at various choices of Baudrates. Keep in mind that I had to bring down the baudrate a few notches (4800) when I started interfacing AC4790 with my Propeller chip.

Once I got a good feel for the chip and how they work, I took out one of the AC4790’s from one of the dev boards and started to think about building a carrier board for my Propeller interface. Which is another posting in this blog.

If you’re looking to using AC4790 in your own projects, you want to keep a few things in your mind

• Read their manuals – found in their site above. There’s the Kit Manual (that explains the dev board and the Software) and then there’s the AC4790 User Manual and DataSheet. Pay extra attention to the data sheet of 4790. Both are very well written.
• In the AC4790 manual (you can get one from this blog), pay special attention to the Pin Configuration. For a simple Tx behavior, you only will only need to tap into a few pins out of the 20 pin lot.
  • 1 (Session Indicator),
  • 2 (Tx – from Propeller to AC4790 device),
  • 3 (Rx – from AC4790 device to Propeller),
  • 5 (GND),
  • 9 (Rx Indicator),
  • 10 and 11 (both need to be 3.3v VDD). and that’s it.
    • I needed pins 1 and 9 for my LEDs (pic below).
    • My carrier board (very simple one BTW), has soldered LEDs and also exposes the pin 1 and 9 (as pin 1 and 4 carrier board) – if in case I need to further use those pins for future work. I am happy w/ the way it turned out.

 You should be able to find more posts on my blog that talk to, “How to interface AC4790 with Propeller” if you are looking to find out how I did it in ALIBE.

ciao

Nagi

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

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