Parabolic Reflector for USB 3G/EDGE/Wifi

I recently started using wireless broadband for my mobile internet access. While I was able to get around 1mbps at my office location, the coverage doesn't extend well to my housing area. I have to be contented with EDGE. EDGE would still be okay for my occasional internet need at home but the signal strength is so bad that I could barely make any connection.

So, again, I'm off to the internet for a solution. A full parabolic dish would probably be an overkill for my need so I settled with parabolic reflector instead. After about 20 minutes on the PC for the parabolic design and g-code generation; and another 20 minutes on the Sherline CNC, my simple parabolic reflector was born. Made from acrylic (left over from other projects, thus the multiple colors), the reflective portion is covered with the kitchen grade aluminum foil.

As shown above, the reflector can be set vertically on the table or attached to a normal handphone holder bracket for more articulated positioning (below).


How did it perform?
I have no way of measuring true dB improvement but the signal meter on the software provided went up by 2-3 bars when the reflector is used. For now, I could utilise EDGE almost full speed (around 200kbps) without fail. Happy at last... :-)

Duit Raya... from Google AdSense

As always, me as skeptical as ever... wondering whether Google will actually make the payment since I've heard various horror stories regarding the AdSense payment. Well, my balance finally hit the magic USD100.00 minimum required for payment and I anxiously waited for the moment.

After typical processing time line, I check my account at AdSense again and it was stated that payment has been issued (without any email advising me on the matter). To avoid possible embarrassment at the bank, I called up Western Union customer care to check if the payment is valid and genuine. The Philippine lady who answered my call confirms it.

So, today I went to the bank. The first time I ever receive any money via Western Union. Rushed to the nearest CIMB Bank, fill up a form, waited for the counter to call my number and voila... the proof in sight...

Cheap interactive screen with WII Remote

Found this video on the net... Did some surfing on the subject... maybe my next project... hmmm.... Link is here

My HariRaya Gift Arrived... ER16 Chuck for my Sherline

Most people get Hariraya greeting cards around this time but not me... :-)

Just took delivery of my new ER16 MT1 chuck and collets yesterday from CTC Tools (eBay Seller). Fixed it to my Sherline and seems to be okay. Just needed to get an M6 x 100 screw to anchor the chuck to the Sherline spindle then I'll be set... No more hammering to get the chuck out... Just twist the collect holder and my bits are free... After fixing the ER16 chuck, I'll loose around 1.5" of vertical travel but that's not much of a concern for me... Photos show the new ER16 chuck next to the various earlier (Sherline) milling collets, drilling chuck and endmill holders.


To all the muslims of the world, Eid Mubarak. May Allah bless us and the whole world. Let us live in peace and harmony...

To my friends, my sincere apologies for any wrongdoings in the past, present and future. Have a safe and wonderful Hariraya.

Naza Sorento 2.5l CRDi Fuel Consumption Chart

Posted here for reference my the Sorento buddies... Click chart for detailed view...

Bye Bye Ferric Chloride...

IMPORTANT UPDATE: 28th August 2009
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Upon further reading, I learn that the HCl + H₂O₂ solution have short shelf life. So I decided to test my solution. True enough, it wasn't able to etch any PCB. I'm not sure what's the cause yet but my guess is that I need to add the 'starter' copper immediately after mixing the HCl + H₂O₂ to stabilise the solution so that the solution is CuCl₂+ H₂O instead of HCl + H₂O₂.
Will update the result after the experimentation... :-)
This site has very complete and full of technical information on the subject.
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After more than 20 years relying on Ferric Chloride as my etchant for PCB, I decided to switch to a new solution for PCB etching that promises faster etching, cleaner solution and recycle-able chemicals. After review of several sites on the internet, I decided to go with the Hydrogen Peroxide/Hydrochloric Acid solution.

Photo below shows the starting chemicals, i.e., muratic acid (31.45% HCl v/v) and Hydrogen Peroxide (6% H2O2 v/v). The muratic acid (1 quart, ~950ml) was obtained from Ace Hardware, normally used as cleaning agent. The hydrogen peroxide (450ml) was obtained from a pharmacy.


For the volume of solution that I required and based on the concentration of chemical available, my etchant is made by adding 600ml of the muratic acid to 900ml of hydrogen peroxide yielding 1.5 liters of etchant.


As usual, I added the bubble ring for solution agitation during etching. However, with the new solution, the air bubble also serves as oxidizer, regenerating the solution. Theoretically, I should not need to throw away the solution for eternity. If the air bubbling isn't enough to regenerate the solution, addition of small amount of new muratic acid should be able to replenish the consumed ions...

Better explanation of the chemistry involved at this site. Excerpts below:

Here's what's going on chemically:

Before there's much copper dissolved in the solution, Cu + 2 HCl + H₂O₂ -> CuCl₂+ 2H₂O is the dominant net reaction. That is, the extra oxygen in solution from the peroxide is oxidizing the copper metal, in presence of the acid, to make copper (II) chloride. That's our starter etchant. The resulting CuCl₂ shoud be a nice emerald green color.

After you've dissolved a lot of copper into the solution, and used up all the peroxide, the copper chloride does most of the etching for you: CuCl₂ + Cu -> 2 CuCl. That's the end etchant.

Eventually you etch so much that you convert all the CuCl2 into CuCl, which doesn't dissolve copper (and is a yucky brown color). As long as you've got enough acid in the solution, you can simply add more oxygen to re-oxidize the copper(I), making more copper(II) chloride and water: 2 CuCl + 2 HCl + O -> 2 CuCl₂ + H₂O. And then you can etch again.

Bottom Line:

Two things to maintain: CuCl₂ levels and acid levels.

CuCl₂: After all the peroxide is used up, and the solution starts turning brownish, you'll have to add oxygen to regenerate the solution again: toss in a few more capfuls of peroxide or bubble air through the solution or swirl it around vigorously, or just pour it into an open container and wait. It's easy to tell when you're ready to etch again, because the solution turns green.

It's also impossible to add too much oxygen by adding air, so bubble/swirl to your heart's content. If you're using peroxide to add oxygen, be sparing -- a little goes a long way, and it's mostly water so you're diluting your etchant by adding it.

Acid: Note that HCl is being consumed in the starter etchant and the regeneration reactions. So we're going to have to add a bit more acid as time goes by. If you notice that it's harder to re-green your brown etchant, it's probably time to start thinking acid.

RFM-USB Interface

The photo shows the RFM-USB interface made using double-sided, non-PTH PCB. As can been seen, the top layer components pads are not soldered. This approach result in higher number of vias but simplify soldering of the double-sided board. 100% homebrewable...

During testing, another problem was identified. The RFM12B has a max VCC of 3.8V so I used a 3.3V regulator for it and simple voltage divider on the signals from PIC to the RFM. Then, the output from RFM12B are wired directly to the PIC. Upon measurement, the voltage of the RFM12B output max to about 3.7V. Unfortunately, the PIC input (SDI) has a schmidt trigger thus requires minimum iput of 0.8xVCC. At 5V, that translated to 4V... thus higher than what the RFM12B can deliver. Hmmm... more thinking/decision required:

1. Run the RFM12B at USB voltage (normally below 5V) which is over the design max but below the absolute max (of 6V).
2. Replace the RFM12B with RFM12 (meant for 5V) and run the interface at USB voltage.
3. Run the PIC at 4.2V (minimum for PIC18F2550) via voltage regulator or simple diode voltage drop.
4. Add level translator on the RFM12B output to bring the output to VCC.

I'm using option 1 for now (using my previous board). The above new board still works since the VCC from USB on my PC is around 4.6V. Thus 0.8x4.6V->3.68V, something the RFM12B still can managed. For actual production, I'll use option 1 and 2, i.e., run everyting at VCC from USB and replaced the RFM12B with RFM12.