Monday, November 26, 2012

PCB Solder Jumpers - Cont'd

For Diptrace my new (proposed) Solder Jumper (see previous post), the buried trace connection point on the pad was created by creating the "shape" with the "initial point" at the desired connection point. The "initial point" is where the construction of the "shape" starts and ends. After construction, the "shape" is converted to a "pad" via a right mouse menu item. Below, for demonstration, the "initial point" was artificially exposed by opening (moving) the adjacent points at the left. The grid is set to 2 mils.

For Demonstration the Trace
Connection Point is Exposed at the Cursor

Normally, the gap would be closed, and the two (moved) points would be located at the same point.

This use of the "initial point" may be documented some place in the Diptrace manuals, but I have not found it.


Saturday, November 24, 2012

PCB Solder Jumpers

I have received some good feedback on Patterns for PCB Solder Jumper (see previous posts).

Experiments with very small 0201 size foot prints were NOT as successful as I would like. The small 0201 pads would not hold enough solder to allow proper bridging of the gap between pads. A usable bridge could only be made with very dry slaggy solder.

I am trying the new Solder Jumper Pattern as I suggest in the previous post. Here are the proposed dimensions, the folded pads should help hold the solder and aid in bridge creation. Or, at least that is the plan.
Overall size is 72 x 32 mils (0703)
Dimension Values Shown are Mils
The trace connection is a point within the thicker section on each end. Finding the method of creating that point was via trial and error. Diptrace uses the first created pattern point as the attachment point, I had to artificially bury the point inside of the pad to make trace connections easy.

The PCB Manufactures that I use, and my own Homebrew PCB processing, should be able to create the pattern without difficulty.

I have recently sent a small board off to Manufacturing with one of these new Solder Jumpers ,  Soon, I will report the results.


Thursday, November 8, 2012

My Preferred Soldering Iron

Several years ago, my very old and faithful Weller finally died, and its replacement, the Wahl - Cordless also died (or was dying). I had always wanted a Hakko 888, so I put one on order along with several tips, of different types and sizes.

But I needed a reliable Soldering Iron for a project that I was working on, and I needed the Soldering Iron NOW! I could not wait for the postal service!

So, I went to Radio Shack or Frys (do not remember which) and found a Hakko 980-V12/P to finish my project. I thought it would be a good (junker) backup iron, as it uses the same tips as the Hakko 888 that I had on order (so I thought, . . . NOT). Well it does not! The tips are different.

Now, after many months of having all three Irons on the bench, I prefer the cheap Hakko 980 (with the standard tip) for most things that I solder, even down to the occasional 0201 resistors. Most of my projects use 0804 or 0603 parts. I use the same old stand that I used with the Weller, along with the wire pad tip cleaner. The new Hakko 888 is very seldom turned on.
Hakko 980 on the far Left
Hakko 888 on the Right

Wahl at the Upper Right
The Hakko 980 has dual heat modes; 20w and 130w. A simple push of a button increases the heat, and only if necessary (very seldom used). A one or two second press of the yellow button on the handle, is generally all that is ever needed.

My dying Wahl is standing in the back (yellow, upper right), it was nice for a while, but its finger switch became too temperamental and needs constant attention, see previous post.

Knowing what I know now, if I were buying a Soldering Iron - I would ONLY buy the Hakko 980-V12/P, which is much cheaper than a Hakko 888, and more reliable than the Wahl.


For reference, I originally provided Amazon links for the Hakko Soldering Irons listed on this post, but now it appears that all of my links are no longer working (what up with that, Amonzon?), so I replaced them with generic Google Links. I hope the Hakko 980 is actually still available?


Monday, November 5, 2012

Bypass Caps

The questions is; where to put Bypass caps in the circuit?

Next to a analog or digital device of course, between the VCC and VSS pins.

But, this is only really easy to do on; push boards, protoboards, deadbug or experimental circuits, just push the caps in, and/or solder as necessary.

But then, if you are actually planning to build a complex PCB's (i.e. more than a few devices), it is a lot of work to make sure the right cap (as per the schematic) is next to its associated device. All of the bypass caps are connected in parallel to the same supply and ground rails (i.e. VCC and VSS), therefore on the initial PCB layout they are connected to the same "rats nest" and not really associated with a particular device. The unscrambling task is even more difficult, because bypass caps are typically all the same value.

Some designers just scatter the bypass caps around the board next to a likely devices. Other (better) designers take the time to place the correct bypass caps near its associated devise, as per the schematic - this can be a lot of work!

But, does it matter? - it is only a reference symbol printed on PCB in silkscreen. To me; "Yes, it does matter". And therefore, I make sure the correct bypass cap is next to its associated device as per the schematic.
Schematic Diagram

I use the following technique to make the PCB layout of bypass caps and associated devices easy. On the schematic, I insert a "Zero Ohm" resistor in the supply line (VCC) that feeds each bypass cap. Now regardless of PCB layout software that is used, the initial "rats nest" will suggest close layout of the correct bypass cap with its associated device. From PCB layout perspective, the Bypass caps are NOT directly attached to the VCC rail, but instead, it is connected to the "Zero Ohm" resistor which is connected to the power VCC rail. The associated "Zero Ohm" series resistor is easily located and placed next to its bypass cap (because it is in series and not parallel on the schematic). Its a simple trick that just makes PCB layout much-much easier!

PCB Layout

Also, for most low current devices where 6 mil traces are typical, I use a 0201 "Zero Ohm" device footprint. Instead of an actual device, a simple solder bridge is all that is needed to make the connection. And, this technique makes troubleshooting a new designs all that much easier. A troubling device can be removed from the circuit with a little solder wick.
As Manufactured

As seen in the schematic diagram, B2 is the symbol that I created for the solder bridge.

This technique; may, or may not, be useful for Production Products, but for the Hobbyist it works great!

BTW, I also put in 0201 "Zero Ohm" in all I2C lines, next to each I2C device, for easy initial testing. A bad I2C device can easily take the entire bus down - which is not fun to troubleshoot.


Note: I am looking for a more appropriate footprint for an easy to use solder jumper.

A "Zero Ohm" resistor can also be used to enforce and make easier a "star grounding" system for a set of parts. Connect the circuits star grounds to one end of the "Zero Ohm" resistor and the real ground to the other. For a PCB layout, a star isolated ground plane can also be attached to the same point (i.e., multiple isolated ground planes can be used on the same board).


I am considering one of the following for future project Solder Jumpers, some additional function and use evaluation is needed.
Proposed Solder Jumpers
  • Jumper SJ2 is about 100 mil diameter with 10 mill isolation.
  • Jumper SJ1 is a 70x40 mil rectangle with 6 mil isolation.

Saturday, November 3, 2012

A Self Photo from Mars - at 41.5M Pixels

OK, this is another Curiosity photo, But,  it is an Absolutely Amazing High Resolution Self Photo taken on Mars.

This photo was stitch together from many smaller photos. The Detail is stunning at 5463 x 7595 pixels that is a 41.5M pixel image !!

Go to the link, it may take a while to download, but zoom in and pan around to see the high resolution details !

For Ham Radio QRP, Hardware, and Robotic Geeks - it does not get better than this !

Thanks JPL and NASA !!

Now we need someone to explain all of the devices on the Rover, like:

  • What is that waveguide driven vertical antenna on the back left-side of the rover (upper right in the photo)?
  • What are thosee funnel shaped cones on the front? Are those small linear actuators used for positioning?
  • What is that Large Grey Cross bar on the Top?

And, maybe someone will make a Trimble (Google) Sketchup of the Rover ?


More Fun with 3D

I recently updated a previous post showing the outside view from my loft. The original photo was taken on Sep 16th, and now the second was taken on Nov 2ed, These photos are arranged for Cross-Eye 3D viewing (CE3D). I took this last photo just because of the very bright fall colors. Not wanting to bore my blog readers with "just another one of my 3D photos", I decided to attach it to a previous blog page (nobody other than myself will really notice).

But, I inadvertently discovered a very interesting artifact of publishing them on the same post page; after clicking on the first image for the expanded browser view, you can quickly flip between the two views with a gentle roll of the middle mouse button. For this scene, only the season's colors change (and maybe a slight unintended zoom scale). The effect can be seen in 2D, but it is not nearly as dramatic as seen in 3D.

Even with only two photos, the time lapse photography is very intriguing in 3D. I now plan to take similar photos at regular intervals to expand the time frame. Maybe a new photo set each week.

I use ImageMagick to combine the Right and Left images into a CE3D view. For example:

convert R.JPG L.JPG -splice 10x0 +append -chop 10x0 -resize 1200  CE3D.JPG

Note: the Right/Left order of the two original images is very important.

Oh, I have been viewing so many Cross-Eye 3D Viewed photos that I now can quickly switch to Cross-Eye 3D mode and without Eye Strain. The images are photos that I have taken, or created from the raw Mars Mission photos, and others found on the web,  I view most online images from about 30 inches (distance to the computer screen).

I like 3D photos, they provide so much more revealing detail, that just can not be perceived in 2D. It is similar to the different listening pleasures of; an AM Mono broadcast, and good a FM Stereo Music Station.

I plan to do a lot more with this interesting viewing mode.

Here is an interesting Cross-Eye 3D Video that may help explain the viewing technique.