Thursday, April 26, 2012

Something old, something new.

Something old ...

As a young boy in Australia my two favorite hangouts were my grandfather's shed or practically anywhere that electronics were sold. The two largest electronic component retailers in my home town were Tandy (Radio Shack) and Dick Smith Electronics. They both sold kits, tools, '100 in 1 Labs' and other assorted gear but Dick Smith eventually became known as the experimenters store due to their greater range.

Original Radio Shack calculator
Tandy is now almost vanished after their aquisition by Woolworths (Despite also owning its competitor Dick Smith) and has converted or closed most of the locations. 

One of the things I have to remember Tandy by is a handy resistor color code calculator. It saw a lot of use in past years while I built kits and experimented but not so much nowdays.

This device also calculated inductor values when flipped over which was handy for some of the older equipment I came across.

If you would like to make one of these yourself then Adafruit Industries has created a PDF document you can print and cut out for create your own resistor value calculator.

The PDF file is available from Adafruit Industries or a copy is also here. Once you print it out, a little cutting and folding should produce something like the example of the right. The Adafruit design uses brass paper fasteners (remember those?) but any fastener could be used that would allow the wheel inside to rotate freely. It would be best to print on heavy card stock if you have the ability as it will give the calculator some strength.

Something new ... 

If you happen to have one of those new fangled iDevices you can download Circuit Playground. It has a few more features than the old Radio Shack calculator and looks great on the iPad.

More features are being added but the list at the moment includes:
  • Decipher resistor & capacitor codes with ease
  • Calculate power, resistance, current, and voltage with the Ohm's Law & Power Calc modules
  • Quickly convert between decimal, hexadecimal, binary or even ASCII characters
  • Calculate values for multiple resistors or capacitors in series & parallel configurations
  • Store, search, and view PDF datasheets
  • Access exclusive sneak peaks, deals & discounts at Adafruit Industries
You can download it from the iTunes Store or, if you have an Android, you can check out ElectroDroid for similar functionality.

As time goes on there are more and more useful utilities available for electronic experimenters on iOS and Android devices. Since more and more equipment today is becoming computerized do iOS and Android devices  represent the future of test equipment?

iMSO-104 iPad Oscilloscope

Tuesday, April 10, 2012

The further adventures of the Heathkit AT-1

Work has been conspiring to eliminate my spare time but I was able to spend a few hours over the Easter holiday to clean up the shack and make space to put the Heathkit AT-1 on the desk again. I have been able to spend a little time going over parts that need to be replaced and making a list.

The Heathkit AT-1 chassis with case and VFO-1 behind.
There doesn't seem to be any show stoppers although the wafer of the meter switch has broken in two and will need to be repaired. If I'm not able to repair it then thankfully it is fairly simple and replacement rotary switch can be substituted.

This isn't going to be a museum quality restoration but the changes that were made to this transmitter in the past were sensible and if left in place are representative of period modifications. The original meter for example was not the highest quality and a Western or Simpson replacement would be an improvement. The original slide switches have been replaced with period snap-toggle switches which are also an improvement over the original.

The Heathkit VFO-1 however has been modified for grid-block keying which is a significant departure from the original and I plan to revert it back to cathode keying. Although a technical improvement it is not in keeping with the original design and needs to be undone. Everyone will have their own opinion but I think if I wanted modern circuits I'd get a more modern rig, so the VFO-1 will be returned to stock.

Hopefully I can carve out a bit of time here and there to work on this and slowly return it to working condition.

Monday, April 2, 2012

It's the future, where is my flying car?

It is the future and here is your flying car.

Although not quite the hover-car of science fiction and movies, it does fly like an light plane and drive like a car.  This will probably be the flavor of the future until we see the development and refinement of different propulsion technology.

The production prototype of the Transition® Street-Legal Airplane completed its successful first flight at Plattsburgh International Airport in Plattsburgh, NY on March 23, 2012.

Go to for more information.