Friday, March 18, 2011

Frequency Counter

I have wanted a frequency counter for awhile now. When I seen this kit from Electronics DIY I couldn't resist. Under 40 dollars and it's good to 60 Mhz.

In all my years as an electronics hobbyist I don't think I have ever built a kit before! I started right out building things from scratch (or scrap). Kits always seemed a bit like cheating. But building a frequency counter with discrete logic chips seemed like a real pain, so I decided to try it.

It was fun! It went smoothly and worked the first time I plugged it in. The sensitivity is not the greatest and it appears to prefer square waves but I can work with this.
As is usually the case the toughest part was the enclosure. Have you ever tried to make a rectangular hole in aluminum?

Monday, February 28, 2011

One Project Leads to Another

I recently found a cool stepper motor controller for sale on ebay called the STEPGENIE. For six dollars (shipped) you get an easy to use controller in a single DIP package. It interfaces nicely with HEXFETs to drive a unipolar motor.

In the past I have always made my own controllers with logic chips, but the STEPGENIE really simplifies things, and puts everything in a nice (small) package. So quicker than you can say BUY IT NOW...........

The IC's arrived (quickly, I might add) and I breadboarded the circuit. I realized I would need a bounce free switch, or a square wave oscillator to drive the chip. These are not particularly hard to make, but it occurred to me I have built this circuit dozens of times.

It's time to build a module to keep on my bench to speed up my breadboarding.

So before I solder up the driver, I will make up a permanent version of the oscillator/bounce free switch circuit ( it's the circuit on the right in the photo)
(By the way, circuit performs flawlessly)

Tuesday, February 15, 2011

Electronic Face(book)

I made this to be my profile photo on Facebook. It took about a half hour. The toughest part was getting the leds to match in brightness. Fun stuff.

Saturday, February 5, 2011

VLF Radio

The lack of summer storms and static crashes makes winter a great time for monitoring the Very Low Frequency band (VLF). These are the radio frequencies below the AM band. Some lower and mid priced shortwave receivers cover this band but the sensitivity is poor and you will hear very little. A few high end receivers cover the band with adequate sensitivity but they are well beyond my price range.

The solution was to build my own VLF receiver. I began with my homebrew 80 meter direct conversion receiver. The salvaged WW2 variable capacitor with built in reduction drive and robust construction made this a great stable base to start with. I next built a VLF converter to bring the signals to the frequency range of the receiver. A low pass filter was added at the input of the converter to reduce unwanted signals.

It works great! On one evening I picked up several low frequency beacons,WWVB out of Colorado , LF AM stations (from Europe?) unidentified burst of sound possibly of a military origin, as they use some of these frequencies. (Low frequencies propagate via ground wave and are largely immune to the problems that would be caused my a nuclear strike. Also VLF waves will penetrate beneath the surface of the water and can be used to talk to submarines).