Lightning Sentinel

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Each year, more people are killed by lighting than by most other natural hazards, including hurricanes and tornadoes. No wonder, then, that lightning protection agencies have described the danger of lightning as "underrated". This Lightning Sentinel (my own design -- click on it to enlarge) was tested over a period of a year and a half. In most cases, it picked up the possibility of a thunderstorm well in advance of any thunder or lightning on the horizon. In its simplest form (see Figure 1) the Lightning Sentinel illuminates a green LED when atmospheric charge lies within normal limits, and a red LED when this rises to a risk level. Figure 2 shows how a 5V relay may be added, so that the circuit may be put to more serious use, e.g. triggering a siren. The Lightning Sentinel may also be used as a monitor of atmospheric charge, and this may yield very interesting results. The charge is presented at point C (Figure 1) as a fluctuating voltage. The "engine room" of the circuit is comparator IC1a, which includes an Antenna and an Earth. Note therefore that the circuit is ground referenced (to Earth), since one is measuring the potential difference between the atmosphere and the earth. IC1a is followed by comparator IC1b, which compares the potential (voltage) at IC1a pin 1 with the fixed potential presented to IC1b pin 6. R2 is initially wired in parallel with R4 to present a lower potential at input pin 6, and is used to calibrate the Lightning Sentinel, through VR1, to the daily minimum charge (which lies between the illumination of the red and green LEDs). This minimum charge is estimated over a week or two. Once calibration is complete, one terminal of R2 is snipped as shown in circuit diagram Fig. 1, and the Lightning Sentinel is ready for long-term service. VR1 is a multi-turn preset. The Lightning Sentinel draws about 10mA current on standby, and is ideally powered by a regulated DC plug-pack power supply between 6V and 35V. See Atmospheric Monitor [2] for the design of the aerial. OBSERVATION: In my view, this is about the most interesting thing one can do with electronics apart from radio and metal detecting. This represents my first (until now) unpublished design in a long time. I know several people who were narrowly missed by lightning, including my late wife Mirjam, who was missed by about four metres / yards.

Solar Spider

I was excited yesterday to discover that, as far as I can see, my 2007 copyrighted concept of an electronic Jumping Spider has gone into production. As simple as it seemed, the prototype took me a year to develop -- the history is told on HubPages. That spider had an external power source -- but I knew that a commercial version would likely need to move most if not all of the power inside the spider. But that was way beyond my engineering skills. It would need to be a very clever engineer who succeeded. Now the Chinese did it, and the end result costs less than R20 / $3 wholesale. It's called the Solar Spider. Although I won't be making any money out of this, and admittedly it's a variation of my design, this could be one of my "big ones" -- and I would think that this is only the first generation -- there'll be better versions to come. OBSERVATION: I also cooked up (unpublished) variations of this theme.

Programmable Robot

One of my claims to fame was a programmable robot I designed (which see), published in Australia in 2004, and in the UK in 2007. It was described like this: "This programmable buggy is fully manoeuvrable and has PWM speed control and H-bridge MOSFET gearmotor drivers. It also sports bump and respond, random motion, programmable sound, light sensing, and EEPROM byte-wise programming." OBSERVATION: I programmed it so that when the Australian publisher unwrapped it and put it on the floor, it wiggled its rear, played a few lines of "Waltzing Matilda", then did a dance. (I have other things to amuse me nowadays).

Flashback 1965

I remember this day. I remember standing there under the tarpaulin. It has to be at the beginning of my parents' missionary term in the Kiribati Republic (then the Gilbert Islands), as I am wearing a vest and socks. Those were cast aside in the years that followed. You may click on the photo to enlarge to 300k. Many photos in the mission -- like this one -- were damaged through heat and humidity.

St. Stephens DRC (3-D)

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It's been a while since I published a photo of a local Church. This is St. Stephens Dutch Reformed Church in central Cape Town (the Christaan Barnard Memorial Hospital in the background on the left). The Church was originally built as a theatre in 1800, and converted to a Church in 1843 -- apparently being named St. Stephens because founder members were pelted with stones (it was established for emancipated slaves). OBSERVATION: This photo is in 3D. Lazily squint your eyes until the images overlap and snap together. You may click on the photo(s) for 450k resolution and enhanced 3D.