Quantum die

The circuit shown here demonstrates that true randomness can be derived from a small quantity of radioactive material, for example in the form of a sample of pitchblende, an ore of uranium, in combination with some electronics.

One the many consequences of stress is an increase in the heart rate. The resulting variation in blood flow can easily be sensed using light transmission, since the absorption of the transmitted light depends on the blood flow. Here an ordinary plastic clothespin is converted into a suiatble sensor.

Inspired by a binary clock he saw at a mathematics museum the author of this design went one step further and came up with a more mathematically challenging timepiece...This unusual large format digital clock in the photo shows the time in binary and is exhibited at the German Museum of Mathematics ‘Mathematikum’ in the town of Giessen, Germany. The museum is the brainchild of Prof. Beutelsbacher and has been described as the fi rst ‘hands-on’ mathematical museum in the world.

This pulse sensor is designed to be used for communication between man and machine, giving a robot the ability to react to the pulse rate of its human mentor. The digital output of the circuit makes it useful in other applications as well.The sensor itself consists of an ordinary LDR (with a resistance when illuminated of 300 Ω and a dark resistance of around 10 MΩ) and a bright LED (D1). The LED must have an output of at least 1000 mcd as light from it must pass through the finger and illuminate the LDR.

MOPS is a small robot which generally bumbles around the floor and performs avoidance manoeuvres whenever it detects an obstacle in its path. MOPS uses a forward facing LED to illuminate its path and a phototransistor to detect light reflected from obstacles, as soon as an obstacle is detected MOPS goes into reverse and turns for a few seconds on its two wheels before setting off again in another direction.

You don’t have to reinvent the wheel for your robot, but you may have to make your own somehow if you can’t or don’t want to buy them ready made. The handicrafts aspect of making your own wheels is relatively undemanding, and one hand (but not a left hand…) is enough.

Most cheap emergency flashing lights at fixed locations employ glass-based bulbs to generate light. The typical filament bulb is fragile, has a short lifetime and requires a (relatively) high voltage. To overcome these disadvantages, the author designed the above circuit, using a solid-state light source, a dimmer function and readily available ICs, all aiming at maximum compactness.