A series of digital clocks, all with LED outputs, were created for the Electronics in Schools Strategy (EiSS) and used in several of the courses run on behalf of SETPOINT (now STEMPOINT) Devon & Cornwall for secondary school teachers in the south west. The original clock had two rows of LEDs that are just about visible on the centre of the image (
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left). It used 16F84 PICs and the code for these was written in assembly language, the ICs being programmed with my parallel port programmer which can be seen in the Programmers section. Due to the expense and complexity of producing the acrylic cases for the original clock a more simple design was created based on a circular pcb board. Again the PIC was programmed in assembly as this gave the option of allocating outputs to twelve of the ports and still leaving an input available for setting the time. The case consisted of a section of aluminium tube with an acrylic front and rear face machined to locate securely on the tube. The acrylic faces also had a small plinth which allowed the clock to stand upright on a smooth surface. As schools gradually adopted the Picaxe PIC programming system, the pcb design above was modified to accommodate a Picaxe 18X ic. In order to acquire the twelve outputs that are necessary for a clock face, six outputs from the PIC were multiplexed via two transistors to switch either bank of LEDs on, hence providing twelve outputs. The whole circuit was assembled in an identical case to that shown above. The PIC was programmed externally to the project in one of Revolution Education`s programmers. The two drawings above indicate the location of the components on the pcb. In order for the clock to work correctly an additional resistor has to be added between pins 3 & 5 - (see right image) This is the...
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In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
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