Circuit Design

Mr BILLINGTON

555 Astable and Seven Segment - This circuit uses the 555 timer to produce the continuous digital pulse which is sent to the 'clock' input of the 4026 seven segment driver. As each full pulse if received (0,1) a binary number is sent to the display to control each LED segment. The numbers are only displayed ascending 0 - 9 and back again

555 Astable - When wired in the astable configuration the 555 timer produces a continuous timed digital pulse. This is controlled by the timing divide (resistor and capacitors) on pins 2, 6, 7

Bargraph Display Sensor Circuit - This circuit uses a bargraph LED display to show the value of the analogue input (LDR) connected. The value can be represented as individual bars from low to high or accumulative from the bottom to top of the display. The SPDT switch allows for this 'mode' change

Op-Amp Compareter - This circuit uses a 741 Op-Amp IC that has two voltage inputs (+,-). It is configured as a 'comparator' which rapidly compares the voltage level at its inputs for any deviation. If the voltage at the non-Inverting input (+) is higher than the Inverting (-) input the output is HIGH (1). As a temperature sensor shown, the required Thermistor temp can be set using the potentiometer on the non-Inverting input to adjust the switching voltage

Up/Down Seven Segment - Using a standard 4017b Logic IC the seven segment will only count up from 0-9. The use of a 4029b & 4511b IC allows you to display the numbers in reverse order from 9-0. This can be alternated between up and down by holding the U/D pin high or low

Circuit Design - Example Circuits

Transistor Sensing Circuit - The transistor acts as an electronic switch, when 0.4V or more is at the base leg the LED turns on, the LDR adjusts its reistance depending on light

555 Monostable - When wired in a monostable configuration the 555 produces a single timed digital pulse when trigger at pin 2. Pin 6 and 7 control the length of pulse.

555 Astable and Decade Counter - This circuit uses the 555 timer to send a continuous digital pulse to trigger the 'clock' input of the 4017. As a complete pulse is received (0,1) the 10 outputs are triggered in order 0 - 9. As with the 4026, there is a 'divide by 10' output which will trigger every complete cycle of the outputs. This can be daisy chained to another 4017.