Hi, For an electronics project, my friend and I created this circuit that we found online: http://www.redcircuits.com/Page72.htm We had no problem putting it together, but we’re not really sure how it works. Our professor wants us to have at least a basic understanding when we present it to him. The diagram is attached and here is the accompanying description: R1______________1K5 1/4W Resistor R2____________680R 1/4W Resistor (Optional, see text) C1_____________47µF 25V Electrolytic Capacitor D1_____________LED any type Q1___________BC337 45V 800mA NPN Transistor P1_____________SPST Pushbutton LP1____________Filament Lamp 12 or 24V (See text) The purpose of this circuit was to create a ring in which LEDs or Lamps illuminate sequentially. Its main feature is a high versatility: you can build a loop containing any number of LEDs or Lamps, as each illuminating device has its own small circuit. The diagrams show three-stage circuits for simplicity: you can add an unlimited number of stages (shown in dashed boxes), provided the last stage output was returned to the first stage input, as shown. P1 pushbutton purpose is to allow a sure start of the sequence at power-on but, when a high number of stages is used, it also allows illumination of more than one LED or Lamp at a time, e.g. one device illuminated and three out and so on. After power-on, P1 should be held closed until only the LED or Lamp related to the module to which the pushbutton is connected remains steady illuminated. When P1 is released the sequencer starts: if P1 is pushed briefly after the sequence is started, several types of sequence can be obtained, depending from the total number of stages. Could someone explain the roles of the components for the basic stage (in the dashed boxes)? The LEDs light gradually, so we think the pattern must be caused by the charge and discharge of the capacitor. But how does the charge flow through the circuit? And in particular, what does the transistor do? Thanks, dusty…….