Electronics Carbon Gauge
Here is a simple circuit which will help driver, engine mechanics or pollution control officials to determine the amount of carbon (partially oxide fuel) emitting from engine. The basic circuit is so popular that it needs no explanation. The trigger pin 2 of IC1 is connected to negative through 1 M-ohm lin. Pot.
The peripheral device of this circuit is a screen with four aluminum or copper foil pieces connected in two sets A and B. These pieces are fixed on a plastics or laminate sheet in dimensions shown in figure. Otherwise it can be made as a PCB by etching. The two set A and B are connected to X and Y terminals of the main circuit.
To measure the amount of carbon, place the metal foil side of the screen in front of the silencer outlet of the working engine, keeping a fixed distance between them. After a preset period (about 3 minutes) remove the device. Turn VR1 to maximum resistance position (B) and switch on the circuit.
The carbon particles sprayed on the metal foil pieces act as resistor between points X and Y. Now rotate VR1 slowly towards minimum resistance position (A). At a critical point, the output of the IC goes high and the LED light up the LED1.
R1 = 47 Ω
R2 = 470 Ω
VR1 = 1 MΩ
IC1 = NC555