Free Electronic Circuit | Oxygen Sensor Simulator

Oxygen Sensor Simulator The oxygen sensor simulator as built on a protoboard. Note the cigarette lighter plug used for power source. The adjustment knob is at the left, and the switch is on the right. The red indicator LED is in the middle. Only use red, because the voltage drop of the LED is part of the circuit! The schematic diagram for the simulator. Closing the switch engages the simulator. Turning the knob clockwise simulates a lean condition, turns the LED off, and the car should start running rich to compensate. The big "V" is a digital voltmeter(not shown in the pictures). Using a smaller value for C1, perhaps 4.7 uF, will make the circuit oscillate faster and might be more like a real oxygen sensor(a new sensor switches more often than an old one). The adapter cable. Note the connector recycled from an old oxygen sensor. Hard to see under the black tape: 100K resistor. The schematic diagram of the adapter cable and oxygen sensor. Note the heater is shown as a resistor, mine measured about 7 ohms. Previous page... Frequently Asked Questions:

Q: Will you build one of these for me, or sell me the one you built? A: No, I won’t do that. If there is a community college or high school near you with an electronics class, you should contact the instructor and ask if there are students looking for a small job. This project is simple enough it should not pose a problem. Q: I built the project but I have to fiddle with the knob all the time. A: The car eventually will get too rich or too lean because it isn’t using the oxygen sensor anymore. This is a diagnostic aid, not a long-term replacement for an oxygen sensor. Q: I do racing on the weekends with my street car. Will this project help me tune the car to different conditions? A: If you do drag racing, yes. The races are short enough you can set a mixture and it will hold long enough. Each time you start the car it will go to the mixture you set. Other forms of racing take too long, and the mixture will creep towards very rich, you’d have to adjust the knob while driving.

Free Electronic Circuit | Infra-red Level Detector

Useful for liquids level detection and proximity devices

Up to 50 cm. range, optional relay operation

Circuit diagram:

Parts:

R1_____________10K   1/4W Resistor R2,R5,R6,R9_____1K   1/4W Resistors R3_____________33R   1/4W Resistor R4,R8___________1M   1/4W Resistors R7_____________10K   Trimmer Cermet R10____________22K   1/4W Resistor   C1,C4___________1µF  63V Electrolytic or Polyester Capacitors C2_____________47pF  63V Ceramic Capacitor C3,C5,C6______100µF  25V Electrolytic Capacitors  D1_____________Infra-red LED D2_____________Infra-red Photo Diode (see Notes) D3,D4________1N4148  75V 150mA Diode D5______________LED  (Any color and size) D6,D7________1N4002  100V 1A Diodes  Q1____________BC327  45V 800mA PNP Transistor  IC1_____________555  Timer IC IC2___________LM358  Low Power Dual Op-amp IC3____________7812  12V 1A Positive voltage regulator IC  RL1____________Relay with SPDT 2A @ 220V switch                Coil Voltage 12V. Coil resistance 200-300 Ohm  J1_____________Two ways output socket 

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Device purpose:

This circuit is useful in liquids level or proximity detection. It operates detecting the distance from the target by reflection of an infra-red beam. It can safely detect the level of a liquid in a tank without any contact with the liquid itself. The device's range can be set from a couple of cm. to about 50 cm. by means of a trimmer.
Range can vary, depending on infra-red transmitting and receiving LEDs used and is mostly affected by the color of the reflecting surface. Black surfaces lower greatly the device's sensitivity.

Circuit operation:

IC1 forms an oscillator driving the infra-red LED by means of 0.8mSec. pulses at 120Hz frequency and about 300mA peak current. D1 & D2 are placed facing the target on the same line, a couple of centimeters apart, on a short breadboard strip. D2 picks-up the infra-red beam generated by D1 and reflected by the surface placed in front of it. The signal is amplified by IC2A and peak detected by D4 & C4. Diode D3, with R5 & R6, compensates for the forward diode drop of D4. A DC voltage proportional to the distance of the reflecting object and D1 & D2 feeds the inverting input of the voltage comparator IC2B. This comparator switches on and off the LED and the optional relay via Q1, comparing its input voltage to the reference voltage at its non-inverting input set by the Trimmer R7.

Notes:

• Power supply must be regulated (hence the use of IC3) for precise reference voltage. The circuit can be fed by a commercial wall plug-in adapter, having a DC output voltage in the range 12-24V.
• Current drawing: LED off 40mA; LED and Relay on 70mA @ 12V DC supply.
• R10, C6, Q1, D6, D7, RL1 and J1 can be omitted if relay operation is not required.
• The infra-red Photo Diode D2, should be of the type incorporating an optical sunlight filter: these components appear in black plastic cases. Some of them resemble TO92 transistors: in this case, please note that the sensitive surface is the curved, not the flat one.
• Avoid sun or artificial light hitting directly D1 & D2.
• Usually D1-D2 optimum distance lies in the range 1.5-3 cm.
• If you are needing a similar circuit driving 3 LEDs in sequence, also suitable as a parking aid