Car Tester Circuit | Electronic Project Circuits

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Car Exhaust Meter

Bridge circuit contains two resistors lOO-ohm (R3 and R4), and two thermistors (Tl and T2). At room temperature, the resistance of T1 and 1’2 is about 2000 ohms. When they are each heated to 150 °C by an RNA 10 current, the resistance value decreases to 100 ohms. So. the four elements include a bridge circuit. CO is a characteristic that conducts heat from a thermistor at a rate different from that of air. A thermistor, TI, is exposed to automobile exhaust, while the other, 1’2, is isolated in an environment of clean air. Unlike thermal conduction bridge imbalance. A voltage difference is caused between points A and C. A differential amplifier. VI, amplifies this difference and leads to the counter with a current sufficient to read the percentage of CO and air-fuel ratio. A control panel before the balance, R5, balances the bridge and calibrates the instrument. The calibration is performed when both thermistors are exposed to outside air.
Cl O-1 uF. Electrolytic capacitor 25 vall diode Dl-silicon, general purpose, or equivalent IN2069 Ml-0.1 RNA ammeter Rl. R3, R4, IS-ohm Lao Si 10%. watt resistor Tor! All resistors are 10%, though. SO0 watll H2-ohm potentiometer, PC mounting potentiometer R5-la-ohm, mounting panel Tront H7, R8-22, OOO ohms resistance R9-570, OOO-resistance Ohrn TAB BOOKS, INC. Fig. 7-3 RL0 S-0.900-ohm resistance thermistor sensor-SR1, num Â¬ ber 100 â€¢ Part 1648 of the heat mode hKit HERE) 080. Heath Company Benton Harbor, MI, 49022 lM309H Ul-S-volt regulator integrated cir- cooked U2-lM741TC op amp circuit intergraled Misc.-PC board, screws, cabinet, welding, hard sections, plastic tubing 10 feet, etc.

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Be the first to comment - What do you think? Posted by admin - August 8, 2011 at 1:27 am

Categories: Automotive, Meter Tags: Airflow sensitive, car tester circuit, exhaust flow meter

Lambda Probe Readout For Carburettor Tuning

A lambda probe (or oxygen sensor) can be found on the exhaust system of most cars running on unleaded fuel. Having reached its normal operating temperature (of about 600 degrees Celsius!) the lambda probe supplies an output voltage proportional to the amount of residual oxygen measured in the exhaust gas. This information is indicative of, among others, the air/fuel ratio supplied by the carburetor(s) and hence the combustion efficiency. In modern car (and motorcycle) engines, this information is used to (electronically) adjust engine parameters like ignition timing and fuel injection. The indicator described here is intended for permanent installation on a motorcycle of which the air/fuel ratio needed to be watched, with the obvious aim engine power tuning after ?tting a different set of carburetors.
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Be the first to comment - What do you think? Posted by admin - October 18, 2010 at 11:34 pm

Categories: Automotive, LED Flasher, Meter Tags: automotive oxygen sensor, car probe circuit, car tester circuit

Simple but reliable car battery tester

author: Jonathan Filippi

This circuit uses the popular and easy to find LM3914 IC. This IC is very simple to drive, needs no voltage regulators (it has a built in voltage regulator) and can be powered from almost every source.

This circuit is very easy to explain:

When the test button is pressed, the Car battery voltage is feed into a high impedance voltage divider. His purpose is to divide 12V to 1,25V (or lower values to lower values). This solution is better than letting the internal voltage regulator set the 12V sample voltage to be feed into the internal voltage divider simply because it cannot regulate 12V when the voltage drops lower (linear regulators only step down). Simply wiring with no adjust, the regulator provides stable 1,25V which is fed into the precision internal resistor cascade to generate sample voltages for the internal comparators. Anyway the default setting let you to measure voltages between 8 and 12V but you can measure even from 0V to 12V setting the offset trimmer to 0 (but i think that under 9 volt your car would not start). There is a smoothing capacitor (4700uF 16V) it is used to adsorb EMF noise produced from the ignition coil if you are measuring the battery during the engine working. Diesel engines would not need it, but i’m not sure. If you like more a point graph rather than a bar graph simply disconnect pin 9 on the IC (MODE) from power. The calculations are simple (default)

For the first comparator the voltage is : 0,833 V corresponding to 8 V
* * * * * voltage is : 0,875 V corresponding to 8,4 V
…
..
for the last comparator the voltage is : 1,25 V corresponding to 12 V

Have fun, learn and don’t let you car battery discharge…
From: http://www.electronics-lab.com/