coll circuit

Saturday, March 30, 2013

Make this Simple Tachometer Circuit

A tachometer is a device which is used for measuring vehicle engine RPM. Thus, it is basically used for checking the performance of the engine and helps an auto mechanic to understand the condition of the engine so that it can be corrected or optimized as per the desired specs.

Generally a tachometer may be considered an expensive equipments as these are highly accurate and intended for obtaining correct RPM rates of the concerned engine under test.

The conventional units are therefore very sophisticated and generate highly accurate results while testing.

However it doesnt mean that a simpler version cannot be built at home. With electronics at its best today, making a tachometer circuit at home isnt at all difficult. Whats more the results obtained from such circuits are fairly accurate and provides the required data for assessing the overall working condition of the system.

The circuit diagram shows a simple configuration utilizing the IC 555. The IC is basically configured as a monstable multivibrator.

The pulse is derived from the spark plug and fed to the end of R6.

The transistor responds to the pulses and conduct in accordance with triggers.

The transistor activates the monostable with every rising pulse of the input.

The monostable stays ON for a particular moment each time its triggered and generates an average ON time at the output which is directly proportional to the average trigger rate.

The capacitor and the resistor at the output of the IC integrate the result so that it can be directly read over a 10V FSD voltmeter.

The pot R3 should be adjusted such that the output generates the exact interpretations of the fed RPM rates.

The above setting up must be done with the help of a good conventional tachometer unit,

Parts List

R1 = 4K7

R2 = 47E

R3 = CAN BE VARIABLE 100K POT

R4 = 3K3,

R5 = 10K,

R6 = 1K,

R7 1K,

R8 = 10K,

R9 = 100K,

C1 = 47n,

C2 = 100n,

C3 = 100n,

C4 = 33uF/25V,

T1 = BC547

IC1 = 555,

M1 = 10V FSD meter,

D1,D2 = 1N4148

Thursday, March 28, 2013

Digital Bike Tachometer SP

This digital SP tachometer for bikes uses 2 reed switches to urge the speed data of the bicycle. The reed switches are put in close to the rim of the wheel where permanent magnets pass by. The permanent magnets are connected to the wheelspokes and activate the reed switches everytime they pass by it. The speed is digitally displayed.

The tachometer circuit works in step with this principle; the pulses created by the reed contacts are counted inside an explicit time interval. The ensuing count is then displayed and represents the speed of the bike. 2 4026 ICs are used to count the pulses, decode the counter and management 2 7-segment LED show. RS flip-flops U3 and U4 perform as anti-bounce.

Electronic bicycle SP tachometer circuit diagram

The pulses arrive at the counter’s input through gate U7. The measuring amount is set by monostable multivibrator U5/U6 and might be adjusted through potentiometer P1 so the tacho are often calibrated. The circuit U1/U2 resets the counters.

Since batteries are used to power the circuit, its not sensible to support the continual show of speed data. This circuit isnt continuously active. The circuit is activated solely once a button is pressed. a minimum of 3 permanent magnets should be put in on the wheel. The circuit are often calibrated with the assistance of another pre-calibrated tachometer.