Wireless Auto Tachometer


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Anyone performing their own automobile tune-ups knows how important it is to know your engines speed. With this tachometer, you can measure your engines speed without any connections or annoying timing lights.

Schematic

This is the schematic of the Tach

PC board layout and parts placement

This is the parts placement and printed circuit pattern of the Tach

Parts

Part
Total Qty.
Description
Substitutions
C110.47uF Capacitor
C2147uF Electrolytic Capacitor
D118V 1W Zener Diode
D2, D3, D431N914 Diode
M11200uA Meter
Q1, Q222N3391A Transistor
R1, R2, R931K 1/2 W Resistor
R3147K 1/2 W Resistor
R4110K 1/2 W Resistor
R5, R6225K Trim Pot
R7110K Trim Pot
R81200 Ohm 2 W Resistor
R10115K 1/2 W Resistor
R1112.2K 1/2 W Resistor
S11SPST Togglae Switch
S21Three Position Single Pole Rotary Switch
MISC1Telescoping Radio Antenna, Enclosure, Power Cable and Battery Connector

Notes

  1. Calibrate the unit as folows:
    1. Set up this circuit:

      This is the setup for calibrating the Tach

    2. Turn on the Tach and allow a few minutes for temperature stabilization.
    3. Set S2 to 4 cylinders and adjust R5 for a meter indication of 180 (1800 rpm).
    4. Set S2 to 6 cylinders and adjust R6 for a meter indication of 120 (1200 rpm).
    5. Set S2 to 8 cylinders and adjust R7 for a meter indication of 90 (900 rpm).

  2. To use the Tach, turn it on and let it sit for one minute to allow for temperature stabilization. Extend the antenna, select the right number of cylinders and hold the unit over the engine. If the reading is erratic or the needle jumps around, move the antenna closer to the ignition coil or spark plug wires.
  3. The unit draws power from the car battery. If it is connected backwards, it will not work, but it won't be damaged.

Related Circuits

Automatic Headlight Brightness Switch, Wireless Auto Tachometer, Car Alarm Arming Horn Beep Canceller

Comments

Ben w.
Wireless Auto Tachometer
Monday, April 07, 2008 12:21:51 PM
hello sir i have been looking at your wireless tach and have choose to do it as a project ror my electronics class could you please send me details on this project thank you
anonymous
Wireless Auto Tachometer
Saturday, March 29, 2008 12:40:52 AM
Very nice!!! I was seraching for a signal conditioning circuit, to sense RPM from the engine. I'll use this circuit to feed pulses to a micro-processor and capture RPM digitally (torque curve up to a scale factor)

(Editor's notes: Also look at the schematics of the Megasquirt project.)

puneet
Wireless Auto Tachometer
Tuesday, March 18, 2008 1:44:41 PM
sir i want to know the detailed working and design of this wireless auto tachometer. can you please send me all information related to this. i will be very thankful to you.
Mihai Stanga
Wireless Auto Tachometer
Monday, March 10, 2008 3:43:00 AM
Hello, sir. Given the fact taht my original car tachometer doesn't work for more that 2 days and i'm really sick and tired of fixing it, I want to build your design. The only problem is that I live in Europe and here we have 220-240V @ 50Hz at mains. Can you please tell me how to calibrate it in these conditions ? Thank you.
alireza
Wireless Auto Tachometer
Monday, March 03, 2008 1:52:19 PM
Hi sir, Can you send me the detail information about the working and making of wireless auto tachometer. As soon as possible . please sir i am requisting u to send the more & more detail about the project.very thanks
sivakumaran
Wireless Auto Tachometer
Monday, February 11, 2008 1:57:46 AM
in the Wireless Auto Tachometer circuit diagram, the M1 refers to the micro ammeter or tachometer.
vinod kumar gautam
Wireless Auto Tachometer
Wednesday, February 06, 2008 4:26:46 AM
Hello sir, Can you send me the detail information about the working and making of wireless auto tachometer. As soon as possible . please sir i am requisting u to send the more & more detail about the project. thanks
senin
Wireless Auto Tachometer
Thursday, January 24, 2008 9:22:28 PM
Hello sir, Can you send me the detail information about the working and making of wireless auto tachometer. As soon as possible . please sir i am requisting u to send the more & more detail about the project. thanks
Rasika M
Wireless Auto Tachometer
Monday, January 14, 2008 3:30:56 AM
Dear Sir , can you send me the full detailed information about the project because I have to submit the project report within 2 weeks.So I kindly request you tu send the information as soon as possible
Manideep
Wireless Auto Tachometer
Friday, January 11, 2008 11:51:21 AM
Sir, u have done a gr8 job and u have been a role model 4 a lot of upcoming Engineers and circuit designers. ypur Wireless Auto tachometer has been very interesting and I will be obliged if u please send me a detailed circuit and a brief overview abt that.Your early reply is very much happier 4 me as i have to submit a paper on this as early as possible
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