Download Step 1Building the circuit

Step 1Building the circuit
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This is the circuit I used in my project. A simple one which costs me about 35 Egyptian Pounds for
components (<6 US Dollars)
:::::::::::::::::::: List of components: ::::::::::::::::::::::::
Integrated Circuits:
1 x LM2917 This is the frequency to voltage converter you need to convert the signal from the car's
ignition coil into voltage
2 x LM3914 This is LED display driver. Each one can drive 10LEDs in either bar mode like this
project or dot mode. Switching between both modes can be done, more instructions in datasheet.
1 x 7809 Volt regulator (outputs +9 Volts)
LEDs:
21 LEDs of any color you want. I used bright white ones. You can use some green, some yellow &
some red for the red zone. You MUST use bright ones if you are planning to put paper covers over
the LEDs or they are going to be simply invisible
The first LED is continously lit as long as the +12V source is connected. The remaining 20 will be lit
one by one as you increase the engine speed
Diodes:
1 x 1N4007
1 x 1N4148
1 x Zener diode 12 Volts
Resistors:
1 x 220 Kohm Trimpot variable resistor (for calibration)
2 x 1 Kohm
3 x 10 Kohm
1 x 22 Kohm
1 x 2.2 Kohm
1 x 470 ohm (I forgot I have one :) So, I connected two 1Kohm in parallel, see photos)
Electrolytic Capacitors:
1 x 470 µFarad 25 Volts (µ = micro)
1 x 2.2 µF
16 Volts
Polypropylene Capacitors:
3 x 100 nF (nano)
1 x 47 nF
1 x 1 µF (Instead,I used 8 x 100nF in parallel = 0.8 µF :$ & it works)