Magic RPM
A very nice project for everyone who is interested in car Tuning.

It is based in the VCRGB Software shown here.

The circuit measures the engine RPM (or Speed) and changes the color of an Instrument illumination (or whole

Dashboard), dependent of the RPM

The senitivity / RPM Levels can be adjusted

Idle Blau


High RPM :Red

The use of modern ultrabright LED's allowth this circuit to be operaten in many applications.

R1 470 Ohm

R2 22kOhm

R3 10kOhm

C1 22nF

R6 100k

C4 1uF

D1 1N4148

R9 15k

R7 100k

R8 15k

R5 15k

C3 4.7 uF

C5 4.7uF/35V

IC3 LM78L05

C6 100nF Keramik

R10 100k

C7 100nF

R14 4.7k

R11, 12,13 150-270 Ohm, je nach LED's

D2 7.5V Siehe Text

The Operating Voltage is connected to Pad1/2 and powers a LM2907/2917 Frequency/Voltage-Converter.

The RPM Signal (connected to Breaker or Tacho Signal Generator) is connected to PAD3.

The LM2907 converts the Frequency (proportional to engine RPM) to a corresponding Voltage, which is used by the Atmel Tiny15 to control the LED's.

With R6 you can adjust Sensitivity, with R7 you can adjust for idle RPM.

The Microcontroller has a 5V Regulator for proper operation.

The LM2917 has a builtin Z-Diode. When using a LM2907, you must use a Z-Diode D2 of about 7.5V to stabilize the Supply Voltage of IC1.

The Controller has to be programmed with this Software

Additional Information,Basics,DIY Kit, Links for Schematic
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