how to make DIY shiftlight

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donCityZ

2,000 RPM
Senior Member
Feb 8, 2006
2,293
33
1,648
wah.. nobody done this before?
wait for it. im gonna DIY this soon for my car but need to do some r&d first.
if success, then i post in DIY section.
 

miriguy

500 RPM
Senior Member
Jun 29, 2008
887
20
1,518
any success story yet?
 

jswong

Known Member
Senior Member
Dec 30, 2004
209
9
3,018
If we can tap voltage input to tacho's coil, then all we need is an analog comparator with a variable resistor to determine which is the comparison point to flag a "higher than reference" condition. This is the low-voltage stage. Run the output to a Schmitt trigger (positive feedback op-amp only) to turn the signal into a higher-voltage on or off instead of a variable signal, and to a voltage-follower amp (buffer op-amp) to drive a lamp.

I think this entire circuit can be designed from a few op-amp ICs.. but since the moving coil input voltages are usually very small, that will mean we'll need a small reference voltage also.. so we might need a low-voltage reference output IC also, e.g. a temperature-stable 2-volt reference IC.
 

donCityZ

2,000 RPM
Senior Member
Feb 8, 2006
2,293
33
1,648
haha.. i tried to search the rpm signal from standard connector of my car.. but cant find any.

now thinking to do my own detection by a simple coil wound around the plug cable. wahaha..

but, this r&d is difficult cause i dont have an oscilloscope.:banghead: lend me an oscilloscope then i can finish it in 1 day.

Bump: haha.. i tried to search the rpm signal from standard connector of my car.. but cant find any.

now thinking to do my own detection by a simple coil wound around the plug cable. wahaha..

but, this r&d is difficult cause i dont have an oscilloscope.:banghead: lend me an oscilloscope then i can finish it in 1 day.