I have made a shift light that works from the stock rev counter. I have a very bright orange LED and ultra bright red LED for up-shifts. I have set the orange LED for about 8200rpm, and the red LED to light at about 8400 rpm. The idea is to change up when you get the red light, with the orange light being warning. The shift lights are still very useful when concentrating in traffic (race traffic, not the other kind), and I hardly ever look at the rev counter. When I first made the shift light I used a green light for down-shifts, and no orange light. I found that I couldn't see the green light very well, and didn't use it anyhow, so I added the orange light in it's place.
Circuit Diagram.
Circuit Description.
The light runs straight off the back of the stock rev
counter, which provides +12V, GND and a pulse from the
ignition. A 2917 frequency to voltage converter converts
the ignition pulse to a voltage proportional to revs,
adjusted for temperature and supply voltage
variations. A two pole Butterworth filter helps to
reduce ripple. A 358 op-amp compares the output to
two fixed voltages, one for each light. The op-amp
is wired so that each output goes high when the 2917
output voltage exceeds the reference voltage for the
light. It is fairly easy to change these so that
there are two up shift lights or one up, one down.
The above circuit diagram was made to mount the
components on strip-board, so there are some strange
connections in order to make the circuit board as small
as possible. There is a connection to pin 6 on the
LM2917, which is unused. This connection is just in order
to connect the two resistors and capacitor on pins3, 4
& 5 together.
The light is stable (i.e. it comes on at a set rpm
despite variations in voltage or temperature) but is
inclined to flicker a few times in the higher gears when
approaching the limit. To me this is quite useful,
but ideally the light shouldn't do this. The
flicker was much worse before I used the Butterworth
filter.
Circuit Construction
See shift light construction.
Warning.
I don't guarantee that this light will work on any other
car than mine, but the triggering mechanism of the 2917
is fairly tolerant so the circuit should work in almost
any Honda with fuel injection and electronic ignition.
Finally.
If you have problems with the shift light, mail me and I'll help you if I
can. Quite a few have been constructed from this design,
and, as far as I know, they have all worked correctly.
There is another page with shift
light construction information, in case you missed
the link above.