speedo signal specs

[ext-peter.betts at nokia.com]

> How sensitive is the speedo to its input? does the duty 
> > cycle of the
> > wave matter or is it just triggering off of rising edges per second?


Sorry. Forgot to answer this bit.

I found it to be quite insensitive to the duty cycle. So I just generated a
modified 50/50 (ish) duty cycle one and that was that. Normally it's just
counting the transistions and not measuring duty. +ve edge triggered.

Sounds like all you need to do is condition the signal going into your
conversion box to prevent the chips from being **** from the high voltage
level. I was happier with a little PIC chip but I can't see why a F-V and
V-F arrangement won't suffice. You might even find the V-F and F-V chips are
CMOS and capable of taking 12V inputs anyway. Just check at what level the
logic switches and make sure your signals reach this threshold.

Pete
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org