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Bleo8onhs
07-27-03, 11:47 AM
New project on the way. I have a car tachometer connected to the pc. I get 12V from the PSU and the green cable that gets the pulses out of the distirbutor of the car at the transmit pin of the serial port(pin#3). That way i can emulate the pulses. In my research i found out that serial port gives in 0 state from -3 to -25 V and in 1 state from 3 to 25 V. I measure mine right now and in 0 state i take -9.63V. With Looks RS232 i send random bytes to the port but i only reached 4V and that only for 1/2 of a sec. Now i m trying to find out how to take only signals from the serial an feed my tachometer with 12V from the PSU.

Does anyone has any ideas? I cant understand why the needle doesnt move, any movement at all! :(

Greetings from Greece, the best place in the world!
nealric
07-27-03, 12:57 PM
wow, thats original!

WELCOME TO THE FORUMS!
:D

I have somewhat of an idea... but you probably know more than me...

why not use the tach as a fan speed monitor and hook it up to a rheobus such as the vantec nexus? That way you can adjust the voltage going to it.
Fast420A
07-27-03, 01:21 PM
http://www.xoxide.com/pctachometer1.html
Moriquendi
07-28-03, 07:29 AM
i dont know how much experience you have with electronics but i would use an opto isolator
Bleo8onhs
07-28-03, 11:21 AM
To do what?
Black_Ops
07-29-03, 12:37 AM
ther serial port was never ment to source or sink any major current.

i dont have a tachometer to play with but i'd interface it to the printer port or write some custom software for a PIC and use that to interface it to the serial port.
Dr Pepper
07-29-03, 06:54 AM
http://SMLITacho.cjb.net
dowmace
07-30-03, 01:56 AM
good link Dr. looks like it's going to be quite a bit of work to run a tach on your system
Bleo8onhs
07-31-03, 07:39 AM
Owen the GREAT(or Dr Pepper if you want) you have my respect...! look at your inbox!!
fiji
07-31-03, 01:38 PM
whats a tachtometer?
eh?
07-31-03, 01:52 PM
mesures RPM's

BTW this has been around for a while. I remember when it first came out a couple of years ago, the tach goes by the load of the CPU.
masterchief
07-31-03, 11:36 PM
it may be easier to just get one from xoxide... just more expensive... but keep at it and you can get it to work