Hi Guys
so far i could intercept signal from other sensors i need and they are in the correct work range.
i also need to intercept engine RPM, i have the cable that controls the needle on tacho but this works from 6 to 5V, how can i meassure this with the arduino wihout busting it? did try resitances and cant get the voltage down to make it work.
i need to get readable voltage for arduino so i can work with and it doenst lock up going beyond 1023 read value.
thanks!!
From the title, it sounds as though you want to COUNT pulses of some sort, but from the wording of the question, it sounds as though you are trying to measure an analogue voltage presented to the existing display.
Which of these two options are you wanting to achieve?
Thanks for reply, i have intercepted the cable that goes to tach controling the needle, that gives me the readout and does change when i do rev the engine.
that is the one i want to use as input but right now i am at hold as the values start at 6.5v and drop later in the 5v region depending on revs.
i need to have a voltage that wont damage the board and gives me a readable input value.
Thank you
Have you scoped it? Are you sure it's DC?
its coming fom the ecu and the work of the ecu is max 12volts.
ecu send signal to tach to move the needle.
how do i scope as you mention?
i could intercept cam sensor,i have read that those values arent really good to take
thank you.
you said that you 'tried resistances', but you did not say how... did you just put a resistor in series with the signal, or did you build a voltage divider (do you understand what a voltage divider is and how to interface one with the signal line)?
assuming the answer to aarg's post in an affirmative,, and that something like a 12K ohm load on the signal line is high enough not to distort (unlikely, but it is just a simple example...),, something like:
signal line tap->2Kohm R->5Kohm R->tap to arduino analog pin->5Kohm R->common ground
should give you something like a 1-5V level at the tap to arduino analog pin for a 1-12V level on the signal line.
thanks for quick reply
i have tried in series, have tried to do divider but no luck there.
i have signal going into A0, ground i am using the engine frame and obvious the ground from the 9v battery.
all the other values i have taped into are good in working range (they are basically potientiometers)
Hi,
You need to make sure the signal you are using is really an analog representation of RPM, not pulses that your meter in DC mode is averaging.
Can you put your DMM in AC volt mode and measure the ECU signal again?
Thanks.. Tom.. 
Hi Tom.
Ddm gives me 6 volt at idle and scales down to 5.5 gradually as i increase revs.
I need to get the input i am setting to the uno split so its readable and so program it.
Thanks for helping
Danny1000:
Hi Tom.Ddm gives me 6 volt at idle and scales down to 5.5 gradually as i increase revs.
I need to get the input i am setting to the uno split so its readable and so program it.
Thanks for helping
Really, 0.5V difference is suspiciously low. Hence my previous question. Your meter is probably averaging a pulse train.
Hi,
aarg:
Really, 0.5V difference is suspiciously low. Hence my previous question. Your meter is probably averaging a pulse train.
Exactly....
Can you put your DMM in AC volt mode and measure the ECU signal again?
Thanks.. Tom...
hi
did the test again
from 6 to down 4.3 at maximum, this only gives signal to needle, the motor for turning that needle is on 12v.
did try voltage divider runing potentiomenters and separately onanother resistors...sends the needle flat dead.
is there any way i can capture coil signal? i rember seing people just strapping a wire around the coil cables to get signal, what do i need to it this way? just wrap a cable around the coils and send it to my input? wont this give messy readings?
i need to read the engine rpm once i have that i can make the system work
cheers
is this viable?
Hi,
Did you try what I suggested in post #7 and post #10?
Tom...
hi, yes i did the tests again, the working range is more or less up tio 1.5 v from 0.1 changes till it hits redline
Hi,
So you got a reading with the DMM in AC volt mode?
If so then the signal is pulses, not a DC level.
Tom..
its in ac mode, how can i get that signal fed to the arduino? just pluging in the wire i get alltime the value 1023.
thank you
From what vehicle (make, model, year) are you trying to read the data?
It has electronic fuel injection, right?
And what type of tachometer are you using?
its gsxr 2006.
fuel injected.
-injectors run on 12v saturated type, 2 injectors per cylinder
-original tacho on it,analog type for rpms, digital for Ve,temp and gears.--i need a way to sesnse the rpms to feed the arduino data
-position sensors no problem,they are potentiometers.
Sorry, I can't help with a bike, but I would suggest that you try putting a scope on the tachometer output from the ECU. I would guess it is a pulse (as others have suggested) that you need to be reading rather than a voltage.