Hi All,
Firstly - I am a tinkerer. Arduino has made it possible for me to play around with electronics despite no formal ed around it.
Now, onto the exciting bit of the post. I'm playing around with rpm interception from vr/mag and hall type sensors (motor vehicles).
VR are not square waved like hall and need to usually be conditioned before using them. Please excuse my elementary terms and simplistic terms that follow.
So the question are:
1.) Arduino allows for 0-5v analog input, because of this if I run my hall signal through a voltage regulator to bring down to 5v the signal should still be visible as a 0-5v square wave. I am not sure what the hall current will be coming into the regulator - I can only think this is between 0 and whatever the alternator can push out. So say 14v. Is something like the LM7805 alright and reliable? The common goes to ground - shared with what I understand are two other capacitors. One on the input side and one on the output. How do I calculate what caps I should use for which side? In an example I saw converting 9V dc to 5v dc their was a .1mF cap on the 9V side with a 22mF cap on the 5V. I would think the larger is on the 5V side to absorb any left over voltage that isn't dealt with in time with the regulator?
2.) As above, however I manage to convert the VR signal into a readable square 0 - 5v - it should be alright to push this through an LM7805 just incase (the chip I'm going to mention next around the conversion I believe already outputs to 5v max - I'd rather be safer than sorry and nuke a pin - or worse the entire board.
3.) With both inputs above - after being regulated - what should I be concerned about Amperage wise? Or are all Hall and VR/Mag type sensors sorta the same with regards to current draw?. Will the inputs handle this?
4.) Following on from point 2 - I would still need to convert the VR/Hall signal into a readable 0 - 5v and I'm thinking of using the LM1815 to do it. My questions are once again very basic so sorry - referring to http://www.ti.com/lit/ds/symlink/lm1815.pdf
4.1) Pin 3 takes the incoming signal from the VR/Mag signal - the docs say it regulates internally. The issue is they say I need to deal with the current (limited to 3mA). Now I don't know what the max voltage is that I'll ever see? Is there a common range. Once this is established. Is it as simple as taking the signal and connecting it up to a resistor and then from that resistor connecting to this pin? Eg: the signal is max 12V+ and the limit is 3mA = 4kohm?
4.2) Do I ground pin 5 or leave open (it controls zero crossing)? I believe you refer to this as pulled low (ground) or high (ungrounded). I have seen dual VR circuits where it looks like this pin is grounded. I don't understand what those other circuits were used for (in the great scheme of the system) but mentioning just in case that detail matters.
4.3) Which output pin do I use? Pin 12 or Pin 10? How do I determine what this voltage is that I'll see here? Do I simply take this output (from which ever is recommended) and run through another LM7805 to limit it to 5V? Once again I wouldn't know what caps to use on either side because of point 1.) and that I don't know what Pin 12 or 10 outputs.
Once again - I do apologise for the terrible terminologies etc. I am not a professional - just playing around.