ssave@caen.engin.umich.edu (Shailendra Anant Save) (10/24/90)
Has anyone built a digital tachometer from parts?
Here is what I have:
4 cylinder car. It has wires that go to the spark plugs.
What I want:
Some way of counting the RPM.
How I have thought of approaching this:
Method 1
Wrap a coil of wire around the spark-plug wires and
get a voltage across the terminals which would be the
average DC voltage. Then DC voltmeter caliberated to
this, would give me the RPM.
Problem: How linear is this?
How accurate is this?
How easy is it to caliberate the voltmeter?
Method 2
Wrap a coil as above. Schmitt trigger the pulses into
square waves. Gate and count the number of pulses in a
time (1/10 sec). Display the count.
Method 3
The fan blades are such that there is a light path
between each blade. Use infra-red transmitter -- detector
pair and get pulses. Count as in 2.
Anyone have any experience with these? The thing is
that I want digital. Analog ones available are about
$35 each. I am hoping that I can make one that costs
even less.
Please send any other suggestions to me.
Thanks,
--Shailendra
ssave@caen.engin.umich.edu
The University of Michigan
Ann Arbor.
robin@uhunix1.uhcc.Hawaii.Edu (Robin Amano) (10/26/90)
>> Anyone have any experience with these? The thing is >>that I want digital. Analog ones available are about >>$35 each. I am hoping that I can make one that costs >>even less. Good ones are more like $80 -- ---------------------------------------------------------------- Robin Amano | Internet: robin@uhunix.uhcc.hawaii.edu UHCC | 2565 The Mall | Honolulu, HI 96822