Re: Building a Cheap Tachometer

On Apr 9, 5:14 am, "luki" <kotaksura...@xxxxxxxxx> wrote:
Hi,
A small DC motor maybe, i don't know (i don't decide it yet) but would
not be very big sized motor. Is there any circuit that would generally
be able to measure motor speed?

How small? All CPU fans (three wires) have pulse sensors. Can you
adapt one of those?

If not, what really caused that? Is there any special attention i must
deal regarding each type/size/speed?

At this point, I can only offer the advice that Don
Lancaster would probably give you......use a PIC (and don't try to get rich
by writing books). ;-)

This is the background\purpose of this tachometer :
1. I was developing a motor controller, so i need a speed sensor to
control my motor

If you need to control it anyway, why not a micro to count the pulse
sensor.

2. The motor would be a small DC motor, to be easy to control
Any suggestion about the motor itself?

not really enough info, but you could start here
http://www.national.com/pf/LM/LM2907.html

A cheap frequency to voltage converter would be nice. That means i
must measure the frequency change according to Doppler? What kind of
signal that must be transmitted?
What if I can't have LM2907, quite hard to find things like that in my
country. Is there any alternative. Or could i made frequency to
voltage my own?

I really appreciate your posts. Looking forward to hear more.

Lukman


.

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