Re: [CAD_CAM_EDM_DRO] Re: D/A converter info

I'm not sure about the range, but most bicycle speedometers use magnetic
pickups and give a digital output. Most have a calibration range to
accomodate different wheel diameters. 40 MPH is roughly 540 RPM on a 700Cx25
wheel. Has anyone tried to use a bicycle speedo as a tach? They're dirt
cheap and pretty rugged and watereproof. Some are even wireless.

D.

----- Original Message -----
From: "caudlet" <thom@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, January 19, 2005 11:59 AM
Subject: [CAD_CAM_EDM_DRO] Re: D/A converter info


>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "gary_vincent_2001"
> <gary_vincent_2001@y...> wrote:
> >
> >
> > Hi guys, I am looking for a D/A converter to take mag pickup pulses
> > and get back a proportional dc voltage. Anything like that out
> there?
> > tks gary
>
> What you are describing is basically a tachometer circuit. How
> linear and how accurate and how many pulse per second will determine
> how/what you spend. A true D/A takes a digital "word" and gives you
> a voltage level that corresponds but is not designed to take serial
> pulses in and give you a voltage level. The process of doing that is
> to use an 'integrator' circuit (simple op amp) but the trick starts
> to become things like linearity and response time. One chip we use a
> lot to take PWM in and output a porportional DC voltage is the LM2907
> chip.
>
> Tell us what you are trying to measure and we can give you a
> suggested approach. If you are trying to measure position or speed
> there are different solutions. If you are trying to control the
> speed RPM of a cutter motor there are known solutions the group have
> developed as well as some vendors.
>
>
>
>
>
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