Encoder

[Andrew Dalgleish]

On Thursday, 7 March 1996 21:53, owner-diy_efi-outgoing wrote:
>
> Jim:
>
> >   Why is the wheel going to be a bear. Spot size will allow me to use   
.2mm
> > marks, the focal points a bit out there but I'll recess the sensor.
>
> This kind of accuracy requires photo reduction techniques, ya can't   
just bang
> one out on your dot matrix...  Not cheep and not quick...

Photo reduction isn't that expensive. I've done it by taking a shot with   
a 120 camera and using the negative. Most wedding photographers could do   
it for you, probably for a few beers.

I've also seen a sticky metalic (so it doesn't stretch) tape with   
light/dark bands on it. You just wrap this around a shaft a few times   
until the stripes line up.

> You'd be much
> better off just buying an encoder.  Newark has 100 ppr units that look   
like
> a pot for around $35, rated for 10,000,000 revolutions.

That's less than 28 hours at 6000 rpm. Are you sure there isn't another   
1000 in there?

>
> > But what is the output voltage? And the transition time?
>
> No idea.  The only app circuit I have for this is pretty easy, though.
> First, supply the LED (pin 6) via about a 120 ohm resistor to 5v, this   
will
> give you around 30 mA LED current. (pin 4 is LED ground)
>
> The detector circuit is dead simple.  Tie the photodiode cathode (pin   
3) to
> +5v.  Put in a 100k resistor from pin 1 to +5v, this is RL.  Put a 10   
Meg
> feedback resistor from pin 1 to pin 2.  Tie pin 8 to ground.  That's   
all
> there is to it.  Oh yeah, output voltage is also taken from pin 1.  I   
have
> no idea what the output voltage from this circuit is, just breadboard   
it up
> and find out.  You may need an extra stage of amplification and a   
schmitt
> trigger to clean it up for your counter logic.
>
> If you need more info than that, you'll have to contact HP and get some
> app notes, I haven't used the thing before, either...
>

Sounds a *lot* better than using separate led/phototransistor.

> regards
> dn
>
>
> --
> ---------------------------------------------------------------------
>  Darrell A. Norquay              Internet: dn at dlogtech.cuc.ab.ca
>  Datalog Technology Inc.         Bang: calgary!debug!dlogtech!darrell
>  Calgary, Alberta, Canada        Voice: +1 (403) 243-2220
>                                  Fax:   +1 (403) 243-2872
>     @ +
>      <
>     __/    "Absolutum Obsoletum" - If it works, it's obsolete
> --------------------------------------------------------------------
>
>

Regards,
Andrew Dalgleish
Senior Software Engineer
Axon Research, Pty Ltd
6 Wallace Ave,
Toorak, VIC
3142
AUSTRALIA
Tel +61-3-9826-5538
Fax +61-3-9824-0083