Re: Proper pull up resistors for optical limits

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "fun2b432002" <fpaul28@h...>
wrote:

> Wondering if anyone could give me advice on the correct pull up
> resistor for my optical limit/home switches. I'm placing slotted
> optical switches on the + side of my X,Y,Z axis to use as limit and
> home. My servos are WorldServo SST1500s and the manual suggests
> using optical switches on the + axis side. There is a diagram in
> the manual that shows connecting them to +5V (which is supplied by
> the servo through the limit switch plug). They show a resistor
> between the +5V and the optical interrupter switch but do not give

a

> value on the resistor. I assume this is a pullup resistor (I know
> very little about this) and I'm wondering if anyone can help me

with

> determining which size resistor to use???? The optical switches

are

> transistor output type, Min Output 0.5 IC @ 20 mA IF. Another type
> I may use are the same except Min Output 1.8 IC @ 20 mA IF.
>
> Thanks,
>
> Frank

I still have my test setup of those laying in front of me.
I had a hard time getting this to work because the first
time I tryed to use it I could not get anything to work,
found out much later that the emitter did not work on my
optical interrupter switch.
That was 1 out of 4 and I sure picked the bad one to start with.
The way I found out was when holding it at the right angle
to a external light source it started to show a current.
The emittler is sort of like a Flashlight shining onto
the detector, you want to prevent a external light from
shinning directly onto the detector when choosing a final
mounting position this could cause trouble.

My test setup is wired as follows.

(+) +5volt power (D) ground
(E) ground (+) Pin 11 on LPT port

This worked fine as is.
The diagrams I have show a 4.7kohm resistor in line
with both (+) lines.
seams to work without these to I think they are just
for protection.
Good Luck