Quadrature Encoder schematic?

[slp_prlzys]

I got the servo(attached),
it has shaft encoder, but I don't
think it has quadrature output
as it has only 3 wires, it's optical tho.
I'm thinking maybe the photosensor
can do quadrature but the circuit board
is design only to read RPM, maybe I
could modify the board to make it
quadrature? any idea if it's possible?
It's a JapanServo type DS48BE25,
can't find info of it.

TIA

[Al_The_Man]

You need at least 4 wires for an incremental quadrature encoder, +, Com., A & B pulse.
If it has three wires as well as + & com. then you are OK.
You would be better off picking up a through-shaft encoder and replacing the 1 channel digital tach, if that is what it is.
Al.

[Mariss Freimanis]

I looked at the picture of the encoder board and it is a single channel encoder.

Mariss

[slp_prlzys]

I was afraid you guys would say that,
I got 3 of these $5CAD each,
I temporarily attached a heds encoder(I got from inkjet printer)
so I could use it with UHUservo, but it doesn't fit very well.
not enough space.

it has 4 pins, but when I open it only 3 leads are connected to the board.

"it is a single channel encoder."

I'm thinking the board is single channel, but
the photosensor? how do I know if dual?
two LED. the top part has one LED like,
and the bottom part has some tiny grills and has 3 wires too.

thanks.

[slp_prlzys]

I think I may have a chance to modify it.
those tree wires coming out of the sensor
red,green,black. Black leads to GND,
bot red and green has signal on them,
I'm just not sure if it is out of phase,
my(unt)rusty oscope shows me kinda of sine wave tho.
I wish I have another probe so I could see both at the same time.
Is my findings make sense?

[Al_The_Man]

If they are in fact sine wave out, that is the way that all differential encoders start out due to the nature of photo detection and they are usually squared up before leaving the encoder, for example Hiedenhain encoders offer both choices.
If in fact it is a sine wave, you could square them up with a schmitt trigger IC and even feed into a differential driver to produce 4 signal channels.
In the absence of you double beam scope, after squaring you could test with a VOM on dc voltage range for each channel high and low, by carefull incrementing by turning the shaft.
Al.

[ez-cnc.com]

I think red and black for the power supply and the yellow onw is one channel output. Why dont you try puting 5V into the red and black cable and use a led and a 470ohm resistorin between the yellow and the black cables. Then rotate the shaft and the led should blink. Its probable that it was used in a speed control where there is no need for dual channel encoder.

[slp_prlzys]

Al:
it's definitely a sinewave, I'm going to try your suggestion.

ez-cnc:
the schematic I found(attached) is what led me to believed
that I may have a chance with modifying the encoder.
On the board that I have there's a separate supply for the infrared LED via,
75ohm resistor apart from the three leads that's coming out of the photo
detector, Black goes to GND, Red goes to 2k7(I think it's a pull up) and Green
to trimmer pot. The IC is a JRC 2903D (if it's the same as LM2903D then it's a
comparator, that's what I found at datasheet archive.com)

thanks.

[slp_prlzys]

AL:

I tried your suggestion and nothing happened.
I got no signal on the output (74hc14) well it's alwasy HI,but
still got signal from those 2 leads, then I noticed
that the oscope is 1mV/cm. That means I'm getting
a very weak signal coming from the sensor, so the input
of the 7414 never go HI. I went looking for signal amplifier,
but it's a little complicated than I thought.
I was going to give up when I decided to separate
the sensor from the LED, and voila!
I found two sets of tiny grills one above the other.
one looks a bit offset from the other. I used a magnifying glass,
and it is offset, where the other has hole the other one is block.
So I'm thinking this is how quadrature encoder works right?
and the board it was attached to, was used only as a tachometer,
by utilising both transition(HI, L0).

so the quest is still on, if anybody could provide me with
schematic so I could turn it into a quadrature encoder
it would be greatly appreciated.
My search on google gives me the idea that
an opamp could be used (maybe like the one on the board)

thanks


EDIT:

After a lot of searching I came up with an schematic,
does it make sense? it's slow but I'm
learning, I think.