rotary shaft encoder

[raman00084]

i am using double shaft stepper motor, at one end i am connecting the shaft encoder. my doubt is how to choose shaft encoders, how much wires it have and how to connect to micro controller. some people say that single channel and two channel what is that?
what output i will get from that encoder, how to connect to micro-controllers
kindly help

regards

 

[paulfjujo]

a simple encoder can have 3 outputs
it is define by the number of pulses per tour example : 500 i/tr
by the mode of output : Totem pole transistor, TTL output, simple transistor, RS485 (for long distance of cable)
the level 5V (TTL) , 12V or 24V or RS485 or open collector....
1 output A with give 500 pulses
1 output B with gives also 500 pulses ,but with 90 ° phase shift
1 output C with gives 1 pulse per tour (*optional)

so they are many types...
2 outputs for 2 way rotation clockwise and anticlock wise.
The phase shift beetwen output A and B determine the direction of rotation..
to connect to a MCU, you will have to adapt the levels ..according to your MCU power supply 3,3V or 5V ?

 

[horace1]

some microcontrollers have a quadrature encoder inferface, e.g. Microchip dsPIC
https://www.youtube.com/watch?v=s1IxKhGERS4

 

[doraemon]

Hello!

a simple encoder can have 3 outputs
it is define by the number of pulses per tour example : 500 i/tr
by the mode of output : Totem pole transistor, TTL output, simple transistor, RS485 (for long distance of cable)
the level 5V (TTL) , 12V or 24V or RS485 or open collector....
1 output A with give 500 pulses
1 output B with gives also 500 pulses ,but with 90 ° phase shift
1 output C with gives 1 pulse per tour (*optional)

That's true. Just some detail: usually, all makers use a "marketing" way to provide information.
Therefore, a 500 steps per rotation usually means that A and B have 125 steps each, and with a
90 degree phase, these means 500 different positions per turn. And the direction is determined
by the 2 signals, depending on which one is leading.
The C signal is also named Z signal by many makers.

Dora.

 

[HTA]

For a stepper motor an absolut encoder might be better than a incremental one since it provides access to the absolut position. In addition to the ABZ signals they have a digital interface like SSI or BiSS(in some cases also SPI). Then the readout is simpler because there is no direction discriminator on the microcontroller is needed(either in software or hardware). See also https://www.edaboard.com/threads/313963/ .

Enjoy your design work!

 

[paulfjujo]

Therefore, a 500 steps per rotation usually means that A and B have 125 steps each,

i allready tested many codeur , mounted on AC (or DC motor) for speed control,
and checked the signal A o(or B) with an oscilloscope of frequencemeter ,
and if the provider said 500 i/tr, it is 500 impuls per tour ! on each canal A or B

it means,if the a moteur is at 3000 Tr/Mn => freq on A signal is = 3000*500/60= 25000 Hz !
and in industrial environnment take care about the distance and cable quality to transport this information...

 

[doraemon]

Hello!

Each manufacturer makes his own choices.
Anyway the manufacturer choices don't change the facts: if you have 500 pulses per turn on A and B,
then you can resolve 2000 different angles per turn because A and B are in quadrature.
And most of the makers I know use the angle resolution (2000 in the above case), not the AB
resolution. Maybe because it's a higher number (and therefore better for marketing issues), and also
maybe because it's the angle resolution which is the information most developers care about.

I'm just reading a documentation that makes a good tradeoff by publishing both numbers:
Kuebler T8.5825. It says: Up to 36000 PPR or 144000 CPR.
PPR = pulse per rotation, CPR = count per rotation.
Another maker: Heidenhain. They give count values per turn (therefore the higher number), not
the pulses per turn. At least in the documentation I have here. They refer that as "position values/rev"
which is 8192 (13 bits).

As for the chip makers, I have right in front of me the documentation of a 25-bit absolute encoder
chip (therefore 33 millions counts per turn). Here again, it's the count number. iC-Haus' iC-MN.

Dora.