Is this Incremental encoder working?

[MaxHeadRoom78]

Hi M,
2.4mA while rotating.
C

So as it stands, there is no current change between resistor fitted and not fitted, which points to the output transistors not switching.
Maybe use something like a 470 ohm pull ups and test (10ma) each.
Max.

 

[Pommie]

Could it be that the distance between indents is so small that it's always stopping in the same position? Can you spin it with a drill or something and scope one of the outputs.

Mike.

 

[camerart]

Hi,
With the 5K resistors:
First I raised the voltage to 10V, poor square waves showed on the oscilloscope, which fell back when the encoder stopped.
Changed to 1K, good square waves, and stayed when encoder stopped.
Changed voltage back down to 5V square waves, which stay.
So it's working

At 5V, how can I find the best resistance 'safely'
Will connecting the outputs to 5v damage them?
C.

 

[dknguyen]

The output transistors can probably handle 20mA max, so size resistors for something like 10mA or even 5mA. I don't know why it doesn't like 1mA though (5K at 5V).

 

[MaxHeadRoom78]

They should take 470 ohm easily, but you should get perfectly square waves out, Do Not connect 5v direct to the outputs.
Max.

 

[camerart]

Hi,

I understand that a too low resistance, would 'pop' the transistors, but is the idea to get as low as possible to get a square wave, but not too low?

C.

 

[dknguyen]

Hi,

I understand that a too low resistance, would 'pop' the transistors, but is the idea to get as low as possible to get a square wave, but not too low?

C.

More current means more heat/power which is bad. But you still want enough current to be able to charge the parasitic capacitances fast enough to get a good square wave. You don't want to get the resistance as low as possible as much as you want to be able to get away with as high a resistance as possible. Just enough to charge those capacitances, have good noise immunity, and good edges so you can minimize heat and power but still have things work.

 

[MaxHeadRoom78]

As long as the transistors switch it really should not make much difference, within reason.
But I would expect to see at least a 10ma collector current.
Have you tried the 470 ohm at 5v?
Max.

 

[camerart]

As long as the transistors switch it really should not make much difference, within reason.
But I would expect to see at least a 10ma collector current.
Have you tried the 470 ohm at 5v?
Max.

Hi D,
Not yet, but I understand, and will follow the 10mA guide.
Thanks to all for the process, most interesting.
C.

 

[camerart]

Hi,
Spoke too soon!

The encoder worked ok, till the battery went below 5.3V, then it stopped outputting.

It appears that these encoders don't work at 5%. I'll simply use it at 12V.

As the output of the encoder, is input to a 3.3V PIC, I will need to watch the voltage.
C

 

[MaxHeadRoom78]

Place a zener clamp on the input signal.
Max.

 

[camerart]

Place a zener clamp on the input signal.
Max.

Hi M,
Is this to control the voltage?
If so, then I presume, I have to get 3.3V zener diodes?
C.

 

[ChrisP58]

Hi M,
Is this to control the voltage?
If so, then I presume, I have to get 3.3V zener diodes?
C.

Or 3V. Probably even 2.7V would be OK. As long as it's high enough that your input still sees it as a logic ONE.

You could also use a resistor. Setup a divider to make ~3.3 when the top is at 12V. The encoder output shorts the lower resistor to GND.

 

[camerart]

Or 3V. Probably even 2.7V would be OK. As long as it's high enough that your input still sees it as a logic ONE.

You could also use a resistor. Setup a divider to make ~3.3 when the top is at 12V. The encoder output shorts the lower resistor to GND.

Hi C,
Are these two drawings correct?
Which one is best?
I have some 3.3V Zenere diodes.
C

 

[ChrisP58]

Hi C,
Are these two drawings correct?
Which one is best?
I have some 3.3V Zenere diodes.
C

No.
The anode of the zener needs to go to GND (0V). The encoder output connects to the zener cathode with the resistor and the PIC pin.
If you use a resistor divider, the bottom of the lower resistor goes to GND. the encoder goes to the midpoint. And if the upper resistor is 1K, the lower resistor needs to be 374 ohms to make 3.3V at the junction.

 

[Pommie]

Why not just have encoder output - 10k resistor - pic input - 3.3k resistor GND.

Mike.
Edit, or replace the 3.3K with a 3.3V reverse biased zener.
Chris, are you assuming the outputs are OC? 12V directly to the zener (or pic pin) could produce a large current. Or did I misunderstand?

 

[ChrisP58]

Why not just have encoder output - 10k resistor - pic input - 3.3k resistor GND.

Mike.
Edit, or replace the 3.3K with a 3.3V reverse biased zener.
Chris, are you assuming the outputs are OC? 12V directly to the zener (or pic pin) could produce a large current. Or did I misunderstand?

Mike,
Yes, this thread started with the OP asking why he got no output from his encoder. The first few posts established that the outputs were OC.

 

[Pommie]

It appears it is OC. Therefore only a pullup to 3.3v is needed.

Mike.

 

[MaxHeadRoom78]

The spec states 5v supply minimum.
Max.

 

[Pommie]

The spec states 5v supply minimum.
Max.

Assuming you are replying to my post, the supply to the sensor can be 12V as stated but the pic input only need a pullup to it's own 3.3V supply.

Mike.