Limitations on of number of writes to Fraba encoder

Ozpeter

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Join Date
Aug 2014
Location
Virginia
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124
Hi all,
I am looking for the maximum number of write cycles to the eprom/eeprom/flash (?) of a Fraba/Posital absolute encoder. I have been digging through the specs of the encoder that I am using but I haven't seen anything obvious.

The reason I am looking is that I will take that limitation into account when designing the homing philosophy of the system I am designing. And homing basically means writing to the encoder and telling it what its current counts should be.

So if the number of allowed writes is absurdly large then I could safely home the encoder every time it passed over a known location.

However if the number is small (with respect to how long the equipment will be in use) then I need to be smarter with what I do.
 
Hi all,
I am looking for the maximum number of write cycles to the eprom/eeprom/flash (?) of a Fraba/Posital absolute encoder. I have been digging through the specs of the encoder that I am using but I haven't seen anything obvious.

The reason I am looking is that I will take that limitation into account when designing the homing philosophy of the system I am designing. And homing basically means writing to the encoder and telling it what its current counts should be.

So if the number of allowed writes is absurdly large then I could safely home the encoder every time it passed over a known location.

However if the number is small (with respect to how long the equipment will be in use) then I need to be smarter with what I do.

I've seen flash memory specs that vary from anywhere from 10k to a million writes.

The only way you're likely to get a real answer, though, would be to ask the manufacturer.
 
I am confused. Normally the controller would contain the actual home value if there is an offset between the encoder and the real world home. I have not used an absolute encoder that allows a value to be loaded to it. Please send the model number of the unit you are using.
 
In the systems I'm familiar with, when you do a homing routine, the axis is stops at the home position and you write the count value of the home position (often zero)to the absolute encoder. I think you'd be introducing a significant error if you tried to do it every time you passed the home position sensor due to the time it takes to write to the encoder memory. Furthermore, would it not make a difference which direction you were moving when you passed the home sensor? Surely there must be a range of encoder count values during which the home sensor is on.
 
I've seen flash memory specs that vary from anywhere from 10k to a million writes.

The only way you're likely to get a real answer, though, would be to ask the manufacturer.
I was hoping for something more experiential than going back to Fraba .. but if I have to I have to
 
I am confused. Normally the controller would contain the actual home value if there is an offset between the encoder and the real world home. I have not used an absolute encoder that allows a value to be loaded to it. Please send the model number of the unit you are using.
The absolute encoder is there so that even if you change out the PLC we still know where we are.

But as for Fraba model number I believe its an OCD-EIB1B-1213-C10S
 
In the systems I'm familiar with, when you do a homing routine, the axis is stops at the home position and you write the count value of the home position (often zero)to the absolute encoder. I think you'd be introducing a significant error if you tried to do it every time you passed the home position sensor due to the time it takes to write to the encoder memory. Furthermore, would it not make a difference which direction you were moving when you passed the home sensor? Surely there must be a range of encoder count values during which the home sensor is on.
This is actually for motion in a crane that will only be moving at 1 m/s, and being homed by a series of RFID tags embedded in the ground every 100 feet. Latency wise we are good given the slow speed, and yes we are aware of directional issues - but in this particular case we don't care.

It's more about balancing code complexity against hardware capabilities.
 
Thanks for the model number. I was able to look at the manual and understand how the preset works. My experience with absolute encoders is with the old type that used discrete outputs to a PLC. You could not set an offset or preset to your real-world position in the encoder. That work had to be done either mechanically by positioning the encoder shaft where you wanted zero, or by doing a mathematical offset in the code. Since this is a network device, there are more soft options.
 

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