Yeah, you were right, that's why I deleted it - you were fast on the draw there!

 

From a single pulse train I can see no way to get direction information. If the system moves very slowly and you can be sure the motor has almost no overrun then you could assume the count is incrementing when the motor is being driven in one direction and the count is decrementing when being driven in the opposite direction. This can drop or pick up extra counts if it stops just on a transition of the pulse from the encoder. This system is used for TV satellite dish positioners.

Les.

while I'm using PID control, the system is uni-directional (with limit switches at both ends). I do not wish to get directional control, I just want to know if I can control it reasonably, period.

 

My guess is it's an optical encoder so no contact bounce.

Your mouth to God's ears...

If the transmission is at all sloppy -- or if the shaft is moving slowly -- he may get spurious pulses at the code transition point.

Quadrature encoding (at the encoder) is inherently immune to this (+/- one count with zero average position error).

 

Your mouth to God's ears...

If the transmission is at all sloppy -- or if the shaft is moving slowly -- he may get spurious pulses at the code transition point.

Quadrature encoding (at the encoder) is inherently immune to this (+/- one count with zero average position error).

Given that the encoder is a hall effect magnetic encoder (I have on idea what it looks like on the inside). Do you think that necessarily implies I have enough room to strip it off and mount my own quadrature encoder on?

 

Given that the encoder is a hall effect magnetic encoder (I have on idea what it looks like on the inside). Do you think that necessarily implies I have enough room to strip it off and mount my own quadrature encoder on?

They come in all shapes, sizes, resolutions, and mounting configurations. There is no way for me to know if you can a) remove the existing encoder, and b) replace it with a different one.

 

@joykid how do you intend controlling the drive? It appears to be either Canbus or RS232.
And with what type of system?
Also it can accept RS422 for the encoder which is recommended but single ended would work in non-noisy conditions.
For a simple linear system where you can just count the number of pulses in either direction, that drive seems a little over-kill!
Max.

 

I'm not sure you need to go so far as to replace the encoder. HE encoders are pretty stable and if fed through a schmitt trigger input (74HC74 dual D FFs clock is schmitt triggered) there shouldn't be problems from slowly changing values. I kind of doubt the original designer would create a clearly bad encoder. I'd just get a 74HC74 and try it out before hacking up the motor.

Or, if you have an arduino, you could test it out to see if the grey converted encoder presents problems.

 

The hall effect is usually a small Honeywell SS400 series.
There must be a registration strip for detection?
Seems like a little overkill going on!
Max.

 

@joykid how do you intend controlling the drive? It appears to be either Canbus or RS232.
And with what type of system?
Also it can accept RS422 for the encoder which is recommended but single ended would work in non-noisy conditions.
For a simple linear system where you can just count the number of pulses in either direction, that drive seems a little over-kill!
Max.

I have a Micro830 PLC. The reason I chose the EPOS controller is because of the software available to easily develop position profiles, and I couldn't find any other good alternatives that provide software (the main controller is just the PLC, no PC or SBC). The expected travel speed is about 50mm/s, which is about 300 pulses/sec. I dont know if thats too fast or may create a noise problem.

 

Not familiar with the Micro830, but I think I would have done it a little differently if using a PLC by way of analogue out to a 'non-intelligent' DC drive and used the single pulse to input to the high speed counter in the PLC, the PLC would 'know' which direction it has commanded .
But that's hind site.
As already mentioned, also a small Picmicro should have done it.
Max.

 

Not familiar with the Micro830, but I think I would have done it a little differently if using a PLC by way of analogue out to a 'non-intelligent' DC drive and used the single pulse to input to the high speed counter in the PLC, the PLC would 'know' which direction it has commanded .
But that's hind site.
As already mentioned, also a small Picmicro should have done it.
Max.

I can still consider doing it that way, but was afraid of the PID capabilities of the PLC for motion control. I also am not sure how much more work I'd need to do developing time respective position profiles as setpoints in the PLC environment, when it seems fairly easy with the smart controller.

 

Is the PID system aiming at controlling the speed or position ? A few years ago I made a PID speed contoller. (For the table feed on my milling machine.) The motor did have a quadrature encoder but I was just using it to give pulses that were counted over a fixed period (20 mS) to give the actual speed. So if it is only speed information you want then the single channel encoder should do what you want.

Edit. Another thought. If you did need position information you could use a linear quadrature optical (Or magnetic) encoder. The sort of thing they use for digital position readout on machine tools.

Les.

 

Generally PID control with a PLC has to be handed off to a dedicated module due to the typical update time of a PLC ladder.
But just checked the linear actuators (Johnson) and they have the positioning and drive all contained in the actuator, with supposedly no need for a separate controller?
At least that is the way I read it.
Max.

 

Generally PID control with a PLC has to be handed off to a dedicated module due to the typical update time of a PLC ladder.
But just checked the linear actuators (Johnson) and they have the positioning and drive all contained in the actuator, with supposedly no need for a separate controller?
At least that is the way I read it.
Max.

The linear actuator I am using is from Thomson Linear

 

I'm not sure you need to go so far as to replace the encoder. HE encoders are pretty stable and if fed through a schmitt trigger input (74HC74 dual D FFs clock is schmitt triggered) there shouldn't be problems from slowly changing values. I kind of doubt the original designer would create a clearly bad encoder. I'd just get a 74HC74 and try it out before hacking up the motor.

Or, if you have an arduino, you could test it out to see if the grey converted encoder presents problems.

Would the wiring be the same as joeyd999's diagram?

 

Would the wiring be the same as joeyd999's diagram?

Yes. Ensure unused inputs are appropriately terminated and include a 0.1uF ceramic cap from Vdd to Vss.

 

The linear actuator I am using is from Thomson Linear

That was the site I went to, they appear to have controller on board, i.e. intelligent linear controller.
Max.

 

That was the site I went to, they appear to have controller on board, i.e. intelligent linear controller.
Max.

Don't think it's the same model. I'm using an Electrak HD

 

Don't think it's the same model. I'm using an Electrak HD

Thats right, they stress onboard control!
This looks like the one you should be using.
Max.

 

Thats right, they stress onboard control!
This looks like the one you should be using.
Max.
View attachment 146002

Yes, though I'm not quite sure what the "smart" part means since it doesn't actually do anything but give you encoder and end stroke signals...