[groov]

got it....the xtal max is 10MHz with an internal PLL (4x) clk running at 40MHz.
however the spec says that it can be run from DC to 40MHz with an externally generated clock through the OSC1/CLKI pin bypassing the PLL.

back to order some 10MHz xtals.
thanks

[Marty_Escarcega]

Steve, a note from my buddy:
I think you need to suggest to the guy who makes the code to port over to the 18F4520. I say this NOT because I have 4 of them ( J ), but the fact that the 18F452 is a "mature product" according to Microchip and they are getting hard to find from the common sources. I have some coming directly from Malaysia or Thailand via the Micro Chip store.



Microchip strongly suggests the port to the 18F4520 in all their documentation.

Steve, how tough would this be. We did find out the hard way it is REALLY close!

[Khalid]

thats a great thread..

[groov]

.....but the fact that the 18F452 is a "mature product" according to Microchip and they are getting hard to find from the common sources. I have some coming directly from Malaysia or Thailand via the Micro Chip store.

Being a "mature product" will probably mean that it will become obsolete soon. It maybe wise to have it ported to another controller.

I ordered a couple of 18F452 from Mouser, however they are more expensive than the 18F4520, in case someone on this side of the pond wants to built this project.

thanks

[Marty_Escarcega]

Being a "mature product" will probably mean that it will become obsolete soon. It maybe wise to have it ported to another controller.

I ordered a couple of 18F452 from Mouser, however they are more expensive than the 18F4520, in case someone on this side of the pond wants to built this project.

thanks

Heh, the two are EXTREMELY close. Read through the thread to find out how I know!

We did get the firmware loaded on the 4520 (yes, we got the wrong chips) but got a LOCKED message as if both pins 7&8 were asserted. This thread is pretty old. Maybe Steve can update the firmware rev for the 4520 fairly easily.
Marty

[toolfool]

Heh, the two are EXTREMELY close. Read through the thread to find out how I know!

We did get the firmware loaded on the 4520 (yes, we got the wrong chips) but got a LOCKED message as if both pins 7&8 were asserted. This thread is pretty old. Maybe Steve can update the firmware rev for the 4520 fairly easily.
Marty

Have a look at post number 132. This question came up late 2009. At that time, Steve wasn't inclined to re-do the code to work with the 4520, although he had tried. He may be working on the Shumatech DRO-550 as a new method of rotary control.

Regards,

Dick K.

[kwackers]

The whole question of moving to another controller is an interesting one.

I had a trivial attempt at moving it to a 4520 and that failed. I am however using a fairly old version of HiSoft C and it's support for the 4520 might be poor.

Since the 452 still seems to be in plentiful supply (I've just had another look now, Farnell for example show close to 800 in stock) it's difficult for me to justify spending time to move it across.

In terms the future I'm not sure where I would go with this, it's fairly full featured - difficult to think of anything else that could be added, simple to build and cheap.
I could make a updated version with GLCD showing nice graphics and fonts, newer chip etc but it would be more expensive, more difficult to build and I can't think of any extra features that might be worth adding and so offer nothing extra in terms of functionality.
In fact the only improvement I think would be worthwhile is making it easier to program, ideally by simply plugging it into a USB port for example (probably using a 4550 rather than a 4520 - sorry Marty!).

With regards the Shumatech, I'm considering porting a version to it as an add on, simply because I already have the 550 for my mill and having the rotary built in saves a box. However it would be a cut down version of this offering basic functionality and I'm not sure how easy it would be for people to obtain the 550 in the future given its surface mount construction.
At the moment I'm up to my neck in it at work, so haven't had time to look at this.

[nuttall]

Hi fellows threaders, i have been following this thread with some interest, i could really use Steve,s design in my workshop, Allthough i have no ability with the electronic side of the build i can do the mechanical . i would appreciate if someone who has built a last version of the unit to build a unit for me, this of course would be a payed for build. could any one assist?
with regards
\brett

[Marty_Escarcega]

The whole question of moving to another controller is an interesting one.

I had a trivial attempt at moving it to a 4520 and that failed. I am however using a fairly old version of HiSoft C and it's support for the 4520 might be poor.

Since the 452 still seems to be in plentiful supply (I've just had another look now, Farnell for example show close to 800 in stock) it's difficult for me to justify spending time to move it across.

In terms the future I'm not sure where I would go with this, it's fairly full featured - difficult to think of anything else that could be added, simple to build and cheap.
I could make a updated version with GLCD showing nice graphics and fonts, newer chip etc but it would be more expensive, more difficult to build and I can't think of any extra features that might be worth adding and so offer nothing extra in terms of functionality.
In fact the only improvement I think would be worthwhile is making it easier to program, ideally by simply plugging it into a USB port for example (probably using a 4550 rather than a 4520 - sorry Marty!).

Understood. I have a couple of questions. We finished our controllers and wired up the 3.0V 4.0A steppers. Power Supply is a 24vdc 2A unit. Stepper drivers can take the 24VDC and can output up to 2.5Amps.

I am running 2.12b. Looks like the change was to Steps per rev instead of worm ratio. Any chance of allowing both in SETUP, but only allow one or the other?

Also, when in JOG or CONTINOUS mode when in speed 1 the motor runs smoothly and quietly. When in speed 2 it runs a little faster but there is a noticeable vibration, in speed 3 and above, the motor starts to turn then stalls and hums. I have the stepper driver set to 2.5A. I'm wondering if I am over driving the stepper?

Marty

[kwackers]

Understood. I have a couple of questions. We finished our controllers and wired up the 3.0V 4.0A steppers. Power Supply is a 24vdc 2A unit. Stepper drivers can take the 24VDC and can output up to 2.5Amps.

I am running 2.12b. Looks like the change was to Steps per rev instead of worm ratio. Any chance of allowing both in SETUP, but only allow one or the other?

Also, when in JOG or CONTINOUS mode when in speed 1 the motor runs smoothly and quietly. When in speed 2 it runs a little faster but there is a noticeable vibration, in speed 3 and above, the motor starts to turn then stalls and hums. I have the stepper driver set to 2.5A. I'm wondering if I am over driving the stepper?

Marty

Hi Marty,
Re the steps per rev, there's not much point allowing both. The worm ratio makes assumptions (such as a half stepping, 200 step motor) which may not be true.
I figure steps per RPM is far more sensible, also allows ratios to be added which wouldn't be possible any other way whilst not precluding any worm ratios.
Obviously it needs a calculator, but as it's in setup and so a once only issue then I wouldn't think it was too troublesome...

For anyone unsure the number to be entered is simpy:
Steps per motor rev * worm ratio

So a half stepping 200 step motor = 400 steps per rev and say a 90:1 worm means
400 * 90 = 36,000

Your other issue, it sounds like the maximum step rate that your motor can accept is being exceeded for the load being driven.
Go into setup and set the max step rate to be say double the min and check that at speed 5 the motor runs ok (if not reduce it), then with a bit of to-ing and fro-ing figure out what the max value can be set to with the motor not stalling (or running roughly).
The speeds should now give you 5 workable values between slow and max - although it's not likely that max will be much use since it'll be close to the motors stall speed.
The current only determines torque at low speed, a high current will give high torque - but only whilst the speed is low. (Such is the nature of stepper motors...)

The maximum rate the motor can run at is determined by the stepper driver/motor and voltage supplied to the driver. High quality drivers running at very high voltages can be driven at very high speeds. I use a cheap driver running off 24v and the value for max speed is around 4000 before it stalls.
May also be worth checking there's no unwanted load (if connected to the table), in the past I've forgotten to slacken off the lock... :-D

Hope this helps,
Steve.

[Marty_Escarcega]

Thanks for the suggestions Steve, I will try them this evening.

What is the difference between the MIN and MAX speed screens since both seem identical?

Thanks again for all your efforts and continuing to support your personal project.
Marty
Mesa, AZ
USA

[Marty_Escarcega]

Hi fellows threaders, i have been following this thread with some interest, i could really use Steve,s design in my workshop, Allthough i have no ability with the electronic side of the build i can do the mechanical . i would appreciate if someone who has built a last version of the unit to build a unit for me, this of course would be a payed for build. could any one assist?
with regards
\brett

Brett, likely based on our experience and time it took us to build, you'd probably be looking around $300 for a complete unit with 2.5a stepper driver. (less if you are creative in looking for surplus parts) You should check with some friends to see if they have the skills to help you. It is fairly easy to build but you do have to have a fine point soldering iron and some fairly decent soldering skills.

Steve, the originator and supporter of this unit, likely wouldn't take too kindly to someone producing his unit without some sort of compensation. After all, its his electronic design and the programming is his intellectual property. A friend of mine was hand "screening" the boards and drilling them for a nominal fee, to help those that could do it, but it takes time, the good ol post office now broke two of them so he had to redo them at his expense. He's not too willing to build anymore. He is looking into having a few commercially made but doubtful it would be the same price and he'd hate to invest his money in something that would sit until someone wanted one.

Since we now have completed our 2 controllers. I'll take pictures and put up a parts list and our sources soon. I ordered most everything from Allied Electronics. Got the displays from eBay, (came from a China vendor) as well as the 2.5a chopper stepper driver. The Keypad came from Allied but I see that Marlin & Associates has surplus 16 key keypads pretty cheap. Ours were membrane type.

Marty

[kwackers]

Hi Marty,

The low speed setting is what's chosen when the speed is set to '1', the high speed is used when speed is set to '5'.

All other values are interpolated between those settings - so a setting of 3 for example will give values that are half way between low and high.

In theory you'd set the max values so that your motor can turn the table without stalling or mis-stepping. And set the low so that the table turns at the minimum you think you'd ever need (i.e. for cutting whilst turning etc). That way you can chose speeds between those two values.

Hope this helps.

[Marty_Escarcega]

Hi Marty,

The low speed setting is what's chosen when the speed is set to '1', the high speed is used when speed is set to '5'.

All other values are interpolated between those settings - so a setting of 3 for example will give values that are half way between low and high.

In theory you'd set the max values so that your motor can turn the table without stalling or mis-stepping. And set the low so that the table turns at the minimum you think you'd ever need (i.e. for cutting whilst turning etc). That way you can chose speeds between those two values.

Hope this helps.

I guess what confuses me as to why there isn't ONE screen with the MIN MAX speed settings instead of the two which BOTH have MIN MAX settings?
Should both screens have identical Hi Low settings?

Another anomally I noticed last night, while the stepper turns smoothly and find in one direction when jogging, when I turn it in the other direction, it turns but oscillates as it turns. Does not seem to matter the speed settings.
I have 3 identical steppers and all exhibit the same.

Thanks for answering my questions Steve. I (we) really appreciate it!
Marty

[kwackers]

So what you're really asking is, could I have set it up better?
Err, yes.

Actually there's another bit I forgot about, as you rightly point out each screen also has min and max settings. In essence this is to do with acceleration, the motor starts at the min speed and accelerates to the max speed (using the acceleration value).
Bit confusing given the two screens....

So to recap.
The min speed screen is speed 1, max is speed 5 (all other speeds are interpolated).
Each screen has a min speed and max speed, min is what the motor starts to move at and max is the max speed the motor attains (and it uses accel to get there).
Hope that makes sense.

Regards your other problem - I don't picture it. In what way does it oscillate?
There should be absolutely no difference between CW and CCW, all the controller is doing is telling the motor driver to step.
Try disconnecting the direction wire, the motor should now always spin in the same direction regardless of whether you choose CW or CCW and more importantly should behave the same.
If you can pull the direction wire high (or low - depending on how your controller works) and this should change the direction. (You can do this with the +5v line for high and 0v for low). Again the motor should turn smoothly and it will make no difference which direction you choose on the controller.
(You have wired it correctly ;-)

[Marty_Escarcega]

So what you're really asking is, could I have set it up better?
Err, yes.

Actually there's another bit I forgot about, as you rightly point out each screen also has min and max settings. In essence this is to do with acceleration, the motor starts at the min speed and accelerates to the max speed (using the acceleration value).
Bit confusing given the two screens....

So to recap.
The min speed screen is speed 1, max is speed 5 (all other speeds are interpolated).
Each screen has a min speed and max speed, min is what the motor starts to move at and max is the max speed the motor attains (and it uses accel to get there).
Hope that makes sense.

Regards your other problem - I don't picture it. In what way does it oscillate?
There should be absolutely no difference between CW and CCW, all the controller is doing is telling the motor driver to step.
Try disconnecting the direction wire, the motor should now always spin in the same direction regardless of whether you choose CW or CCW and more importantly should behave the same.
If you can pull the direction wire high (or low - depending on how your controller works) and this should change the direction. (You can do this with the +5v line for high and 0v for low). Again the motor should turn smoothly and it will make no difference which direction you choose on the controller.
(You have wired it correctly ;-)

Still a little confused. SO, should the min/max settings in EACH MIN and MAX screen be the same? I'm having a tough time figuring it out. Should both screens have identical MIN MAX settings?

Regards to the oscillation. The motor advances decisively in one direction. It does go back in the other direction but it twitches in the opposite direction. All 3 motors exhibit this.

Thanks Steve

[kwackers]

Ok - I'll do two posts.

First the motor oscillation. I'm still confused by what you mean by this.

Here's the acid test, run the controller in continuous mode (i.e always turning). There should be no difference in the smoothness of the motor whichever direction you choose. If this isn't the case then there's something wrong with the driver/motor combination.

If this is fine and what you're talking about is the motor 'backtracking' slightly (in one direction only) at the end of it's motion, then all you're observing is the backlash being taken up - i.e the controller will rotate the motor past the chosen division and then rotate it back to the correct position. This means all movements complete in the same direction so has to remove any backlash, this is identical to how you'd do it manually.
(If you set the backlash to 0 in settings this won't happen)

[kwackers]

OK, setting speed.

First, when using the device you can choose one of five speeds (shown in the top right of the display: 1 - 5).
Logically enough, 1 is min speed and 5 is max speed.

In setup you can set values for 1 (set min speed) and 5 (set max speed). Speeds in between (2,3,4) are linearly interpolated between the two settings. So for example 3 uses values that are mid way between what you entered in "set min speed" and "set max speed".

So lets say we're going to enter the values for "set max speed".
There are 3 values, lo, hi and ramp.
In simple terms, lo is the speed the motor instantly starts to turn at, hi is the speed the motor eventually reaches and ramp is how fast it gets there.

The reason for these 3 values is that due to inertia you can't just start a stepper motor at it's final speed - you have to start it slower and accelerate it to it's maximum speed. So in this case the setting "hi" is easy - it's the maximum speed (in steps per second) that we get for this speed setting.
Since we must start it slower than this - we set the "lo" setting to a safe (but not too low) value that the motor will easily start to spin at.
Finally we set the ramp value to a number that will accelerate the motor quickly (but safely) to our "hi" value.

So assume we set these values in "max speed" to: lo = 100, hi = 5000, ramp = 10. When we use speed '5' any movement of the motor will start at 100, and increase quickly (10 per step) until it reaches 5000.
The values we choose for max speed are chosen to run the table at the maximum the motor is capable of driving before it stalls. So you may want to start with a value of say 500 and increase it until it stops working. Note that too high a ramp (acceleration) value will cause the motor to stall before it reaches it's maximum speed.

Next I'd do the same with the "min speed" page (for setting 1), choose a "hi" value that gives a speed at setting 1 that is as slow as you think you may need. The lo and ramp values can be copied directly from the high settings (since if they work in there, they'll work in min speed too).

Once min and max are set then the other speeds (2,3,4) will just work.

So to summarise, in reality you set the maximum speed the table can work at in "set max speed", "hi" and the minimum speed you need it to run at in "set min speed", "hi". In both the "lo" and "ramp" values can be the same but are chosen to enable the motor to start to spin and accelerate to the hi values without issue.

To be honest this is more complex than it needs to be since the acceleration isn't linear (ideally it would be), but for this application when I wrote it I felt linear acceleration wasn't important and code simplicity was...

[Marty_Escarcega]

Ok - I'll do two posts.

First the motor oscillation. I'm still confused by what you mean by this.

Here's the acid test, run the controller in continuous mode (i.e always turning). There should be no difference in the smoothness of the motor whichever direction you choose. If this isn't the case then there's something wrong with the driver/motor combination.

If this is fine and what you're talking about is the motor 'backtracking' slightly (in one direction only) at the end of it's motion, then all you're observing is the backlash being taken up - i.e the controller will rotate the motor past the chosen division and then rotate it back to the correct position. This means all movements complete in the same direction so has to remove any backlash, this is identical to how you'd do it manually.
(If you set the backlash to 0 in settings this won't happen)

Yup, you're right! Problem solved! I don't have the motors mounted to my rotab and dividing head yet. I'll know now how and where to set any backlash. Thanks Steve
Marty

[Marty_Escarcega]

OK, setting speed.

The values we choose for max speed are chosen to run the table at the maximum the motor is capable of driving before it stalls. So you may want to start with a value of say 500 and increase it until it stops working. Note that too high a ramp (acceleration) value will cause the motor to stall before it reaches it's maximum speed.

Next I'd do the same with the "min speed" page (for setting 1), choose a "hi" value that gives a speed at setting 1 that is as slow as you think you may need. The lo and ramp values can be copied directly from the high settings (since if they work in there, they'll work in min speed too).

Once min and max are set then the other speeds (2,3,4) will just work.

So to summarise, in reality you set the maximum speed the table can work at in "set max speed", "hi" and the minimum speed you need it to run at in "set min speed", "hi". In both the "lo" and "ramp" values can be the same but are chosen to enable the motor to start to spin and accelerate to the hi values without issue.

To be honest this is more complex than it needs to be since the acceleration isn't linear (ideally it would be), but for this application when I wrote it I felt linear acceleration wasn't important and code simplicity was...

Thanks Steve, I played with the settings and was able to set the low end to 50 and the high end to 1800 with a ramp of 5. I am half stepping the motor.
Any higher while the motor runs fine, I can stall it by grabbing the shaft. So I figured this was a good starting point until I can get the motors mounted to the rotary table. I need to come up with ideas to mount to my Rotab and Dividing head. I sort of wanted to direct drive them. My motor is 300 oz in motors, rotab is a 6" and my dividing head is a 6".

Marty