Which board to buy?
- ScottBouch
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10 Mar 2013 14:42 #31162
by ScottBouch
Replied by ScottBouch on topic Which board to buy?
Hi Andy, Thanks!
My frustration with the Ebay boards is that the only board I csn find with spindle speed control is the one I posted with the pointless keypad and display.
Unfortunately the better kit you shared doesnt have the spindle speed connector.
I think I've figured out a little more about the board in question ( no datasheet, just lookong at their pretty picture).. I think its open ended spindle speed control, I'd have to build my own PIDcontroller externally.
There are two connectors for the spindle, green one (I had thought this was a PWM output), and a white smaller connector (I had believed this to be PWM feedback). However, I now think the Green connector is just a relay output for spindle on/off, and the white connector is just open loop PWM output.
Thanks for the tip about keeping these boards safe, a friend at work has one on his desktop mill (4 axis) with one channel blown, could be that he unplugged live. Lucky fot him he seldom used the 4th axis so still can machine 3 axis!
I think I may contact the sellerto see what price he'd so the kit for with bigger motors and minus the handheld boards.
Thanks again, Scott
My frustration with the Ebay boards is that the only board I csn find with spindle speed control is the one I posted with the pointless keypad and display.
Unfortunately the better kit you shared doesnt have the spindle speed connector.
I think I've figured out a little more about the board in question ( no datasheet, just lookong at their pretty picture).. I think its open ended spindle speed control, I'd have to build my own PIDcontroller externally.
There are two connectors for the spindle, green one (I had thought this was a PWM output), and a white smaller connector (I had believed this to be PWM feedback). However, I now think the Green connector is just a relay output for spindle on/off, and the white connector is just open loop PWM output.
Thanks for the tip about keeping these boards safe, a friend at work has one on his desktop mill (4 axis) with one channel blown, could be that he unplugged live. Lucky fot him he seldom used the 4th axis so still can machine 3 axis!
I think I may contact the sellerto see what price he'd so the kit for with bigger motors and minus the handheld boards.
Thanks again, Scott
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10 Mar 2013 16:53 - 10 Mar 2013 17:30 #31163
by ScottBouch
Replied by ScottBouch on topic Which board to buy?
I've just had a quick play with EMC2 on the trial Ubuntu ISO, and I quite like it!
Andy, with your experience of these Ebay boards, and motor rating, are they 1 size fits all? Ie: do you have to match the motor and machine current demands to the capabilities of the board, or do the boards only come with one type of output stage?
PS, does my Avatar need approvong before it appears? I uploaded it a few days ago.
Cheers, Scott
Andy, with your experience of these Ebay boards, and motor rating, are they 1 size fits all? Ie: do you have to match the motor and machine current demands to the capabilities of the board, or do the boards only come with one type of output stage?
PS, does my Avatar need approvong before it appears? I uploaded it a few days ago.
Cheers, Scott
Last edit: 10 Mar 2013 17:30 by ScottBouch.
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10 Mar 2013 22:57 #31181
by andypugh
No need for anything quite so elaborate. LinuxCNC can run PID in software and vary the output duty cycle of a PWM generator on a spare p-port pin to suit.
To convert pwm to voltage to drive a VFD I have found docs-europe.electrocomponents.com/webdoc...0900766b80f8ba5d.pdf to be ideal.
Note that the boards with a spindle drive output almost certainly only do PWM to voltage for a VFD, they won't drive the spindle directly (in case you are thinking that)
Replied by andypugh on topic Which board to buy?
I think I've figured out a little more about the board in question ( no datasheet, just lookong at their pretty picture).. I think its open ended spindle speed control, I'd have to build my own PIDcontroller externally.
No need for anything quite so elaborate. LinuxCNC can run PID in software and vary the output duty cycle of a PWM generator on a spare p-port pin to suit.
To convert pwm to voltage to drive a VFD I have found docs-europe.electrocomponents.com/webdoc...0900766b80f8ba5d.pdf to be ideal.
Note that the boards with a spindle drive output almost certainly only do PWM to voltage for a VFD, they won't drive the spindle directly (in case you are thinking that)
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11 Mar 2013 03:27 #31190
by ScottBouch
Replied by ScottBouch on topic Which board to buy?
If the frequency of the PWM output is suitable for the motor drive, then I can keep it quite simple by using a low resistance FET or IGBT to drive the motor directly from the PWM output.
My motor is 24Vdc, so using the PWM output from one of these boards, through a transistor circuit will be a simple way of doing it.
My only reason for an external circuit to deal with the speed feedback is that these Chinese boards don't appear to have a feedback connection, so I'd have no way of getting the signal back into the PC.
Although, I did wonder if anyone has tried using the PC's microphone socket as an input? If a signal of 20Hz = 0rpm, and 20Khz = Full spindle rpm, then this could work as simple low cost I/O. You'd only be able to use a variable frequency, not a PWM signal, but this could work just as well...
In fact, if the PC's audio OUT could be driven by EMC2 over a similar frequency range, then spindle demand and feedback could both be done via the audio sockets! Then I could buy the cheaper kit you found with bigger motors and leave the spindle control to the PC's in built I/O!
Cheers, Scott
My motor is 24Vdc, so using the PWM output from one of these boards, through a transistor circuit will be a simple way of doing it.
My only reason for an external circuit to deal with the speed feedback is that these Chinese boards don't appear to have a feedback connection, so I'd have no way of getting the signal back into the PC.
Although, I did wonder if anyone has tried using the PC's microphone socket as an input? If a signal of 20Hz = 0rpm, and 20Khz = Full spindle rpm, then this could work as simple low cost I/O. You'd only be able to use a variable frequency, not a PWM signal, but this could work just as well...
In fact, if the PC's audio OUT could be driven by EMC2 over a similar frequency range, then spindle demand and feedback could both be done via the audio sockets! Then I could buy the cheaper kit you found with bigger motors and leave the spindle control to the PC's in built I/O!
Cheers, Scott
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11 Mar 2013 06:21 #31192
by andypugh
Replied by andypugh on topic Which board to buy?
I think that there are always pins to connect the P-port inputs. They might have arbitrary names (like X-lim etc) but it's entirely up to you what you actually use them for.My only reason for an external circuit to deal with the speed feedback is that these Chinese boards don't appear to have a feedback connection, so I'd have no way of getting the signal back into the PC.
I looked at it briefly, but it seems that low-level access to the sound hardware isn't easy.Although, I did wonder if anyone has tried using the PC's microphone socket as an input? If a signal of 20Hz = 0rpm, and 20Khz = Full spindle rpm, then this could work as simple low cost I/O. You'd only be able to use a variable frequency, not a PWM signal, but this could work just as well...
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11 Mar 2013 16:46 #31210
by ScottBouch
Replied by ScottBouch on topic Which board to buy?
Thanks again Andy,
Shame it's not that easy to use the audio sockets, could have been useful... ho hum...
Thanks for the advice on the use of the other connections on the Chinese boards, I'll have to see what's available on them to use. I had assumed their purpose is just what they are labelled for. Good to know it can be configured to suit.
When I've found out some more data on the boards (An English Datasheet would be good!), IF it turns out that the Parallel port's input pins are not all used by (or not accessible via) the Chinese board; can I hack into the cable to make use of the unused pins? (Obviously opto-isolate etc..) I don't know how flexible EMC2 is in it's configuration, or indeed much a bout the PC Parallel interface. Just trying to think about how to get the most out of as little kit and expense as possible.
Is it generally recommended to use limit switches to feed back to EMC2? I could free up the limit switch inputs as you suggested by just wiring up my limit switches to cut the motor power (Spindle and Steppers) and send a stop command to EMC2. This will save crunching tools at least. Do people use limit switches to help Zero or calibrate their machines movement range?
Learning lots! So glad I'm asking the questions before spending!
Cheers, Scott.
Shame it's not that easy to use the audio sockets, could have been useful... ho hum...
Thanks for the advice on the use of the other connections on the Chinese boards, I'll have to see what's available on them to use. I had assumed their purpose is just what they are labelled for. Good to know it can be configured to suit.
When I've found out some more data on the boards (An English Datasheet would be good!), IF it turns out that the Parallel port's input pins are not all used by (or not accessible via) the Chinese board; can I hack into the cable to make use of the unused pins? (Obviously opto-isolate etc..) I don't know how flexible EMC2 is in it's configuration, or indeed much a bout the PC Parallel interface. Just trying to think about how to get the most out of as little kit and expense as possible.
Is it generally recommended to use limit switches to feed back to EMC2? I could free up the limit switch inputs as you suggested by just wiring up my limit switches to cut the motor power (Spindle and Steppers) and send a stop command to EMC2. This will save crunching tools at least. Do people use limit switches to help Zero or calibrate their machines movement range?
Learning lots! So glad I'm asking the questions before spending!
Cheers, Scott.
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11 Mar 2013 18:45 #31213
by BigJohnT
LinuxCNC is so flexible it can be intimating at times. With all the quality help you can find here and on the IRC and mailing list your sure to find what you need.
If you can spare one input per axis you can share the limits and also use the limit to home to. This will let LinuxCNC know where your axes are so the soft limits work. You can have all the limits on one input but that complicates homing IIRC.
John
Replied by BigJohnT on topic Which board to buy?
I don't know how flexible EMC2 is in it's configuration...
Is it generally recommended to use limit switches to feed back to EMC2? I could free up the limit switch inputs as you suggested by just wiring up my limit switches to cut the motor power (Spindle and Steppers) and send a stop command to EMC2. This will save crunching tools at least. Do people use limit switches to help Zero or calibrate their machines movement range?
Learning lots! So glad I'm asking the questions before spending!
Cheers, Scott.
LinuxCNC is so flexible it can be intimating at times. With all the quality help you can find here and on the IRC and mailing list your sure to find what you need.
If you can spare one input per axis you can share the limits and also use the limit to home to. This will let LinuxCNC know where your axes are so the soft limits work. You can have all the limits on one input but that complicates homing IIRC.
John
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11 Mar 2013 18:49 #31214
by andypugh
LinuxCNC has a Hardware Abstraction Layer which allows you to wire any physical input or output to any software signal. Optionally through functions such as gain and logic blocks. Think of it as a breadboard-in-software.
LinuxCNC is written by geeks, anything you can imagine wanting to do is probably already possible, because someone else wanted to do it. Except for realtime USB.
Replied by andypugh on topic Which board to buy?
Yes, absolutely.When I've found out some more data on the boards (An English Datasheet would be good!), IF it turns out that the Parallel port's input pins are not all used by (or not accessible via) the Chinese board; can I hack into the cable to make use of the unused pins?
It is is as flexible as it is possible to be within the constraints of the parallel port (which specifies that some pins are inputs, some are outputs, and some can be configured both ways as a block). You also don't _have_ to use the parallel port. There are several better interfaces that are supported, but they all cost more.I don't know how flexible EMC2 is in it's configuration,
Yes, absolutely. Limit and home switches are very strongly encouraged. Though it is possible to make all axes share one pin for all the functions.Is it generally recommended to use limit switches to feed back to EMC2?
LinuxCNC has a Hardware Abstraction Layer which allows you to wire any physical input or output to any software signal. Optionally through functions such as gain and logic blocks. Think of it as a breadboard-in-software.
LinuxCNC is written by geeks, anything you can imagine wanting to do is probably already possible, because someone else wanted to do it. Except for realtime USB.
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11 Mar 2013 20:40 - 11 Mar 2013 20:41 #31222
by ScottBouch
It'd be good to learn more about this, is it covered in the manuals? Or does the Wiki contain info on this? Does one have to send a short string of pulses depending on which switch is pressed? or is it a matter of the Software knowing which axis is moving toward and near to the limit at the time of a switch being pressed?
I've seen images of Ladder-Logic on this site, this is something I'm familiar with as a Gas Turbine Controls Engineer - dealing with PLC's is part of my job!
Thanks, Scott
Replied by ScottBouch on topic Which board to buy?
Limit and home switches are very strongly encouraged. Though it is possible to make all axes share one pin for all the functions.
It'd be good to learn more about this, is it covered in the manuals? Or does the Wiki contain info on this? Does one have to send a short string of pulses depending on which switch is pressed? or is it a matter of the Software knowing which axis is moving toward and near to the limit at the time of a switch being pressed?
functions such as gain and logic blocks. Think of it as a breadboard-in-software.
I've seen images of Ladder-Logic on this site, this is something I'm familiar with as a Gas Turbine Controls Engineer - dealing with PLC's is part of my job!
Thanks, Scott
Last edit: 11 Mar 2013 20:41 by ScottBouch.
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11 Mar 2013 21:09 #31227
by andypugh
Replied by andypugh on topic Which board to buy?
Probably. The manuals are pretty good. You probably need to read the Integrator manual.It'd be good to learn more about this, is it covered in the manuals?
The latter. It homes one axis at a time, and during normal use it only knows that a limit has been hit, not which one.Or does the Wiki contain info on this? Does one have to send a short string of pulses depending on which switch is pressed? or is it a matter of the Software knowing which axis is moving toward and near to the limit at the time of a switch being pressed?
There is a software PLC too, though I have never used it. HAL is where the PLC is connected up too. www.linuxcnc.org/docs/html/hal/intro.htmlI've seen images of Ladder-Logic on this site, this is something I'm familiar with as a Gas Turbine Controls Enginee
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