Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
Inductosyn has a major cost advantage over Accupins. It is a copper film bonded to a steel backplate. It is a photo etch process like a circuit board. The slider is the same process with a thin foil protection over it. The slider provides sine and cosine, and the scale reads displacement. They use a varnish to protect the copper left after the etching. Scott On Tuesday, January 25, 2022, 11:55:13 PM CST, Lawrence Glaister wrote: Very cool Sam. It looks like the pin rail may be reproducible, but do you have any idea what the coil pickup structure is? Probably 3 coils... excitation, and the 2 quadrature phase or possibly many coils on a 1." spacing. The concept is very interesting if we could reproduce sensors like this at a reasonable cost. A similar product was call inductosyn I believe. https://www.maccon.com/rotary-linear-encoders/magnetic-encoders/inductosyn.html http://what-when-how.com/electric-motors/linear-and-rotary-inductosyns-electric-motors/ I have seen a similar sensor that used ball bearings in a tube. http://www.newall.com/technology/ this seems to show a good cutaway view. One idea I had was to try and use a ground ball screw as the sensor rail with magnetic pickups on several of the threads. Thus the rod providing the positioning would also provide position feedback of the nut (sensor coils ride on the nut). A slightly different idea (and probably less precise) is to use a rack as the sensor. With optical encoders being so cheap these days, its probably just an academic interest, but any ideas you have on the pickup coil design would be very interesting. cheers Lawrence VE7IT Nanoose Bay BC, Canada ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
On Tue, Jan 25, 2022 at 6:37 PM John Dammeyer wrote: > > So how exactly are you going to count it?Time between the top trace > edge and the bottom trace edge? As you cross the threshold into the next > 0.1" and it mechanically jitters at that point what will you do to not have > counts go wild? > I would guess that something similar to a switch debounce would be used. This can be implemented in software.One simple algorithm is to sample the voltage and wait until you get let's say 5 identical readings. There are other tricks like low pass filtering. But the "N identical" method is easy to do and works well. -- Chris Albertson Redondo Beach, California ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
Very cool Sam. It looks like the pin rail may be reproducible, but do you have any idea what the coil pickup structure is? Probably 3 coils... excitation, and the 2 quadrature phase or possibly many coils on a 1." spacing. The concept is very interesting if we could reproduce sensors like this at a reasonable cost. A similar product was call inductosyn I believe. https://www.maccon.com/rotary-linear-encoders/magnetic-encoders/inductosyn.html http://what-when-how.com/electric-motors/linear-and-rotary-inductosyns-electric-motors/ I have seen a similar sensor that used ball bearings in a tube. http://www.newall.com/technology/ this seems to show a good cutaway view. One idea I had was to try and use a ground ball screw as the sensor rail with magnetic pickups on several of the threads. Thus the rod providing the positioning would also provide position feedback of the nut (sensor coils ride on the nut). A slightly different idea (and probably less precise) is to use a rack as the sensor. With optical encoders being so cheap these days, its probably just an academic interest, but any ideas you have on the pickup coil design would be very interesting. cheers Lawrence VE7IT Nanoose Bay BC, Canada ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
Hi Sam, So how exactly are you going to count it?Time between the top trace edge and the bottom trace edge? As you cross the threshold into the next 0.1" and it mechanically jitters at that point what will you do to not have counts go wild? John > -Original Message- > From: Sam Sokolik [mailto:samco...@gmail.com] > Sent: January-25-22 6:19 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] 60's vintage position feedback.. (GE Accupins) > > https://youtu.be/7HtqwcKDlCk > > On Sun, Jan 23, 2022, 6:47 PM Chris Albertson > wrote: > > > This > > > > On Sun, Jan 23, 2022 at 4:30 PM andy pugh wrote: > > > > > On Sat, 22 Jan 2022 at 04:49, Chris Albertson > > > > > wrote: > > > > > > > > Arduino? Too slow to coune pulses if they happen every 0.0001 inch > > > unless > > > > the table moves slow. > > > > > > As long as it gets a couple of samples every 0.1" it should be fine. > > > Between the pins it's an absolute encoder, like a multi-turn resolver. > > > > > > Though I would still suggest using one of the M4 or M0 boards from > > > Adafruit, as the clock rate and floating point performance are just > > > orders of magnitude higher, for about twice the cost. > > > > > > > That is about what I suggested. "Pico" is a dual core M0. Adafruit has them > > for $4 each. > > https://www.adafruit.com/product/4864 > > So yes, orders of magnitude better but half, not twice the cost. > > > > The price is so low that it is little different from free. That for two > > M0 cores at 125 MHz and 8 of those programmable state machine, also at > > 125MHz. and 2 MB of flash. Very good documentation. > > > > Works with Arduino IDE and runs most Arduio code but you can program it > > with Python too. > > > > > > > > > > > -- > > > atp > > > "A motorcycle is a bicycle with a pandemonium attachment and is > > > designed for the especial use of mechanical geniuses, daredevils and > > > lunatics." > > > � George Fitch, Atlanta Constitution Newspaper, 1912 > > > > > > > > > ___ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > -- > > > > Chris Albertson > > Redondo Beach, California > > > > ___ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
https://youtu.be/7HtqwcKDlCk On Sun, Jan 23, 2022, 6:47 PM Chris Albertson wrote: > This > > On Sun, Jan 23, 2022 at 4:30 PM andy pugh wrote: > > > On Sat, 22 Jan 2022 at 04:49, Chris Albertson > > > wrote: > > > > > > Arduino? Too slow to coune pulses if they happen every 0.0001 inch > > unless > > > the table moves slow. > > > > As long as it gets a couple of samples every 0.1" it should be fine. > > Between the pins it's an absolute encoder, like a multi-turn resolver. > > > > Though I would still suggest using one of the M4 or M0 boards from > > Adafruit, as the clock rate and floating point performance are just > > orders of magnitude higher, for about twice the cost. > > > > That is about what I suggested. "Pico" is a dual core M0. Adafruit has them > for $4 each. > https://www.adafruit.com/product/4864 > So yes, orders of magnitude better but half, not twice the cost. > > The price is so low that it is little different from free. That for two > M0 cores at 125 MHz and 8 of those programmable state machine, also at > 125MHz. and 2 MB of flash. Very good documentation. > > Works with Arduino IDE and runs most Arduio code but you can program it > with Python too. > > > > > > -- > > atp > > "A motorcycle is a bicycle with a pandemonium attachment and is > > designed for the especial use of mechanical geniuses, daredevils and > > lunatics." > > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > > > > ___ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > -- > > Chris Albertson > Redondo Beach, California > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
This On Sun, Jan 23, 2022 at 4:30 PM andy pugh wrote: > On Sat, 22 Jan 2022 at 04:49, Chris Albertson > wrote: > > > > Arduino? Too slow to coune pulses if they happen every 0.0001 inch > unless > > the table moves slow. > > As long as it gets a couple of samples every 0.1" it should be fine. > Between the pins it's an absolute encoder, like a multi-turn resolver. > > Though I would still suggest using one of the M4 or M0 boards from > Adafruit, as the clock rate and floating point performance are just > orders of magnitude higher, for about twice the cost. > That is about what I suggested. "Pico" is a dual core M0. Adafruit has them for $4 each. https://www.adafruit.com/product/4864 So yes, orders of magnitude better but half, not twice the cost. The price is so low that it is little different from free. That for two M0 cores at 125 MHz and 8 of those programmable state machine, also at 125MHz. and 2 MB of flash. Very good documentation. Works with Arduino IDE and runs most Arduio code but you can program it with Python too. > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
On Sat, 22 Jan 2022 at 04:49, Chris Albertson wrote: > > Arduino? Too slow to coune pulses if they happen every 0.0001 inch unless > the table moves slow. As long as it gets a couple of samples every 0.1" it should be fine. Between the pins it's an absolute encoder, like a multi-turn resolver. Though I would still suggest using one of the M4 or M0 boards from Adafruit, as the clock rate and floating point performance are just orders of magnitude higher, for about twice the cost. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
Arduino? Too slow to coune pulses if they happen every 0.0001 inch unless the table moves slow. Look at the new Raspberry Pi "Pico". First off it only costs $4.Next if you looks, it can be programmed in Python and here I the Key: In addition to the two CPU cores it has 8 "PIO" processors and other can count pulses at about 100 MHz.A "PIO is a very fast hardware state machine and there are 8 of these on the chip. Not bad at 4 bucks. You can read the encoders with nearly zero CPU time, no pooling and no interrupts. The PIO is a way-simple processor. It has 8 instructions and 32 words of memory. but that is enough to handle quadrature. These state machines run at 125 Mhz The other thing about Pico, is the outstandingly good documentation. With 8 of these you can do multiple axis. There are several ways to program Pico. You can use the Arduino IDE and most Ardno stuff "just works". Or you can write in Python. uge the Pico into a USB and the PC thinks it is a thin drive. Sve the Python program to the thum drive and the chip is programmed. On Fri, Jan 21, 2022 at 12:59 AM andy pugh wrote: > On Fri, 21 Jan 2022 at 04:50, Sam Sokolik wrote: > > > > https://www.youtube.com/watch?v=ogUdjX3zerY > > > > The plan is to use the arduino to count the phase difference between the > > input and output. The original control used a 250khz clock frequency to > > count > > You might be able to do a lot better than that if you can find a way > to have the Arduino set timers on interrupts. > (How fast does the Arduino run a polling loop?) > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
day 2... https://www.youtube.com/watch?v=UZ6Xuvo6zWs On Fri, Jan 21, 2022 at 9:12 AM Sam Sokolik wrote: > Remember - the excitation signal is 250hz I want to measure wave > form to wave form within that at a minimum of 1000 counts. Not much power > needed.. > > sam > > On Fri, Jan 21, 2022 at 9:09 AM Les Newell > wrote: > >> The only issue on an Uno would be interrupt latency. If you disable all >> other interrupts, latency should be easily low enough. The only real >> advantage of going to ARM is interrupt priority. You could assign the >> sampling interrupt to maximum priority without having to disable other >> interrupts. >> >> Les >> >> On 21/01/2022 14:55, Ralph Stirling wrote: >> > I would suggest starting with a more capable microcontroller. I like >> the $15 Adafruit ItsyBitsy M4 modules, which are programmable with the >> Arduino IDE, but have a 120MHz clock, 32 bit timers, floating point >> hardware, and two 1Mhz 12bit adc's. Their processor is an ATSAMD51 (Cortex >> M4). The original Uno is very limited for precision timing. >> > >> > -- Ralph >> >> >> >> ___ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
Remember - the excitation signal is 250hz I want to measure wave form to wave form within that at a minimum of 1000 counts. Not much power needed.. sam On Fri, Jan 21, 2022 at 9:09 AM Les Newell wrote: > The only issue on an Uno would be interrupt latency. If you disable all > other interrupts, latency should be easily low enough. The only real > advantage of going to ARM is interrupt priority. You could assign the > sampling interrupt to maximum priority without having to disable other > interrupts. > > Les > > On 21/01/2022 14:55, Ralph Stirling wrote: > > I would suggest starting with a more capable microcontroller. I like > the $15 Adafruit ItsyBitsy M4 modules, which are programmable with the > Arduino IDE, but have a 120MHz clock, 32 bit timers, floating point > hardware, and two 1Mhz 12bit adc's. Their processor is an ATSAMD51 (Cortex > M4). The original Uno is very limited for precision timing. > > > > -- Ralph > > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
The only issue on an Uno would be interrupt latency. If you disable all other interrupts, latency should be easily low enough. The only real advantage of going to ARM is interrupt priority. You could assign the sampling interrupt to maximum priority without having to disable other interrupts. Les On 21/01/2022 14:55, Ralph Stirling wrote: I would suggest starting with a more capable microcontroller. I like the $15 Adafruit ItsyBitsy M4 modules, which are programmable with the Arduino IDE, but have a 120MHz clock, 32 bit timers, floating point hardware, and two 1Mhz 12bit adc's. Their processor is an ATSAMD51 (Cortex M4). The original Uno is very limited for precision timing. -- Ralph ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
I would suggest starting with a more capable microcontroller. I like the $15 Adafruit ItsyBitsy M4 modules, which are programmable with the Arduino IDE, but have a 120MHz clock, 32 bit timers, floating point hardware, and two 1Mhz 12bit adc's. Their processor is an ATSAMD51 (Cortex M4). The original Uno is very limited for precision timing. -- Ralph On Jan 21, 2022 6:02 AM, Sam Sokolik wrote: CAUTION: This email originated from outside the Walla Walla University email system. My plan is to use the 16 bit timer on the arduino to trigger on the input square wave rising edge and then count until it see's the return wave form rising edge. (the return waveform will get converted to a square wave) Atleast that is the plan... SO - I guess it comes down to how accurate the phase relationship is between the 2 signals and how high a frequency you are using to count between edgees... On Fri, Jan 21, 2022 at 3:00 AM andy pugh wrote: > On Fri, 21 Jan 2022 at 08:54, andy pugh wrote: > > > You might be able to do a lot better than that if you can find a way > > to have the Arduino set timers on interrupts. > > (How fast does the Arduino run a polling loop?) > > I haven't watched the video yet (I am in a meeting :-) but I am not > clear on how the sampling rate relates to the positional accuracy. > > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.sourceforge.net%2Flists%2Flistinfo%2Femc-usersdata=04%7C01%7Cralph.stirling%40wallawalla.edu%7Cdfa38b93e38b42f0902308d9dce6a271%7Cd958f048e43142779c8debfb75e7aa64%7C0%7C1%7C637783705402242390%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=AOgGXwU5Fbxni7m6GdKayjNCf6jHIFosqzCA6%2B%2FWKHs%3Dreserved=0 > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.sourceforge.net%2Flists%2Flistinfo%2Femc-usersdata=04%7C01%7Cralph.stirling%40wallawalla.edu%7Cdfa38b93e38b42f0902308d9dce6a271%7Cd958f048e43142779c8debfb75e7aa64%7C0%7C1%7C637783705402242390%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=AOgGXwU5Fbxni7m6GdKayjNCf6jHIFosqzCA6%2B%2FWKHs%3Dreserved=0 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
My plan is to use the 16 bit timer on the arduino to trigger on the input square wave rising edge and then count until it see's the return wave form rising edge. (the return waveform will get converted to a square wave) Atleast that is the plan... SO - I guess it comes down to how accurate the phase relationship is between the 2 signals and how high a frequency you are using to count between edgees... On Fri, Jan 21, 2022 at 3:00 AM andy pugh wrote: > On Fri, 21 Jan 2022 at 08:54, andy pugh wrote: > > > You might be able to do a lot better than that if you can find a way > > to have the Arduino set timers on interrupts. > > (How fast does the Arduino run a polling loop?) > > I haven't watched the video yet (I am in a meeting :-) but I am not > clear on how the sampling rate relates to the positional accuracy. > > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
On Fri, 21 Jan 2022 at 08:54, andy pugh wrote: > You might be able to do a lot better than that if you can find a way > to have the Arduino set timers on interrupts. > (How fast does the Arduino run a polling loop?) I haven't watched the video yet (I am in a meeting :-) but I am not clear on how the sampling rate relates to the positional accuracy. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 60's vintage position feedback.. (GE Accupins)
On Fri, 21 Jan 2022 at 04:50, Sam Sokolik wrote: > > https://www.youtube.com/watch?v=ogUdjX3zerY > > The plan is to use the arduino to count the phase difference between the > input and output. The original control used a 250khz clock frequency to > count You might be able to do a lot better than that if you can find a way to have the Arduino set timers on interrupts. (How fast does the Arduino run a polling loop?) -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
[Emc-users] 60's vintage position feedback.. (GE Accupins)
https://www.youtube.com/watch?v=ogUdjX3zerY The plan is to use the arduino to count the phase difference between the input and output. The original control used a 250khz clock frequency to count - the coils are driven with 250hz. So they could divide each .1" pin by 1000. This gave the machine a .0001 resolution. sam ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
