Does this chip exsist?

I have an old indexer controller that drives a stepper motor directly.
The controller is a programmable unit that is made to interface with a
machine tool, for example a CNC mill. The controller is made to drive
a stepper motor directly. I do not have the original indexer. Which
doesn't matter because I am building a special one for one of my
machines. The controller has no provisions for position feedback so if
steps are missed scrap parts might be the result. I have been using
Gecko Drives that accept step and direction input and drive a servo
motor. The drive itself closes the loop so that if a position error
happens the drive shuts down and provides a signal which I can use to
stop the CNC mill. So I have been looking for a chip that will accept
the 6 0r 4 wire stepper motor signals and output step and direction.
It seems like this device must exsist but I must be using the wrong
search terms. Anybody here know of such a device? I could just connect
a stepper to an encoder and use the encoder signals for step and
direction, because I have the chips that convert encoder signals to
step and direction, but that seems kind of kludgy.
Thanks,
Eric

 

[Tim Wescott]

On Tue, 24 Jun 2014 08:58:48 -0700, etpm wrote:

I have an old indexer controller that drives a stepper motor directly.
The controller is a programmable unit that is made to interface with a
machine tool, for example a CNC mill. The controller is made to drive a
stepper motor directly. I do not have the original indexer. Which
doesn't matter because I am building a special one for one of my
machines. The controller has no provisions for position feedback so if
steps are missed scrap parts might be the result. I have been using
Gecko Drives that accept step and direction input and drive a servo
motor. The drive itself closes the loop so that if a position error
happens the drive shuts down and provides a signal which I can use to
stop the CNC mill. So I have been looking for a chip that will accept
the 6 0r 4 wire stepper motor signals and output step and direction. It
seems like this device must exsist but I must be using the wrong search
terms. Anybody here know of such a device? I could just connect a
stepper to an encoder and use the encoder signals for step and
direction, because I have the chips that convert encoder signals to step
and direction, but that seems kind of kludgy.
Thanks,
Eric

There's a problem with all these cool little specialist applications that
you'd like to just buy a chip and solder it into your circuit.

The problem is that the chip that does that is called a "microcontroller",
and all you need to do is add some programming. I'm almost certain
that's what the Gekko does -- it's what nearly any company that's
producing between 10 and 10,000 a year wants.

A 4-wire stepper motor signal should be pretty close to an encoder
signal: if no microstepping is going on then the stepper drive is pretty
much encoder A, encoder B, not encoder A and not encoder B, with a whole
lot more current drive capability than an encoder would ever produce. If
you couldn't just ignore the "not" side, you could get to an encoder
output pretty quickly with some resistor networks and a couple of
comparators.

I'm pretty sure you could do something similar with the 6-wire encoder,
but I've never messed around with those, so I'd be talking through my hat.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Maynard A. Philbrook Jr.]

In article <2l6jq9987post4m0e7llr74kckbtg0c0so@4ax.com>,
etpm@whidbey.com says...

I have an old indexer controller that drives a stepper motor directly.
The controller is a programmable unit that is made to interface with a
machine tool, for example a CNC mill. The controller is made to drive
a stepper motor directly. I do not have the original indexer. Which
doesn't matter because I am building a special one for one of my
machines. The controller has no provisions for position feedback so if
steps are missed scrap parts might be the result. I have been using
Gecko Drives that accept step and direction input and drive a servo
motor. The drive itself closes the loop so that if a position error
happens the drive shuts down and provides a signal which I can use to
stop the CNC mill. So I have been looking for a chip that will accept
the 6 0r 4 wire stepper motor signals and output step and direction.
It seems like this device must exsist but I must be using the wrong
search terms. Anybody here know of such a device? I could just connect
a stepper to an encoder and use the encoder signals for step and
direction, because I have the chips that convert encoder signals to
step and direction, but that seems kind of kludgy.
Thanks,
Eric

If you're using a Full step output, which you should be for maximum
holding torque, a pair of Data RS flip flips will convert the signal
to two different outputs left or right turn pulses.
The output of a full step looks like a quadrature encoder so there
are overlapping signals. You do need to buffer the signal to prevent
over voltage to your converting electronics.

if you use two Data flip flops with a clr pin(Reset) you can get
a Up/down signal pulse. CW would produce a pulse output while the
other output would produce nothing.. etc.
since the motor outputs of coil 1 and coil 2 act as A and B
channel encoders you can decode them like an quadrature encoder.

I'll try to explain the lay out.

On each ff, connect the data pin and CLR pin together.
FF-A clock pin connects to FF-B Data+Clr pin.
FF-B clock pin connects to FF-A Data+Clr pin.

FF-A clock pin will be the input signal from a A channel encoder
FF-B clock pin will be the input signal from a B channel encoder

FF-A Q (output) will be CW (clock wise) pulses.
FF-B Q (output) will be CCW pules.


This gives you two separate pulse outputs, CW and CWW.

If you are half stepping your motors then things get messy..

Jamie

 

On Tue, 24 Jun 2014 18:34:00 -0500, Tim Wescott
<tim@seemywebsite.really> wrote:

On Tue, 24 Jun 2014 08:58:48 -0700, etpm wrote:

I have an old indexer controller that drives a stepper motor directly.
The controller is a programmable unit that is made to interface with a
machine tool, for example a CNC mill. The controller is made to drive a
stepper motor directly. I do not have the original indexer. Which
doesn't matter because I am building a special one for one of my
machines. The controller has no provisions for position feedback so if
steps are missed scrap parts might be the result. I have been using
Gecko Drives that accept step and direction input and drive a servo
motor. The drive itself closes the loop so that if a position error
happens the drive shuts down and provides a signal which I can use to
stop the CNC mill. So I have been looking for a chip that will accept
the 6 0r 4 wire stepper motor signals and output step and direction. It
seems like this device must exsist but I must be using the wrong search
terms. Anybody here know of such a device? I could just connect a
stepper to an encoder and use the encoder signals for step and
direction, because I have the chips that convert encoder signals to step
and direction, but that seems kind of kludgy.
Thanks,
Eric

There's a problem with all these cool little specialist applications that
you'd like to just buy a chip and solder it into your circuit.

The problem is that the chip that does that is called a "microcontroller",
and all you need to do is add some programming. I'm almost certain
that's what the Gekko does -- it's what nearly any company that's
producing between 10 and 10,000 a year wants.

A 4-wire stepper motor signal should be pretty close to an encoder
signal: if no microstepping is going on then the stepper drive is pretty
much encoder A, encoder B, not encoder A and not encoder B, with a whole
lot more current drive capability than an encoder would ever produce. If
you couldn't just ignore the "not" side, you could get to an encoder
output pretty quickly with some resistor networks and a couple of
comparators.

I'm pretty sure you could do something similar with the 6-wire encoder,
but I've never messed around with those, so I'd be talking through my hat.

Greetings Tim,
I was thinking about the encoder business which is why I thought there
mightg be a chip. Since it's a 6 wire stepper with 2 wires being
common and always connected to the positive supply it means that the
stepper is being driven in unipolar mode. I should have said this in
my first post. Becuase it is a unipolar drive the 4 wires will always
be powered in pairs if the drive is full stepping. I am assuming it is
because this would result in the most torque which is important to the
drive. Though I have the drive I do not have the indexer it was
originally connected to. The drive can only be moved by programming a
certain amount of rotation in degrees or part of a degree or by
pressing the jog button which just causes the stepper to rotate
continuously. There is no single step provision. Anyway, assuming
unipolar full step drive the wires would be energised in the order
below:
1&2
2&3
3&4
4&1
Or the opposite for opposite rotation.
My encoders have two channels, A & B. The signals from the encoders,
when read in quadrature, are below:
A high
B high
A low
B low
There are 4 MOSFETs in the drive. I should be able to use the signals
to the gates of these MOSFETs to somehow emulate the signals from an
encoder. So when 1&2 are high I need +5 volts. When 2&3 are high +5
volts. 3&4 high 0 volts. 4&1 high 0 volts. I was hoping there was a
chip that did exactly this. I could use a microcontroller. I think I
would rather use discrete logic. I just wanna wire it up once and have
it work.
Eric

 

On Tue, 24 Jun 2014 21:23:32 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <2l6jq9987post4m0e7llr74kckbtg0c0so@4ax.com>,
etpm@whidbey.com says...

I have an old indexer controller that drives a stepper motor directly.
The controller is a programmable unit that is made to interface with a
machine tool, for example a CNC mill. The controller is made to drive
a stepper motor directly. I do not have the original indexer. Which
doesn't matter because I am building a special one for one of my
machines. The controller has no provisions for position feedback so if
steps are missed scrap parts might be the result. I have been using
Gecko Drives that accept step and direction input and drive a servo
motor. The drive itself closes the loop so that if a position error
happens the drive shuts down and provides a signal which I can use to
stop the CNC mill. So I have been looking for a chip that will accept
the 6 0r 4 wire stepper motor signals and output step and direction.
It seems like this device must exsist but I must be using the wrong
search terms. Anybody here know of such a device? I could just connect
a stepper to an encoder and use the encoder signals for step and
direction, because I have the chips that convert encoder signals to
step and direction, but that seems kind of kludgy.
Thanks,
Eric

If you're using a Full step output, which you should be for maximum
holding torque, a pair of Data RS flip flips will convert the signal
to two different outputs left or right turn pulses.
The output of a full step looks like a quadrature encoder so there
are overlapping signals. You do need to buffer the signal to prevent
over voltage to your converting electronics.

if you use two Data flip flops with a clr pin(Reset) you can get
a Up/down signal pulse. CW would produce a pulse output while the
other output would produce nothing.. etc.
since the motor outputs of coil 1 and coil 2 act as A and B
channel encoders you can decode them like an quadrature encoder.

I'll try to explain the lay out.

On each ff, connect the data pin and CLR pin together.
FF-A clock pin connects to FF-B Data+Clr pin.
FF-B clock pin connects to FF-A Data+Clr pin.

FF-A clock pin will be the input signal from a A channel encoder
FF-B clock pin will be the input signal from a B channel encoder

FF-A Q (output) will be CW (clock wise) pulses.
FF-B Q (output) will be CCW pules.


This gives you two separate pulse outputs, CW and CWW.

If you are half stepping your motors then things get messy..

Jamie

Greetings Jamie,
I sorta understand what you are saying above. If you read my reply to
Tim you will see that you are correct about the full steps. From your
reply above it looks like all I get are either CW or CCW pulses. What
I ultimately need is pulses and direction outputs. So if I can convert
the motor coil on and off states into regular quadrature encoder type
outputs I can use those signals with a chip I have to get two outputs.
One is high or low depending on whether it is CW or CCW and the other
goes high for each step. With the FF version above maybe I can
eliminate the chip that goes between encoder type outputs and the
GeckoDrive. But I can't just use CW and CCW pulses. The GeckoDrive
wants pulses on one input for each step and high or low to tell it
which direction on the other input.
Cheers,
Eric

 

[Tim Wescott]

On Wed, 25 Jun 2014 16:04:58 -0700, etpm wrote:

On Tue, 24 Jun 2014 18:34:00 -0500, Tim Wescott
tim@seemywebsite.really> wrote:

On Tue, 24 Jun 2014 08:58:48 -0700, etpm wrote:

I have an old indexer controller that drives a stepper motor directly.
The controller is a programmable unit that is made to interface with a
machine tool, for example a CNC mill. The controller is made to drive
a stepper motor directly. I do not have the original indexer. Which
doesn't matter because I am building a special one for one of my
machines. The controller has no provisions for position feedback so if
steps are missed scrap parts might be the result. I have been using
Gecko Drives that accept step and direction input and drive a servo
motor. The drive itself closes the loop so that if a position error
happens the drive shuts down and provides a signal which I can use to
stop the CNC mill. So I have been looking for a chip that will accept
the 6 0r 4 wire stepper motor signals and output step and direction.
It seems like this device must exsist but I must be using the wrong
search terms. Anybody here know of such a device? I could just connect
a stepper to an encoder and use the encoder signals for step and
direction, because I have the chips that convert encoder signals to
step and direction, but that seems kind of kludgy.
Thanks,
Eric

There's a problem with all these cool little specialist applications
that you'd like to just buy a chip and solder it into your circuit.

The problem is that the chip that does that is called a
"microcontroller",
and all you need to do is add some programming. I'm almost certain
that's what the Gekko does -- it's what nearly any company that's
producing between 10 and 10,000 a year wants.

A 4-wire stepper motor signal should be pretty close to an encoder
signal: if no microstepping is going on then the stepper drive is pretty
much encoder A, encoder B, not encoder A and not encoder B, with a whole
lot more current drive capability than an encoder would ever produce.
If you couldn't just ignore the "not" side, you could get to an encoder
output pretty quickly with some resistor networks and a couple of
comparators.

I'm pretty sure you could do something similar with the 6-wire encoder,
but I've never messed around with those, so I'd be talking through my
hat.
Greetings Tim,
I was thinking about the encoder business which is why I thought there
mightg be a chip. Since it's a 6 wire stepper with 2 wires being common
and always connected to the positive supply it means that the stepper is
being driven in unipolar mode. I should have said this in my first post.
Becuase it is a unipolar drive the 4 wires will always be powered in
pairs if the drive is full stepping. I am assuming it is because this
would result in the most torque which is important to the drive. Though
I have the drive I do not have the indexer it was originally connected
to. The drive can only be moved by programming a certain amount of
rotation in degrees or part of a degree or by pressing the jog button
which just causes the stepper to rotate continuously. There is no single
step provision. Anyway, assuming unipolar full step drive the wires
would be energised in the order below:
1&2 2&3 3&4 4&1 Or the opposite for opposite rotation.
My encoders have two channels, A & B. The signals from the encoders,
when read in quadrature, are below:
A high B high A low B low There are 4 MOSFETs in the drive. I should be
able to use the signals to the gates of these MOSFETs to somehow emulate
the signals from an encoder. So when 1&2 are high I need +5 volts. When
2&3 are high +5 volts. 3&4 high 0 volts. 4&1 high 0 volts. I was hoping
there was a chip that did exactly this. I could use a microcontroller. I
think I would rather use discrete logic. I just wanna wire it up once
and have it work.
Eric

Basically 3 is only energized when 1 isn't. Ditto 2 & 4.

Feed 1 into channel A, 2 into channel B, enjoy.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Maynard A. Philbrook Jr.]

In article <tcmmq9hccnulp5n9rekac4fqqh0kefsf0n@4ax.com>,
etpm@whidbey.com says...

reetings Jamie,
I sorta understand what you are saying above. If you read my reply to
Tim you will see that you are correct about the full steps. From your
reply above it looks like all I get are either CW or CCW pulses. What
I ultimately need is pulses and direction outputs. So if I can convert
the motor coil on and off states into regular quadrature encoder type
outputs I can use those signals with a chip I have to get two outputs.
One is high or low depending on whether it is CW or CCW and the other
goes high for each step. With the FF version above maybe I can
eliminate the chip that goes between encoder type outputs and the
GeckoDrive. But I can't just use CW and CCW pulses. The GeckoDrive
wants pulses on one input for each step and high or low to tell it
which direction on the other input.
Cheers,
Eric

A data flip flop can capture direction.

Data input reads coil ONE for A channel and
and coil 2 used as the clock pulse to capture
the data and latch it to the output..

These signals are 90 degrees out of phase so it
works out fine. In the end what you get is a digital
signal that is ether High or low, depending on the direction
you are going. Since a FF has Q and a Q not (complementary)
outputs, you can use it to drive independent FWD and REV
inputs of some controller.

We have done that ourself on a machine that had a frequency
to voltage converter coming from an encoder. The problem was
that the converter didn't know which direction the encoder was
turning and that was very important because the machine would
get confused and do something damaging at times. I employed that Data
flip floppy thing so that I could get a digital signal that would allow
the frequency to pass to the converter only when it was going the
correct
direction, if not, I simply clamped the signal. Worked out fine.

As for a pulse I guess you can take it from one of the coils?

Jamie

 

[Jasen Betts]

On 2014-06-24, etpm@whidbey.com <etpm@whidbey.com> wrote:

I have an old indexer controller that drives a stepper motor directly.
The controller is a programmable unit that is made to interface with a
machine tool, for example a CNC mill. The controller is made to drive
a stepper motor directly. I do not have the original indexer. Which
doesn't matter because I am building a special one for one of my
machines. The controller has no provisions for position feedback so if
steps are missed scrap parts might be the result.

Or broken tools.

I have been using Gecko Drives that accept step and direction input
and drive a servo motor. The drive itself closes the loop so that
if a position error happens the drive shuts down and provides a signal
which I can use to stop the CNC mill. So I have been looking for a chip
that will accept the 6 0r 4 wire stepper motor signals and output step
and direction. It seems like this device must exsist but I must be using
the wrong search terms.

that sounds like the sort of thing that could ve done with about 5
CMOS logic chips or an 8-bit microcontroller.

Anybody here know of such a device? I could just connect
a stepper to an encoder and use the encoder signals for step and
direction, because I have the chips that convert encoder signals to
step and direction, but that seems kind of kludgy.

How different are encoder outputs to stepper inputs?

might be just some resistors needed.

If you're half stepping I'm thinking maybe a quad XOR and
some resistors.

Of course this all turns to shit if you're microstepping.

--
umop apisdn


--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Tim Wescott]

On Wed, 25 Jun 2014 21:21:25 -0400, Maynard A. Philbrook Jr. wrote:

In article <tcmmq9hccnulp5n9rekac4fqqh0kefsf0n@4ax.com>,
etpm@whidbey.com says...
reetings Jamie,
I sorta understand what you are saying above. If you read my reply to
Tim you will see that you are correct about the full steps. From your
reply above it looks like all I get are either CW or CCW pulses. What I
ultimately need is pulses and direction outputs. So if I can convert
the motor coil on and off states into regular quadrature encoder type
outputs I can use those signals with a chip I have to get two outputs.
One is high or low depending on whether it is CW or CCW and the other
goes high for each step. With the FF version above maybe I can
eliminate the chip that goes between encoder type outputs and the
GeckoDrive. But I can't just use CW and CCW pulses. The GeckoDrive
wants pulses on one input for each step and high or low to tell it
which direction on the other input.
Cheers,
Eric



A data flip flop can capture direction.

Data input reads coil ONE for A channel and and coil 2 used as the
clock pulse to capture
the data and latch it to the output..

These signals are 90 degrees out of phase so it
works out fine. In the end what you get is a digital signal that is
ether High or low, depending on the direction you are going. Since a FF
has Q and a Q not (complementary)
outputs, you can use it to drive independent FWD and REV inputs of some
controller.

We have done that ourself on a machine that had a frequency
to voltage converter coming from an encoder. The problem was that the
converter didn't know which direction the encoder was turning and that
was very important because the machine would get confused and do
something damaging at times. I employed that Data flip floppy thing so
that I could get a digital signal that would allow the frequency to pass
to the converter only when it was going the correct direction, if not, I
simply clamped the signal. Worked out fine.

As for a pulse I guess you can take it from one of the coils?

Jamie

That works in the main, but as the mechanism comes to a stop it can fail
miserably -- if the "clock" channel is dithering while the "data" channel
is stuck on high or low, then you'll register a lot of motion in one
direction when what's really happening is no motion at all. Even if it's
a "clean, no dither" system, you still have troubles keeping an exact
count when you reverse direction.

If Eric has an existing chip and knows how to use it with an encoder
input, then that's probably the best way to go. If he can't get the chip
anymore (aren't those obsolete yet???) then it'd be a simple thing to
code into a microprocessor, or a PAL if you have a clock input to it, or
three or four logic chips, including the 555 timer.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Maynard A. Philbrook Jr.]

In article <PradnQE_JJ2K2jLOnZ2dnUVZ5rydnZ2d@giganews.com>,
tim@seemywebsite.really says...

hat works in the main, but as the mechanism comes to a stop it can fail
miserably -- if the "clock" channel is dithering while the "data" channel
is stuck on high or low, then you'll register a lot of motion in one
direction when what's really happening is no motion at all. Even if it's
a "clean, no dither" system, you still have troubles keeping an exact
count when you reverse direction.

If Eric has an existing chip and knows how to use it with an encoder
input, then that's probably the best way to go. If he can't get the chip
anymore (aren't those obsolete yet???) then it'd be a simple thing to
code into a microprocessor, or a PAL if you have a clock input to it, or
three or four logic chips, including the 555 timer.

Don't know what to tell ya, it works for me.

two edge data flip flops for pulse reading in either
direction as I explained earlier and it works fine, I
use it with no loses.

As for direction and count pulse you don't need to use a
quadrature detection for a stand alone that was just an example I
used that only needed to know one direction You can use the steps I
outlined for pulse detection in either direction that offer a separate
output for each direction. From that, you use a RS flip
flop to set the direction state from either output..

And if you want to integrate it down to a single pulse output that
can be done via an OR gate.

For some reason I think you have your mind wrapped around a non edge
trigger data flop.

Jamie

 

[Jasen Betts]

On 2014-06-29, Maynard A. Philbrook Jr. <jamie_ka1lpa@charter.net> wrote:

In article <PradnQE_JJ2K2jLOnZ2dnUVZ5rydnZ2d@giganews.com>,
tim@seemywebsite.really says...
hat works in the main, but as the mechanism comes to a stop it can fail
miserably -- if the "clock" channel is dithering while the "data" channel
is stuck on high or low, then you'll register a lot of motion in one
direction when what's really happening is no motion at all. Even if it's
a "clean, no dither" system, you still have troubles keeping an exact
count when you reverse direction.

If Eric has an existing chip and knows how to use it with an encoder
input, then that's probably the best way to go. If he can't get the chip
anymore (aren't those obsolete yet???) then it'd be a simple thing to
code into a microprocessor, or a PAL if you have a clock input to it, or
three or four logic chips, including the 555 timer.


Don't know what to tell ya, it works for me.

two edge data flip flops for pulse reading in either
direction as I explained earlier and it works fine, I
use it with no loses.

it sounds like it would only output once per cycle. so there would be
quite a lot of slop.


--
umop apisdn


--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Tim Wescott]

On Sat, 28 Jun 2014 20:58:51 -0400, Maynard A. Philbrook Jr. wrote:

In article <PradnQE_JJ2K2jLOnZ2dnUVZ5rydnZ2d@giganews.com>,
tim@seemywebsite.really says...
hat works in the main, but as the mechanism comes to a stop it can fail
miserably -- if the "clock" channel is dithering while the "data"
channel is stuck on high or low, then you'll register a lot of motion
in one direction when what's really happening is no motion at all.
Even if it's a "clean, no dither" system, you still have troubles
keeping an exact count when you reverse direction.

If Eric has an existing chip and knows how to use it with an encoder
input, then that's probably the best way to go. If he can't get the
chip anymore (aren't those obsolete yet???) then it'd be a simple thing
to code into a microprocessor, or a PAL if you have a clock input to
it, or three or four logic chips, including the 555 timer.


Don't know what to tell ya, it works for me.

two edge data flip flops for pulse reading in either
direction as I explained earlier and it works fine, I use it with no
loses.

As for direction and count pulse you don't need to use a
quadrature detection for a stand alone that was just an example I used
that only needed to know one direction You can use the steps I outlined
for pulse detection in either direction that offer a separate output for
each direction. From that, you use a RS flip flop to set the direction
state from either output..

And if you want to integrate it down to a single pulse output that
can be done via an OR gate.

For some reason I think you have your mind wrapped around a non edge
trigger data flop.

For some reason, having fixed numerous broken systems that use that
method or variations of it has poisoned my mind against it. The
designers of those systems insisted that they worked well, too -- often
while they were watching it go out, stop, reverse, then fail to come back
to the place where it started.

Like I said, it works fine as long as all you need is velocity, or if you
can get by with some cumulative error, particularly if you're not
stopping and starting or stopping and reversing. But if your problem
does not meet all those conditions, then it doesn't work so well.

But you don't have to take my word for it! Just look at your own
description, and engage your brain! What happens when your A input says
"forward" and your B input is dithering up and down? I'll tell you --
you're getting a signal out that says "go, go, go!" at the same time that
your actual mechanism is sitting still, or barely vibrating. So if you
have to get accurate encoder outputs in a situation where the mechanism
can come to a stop (or almost to a stop), then your suggested method is a
no-go.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

On Wed, 25 Jun 2014 18:33:48 -0500, Tim Wescott
<tim@seemywebsite.really> wrote:

On Wed, 25 Jun 2014 16:04:58 -0700, etpm wrote:

On Tue, 24 Jun 2014 18:34:00 -0500, Tim Wescott
tim@seemywebsite.really> wrote:

On Tue, 24 Jun 2014 08:58:48 -0700, etpm wrote:

I have an old indexer controller that drives a stepper motor directly.
The controller is a programmable unit that is made to interface with a
machine tool, for example a CNC mill. The controller is made to drive
a stepper motor directly. I do not have the original indexer. Which
doesn't matter because I am building a special one for one of my
machines. The controller has no provisions for position feedback so if
steps are missed scrap parts might be the result. I have been using
Gecko Drives that accept step and direction input and drive a servo
motor. The drive itself closes the loop so that if a position error
happens the drive shuts down and provides a signal which I can use to
stop the CNC mill. So I have been looking for a chip that will accept
the 6 0r 4 wire stepper motor signals and output step and direction.
It seems like this device must exsist but I must be using the wrong
search terms. Anybody here know of such a device? I could just connect
a stepper to an encoder and use the encoder signals for step and
direction, because I have the chips that convert encoder signals to
step and direction, but that seems kind of kludgy.
Thanks,
Eric

There's a problem with all these cool little specialist applications
that you'd like to just buy a chip and solder it into your circuit.

The problem is that the chip that does that is called a
"microcontroller",
and all you need to do is add some programming. I'm almost certain
that's what the Gekko does -- it's what nearly any company that's
producing between 10 and 10,000 a year wants.

A 4-wire stepper motor signal should be pretty close to an encoder
signal: if no microstepping is going on then the stepper drive is pretty
much encoder A, encoder B, not encoder A and not encoder B, with a whole
lot more current drive capability than an encoder would ever produce.
If you couldn't just ignore the "not" side, you could get to an encoder
output pretty quickly with some resistor networks and a couple of
comparators.

I'm pretty sure you could do something similar with the 6-wire encoder,
but I've never messed around with those, so I'd be talking through my
hat.
Greetings Tim,
I was thinking about the encoder business which is why I thought there
mightg be a chip. Since it's a 6 wire stepper with 2 wires being common
and always connected to the positive supply it means that the stepper is
being driven in unipolar mode. I should have said this in my first post.
Becuase it is a unipolar drive the 4 wires will always be powered in
pairs if the drive is full stepping. I am assuming it is because this
would result in the most torque which is important to the drive. Though
I have the drive I do not have the indexer it was originally connected
to. The drive can only be moved by programming a certain amount of
rotation in degrees or part of a degree or by pressing the jog button
which just causes the stepper to rotate continuously. There is no single
step provision. Anyway, assuming unipolar full step drive the wires
would be energised in the order below:
1&2 2&3 3&4 4&1 Or the opposite for opposite rotation.
My encoders have two channels, A & B. The signals from the encoders,
when read in quadrature, are below:
A high B high A low B low There are 4 MOSFETs in the drive. I should be
able to use the signals to the gates of these MOSFETs to somehow emulate
the signals from an encoder. So when 1&2 are high I need +5 volts. When
2&3 are high +5 volts. 3&4 high 0 volts. 4&1 high 0 volts. I was hoping
there was a chip that did exactly this. I could use a microcontroller. I
think I would rather use discrete logic. I just wanna wire it up once
and have it work.
Eric

Basically 3 is only energized when 1 isn't. Ditto 2 & 4.

Feed 1 into channel A, 2 into channel B, enjoy.

Greetings Tim,
I haven't been able to mess with the indexer because of time issues
but will have time in a week or so to try your advice. I will be using
the outputs from the transistors that turn on the mosfets for my
signals.
Eric

 

On 28 Jun 2014 06:32:27 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2014-06-24, etpm@whidbey.com <etpm@whidbey.com> wrote:
I have an old indexer controller that drives a stepper motor directly.
The controller is a programmable unit that is made to interface with a
machine tool, for example a CNC mill. The controller is made to drive
a stepper motor directly. I do not have the original indexer. Which
doesn't matter because I am building a special one for one of my
machines. The controller has no provisions for position feedback so if
steps are missed scrap parts might be the result.

Or broken tools.

I have been using Gecko Drives that accept step and direction input
and drive a servo motor. The drive itself closes the loop so that
if a position error happens the drive shuts down and provides a signal
which I can use to stop the CNC mill. So I have been looking for a chip
that will accept the 6 0r 4 wire stepper motor signals and output step
and direction. It seems like this device must exsist but I must be using
the wrong search terms.

that sounds like the sort of thing that could ve done with about 5
CMOS logic chips or an 8-bit microcontroller.

Anybody here know of such a device? I could just connect
a stepper to an encoder and use the encoder signals for step and
direction, because I have the chips that convert encoder signals to
step and direction, but that seems kind of kludgy.

How different are encoder outputs to stepper inputs?

might be just some resistors needed.

If you're half stepping I'm thinking maybe a quad XOR and
some resistors.

Of course this all turns to shit if you're microstepping.

I don't know if the indexer is microstepping. But I don't think it is
because of the load it was driving and the resolution of the system
according to the manual. It will be a hassle if the thing microsteps.
The chips I have that use the signals from encoders and convert to
step and direction are still available from US Digital. I use them for
electronic gearing setups where I use spindle rotation to advance a
linear axis on a machine tool.
Eric