Quadrature Encoder interfacing the BS2
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Posts: 46,084
Hello,
New to the group here and STAMP.
My original plan was to use the BS2 to take in quadrature inputs of
up to 1000ppr or per inch for linear position and angle measurements.
The counter and associated data would be output in a specific string
format, receivable by dedicated external devices for Blind personnel
adaptive equipment. This could open the door for more "VOICE" display
interfaces.
Now that I have searched the archive files and found the BS2 may have
limitations of less than 100ppr directly connected, I am considering
the external circuitry required to do the quad/counting.
The string output from the BS2 would have a max of 10 times/min.
Theoretically, a condition exists there in, where counts could be
missed while doing this portion of the program with no
buffer/interrupt to catch incoming changes of state.
The US Digital IC LS7266/7166 has the quadrature up/dn count taken
care of but not the storage of counts. If this be the case then, it
would only be cutting the count period by 4. Still in a pinch if an
axis moved at a rate greater than 100 pulses in the same time frame
to a BS2 input limit, considering the programs loop time as the
program grows. That makes a decade counter array or buffer necessary
along with a means of tranfering the data to the BS2.
The critical factor is the input timing vs program runtime. The
output is only upon request by a button press. The input should not
be changing at the same time, but if it does, precision could be
compromised by accumulated error.
Any successes/experiences out there under similar circumstances?
If so, what did the input conditioning circuitry consist of?
Having already purchased the BS2 BOE and OEM's, I wonder if I have
been mislead for this application?
TIA,
Doug
New to the group here and STAMP.
My original plan was to use the BS2 to take in quadrature inputs of
up to 1000ppr or per inch for linear position and angle measurements.
The counter and associated data would be output in a specific string
format, receivable by dedicated external devices for Blind personnel
adaptive equipment. This could open the door for more "VOICE" display
interfaces.
Now that I have searched the archive files and found the BS2 may have
limitations of less than 100ppr directly connected, I am considering
the external circuitry required to do the quad/counting.
The string output from the BS2 would have a max of 10 times/min.
Theoretically, a condition exists there in, where counts could be
missed while doing this portion of the program with no
buffer/interrupt to catch incoming changes of state.
The US Digital IC LS7266/7166 has the quadrature up/dn count taken
care of but not the storage of counts. If this be the case then, it
would only be cutting the count period by 4. Still in a pinch if an
axis moved at a rate greater than 100 pulses in the same time frame
to a BS2 input limit, considering the programs loop time as the
program grows. That makes a decade counter array or buffer necessary
along with a means of tranfering the data to the BS2.
The critical factor is the input timing vs program runtime. The
output is only upon request by a button press. The input should not
be changing at the same time, but if it does, precision could be
compromised by accumulated error.
Any successes/experiences out there under similar circumstances?
If so, what did the input conditioning circuitry consist of?
Having already purchased the BS2 BOE and OEM's, I wonder if I have
been mislead for this application?
TIA,
Doug
Comments
The US Digital IC LS7266/7166 does store counts for you.
That's the beauty of this chip, it takes care of all the up/down counting
and count storage plus synchronizes latching of the count so the
multi-byte read doesn't get confused during interbyte count rollover.
Your program can be busy doing whatever and when it's ready to
get the counts, you send a count latch command and read the
latched value. The 7266/7166 won't miss any counts.
I don't think you will need the decade counter or buffer.
You may contact me privately if you need an example
of the hardware interface to the stamp and some starter
code. I did a project a couple years ago to use the encoders
and interface chip for reading telescope position.
Hope this helps,
Dennis
In a message dated 8/19/2002 7:59:37 PM Central Daylight Time,
basicstamps@yahoogroups.com writes:
> Date: Mon, 19 Aug 2002 03:32:16 -0000
> From: "sleyed" <Sleyed@a...>
> Subject: Quadrature Encoder interfacing the BS2
>
> Hello,
>
> New to the group here and STAMP.
>
> My original plan was to use the BS2 to take in quadrature inputs of
> up to 1000ppr or per inch for linear position and angle measurements.
> The counter and associated data would be output in a specific string
> format, receivable by dedicated external devices for Blind personnel
> adaptive equipment. This could open the door for more "VOICE" display
> interfaces.
>
> Now that I have searched the archive files and found the BS2 may have
> limitations of less than 100ppr directly connected, I am considering
> the external circuitry required to do the quad/counting.
>
> The string output from the BS2 would have a max of 10 times/min.
> Theoretically, a condition exists there in, where counts could be
> missed while doing this portion of the program with no
> buffer/interrupt to catch incoming changes of state.
>
> The US Digital IC LS7266/7166 has the quadrature up/dn count taken
> care of but not the storage of counts. If this be the case then, it
> would only be cutting the count period by 4. Still in a pinch if an
> axis moved at a rate greater than 100 pulses in the same time frame
> to a BS2 input limit, considering the programs loop time as the
> program grows. That makes a decade counter array or buffer necessary
> along with a means of tranfering the data to the BS2.
>
> The critical factor is the input timing vs program runtime. The
> output is only upon request by a button press. The input should not
> be changing at the same time, but if it does, precision could be
> compromised by accumulated error.
>
> Any successes/experiences out there under similar circumstances?
>
> If so, what did the input conditioning circuitry consist of?
>
> Having already purchased the BS2 BOE and OEM's, I wonder if I have
> been mislead for this application?
>
>
> TIA,
>
> Doug
>
[noparse][[/noparse]Non-text portions of this message have been removed]
I would be very interested in your circuits and code. I am think about using an
encoder and tilt sensor from US Digital for a project. US Digital parts are
kind of expensive. I would like to have a better idea of what I'm getting into
before I give them my hard earned cash.
Thanks in Advance.
Randy Wahlfeldt
Email: randyw@w...
Web: http://www.staff.uiuc.edu/~rwahlfel
Original Message
From: <borgmandl@c...>
To: <basicstamps@yahoogroups.com>
Sent: Thursday, August 22, 2002 12:20 AM
Subject: Re: [noparse][[/noparse]basicstamps] Quadrature Encoder interfacing the BS2
> Doug,
> The US Digital IC LS7266/7166 does store counts for you.