Provided by: linuxcnc-uspace_2.9.4-2ubuntu1_amd64 
NAME
carousel - Orient a toolchanger carousel using various encoding schemes
SYNOPSIS
loadrt carousel pockets=N[,N] encoding=ssss[,sss] num_sense=N[,N] dir=N[,N]
pockets The number of pockets in each toolchanger.
Use up to 8 numbers separated by commas to create multiple carousel components.
encoding The position encoding.
gray, binary, bcd, index, edge, counts or single. Default = 'gray'
num_sense The number of position sense pins.
Default = 4.
dir Set to 1 for unidirectional or 2 for bidirectional operation.
Default = bidirectional
parity Set to 1 for odd parity, 0 for even parity checking.
Default = 0 (even)
DESCRIPTION
This component is intended to help operate various types of carousel-type toolchangers.
The component can be configured to operate with binary, binary-coded decimal (BCD) or gray-coded position
feedback ('binary;, 'bcd' and 'gray' modes) It can alternatively work with an individual sensor for each
tool position ('single' mode) or with a sensor at each tool position and a separate index ('index' mode).
Systems using a stepper motor or quadrature encoder are also supported ('counts' mode). edge is a
special case of index mode for tool changers with pockets on both the rising and falling edges of the
position sensor. (Seen on at least one Denford Orac.)
Both unidirectional and bidirectional systems are supported and those that reverse against a stop when in
position.
The number of carousel component instances created depends on the number of entries in the 'pockets'
modparam. For example
loadrt carousel pockets=10,10,8
Would create 3 carousel instances with 10, 10 and 8 pockets. The other parameters are optional. If absent
then defaults will be used. Any missing entry will assume the previous value.
When the enable pin is set to true the component will immediately set the "active" pin to true and then
(for a bidirectional instance) calculate the shortest path to the requested pocket number. The
appropriate motor direction output pins will then be set. Bit outputs for forward and reverse are
provided as well as a three-state velocity output for driving a DC motor PWM or a velocity-mode stepgen.
The component will monitor the carousel position and, when the correct position is reached, set the
motor-control pins to 0, set "active" to 0 and set "ready" to 1.
In 'index', 'edge' or 'counts'mode there is a need to find the initial home position of the carousel.
The first time that the "enable" pin is set; the carousel will rotate forwards searching for a home
signal. In 'index' and 'edge' mode this is when both the index and pulse inputs are true. In 'counts'
mode only the index input needs to be set to set home. Additionally in 'counts' mode the usual index-
enable logic of the encoder counters is supported.
With some carousel designs the carousel will not stop immediately. To allow for this set the align-dc pin
to a low velocity to be used for a final latching move, and set the decel-time to a suitable value. Once
the decel-time has expired the carousel will, if it was moving forwards, reverse back on to the position
marker, off of the marker and then back on to the FWD edge. If moving in reverse it will continue off the
marker and then reverse slowly on to the FWD edge. This alignment is only possible with a motor-vel
controlled bidirectional carousel, Other combinations will be acepted but probably will not have the
desired behaviour. Some tuning will be needed of align-dc and decel-time to achieve reliable operation.
In the unusual case that the index and pulse signals do not align it is possible to use HAL logic to
achieve the desired pin switching during homing.
Setting "enable" low does not halt the homing move, so if homing on first tool change is not needed then
the enable pin can be toggled by an axis homing pin or a script and the homing process will continue even
if that driving signal resets during the carousel homing move.
To operate the component with an encoder or stepgen use mode "C". The scale pin should be the number of
steps or encoder counts between pocket centres. The width pin can be used to stop the motor some distance
before the centre of the pocket to allow the motor time to decelerate. In mode "C" it is possible to use
either the speed/direction control used in other modes or to use direct position mode using the counts-
target pin. The internal scaling of the encoder or stepgen should be set to 1.0. A PID hal component will
be needed for encoder applications whereas stepgen configurations can use a stepgen in position control
mode or in velocity control mode with a PID.
For tool changers which lock the carousel against a stop the rev-pulse pin can be set to a non-zero
value. The motor-rev pin will then be set for this many seconds at the completion of the tool search and
at the same time the reverse duty/cycle velocity value will be sent to the motor-vel pin.
FUNCTIONS
carousel.N (requires a floating-point thread)
PINS
carousel.N.pocket-number s32 in
The pocket to move to when the .enable pin goes high. If the value passed is higher than the
number of pockets specified in the "pockets" modparam then modulo arithmetic is used. This is
intended to allow the use of multiple tools in the same holder, as is sometimes useful with
lathes.
carousel.N.enable bit in
Set this pin high to start movement. Setting it low will stop movement
carousel.N.active bit out
indicates that the component is active
carousel.N.ready bit out
This pin goes high when the carousel is in-position
carousel.N.strobe bit in (default: 1)
Use this pin to indicate that the position feedback is valid. Often provided by binary encoders
carousel.N.parity bit in
Some encoders supply a parity bit, if this is connected then the parity-error output bit will
indicate parity errors
carousel.N.sense-M bit in (M=0..personality)
Carousel position feedback pins. In 'index' mode there will be only 2 pins. sense-0 is the index
and sense-1 is the pocket sensor.
carousel.N.rev-pulse float in
The duration in seconds for which a ratchet changer (Boxford, Emco) should pulse the reverse pin
to lock the holder
carousel.N.fwd-dc float in
Velocity or duty cycle when forwards rotation is desired
carousel.N.rev-dc float in
Velocity or duty cycle when reverse rotation is desired
carousel.N.hold-dc float in
Duty cycle when carousel is in-position (to hold against stop)
carousel.N.align-dc float in
Use this pin to set the speed of a slower alignment move once the changer is in position. Such a
system almost certainly needs decel-time setting too
carousel.N.decel-time float in
Time to wait for carousel to stop before final alignment and position check
carousel.N.counts s32 in
Connect to the rawcounts of an encoder or a stepgen in 'counts' mode
carousel.N.scale s32 in (default: 100)
The number of stepgen or encoder counts between successive pockets
carousel.N.width s32 in (default: 10)
How far each side of the exact scale to signal a new pocket
carousel.N.home-offset s32 in (default: 0)
The offset (in counts) between the index and pocket 1
carousel.N.index-enable bit io
Used to home to an encoder index
carousel.N.jog-fwd bit in
Jog the carousel forwards one tool position
carousel.N.jog-rev bit in
Jog the carousel in reverse (only if dir = 2). It is very important that these pins should be
debounced and should probably also be interlocked to only operate when the machine is idle.
carousel.N.motor-fwd bit out
Indicates the motor should run forwards (bigger numbers)
carousel.N.motor-rev bit out
Indicates the motor should run reverse.
carousel.N.parity-error bit out
Indicates a parity error
carousel.N.current-position s32 out
This pin indicates the current position feedback
carousel.N.motor-vel float out
The duty-cycle or velocity to drive a DC motor or stepgen
carousel.N.homed bit out (default: 0)
Shows that homing is complete. Only used in index and edge modes
carousel.N.unhome bit in (default: 0)
Should only really be necessary for testing
carousel.N.counts-target float out
Target position for a stepgen or external PID controller
PARAMETERS
carousel.N.state s32 r (default: 0)
Current component state
carousel.N.homing bit r (default: 0)
Shows that homing is in progress. Only used for index mode
carousel.N.timer float r
Shows the value of the internal timer
carousel.N.motor-dir s32 r
Internal tag for search direction
carousel.N.counts-offset s32 r
Internal offset of index pin
carousel.N.debounce u32 rw
How many thread cycles to wait for the position to stabilise
carousel.N.target s32 r
Current target pocket, debug
carousel.N.base-counts s32 r (default: 0)
AUTHOR
Andy Pugh
LICENSE
GPL
LinuxCNC Documentation 2025-06-19 CAROUSEL(9)