# Chopper Control

POLDI is equipped with a Dornier Disk Chopper. The SICS program handling RS-232 requests at the chopper control computer is rather slow. This would slow the SICS server to unacceptable levels, if any request would be handled through the RS-232 interface. In order to cope with the problem, the SICS server buffers chopper information. This information is updated any minute if not set otherwise.

The chopper system control is divided into several distinct objects: There is the actual chopper controller which mainly serves for answering status requests. One virtual motor (chopperspeed) is available which represent the modifiable parameter of the disk chopper. The parameter can be driven through the normal drive command. The commands understood by the chopper controller object are:

choco list
  prints a listing of all known chopper parameters. Parameters phase and ratio are not used.
choco name
  print only the value of parameter name. Possible values for name can be extracted from the list printed with choco list (example choco speed).

The following virtual motor variable exists.

chopperspeed
  disk chopper speed

The variable chopperspeed kindly prints its current value when given as a command. Modifying the value happens through the normal drive command. For instance the command:

    drive chopperspeed 10000

will drive the disk chopper to 10000 RPM eventually and if no problem occurs. Please check your input carefully for all chopper commands. Dornier has provided no way to stop an erraneous command in its software. So, if you intend to run the chopper to 1000 RPM and mistyped it as 10000 then you'll wait for 20 minutes until the chopper is at speed!