"LunchBox" is a nicname given to the amplifier box that used be sold with PHANToMs that interfaced with a PC via ISA or PCI cards (current PHANToMs interface with a PC via either parallel or firewire port and contain the PWM amps in the base of the device). The amplifiers in the "lunchboxes" are PWM amplifiers from Copley Motion Systems (model 303). They are factory calibrated for peak current output of 12 Amps, corresponding to a 10 volt output from the DAC on the PCI card. However, rarely, if ever, would such high currents be commanded. Currents of an amp or two are more typical, hence the nominal resolution of the DAC is unnecesarily reduced. Gunter Niemeyer, of the Stanford Telerobotics Lab, has advocated dialing all of the amplifiers down to take advantage of the full resolution of the DAC output, and has written all of the RTai drivers assuming a peak output of 2.5 Amps from the "lunch box" amplifiers.

To calibrate the amplifiers to the 2.5 Amp peak output, a few of the fixed resistors on the Copley #303 amps need to be replaced. In addition, fine calibration needs to be done by adjusting the two potentiometers located on the side of the amps. The potentiometer labeled FB is used to adjust the gain (full scale current output) and the potentiometer labeled BHL is used to adjust the offset. It is suggested to run the current through a dummy motor OR power resistor in series with an inductor when calibrating the amplifiers.

It is only necessary to replace the 1st resistor (counting from the left), leaving all other resistors and capacitors unchanged. Make sure to use high quality 1% tolerance resistors. Currently shown as 262.1 k-Ohm, but anywhere form 262-350 k-Ohm is an acceptable value here (the amplifiers originally had a 49.9K resistor).

Ballpark values for the fixed resistors and capacitors in the amp chip carrier for 2.5 amp peak output are (from measurement with an ohm-meter):

262.1 k-Ohm | 48.9 k-Ohm | - | 9.86 k-Ohm | - | cap | 45.5 k-Ohm | cap | empty | 39.6 k-Ohm | 9.79 k-Ohm |

• labeled gain resistor for 2.5 Amp peak current output on Copley 303 amplifiier:
  

More information about the CopleyAmplifiers. -- WillP? - 20 Oct 2004

• Pinouts for PHANToM PCI (& ISA) control card and PHANToM amplifier box headers:
  

Note that the 3-Axis amp box will have an additional 3 encoders coming into (the currently 6 open pins on) header A from the stylus gimbal. These are presumably wired to the same pins on "header P" as the encoder pins coming from "header B" on this 6-Axis box.

• 6axis lunchbox :
  

• Current Setup: