Hi,
I've got an intermittent problem using a National Instruments DAQ (usb-6008). The DAQ is controlled using labview. Partial Schematic is included.
When P0.0 (as per the schematic) is driven high, the SSR switches power to a Xenon Arc Lamp ballast. The ballast first charges, then sparks the lamp, then runs the lamp in a steady state. Upon the sparking event, seemingly randomly (about 25% of the time), the USB will lose power temporarily, and the connection will be lost, and DAQ will need re-initializing. The usb power is provided independently via the computer (no usb hub is used etc).
If I use a scope to monitor the the PWR and GND of another USB port on the same computer, when the lamp sparks i see a spike on the USB VCC line, where it drops down to 2Volts for 40ns or so. I don't know if this is a valid way of monitoring USB power for transient conditions, but if it isn't i'm open to any advice. I'm wondering if this could be the cause, and if so, how could i go about solving it.
The ballast has a lot of EMF issues, but I am stuck using it in my design. The noise issues appear largely as conducted noise on J7, with 30-40Vp-p spikes riding on the 120Vac line once the lamp is running. During the initial lamp spark, there is a 40-100ns enormous spike that conducts and radiates throughout the system. I have tried to reduce the conducted and radiated noise by using a Corcom 6EMC3 between J7 and the ballast, keeping it as close as possible to the ballast to reduce radiated noise. There is a ferrite bead on the power cord where it enters the equipment, to try and stifle any noise cross talk to the usb cable. There are low voltage MOVs throughout the system to stop radiated noise from causing overvoltage spikes on MOSFETS during the spark.
I'm sure I have missed important information here, so fire away and i'll answer everything i've missed to the best of my ability. Any help solving this would be greatly appreciated.
Thanks,
Dom
I've got an intermittent problem using a National Instruments DAQ (usb-6008). The DAQ is controlled using labview. Partial Schematic is included.
When P0.0 (as per the schematic) is driven high, the SSR switches power to a Xenon Arc Lamp ballast. The ballast first charges, then sparks the lamp, then runs the lamp in a steady state. Upon the sparking event, seemingly randomly (about 25% of the time), the USB will lose power temporarily, and the connection will be lost, and DAQ will need re-initializing. The usb power is provided independently via the computer (no usb hub is used etc).
If I use a scope to monitor the the PWR and GND of another USB port on the same computer, when the lamp sparks i see a spike on the USB VCC line, where it drops down to 2Volts for 40ns or so. I don't know if this is a valid way of monitoring USB power for transient conditions, but if it isn't i'm open to any advice. I'm wondering if this could be the cause, and if so, how could i go about solving it.
The ballast has a lot of EMF issues, but I am stuck using it in my design. The noise issues appear largely as conducted noise on J7, with 30-40Vp-p spikes riding on the 120Vac line once the lamp is running. During the initial lamp spark, there is a 40-100ns enormous spike that conducts and radiates throughout the system. I have tried to reduce the conducted and radiated noise by using a Corcom 6EMC3 between J7 and the ballast, keeping it as close as possible to the ballast to reduce radiated noise. There is a ferrite bead on the power cord where it enters the equipment, to try and stifle any noise cross talk to the usb cable. There are low voltage MOVs throughout the system to stop radiated noise from causing overvoltage spikes on MOSFETS during the spark.
I'm sure I have missed important information here, so fire away and i'll answer everything i've missed to the best of my ability. Any help solving this would be greatly appreciated.
Thanks,
Dom