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Recent content by mfilippa

  1. M

    How i can Create a new logic symbol for DSP in Concept?

    Did you try XML? I got it working some time ago, but now I can't seem to make it work. Unfortunately Cadence has no script capabilities (that I know of) in Part Developer. XML can be a good choice if you want to import the pins from other software (excel spreadsheet). Hope this helps... Mariano
  2. M

    Information about High Voltage PCBs

    book on creepage on pcb Varuzhan, You are absolutely right. This values are too much, but this is what the standard says. I wonder in what kind of applications somebody would use cleareances this big. On the other hand, there are groups in this standard where the clearances change...
  3. M

    Swtiching from Protel DXP to Cadence...

    exporting to .brd from protel I'm in the process of switching to Cadence because I work in a company that uses Cadence. I am having a HARD time trying to learn the software. I find Protel to be more user friendly than Cadence. Anyway, Can somebody point me to commands/functions/etc in Cadence...
  4. M

    List of PCB vendors in the USA

    Re: pcb vendors I worked with www.pcbexpress.com and www.barebonespcb.com for prototypes. PCBExpress has a very good quality. BarebonesPCB has a very good price. You should tell us if you need a few prototypes or a couple thousand boards. Anyone knows of a cheaper prototype manufacturer that...
  5. M

    Information about High Voltage PCBs

    pcb high voltage clearance I have a NEMA standard which I cannot post here, but can give you some data. The NEMA standard is 1-111-1 & 2 and specifies minimum clearances and creepage distance in inches. For example: Industrial control, 2500~5000V-> 2" clearance, 3.5" creepage Does this make...
  6. M

    Analog isolation circuits: any experience on this?

    I finally gave up on optoisolators. I am trying to do AM modulation using LAN transformers. LAN transformers are cheap, small and offer an excellent isolation. Any ideas on AM modulation? I chopped the signal (DC to 1MHz) with a 10MHz square wave (carrier), then did a low pass at around 15MHz...
  7. M

    Phase and voltage detector design (PLL?)

    Hello, I need to synchronize an inverter to the power grid. So far I can easily track 3-phase voltages with high immunity to noise and other power failures. I am using a abc->dq conversion (3phase to 2phase, rotating frame) and with this I can easily track the phase, the sequence and peak...
  8. M

    what is the difference between DSPs and MCUs

    I've noticed lately that the differences between DSPs and MCUs are tending to disappear. I use Motorola DSPs (56800 series) and they are as simple to use and program as an MCU. The real power comes when you optimize your software for signal processing, especially if you program in assembly...
  9. M

    Analog isolation circuits: any experience on this?

    Thanks mabbri for the suggestion, but unfortunately I've been playing around with HCNR201 for a while without getting good results. I could never design a circuit with HCNR201 and opamps that operate at 1MHz. I could do it with transistors, but the accuracy was not good. I gave up on this...
  10. M

    Analog isolation circuits: any experience on this?

    Just a quick question: Regarding the chopping frequency, for a bandwidth of 1MHz, I selected a chopping frequency of 5MHz. I figured that it has to be greater than the bandwidth to avoid transformer saturation. Unfortunately, I wasn't able to find any analog switch (in DIP flavor) fast enough...
  11. M

    RS 232 Serial Communication

    Just browsing this forum, I found this topic on RS232 and Visual Basic. Here goes a small software I did to interfase a DSP through the serial port. Check the subroutines and you will find how to communicate, send and receive characters. You can try this easily: Get a computer with two serial...
  12. M

    Analog isolation circuits: any experience on this?

    Excellent ! I never thought of grounding the CT and switch the output. This is an excellent idea. I think this is the final solution. It is very cheap and simple, plus I can synchronize all signals to a same clock, thus saving costs and parts. Thank you Flatulent. I was a little concerned...
  13. M

    Analog isolation circuits: any experience on this?

    Flatulent idea is excellent ! Check the schematic and let me know if you agree with this: On the HV side: 1) run the signal through two opamps: follower and inverting 2) switch the signals using a fast analog CMOS switch 3) couple it through a transformer 4) Swtiching frequency must be 5 to...
  14. M

    Analog isolation circuits: any experience on this?

    I am already using matched optocouplers. Check the picture I'm sending. It is a simulation of the actual circuit I'm working with. It has a good response to about 500kHz. This circuit is Ok, BUT : a) it is not accurate, it has a 3% error in the full scale signal at low frequencies b) uses...
  15. M

    Analog isolation circuits: any experience on this?

    vco optocoupler galvanic I thought about the ADC and digital optocouplers. However, I believe it is a very expensive method for signals up to 1Mhz. First of all, the ADC should sample at 2Mhz or above, which makes this expensive. Besides, there are not many serial ADC for such speeds. And if...

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