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Recent content by cdh7

  1. C

    Isolated voltage sensing using transformer

    Hi Richard, That looks alright to me. You'll lose some accuracy though due to the relatively weak voltage divider supplying the offset. Maybe stiffen it up a bit with 1k resistors instead of 100k. You might want to add protection diodes to ground and Vcc at the input of the opamp to prevent...
  2. C

    Isolated voltage sensing using transformer

    Hi Rich, I'm not sure but I guess you don't need any load resistor. Is there anything in the datasheet saying one is required? You should get a center tapped transformer and use an ADC with differential inputs to make things easier for measuring AC voltage. There are plenty of application...
  3. C

    Help me set the VCO frequency on HCF4046

    Re: Help On 4046 But the HCT4046 VCO seems to be different from the HCF4046. The HCF datasheet gives a maximum frequency of 1.4 MHz, whereas the HCT can do 17 MHz. Can you figure out some component values just by experimenting? Regards, Chris
  4. C

    What's the advantage of constant off time

    Hi, PWM is the basic standard control method. Constant on-time has the advantage over PWM that switching frequency is reduced under light loads, which improves efficiency because the switching loss is lessened. Constant off-time has the advantage that it helps keep the converter in continuous...
  5. C

    How to write arg(x(t)) in matlab

    Hi, What about the angle function? https://www.mathworks.com/access/helpdesk/help/techdoc/ref/angle.html Regards, Chris
  6. C

    questions on current source

    Hi, I guess PMOS is usually used because then the load can be referenced to ground. With an NMOS circuit, the load usually has to be floating since you would normally connect the source to ground. Regards, Chris
  7. C

    Help needed about Mechinical Systems

    Hi, Without having the book here in front of me, it looks like you're summing up forces. Using F=m*a, acceleration a is the second derivative of position. And the force from a damper is proportional to velocity, the first derivative of position. Regards, Chris
  8. C

    BTFSC error (PIC Assembly)

    Hi, The BTFSC instruction works fine (skip if clear). You're testing if the carry flag (STATUS register bit 0) is set or clear so that the overall effect is to skip an instruction if carry is clear. Regards, Chris
  9. C

    to get the exact envelope of the 40khz signal

    Hi, You can get a pretty good result using a low pass filter followed by a Schmitt trigger to generate clean logic transitions. Select the cutoff frequency of the LPF so that the resulting 40 kHz ripple has a low enough amplitude to prevent the Schmitt trigger from switching. I don't know what...
  10. C

    why pinging works on hub but not on switch

    Hi, It could be a problem with Auto-MDIX support in your PHY and/or transformer. Have you tried both crossover and straight through cables? You might also want to check if autonegotiation is working properly and optionally try to configure all of your hardware manually. Regards, Chris
  11. C

    switching frequency will be decided in PWM buck converter...

    Re: switching frequency will be decided in PWM buck converte Hi, It's a trade off between inductor size and switching loss. Faster switching speeds mean a smaller inductor can be used, making the power supply relatively small. However, when the transistor switching time becomes significant...
  12. C

    What's the integral of (e^x2) ?

    Re: integration According to integrals.com it's Sqrt[Pi] Erfi[x] ---------------- 2 where Erfi is the imaginary error function.
  13. C

    Noise pickup in audio transformer

    Hi, I'm currently working on an audio circuit that seems to be picking up noise in an isolation transformer and hope to get some good advice from you all. It's not my design and the circuit board is complete, so I need a good "band-aid" fix. An on-board op-amp amplifies a 1Vpp audio signal a...
  14. C

    hyperterminal siemens c25 problem

    Hi ttn1, Yep, it sounds like those are handshaking pins, although the reference designs out there don't seem to use them, so no idea if they help. :-) Just connect them to the second set of TTL pins on your MAX233, and wire the RS-232 pins to the appropriate pins on your serial connector (CTS...
  15. C

    Inrush Current in LDO

    Hi, Here is the application note. Regards, Chris
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