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  1. scoobyrollz

    Earth ground and signal ground . . . connect or NOT?!?!?

    I am designing a digital communications/controller PCB (w/ RS-485, RS-232, USB, Fiber Optics, Ethernet). I am designing this board to be inserted into an existing card cage design. The card cage has a switching power supply that generates 5V. The 5V signal ground is directly connected to...
  2. scoobyrollz

    Connecting a capacitor in parallel with each diode in a FWBR?

    The application is diode stacks for T/R sets. These convert 480Vac to 50kVdc. So there will be multiple diodes in series, the amount I couldn't tell you since I haven't designed it yet. My question is really for understanding the purpose of the capacitor and how to calculate the capacitance...
  3. scoobyrollz

    How to calculate RC comp network for diode stack?

    I am trying to design HV diode stacks for T/R sets. I was wondering about when adding an RC compensation network, if I should match the line frequency or the reverse recovery time of the diode? Also should I use T = RC and then f = 1/T or f = 1/(2*pi*RC) to calculate the frequency...
  4. scoobyrollz

    Connecting a capacitor in parallel with each diode in a FWBR?

    I am trying to design HV diode stacks for T/R sets. I was wondering about when adding an RC compensation network, if I should match the line frequency or the reverse recovery time of the diode? Also should I use T = RC and then f = 1/T or f = 1/(2*pi*RC) to calculate the frequency...
  5. scoobyrollz

    RC compensation in a diode stack

    I am trying to design HV diode stacks for T/R sets. I was wondering about when adding an RC compensation network, if I should match the line frequency or the reverse recovery time of the diode? Also should I use T = RC and then f = 1/T or f = 1/(2*pi*RC) to calculate the frequency...
  6. scoobyrollz

    Connecting a capacitor in parallel with each diode in a FWBR?

    What is the purpose of adding a capacitor in parallel with each of the 4 diodes in a full-wave bridge rectifier? Does it help with noise rejection, or what? Any help will be greatly appreciated.
  7. scoobyrollz

    Loop powered 4-20 mA transmitter

    I need help!!!!!!!!!!!!!! I am struggling with the idea of designing a loop powered transmitter. I have the circuit designed for the V-I transmitter portion, but I need power for the op-amp IC I am using. I know I can get this required power from the 4-20 loop, but how without effecting the...
  8. scoobyrollz

    Optocoupler Help?!?!?

    I am using an optocoupler for isolation. I plugged some numbers in wrong, therefore I came up with a larger wattage than needed. I'm ending up using a 5W, 15k resistor. Operahouse and/or sdmays can you explain this capacitor idea in more detail?
  9. scoobyrollz

    Optocoupler Help?!?!?

    I have to interface 120V or 240V ac into a parallel port. The voltage varies mattering on what country the product will be installed. My question is, if I have an optocoupler with reverse diodes to activate for ac, what size resistor do I use for current limiting the input? I know I can use...
  10. scoobyrollz

    Short circuit protection for 4-20mA outputs?

    I have 4-20mA outputs that need to be short-circuit protected and a resistance of 100 - 500 ohms. What are some suggestion for the protection circuitry and to comply with the required resistance?
  11. scoobyrollz

    How to filter power supply noise and spikes

    I have a circuit driving an SCR and when this circuit is enabled, the 5V rail has noise on it. When the load of the SCR is connected, then there are 200mV spikes of noise on the 5V line. I need to reduce and/or eliminate this noise b/c it caues problems with the connected logic board that is...

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