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Circuit Review

s1buell

  I`m currently making some proto circuits and I would love some feed back/Ideas etc.

 

All these circuits will connect to Arduino or Arduino compatible devices.

 

Anyone have time to help out with some reviews?

 

First circuit is a 4-20ma board

Parents

  • Picking the right TVS Diode

     

    Look at the Max Driver Output from here you need to pick a diode that works in the range

     

    Figure 1: MAX3232 Driver Operation Voltage

    image

     

    MAX481CSA+-ND

     

    Driver Input Voltage (DI).............................-0.5V to (VCC+ 0.5V)

    Driver Output Voltage (A, B)...................................-8V to +12.5V

     

    In this case I took the  SMBJ7.0CA-E3/52SMBJ7.0CA-E3/52 as it will cover both circuits(7 to 12VDC

     

    T

  • in reply to s1buell

    Tom.

     

    This is a somewhat confusing specification.  The 'Absolute Maximum Ratings' section of a specification is more about the worst possible case or the point were you are most likely going to damage the device.  Typical specifications are usually a better guide as to what range yo want to protect.  If the device you are communicating with is also powered at 5V (not sure if you have stated what Vcc is), it is unlikely that you would see -8 to +12.5V swings.

     

    Gene

  • in reply to genebren

    Yes agree. I reviewed the worst-case spec`s (13VDC upper end for example) and then put the TVS inside these specs to save the components. I really like these TVS diodes they are an easy way to protect bus side of the solution.

    So, do you think its worth keeping the optical chips?

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  • in reply to s1buell

    Tom,

     

    Strange, but I had replied earlier, and stated that I think you should leave out the Optoisolators.  They really are buying you and protection given that the transceiver is now protected nicely.  About the only time I would use the optoisolators is if the transceiver was power by an isolated DC-to-DC supply, or if there was a high voltage source nearby (on the other side of the 485 bus).

     

    Good job!

    Gene