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  1. T

    A question about audio output impedance

    Y2KEDDIE, read this thread: http://www.electro-tech-online.com/general-electronics-chat/124189-how-do-you-determine-primary-winding-ohms-unknown-audio-transformer.html and then this one: http://www.electro-tech-online.com/general-electronics-chat/124261-audio-transformers-two-ports.html
  2. T

    diode for collapsing magnetic field

    Like I said, if that happens it will be up to Blank Stare, not me. What's going to happen is that if Blank Stare does add the suppression network, and if he does find that the arc is eliminated, we still won't know if the arcing is the reason for relay failure for some time, maybe weeks or...
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    diode for collapsing magnetic field

    The purpose of my PM is not necessarily going to terminate this thread. I simply offered to mail the necessary parts to Blank Stare, and if he wants to accept my offer he will need to give me his mailing address--hence the need for privacy. I, probably like you, have a lot of parts accumulated...
  4. T

    diode for collapsing magnetic field

    I was wishing you had a scope. :D Yes, cut the "box" part away from the leads. I sent you a PM (Private Message). At the very top right of the page you'll see "Private Messages". It should say "Unread 1" now that I've sent you one. Just click on it and you can also reply on the page...
  5. T

    diode for collapsing magnetic field

    Yes, it was. With nothing to suppress the arc, it was substantial--quite a bit of fire, spread over the full diameter of the contacts! With only the RC snubber, the arc was much reduced, a less fat arc, but still present.
  6. T

    diode for collapsing magnetic field

    Ask, and ye shall receive. Edit: I should mention that with only the RC snubber, sparking is still present at the relay contacts; with the diode also connected, I see no sparking.
  7. T

    diode for collapsing magnetic field

    I did some experiments using the primary of a 200 VA power transformer for an inductor and a 5 amp bench supply, with a small relay to apply 5 amps to the inductor and then turn it off. I needed to apply 22 volts to get 5 amps in the inductor. I used a 100x probe on my scope and captured the...
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    diode for collapsing magnetic field

    You should have given us this web page on your very first post. :D As far as what it would draw at higher pressures, the chart on that web page gives all the numbers up to 150 PSI. Knowing all the data on the pump is good. For example, they say that it comes with a 40 amp inline fuse. They...
  9. T

    diode for collapsing magnetic field

    Blank Stare, in your first post, you said that the motor load is 20 amps. How do you know this? Did you measure it? The reason I ask is that 20 amps seems high for a device intended to plug into a cigarette lighter outlet.
  10. T

    diode for collapsing magnetic field

    I'm thinking that he needs a bigger relay; something like a starter solenoid, actually. I can't imagine how erosion of the relay contacts due to switching off an inductive could lead to failing open unless the process went on for a very long time. I had this happen to the starter solenoid in...
  11. T

    diode for collapsing magnetic field

    In post #5 you said; "Sometimes they fail open, sometimes they fail closed." Perhaps I misunderstood; what did you mean by "fail open"? I took that to mean that when your circuit attempted to energize the relay it didn't send power to the pump.
  12. T

    diode for collapsing magnetic field

    Immediately after the relay opens the motor armature will still be rotating. The motor will act as a generator (assuming it's a permanent magnet motor), generating a voltage just about equal to the applied voltage. The polarity of this voltage will match the applied 12 volts--in other words...
  13. T

    diode for collapsing magnetic field

    You don't need a 40 amp diode for your purpose. The 20 amp motor current will only flow in the suppression diode for a few milliseconds at turnoff. Most rectifier diodes can withstand a half-cycle (that's half a cycle of the power line frequency, 8.3 milliseconds) many times their steady state...
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    diode for collapsing magnetic field

    Blank Stare, you should read these: http://relays.te.com/appnotes/app_pdfs/13c3203.pdf http://relays.te.com/appnotes/app_pdfs/diagnostics.pdf http://relays.te.com/appnotes/app_pdfs/13c3311.pdf http://relays.te.com/appnotes/app_pdfs/13c3236.pdf The reason I asked if you still have...
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    diode for collapsing magnetic field

    Do you still have any of the relays that failed open?
  16. T

    What is the best way of solving the circuit?

    If by efficient, you mean less work to find a solution, letting a computer do most of the work is about as efficient as it gets. If you don't care about the current through the 100 volt source, you could use a nodal formulation of 3 equations in 3 unknowns, since the voltage at the node where...
  17. T

    What is the best way of solving the circuit?

    The OP posted this on at least 2 other forums, and got a solution on one of them right away.
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