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  1. M

    Switching idea

    So if the inverting opamp receives a decent +ve input, then it will still only be close to ground for the output? Have you had any experience with absolute value circuits? I think thats what I need, so I can preserve the value of the input (regardless of whether its positive or negative). That...
  2. M

    Switching idea

    Wouldnt an inverting op-amp cause any positive voltage on the input to change to negative? The Vin for the circuit is from the sense resistor from one leg of the motor H-bridge. Depending on what the motor is doing, it could be positive or negative. If it's positive, it needs to stay positive...
  3. M

    Switching idea

    Hmm, it might be more sensible to ensure that the Vin is always going to be +ve, then I could get away with a normal comparator instead of a window comparator. Is there such a device that can leave a +ve voltage alone, but change a -ve voltage to a positive one?
  4. M

    Switching idea

    Is it going to be alright to have a negative voltage as a reference on the window comparator? I vaguely remember seeing something in a datasheet saying inputs needed to not go below -0.3v.
  5. M

    Switching idea

    Just to clarify.... Am I correct in thinking that your standard comparator can only sink current on the output (ie drag the output to ground), and that op-amps can either source or sink current on their output?
  6. M

    Switching idea

    Hi guys, here is the latest incarnation of the inhibitor switch.... Hopefully, it works like this (please correct me if I am wrong).... When the window comparator is outside the range of say -0.5v to +0.5v then it will be off. That will mean that on the next comparator the - input (9v) is...
  7. M

    Switching idea

    HA! Maybe I should start all my posts with "is there such a device that does this ....." Okay, i'll look up transmission gates and redesign it. Is the window comparator (with the negative reference for the lower end) and the schmitt trigger to keep it on all kosher?
  8. M

    Switching idea

    Yip, but we compensate by walking around on our hands alot of the time, and watching tv standing on our heads so we can understand our northern hemisphere brothers. That and the water swirls the opposite down the plug hole. Freaks alot of tourists out. They think its some kind of south pacific...
  9. M

    Switching idea

    Okay - the PWM signal is generated by an SG3524 chip. The output is the 2 open emitters of the chip joined together. The datasheet says the emitter output voltage is typically 18v, though since the chip is being driven by 12v (or close enough to) I would say that it would be at most 13v (since...
  10. M

    Switching idea

    Okay, how about this setup? It should have a much lower voltage going to the base of the PNP transistor. I must admit though, I dont really understand how this whole emitter-base voltage limitation works.
  11. M

    Switching idea

    So, is the schmitt trigger better with the diode, or the 10k resistor? The PWM signal should be sourcing from the left, and sinking to the right (if that makes sense). Should I set up a voltage divider to get 5v or so (my one has 6v emitter-base voltage) to the base of the PNP transistor. The...
  12. M

    Switching idea

    How about this? When the window comparator turns on, it pulls the + input of the right comparator below the - input, turning it on. The output of that right comparator pulls the + input low aswell, thus keeping it on (at least until power is removed from the whole circuit) even if the window...
  13. M

    Switching idea

    Okay, here is a schematic for my idea. At the moment, the window is set between about 3.4v and 1.7v. My big question is.... will this work?
  14. M

    Switching idea

    Hey everyone, I would like to design a setup that switches a PNP transistor on when a signal reaches near 0v (it would normally be either +ve or -ve), and then keeps that transistor on until the system is reset. My current thoughts on the matter are to have a window comparator to detect the...
  15. M

    Mosfet driver not outputing properly

    Super yachts aye? Made the changes you suggested. Works a treat now. Many thanks
  16. M

    Mosfet driver not outputing properly

    On a boat?
  17. M

    Mosfet driver not outputing properly

    Heh heh, okay no more fuzzies from me. Thanks audioguru I'll give it a try. BTW, where in Canada do you reside?
  18. M

    Mosfet driver not outputing properly

    Hi guys. I have constructed this circuit. Everything seems to work as expected, except for one small problem. The high output of both the IR2184 drivers is not high enough. I ran into this problem with an earlier circuit (also posted) and was helped to solve it by decoupling the driver...
  19. M

    Glaringly obvious errors

    Okay, how about this then. I figure with this setup, when the PWM signal is switched to the other half-bridge driver, the one not selected will hold the lowside mosfet on (which is needed for the reverse). The selected driver will switch the highside and lowside mosfets on as needed. Comments?
  20. M

    Glaringly obvious errors

    My idea behind this mess was to have a motor driver that would have variable forward speed, and when the throttle pot was pulled all the way back, trip a microswitch to activate a preset reverse speed. I thought that I could use the transistors as switches to enable or disable the pulse train...
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