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  1. J

    Multisim simulation help

    Thanks for taking time to help. Background: What I am trying to do is use a cd4060 binary counter IC. What I am trying to simulate in multisim is the square wave produced from the connected RC network. I am working on this so I can use it to double check my math through the proof of concept...
  2. J

    Multisim simulation help

    Ok so I am trying out multisim because it has a pspice model for the 4060. I add it to the design and hooked it up exactly as the datasheet shows and what do you know? It won't work... :mad: This should be so simple it's stupid. But someone please tell me what I am doing wrong. Link to my...
  3. J

    using garage door sensors for a driveway alarm

    How do the devices work? Most trip devices will either start producing a voltage or stop producing one when the device is tripped. Knowing this will help you make the rest of the circuit. The other question to answer is do you want to run wire over the ~400ft or do you want it to be a...
  4. J

    12 volt fan to 12 volt transformer

    alternators on a car produce AC but there is also a rectifier bridge on them that only outputs DC. My guess is its a DC fan.
  5. J

    12 volt fan to 12 volt transformer

    the fan is probably DC and if there is no rectifier on the transformer then it is putting out AC.
  6. J

    741 differential amplifier question

    What I have here is the original circuit that was working before plus a 555 timer in astable mode that is driving a cd4020 binary counter. I setup the 555 timer in astable mode with a 50% duty cycle. I want a 20 min timer, so I took 20 mins * 60 seconds and got 1200 seconds. Divided that by...
  7. J

    Beginner electrical question

    if you take some high power resistors and wire them in series, attach a piece of metal and you have a heating pad. You might even find a piece of highly resistive cord wire or something. The approach is all the same, add some more resistance to control the current and power output.
  8. J

    Switching a relay from a low voltage ac source

    pretty much what I just said, but I am still concerned over the low voltage. diode will drop ~.7 volts. that leaves you with .7V Add in a resistor to control current and you on the lower limit of what a transistor will need for it to saturate fully.
  9. J

    Switching a relay from a low voltage ac source

    I had plans to do the same thing. I figured a couple diodes would rectify the ac to dc then have that turn on a transistor to switch the relay. But 1.3 volts is really low voltage for a pair of diodes. You'd be losing half of that across the diode. Maybe a transformer is needed to boost the ac...
  10. J

    Beginner electrical question

    without some form of resistance greater then .722 ohms you won't make anything but a short circuit. with the numbers you got 120V/.722 Ohms = 166 Amps x 120 V = 19944 Watts. I don't know of to many devices that can handle that sort of power. If any...
  11. J

    741 differential amplifier question

    You was right, I had changed the I_DROP and I_PULL values, at the time i thought that was my current draw, now I see those values are when the relay switches. Once I increased R_COIL to 200 everything looks good again.
  12. J

    741 differential amplifier question

    Orcad/pspice simulation help I am trying to understand what I am doing wrong here. I am sure it's just a lack of experience on my part that is holding me back again. I made this circuit and simulated it using a 200 ohm resistor for the relay to make it simpler in the beginning. But now I would...
  13. J

    741 differential amplifier question

    ~.6V at the collector. From what I know that means the transistor is fully saturated.
  14. J

    741 differential amplifier question

    Had to teach myself to learn orcad/pspice. But man am I glad I did. What a great tool. :) I chose R5 to be an arbitrary value of 3k, same as datasheet. Graph says it all though, this will work out nicely. What do you think? edit: R6 is also arbitrary, I chose 200 Ohms because if I remember...
  15. J

    741 differential amplifier question

    You'll have to excuse my ignorance with the differential amplifier I "supposedly" wanted. As I stated in another thread, my electronic engineering skills are zilch. I am learning by doing. NOTE: I would like to use a battery or two to run this circuit. My only criteria! I guess I don't...
  16. J

    741 differential amplifier question

    I assume this is what you had in mind? The only question I have is why does my transistor not blow up when there is 10 volt potential difference between the BE junction? In the simulation the only way I can make the transistor blow is to hook up a neg supply rail to the Emitter and ground to...
  17. J

    741 differential amplifier question

    Well why didn't you say this before? You do make a very good point. I was trying to over complicate the problem. thanks again steve.
  18. J

    741 differential amplifier question

    guess that's a no? lol
  19. J

    741 differential amplifier question

    Well, here is what I ended up with. I chose to make the V output of R2, R3 to be closer to R1, R4 when R4 has a lower resistance. I am assuming R4 is a variable resistance. This keeps the negative voltage drop across the transistor at about -1V. Wouldn't a negative voltage (>-6) drop across...
  20. J

    741 differential amplifier question

    I am not sure what you mean by this? I want to do things by the book, the way it should be done. I am experimenting to try and learn as much as I can on my own. So I am not looking for a shortcut, if my design is flawed or the material I am reading is wrong. So be it, just point me in the right...
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