Need help With my circuit. If you have a simulator program, definantly look. thanks.

Discussion in 'The Projects Forum' started by fordrule1, Jun 25, 2010.

  1. fordrule1

    Thread Starter New Member

    Jun 25, 2010
    24
    0
    Hello all, i am new to this site, and i am relativley new to electronics.

    So here's the deal. I have to build a Electronic switching cicuit to control headlight on a vehicle with the following requirements:
    • The head lights must start their cycle in low beam when first turned on.
    • The low beam bulbs are to be wired in parrallel and will be 13.9v 100w bulbs.
    • The high beam bulbs are to be wired in parrallel and will be 13.9v 130w bulbs.
    • The circuit must automatically shut down in 90 seconds after the ignition is switched off, if it is still enabled.
    • The latch signal (the trigger or dip switch between high and low) will be a momentary short to earth and it must switch an electronic cct NOT A RELAY.
    Ok so far i have got the timing close with a 555 timer, when you turn it on the lights go on and then when you flick the second switch the circuit turns off after about 70-80seconds which is fine.

    I have attached a copy of what i have come up with. Im using a simulator program called yenka, and it says what i came up won't work, but the guy at the electronics shop reckons it will. I tryed to wire it up today exactly like the schematic i have attached, but it didnt work, it could be because I messed up the wiring. But can people have a look and see what you think?
    Please can you give me idea, upload schematics and keep what you say simple as i am new to this stuff. If you can, please take my design and modify it so it work and upload the schematic, im not saying actualy build it, but for those of you who have a simulator program, please help.

    BTW, im using a bread board for all the IC's.

    thanks.
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,692
    901
    Welcome to AAC.

    Please tell us a little about the electronic switch that you are using. I assume they are mosfets. What part number?

    If they are N-channel, they will not switch in that circuit, because the gates will not be driven higher than the source by the requisite 10V or so. The N-channel mosfet source pin must be connected to ground and the drain pin to the load. The load is then connected to the power source positive. There are ways around that requirement, but you wanted to keep it simple. Right?

    What you show is a common error.

    John
     
  3. fordrule1

    Thread Starter New Member

    Jun 25, 2010
    24
    0
    yes you are right, i am using N channel mosfets, the reciept says MOSFET IRF1405 N-CH 55V 169A.
    is there anyway i can still use the same Mosfet i bought?
    Yes, definantly keep it simple please.
    thanks.
     
  4. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
    92
    Put the mosfets on the low side and the lamps on the high side.
     
  5. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
    92
    Interrupting the ground side is not really an option for a car -sorry about that - I was only looking at the circuit diagram and hadn't really processed your whole post of requirements.

    Not sure how to help you with this.
     
  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,692
    901
    Yes. Just connect the load (lamps) to supply positive. Connect the other terminal from the load to the Drain of the mosfet. Connect the mosfet Source to ground (power negative in your circuit). N-channel mosfets work most simply when they switch the connection to ground, which is called "low side."

    The configuration you show is called "high side." It is an easy error to make, because that is how many mechanical switches are wired. Remember that when the mosfet turns on with the load connected to its source, the source voltage will approximate the supply voltage, because, hopefully, there is minimal voltage drop across the mosfet. Thus, in that configuration, the gate must be supply + 10V so the gate remains 10V higher than the source. That can be done with special gate drive circuits. But, you don't need to do that, if you simply change the configuration so the mosfet switches the low side.

    I did not looked at your drive circuits for the mosfet initially. Remember, while mosfets are said to be voltage controlled, the gate requires substantial current to be turned on. It acts like charging a capacitor. the current and voltage capability of the 74HC08's you are using to drive the gates will not be adequate. Their voltage supply and output are limited to about 5V. The IRF1405 requires 10 volts for the gate. Something in the CD4000 series might work, or you could just use a couple of transistors.

    Basically, you seem to have the timing and logic issues solved based on what you claim. All you need is to solve the mosfet drive issues. Note, the current ratings of mosfets are related to the on resistance and heating effects. The package limitations (i.e., the tiny connection pins) might be considerably lower.

    John
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,692
    901
    If you can't interrupt the ground (assuming it is negative ground and not a pre-1956 Ford), then for high side you can use a solid state relay, mechanical relay (cars have lots of them), high-side N-channel mosfets with appropriate drivers, high-side P-channel mosfets with appropriate drivers, or standard junction power transistors.

    I would lean toward using a relay for this purpose. Why do you not want to use one?

    John
     
  8. fordrule1

    Thread Starter New Member

    Jun 25, 2010
    24
    0
    hey that is alot of useful info you guys have given me, thanks.
    If you could provide a schematic aswell, please do. Or ill try what you've said about goin low on the mosfets, and then get back to you's.

    Btw, this isnt actualy going in a car, its just a project.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I am VERY glad to hear that it is not going to actually be used on a vehicle.

    Such a circuit would likely fail quickly in a real-world automotive environment, possibly leading to property damage (crash) and injuries.

    Few, if any of us are automotive engineers.

    However, any such changes would require extensive testing under severe conditions to be reasonably certain that it would be reliable in actual use. Failure of automotive lighting while the vehicle is in use is a very serious matter.
     
  10. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The original schematic is a nightmare with wires all over the place.
    Instead it should use "+" and "GND" symbols, and not have wires to the left switch so long that they cross over 5 other wires that are also too long.
     
  11. fordrule1

    Thread Starter New Member

    Jun 25, 2010
    24
    0
    Hello everyone, sorry it took me so long to get back to this post. I have been very busy, as most of you probably are too.

    So anyway, i went back to the design and i changed it from "high side" to "low side". Now the problem i have is its blowing stuff up? ill upload a print screen from my simulator. I alos chnged the parts, i changed the Flip flop and the AND gates to 4000 series.

    Can anyone tell me if the Flip flop is set up correctly? Coz when i hit the ground trigger switch, it does nothing??

    Does the NOT look right? coz its blowing up, along with the AND gates?

    Please if anyone at all knows how to get the second part the circuit to work (NOT + Flip flop through to mosfets), please tell me im stressing out soo bad with this. I go to the electronics shop, and coz they dont have a simulator i have to go home every time, and then back to the shop, and what they tell me will work, doesn't, then when i go back and show them they say "no you not following it properly", even though ive i got it set up EXACTLY the way they tell me to do it, And then they change the design again??

    please some one with some experience help!!!!!
    Thanks
     
    • 1.JPG
      1.JPG
      File size:
      61.1 KB
      Views:
      40
  12. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    The error said you were above the normal Vcc voltage on the Gate by 9 volts when they expect the maximum to be Vcc +1. Now you are supplying the circuit with 14 volts and you are 9 volts above the normal voltage expected for the pin.

    I don't know why your software won't allow 14 Vdc on the Vcc pin ... it is within the specifications for both the inverter and the gate.

    What software are you using?
     
    Last edited: Jul 5, 2010
  13. fordrule1

    Thread Starter New Member

    Jun 25, 2010
    24
    0
    I am using a program called Yenka.
    Well if all the parts are able to handle the power im putting into it, how am i suppose 2 test the circuit???

    is there a better simulator i could use that is free?
    what can i do about this? can someone test it with there simulator for me?

    please i need help with this, thanks.
     
  14. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The clock input of the flip-flop is floating when the pushbutton is not pressed.
    The CD4013 flip-flop is activated when its clock pin goes high but your circuit does not have anything to make it high.
     
  15. fordrule1

    Thread Starter New Member

    Jun 25, 2010
    24
    0
    how to i make the clock input 'high'?
     
  16. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Use a pullup resistor (47k ohms) connected from the clock input to the positive supply.

    But you have the clock logic backwards. The clock input should have a 47k resistor to ground to make it low and the pushbutton should be connected to the positive supply to make it high to activate the flip-flop.

    You have another problem:
    Pushbutton switches and relay contacts "bounce" when closed so your flip-flop will be activated a few times each push of the button unless you add a "debounce" circuit.
     
    fordrule1 likes this.
  17. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    If you want supply CMOS gate in yenka you must use power connector from power supplies folder.
    See the attached yenka file
     
    • try.zip
      File size:
      10.3 KB
      Views:
      15
  18. fordrule1

    Thread Starter New Member

    Jun 25, 2010
    24
    0
    thank you soooo much, now the the flip flop switches i think.
    Just i cant test it because those inverter and 2 AND gates keep blowing up?? why is that??
     
  19. fordrule1

    Thread Starter New Member

    Jun 25, 2010
    24
    0
    sorry i dont understand what you mean? why would i want to use a CMOS gate? what do they do? (i dont know what they are)
     
  20. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    You already are using CMOS gates. .... the inverter and the and gates.
     
Loading...