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Selectable voltage switch

Discussion in 'General Electronics Discussion' started by Foose, Mar 17, 2013.

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  1. Foose

    Foose

    6
    0
    Mar 17, 2013
    Hi all, require help with a project I am working on. I have a input voltage of 0 to 8v DC (on a speed sensor output) I need to select a voltage within this range (0 to 8v) and when the voltage is reached will past a 12v signal (voltage) on to a relay.
    Any help offed would be a great help.
     
  2. john monks

    john monks

    693
    2
    Mar 9, 2012
    Maybe a 12 volt relay with a series resistor in the coil.
    What is this going to be used for?
    What current do you intend to supply?
     
  3. Foose

    Foose

    6
    0
    Mar 17, 2013
    It wiil be used for......

    Part 1
    I have build a active aero wing for a car. I required the tilt function on the wing to work once the car is travelling a 60 Km/Hour (no sure what that is in miles). So getting a reading of the voltage from the speedo wire which can be between 0-8 votes, I would like this to be adjustable so it can be set at different speed if necessary. Once the voltage that is set is reach it can then pass a 12 volt signal to activate a relay.
    There is also a second part to all this as well
    Part 2
    Also I have to work a way to get a steering angle signal that works on a 5 volt 10 turn penetrometer (already have penetrometer ) That when the voltage is greater the x volts (with centre being 0 volts) it can then pass a 12 volt signal to activate a relay

    The relay control part of this is already done, I really required a way to get the low voltage devices to give a volt signal to the relays I have installed to control the wing.

    I though I would start with one thing at a time but to help you get a better idea of what I up to a need to do.

    thanks for any help you can offer.
     
  4. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    1. You just need a simple comparator circuit. I suppose you need some hysteresis as well?

    2. Do you really mean "penetrometer"? I suppose you mean potentiometer.
    It's not really clear what you want, but it sounds as if you want the same type of circuit as in 1.
     
  5. Foose

    Foose

    6
    0
    Mar 17, 2013
    Yes that is potentiometer, Yes that would be correct it would be almost the same just a smaller voltage variance as the potentiometer only has a 5v across + - terminals
     
  6. Foose

    Foose

    6
    0
    Mar 17, 2013
    The picture very basic diagram what I think I need any circuit layouts and components help would be a great help.
     

    Attached Files:

  7. Six_Shooter

    Six_Shooter

    98
    0
    Nov 16, 2012
    I'm planning a similar idea, aka, active wing/spoiler control, but I plan to use a micro controller to do it, it will read the frequency directly, which IMO is a more reliable way to read speed.

    Depending on the VSS you will be using, it could be putting out an AC current, which could complicate the circuit.
     
  8. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    Here is a "bare bone", very simple and cheap circuit that should work well for your application (though I did not test it).

    R1 and R2 add hysteresis to the circuit, so that you don't get "chattering relays" from the outputs. The hysteresis varies a bit with the position of P1 and P2.
    Down very near 0V set points, the circuit might not switch very well. If you really need that region as input, the circuit could be adapted a bit (by creating a virtual ground).

    Also if very high accuracy is needed, you could use a reference voltage instead of the 12V supply.

    The IC is given, the other components can quite easily be calculated (good task). R1, R2 are "big" (Mega-Ohm).

    [​IMG]
     
  9. Foose

    Foose

    6
    0
    Mar 17, 2013
    Hi thanks for the diagrams this looks like what I need exactly Will try to work out the resistor values form my limited knowledge of electronics. I thinking that R7,R7 drop the voltage for the P1,P2 Pots and R8 does the same for the Steering Pot.

    Add a picture of virtual ground that could be incorporated to supply 5v to the diagrams


    thanks again Electrobrain
     

    Attached Files:

  10. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    If your steering pot is a simple potentiometer, you don't need any 5V power source. You just adapt R8 so that the voltage drop over the potentiometer is whatever you like it to be (for instance 5V). But first you need to know the value of it. Read what is written on the potentiometer or directly measure on it.

    The circuit diagram you show is a good way of making a split power supply with a virtual ground.
    In your case, you would just need a few added resistors to push up the 0V input signal a little. But I doubt that the circuit even needs such "surgery".
     
  11. Foose

    Foose

    6
    0
    Mar 17, 2013
    I unloaded a picture of a circuited I put together. I’m not sure if I’m on the right track as this is the first one I’ve done but if anyone has a better idea please let me know. This a bit different layout than I was going for but if it works it will do the job very well and will do more things than what I have thought of yet. The circuit uses a Picaxe 28X1 chip I think I have used it correctly. The aim of this is when the Accessory (input (6)) is turned on the circuit will turn ON. Then though programming M1 and M2 motors (Output 7 and 8) will run, raising the wing. The Actuators have inbuilt potentiometers so these can be used with a timer function I hope (or something) to set the height that the wing will raise and again when Accessory is turned off to lower the wing again (may have problem there with power being cut off and ideas).

    Now for the fun part of all this, the wing’s tilt, when the car is at a set speed rate (Speedo input (5)) and the Steering angle senor is at a set voltage( I think with programming) to indicate that the car is turning or on a bend (steering wheel not a zero position)the wing tilt will raise. The amount that the wing will raise can be set using the 4 way position switch so again with the aid of the Actuators inbuilt potentiometers (Motor 3 and 4) so these can be used with a timer functions and the last thing is the brake input when the brake pedal is pressed the wing tilt will raise up to the full amount or when ever is set in the program.

    Voltage info
    Accessory input 6 – 12v +
    Speedo Input 5 – 0-8v +
    Brake Input – 12v +
    Steering angle sensor – Run on 5v from circuit.
    4 ways Position switch - Run on 5v from circuit.
    Power to Circuit – to run on 12v Mains.
    Not included in circuit but would be nice is a manual operation for maintenance of the wings mechanical components (just thought of that).
    Actuators will run off relay already installed so the motor output of the circuit will only have to run the relay coils.
    Really need help with this circuit. The value for the Resistors, Transistor etc. Very new to all of this and any info about now to work that out and the cucuit would be helpful.
     

    Attached Files:

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