PIR operated DC motor project odd behaviour help

Discussion in 'Circuit Help' started by spyder9, Feb 15, 2017.

  1. spyder9

    spyder9

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    So i started making PIR sensor operated dc motor
    I got pir sensor switch with + and - input and output ports
    When i connect dc to output ports it starts when it detects signal,but doesn't stop ever.
    But when I plug multimeter on the output current stops when there is no signal
    i can't figure out why
    Maybe some resistors between pir out and dc ?
     
    spyder9, Feb 15, 2017
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  2. spyder9

    shrtrnd

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    Do you have a part # or data on your Passive Infra-Red sensor?
    You might have a 'switch', but you might instead have a 'sensor'.
    If it's a sensor, it will have varying degrees of sensitivity associated with it, not an 'on-off' 'switch' function.
     
    shrtrnd, Feb 15, 2017
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  3. spyder9

    spyder9

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    It is exact same as this one on the picture
     

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    spyder9, Feb 15, 2017
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  4. spyder9

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    CDRIVE, Feb 16, 2017
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  5. spyder9

    spyder9

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    It is at 5sec
    I added 1.5 ohm resistor to the output before the motor
    Now motor stops when it should but only for 1-2 seconds and then starts again and stops after 5 sec and again goes into loop
     
    spyder9, Feb 16, 2017
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  6. spyder9

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Should we assume that you've played with the sensitivity adjustment? Also, what's the motor current draw at this voltage?

    BTW, welcome to Electronics Point.

    Chris
     
    CDRIVE, Feb 16, 2017
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  7. spyder9

    spyder9

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    There isn't sensitivity adjuster
    Only delay
    Really don't know
    My current meter is broken

    Thanks,loving it so far..so many great posts and very helpful
     
    spyder9, Feb 16, 2017
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  8. spyder9

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    According to the link and image I posted there is a sensitivity adjustment. Actually I'd be surprised if it didn't.

    Chris
     
    CDRIVE, Feb 17, 2017
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  9. spyder9

    spyder9

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    It doesn't have it
    Only delay adjuster
    I tried adding a diode to the motor,on the basis that it will act likea flyback diode. now it stops for longer period but still goes into on-off loop
     
    Last edited: Feb 17, 2017
    spyder9, Feb 17, 2017
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  10. spyder9

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    OK, I had to go back to your original post to verify this. You didn't specify this but should we assume that only the multimeter is connected to the output (no motor) when measuring? Did you try driving only a resistive load?

    You never did answer my questions about your motor specs. Please post them and or a link to your motor. You may well be overtaxing the output capabilities of your detector. For all we know your also exceeding the capabilities of your power source. Is it a wallwart? Motors can pull many times their run current when starting.

    Not knowing anything about your motor and taking into account (if I assume correctly) that it works as expected when only the multimeter is connected to the output, I think you'd be well advised to use the output voltage to drive a Relay or Transistor switch. There's a good chance that you may need a separate power supply for the motor as well. On the other hand this might be a decoupling issue that might be cured with some bypassing caps on the detector's output.

    BTW, the flyback Diode that you added is something you should have done from the get go but I think you know that.

    Chris
     
    CDRIVE, Feb 17, 2017
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  11. spyder9

    spyder9

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    Thanks for the comperhensive answer
    Motor specifics are not important because in the end motor will be windscreen wiper motor and it will run off 12v dc power supply
    Now at home i'm testing with 5v supply and toy dc motor

    I solved the problem

    This pir sensor switch can be triggered by unstable voltage.
    And when motor is running voltage on output is 1.5v to 3v
    I added L7808cv voltage regulator and now i have stable 4.8 v output
    And sensor works as it should

    Thanks for help
     
    spyder9, Feb 17, 2017
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  12. spyder9

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    This is going to leave this thread supposedly resolved with more questions than answers. For one thing how and why does an 8V linear regulator output 4.8V and moreover do it with only 5V input? :confused: Are you omitting important details, like your no longer using a 5V supply?

    Chris
     
    CDRIVE, Feb 17, 2017
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  13. spyder9

    spyder9

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    Supply is 5.0v cell phone charger
    With no load it gives 5.8v at 500mA
    I don't know about the regulator and why it is working
    Here is a pic of the connection
    Ir diode gives signal to pir
    That is why it is covered with tape,so that no outside parameters can get in

    Also can you suggest me what model regulators to use for 12-14v dc supply
    Cheap as possible,budget is an issue
     

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    Last edited: Feb 17, 2017
    spyder9, Feb 17, 2017
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  14. spyder9

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    It's a miracle that thing is working at all. First off I had no idea that the only thing the regulator is regulating is the motor voltage not the entire PIR circuit. Besides that your regulator is not wired properly, as I don't see a GND connection between the motor and the regulator's GND pin. Quite frankly I'm so confused I'm getting dizzy! :confused:

    I'm going to be heading out to my Saturday watering hole. When I return I'm sure I'll be a lot sharper. So much so that this is all going to make perfect sense to me. :rolleyes:

    Chris

    Edit: Your color codes threw me. I guess there is a GND connection but it still doesn't answer how an 8V regulator is working with 5V input.
     
    CDRIVE, Feb 18, 2017
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  15. spyder9

    spyder9

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    This is only temp. wiring,there is a GND connection,to the - pin,together with motor negative
    I also dont know,that is only one i had and i put it in no idea that it will work
    Only later i found out that it is meant for 8v

    For 12v i'll put either 7812 or 7815
    And will report results
     
    spyder9, Feb 18, 2017
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  16. spyder9

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Linear Voltage Regulators must be powered by a source voltage higher than the Vreg voltage it's spec'd at. Take a look at this simulation of a 7808 regulator and tell me if you understand it. VS1 is a voltage source (Input) being swept from 0V to 20V. Observe the input voltage (X Axis) versus the output voltage (Y Axis).

    Chris
    upload_2017-2-18_22-39-39.png
     
    CDRIVE, Feb 19, 2017
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  17. spyder9

    spyder9

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    Well i do understand it
    It must be powered by voltage above 8v so that it can reduce it to 8v and keep it stable at 8v under load

    Today i'll put 14v input and see what happens
    This DC motor is rated 3-6v,but i'm sure that it can handle 8 for testing purposes

    One more thing
    I'm planning to use car wiper motor (12v dc)
    And i was thinking to use 12v regulator 7812
    And power it from 14v 1A supply
    Can this regulator keep motor working when i put some load on it ?
    Or do i need to put 14v regulator (i think 7815)
    And run it on 14v with 18v 1.5A supply
    Thanks in advance
     
    spyder9, Feb 19, 2017
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  18. spyder9

    duke37

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    I would think that a wiper motor could take much more than 1A, measure the free load current. The running current all depends on the torque required.
    The motor will behave as almost a short when turned on. What is the reason for a regulated supply when you are happy with either 12V or 15V.?

    If the supply comes from a transformer, rectifier and reservoir capacitor, then look at the amplitude of the ripple and make sure that the minimum voltage is sufficient.

    I have used an unsmoothed rectified supply controlled by a SCR, the SCR is triggered when the back EMF is too low. Ths supplied a 12V car fan motor to drive a coil winder so speed not critical but needed controlling.
    Start with a 12V 5A old style battery charger to give sufficient current and isolation.
     
    duke37, Feb 19, 2017
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  19. spyder9

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    This thread spawns more questions than answers. What are the Red & Black conductors coming off the left side of your PIR module?

    Chris
     
    Last edited: Feb 19, 2017
    CDRIVE, Feb 19, 2017
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  20. spyder9

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Let's see if I can get the image pasted this time..
    Chris
    upload_2017-2-19_10-3-7.png
     
    CDRIVE, Feb 19, 2017
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