How do I get my Sensor Switch transistors

Discussion in 'General Electronics Chat' started by RodneyB, Jul 24, 2015.

  1. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    The post below was the original with incorrect information. the out put is from 0 to 3V3 so I would like to have an out put at 1,2 and 3 volts.

    I have a sensor that has a range from 0 - 20mA.

    I would like it to switch on something at every 5mA (4,10,15,20mA's) So I could in turn switch on something Larger. Like switch on a transistor that in turn switches on a relay.

    Please can I have some guidance as where to start.
     
    Last edited: Jul 24, 2015
  2. cmartinez

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    I'd first convert its current output into a voltage output, then I'd connect its output to comparators to digitize the signal, and then switch whatever you want to switch using the comparators outputs...
     
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  3. RodneyB

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    Thank you

    I will look at the sensor Data sheet and take it from there
     
  4. cmartinez

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  5. MaxHeadRoom

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  6. RodneyB

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    Thank you I will look for the components and then try to build it. I would have to build 4 of each of the circuits to switch at the required voltage if my understanding is correct
     
  7. RodneyB

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  8. cmartinez

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    No... you only need to build one circuit as shown in the application note, then you use its 0-5V output and add four comparators to it.
    Using a comparator is rather easy, but do you need assistance with that too?
     
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  9. RodneyB

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    Thank you for your help, I made a mistake on the reading. Its 0 - 3V3 with a 5mA power consumption. I am going to edit my orginal post
     
  10. cmartinez

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    Well then, that simplifies things a lot. You no longer need the circuit in the application note, just the four comparators. How are you going to power your device?
     
  11. RodneyB

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    I am going to have a 12volt battery. I will use a 7805 to power the sensor. is there a single IC with four comparator
     
  12. bertus

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    Hello,

    Do you have a datasheet of the sensor to post?
    With the information, we can provide better solutions.

    Bertus
     
  13. cmartinez

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    Then you have to think about battery usage, and overall efficiency. I do not recommend you use the 7805, but rather a small smps like these ones, that has a much higher efficiency.
    Bertus, he posted the DS in post #9
     
  14. bertus

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    Hello,

    Ah, I see. The sensor is already producing a voltage, wich can be used for a comparator to switch at the points needed.

    Bertus
     
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  15. cmartinez

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    yup.... it's so easy that even I can help the TS Emoji Smiley-06.png
     
  16. RodneyB

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    In post #9 I attached the datasheet
     
  17. RodneyB

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    I have no idea where to begin
     
  18. cmartinez

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    First question, why a 12V battery? Is it a large battery? Can't you use a power adapter instead?
     
  19. RodneyB

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    I can use a power adapter. I chose a 12 volt battery 7Ah as I had successful with the help of this forum made a 12volt charger for this battery
     
  20. cmartinez

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    It's far better if you use a power adapter, since I'm under the impression that you intend to use your device continuously. Also, efficiency would cease to be a concern and the design would be far simpler.
    Question #2, how do you intend to mount the components? Can you make your own PCB's?
     
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