How can i amplify the pir output

Discussion in 'The Projects Forum' started by panayiotis, Feb 25, 2014.

  1. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    dear sirs,
    I need help with a project I am making. It is a solar LED light that turns on at night when the PIR sensor detects motion. Batteries are 2x 3.7V 18650. PIR sensor is a standard BISS0001. LEDs are 12x 5V and 5 extra LEDs, 10mm.

    I connect the LDR with 2 npn BC547 transistors, and I have the result I wanted, the lights turn on at night. Then I connect the PIR sensor in the circuit, and with a tester I measure 3.03V in the output of the PIR.

    The LEDs work but the light is low. It is not the same as if I connect the batteries directly to the LEDs. The voltage with NPN transistors is 3.52. The battery voltage is 4.2 volts when charged.

    is it possible to increase the volt from pir to leds somehow?
    thanks
     
    Last edited: Feb 25, 2014
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    What is the LED specification?
    Are you connecting LED's in series or parallel ?
    Did you use current limiting resistors for the LED's ?
     
  3. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    dear sir ,
    the leds are parallel , but now that you mentioned it , yes the leds are kit with their resistors. should i remove resistors?
    leds specifications sy 12- led- 5v and other 4 10mm leds i do not know their specifications. i also add some photos for helping
    thanks
     
  4. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    dear sir ,
    thanks for answering
    i test just now
    from my 2 batteries i have 4.2v.
    i connect directly all the leds and they are bright
    now from npn transistor 2n2222 (as shown in the circuit) i measure 3.5v only.
    so if i connect it to the leds are dim.
     
  5. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,393
    497
    I said we need current. You measured voltage.
    Good luck to you.
    I am out of here.
     
  6. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1

    please sir dont get mad i am not a professional in circuits and i never go to any school i just read and learn from google.
    current is ampere i learn that now
    with multimeter in 10a and leds connected directly to batteries current is measure 0.12
    when leds are connected as circuit current is 0.02
     
    Last edited: Feb 25, 2014
  7. burger2227

    Member

    Feb 3, 2014
    190
    24
    Not to fear, shteii01 only posted once so he never told you anything.

    The schematic looks backward to me. NPN transistors need a voltage to trip and the photocell should pull it to ground during the day when it is low in resistance. Q2 is wired backwards. The emitter should go to ground like the arrow says. The collector goes to what you want to ground.

    The second two transistors are trying to amplify the PIR signal. Not sure what else would work better.

    If you are reading amps and you got .12, then you are pulling 120 ma, which is a lot for 2 LED's even in parallel. Check immediately before the LED anodes(+ long leg) and see what they read. Add some resistance to get them down to .020 A.
     
    Last edited: Feb 25, 2014
    panayiotis likes this.
  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    No one is mad. shteii01 just said he was leaving tht's all.
    we tend to talk like tht but we hardly get mad. Okay.

    So the LED's light with battery of 4.2V the way you want, right?
    If so you do not need a resistor

    I am confused in the way the circuit you posted is wired.

    Can you draw a circuit how you connect with the PIR, but without LDR if you are not using it.
    I am asking the circuit that you want to work. Any thing you do not use should be left out of the circuit.

    Your circuit (posted) won't work properly I think.

    PS. I rejected ur friend request cause you need to have your info properly entered into the forum and should have minimum of around 100 posts or so. I am doing this cause I get too many request from new members who do not hang around after they are done.
     
  9. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    dear sir ,
    many thanks for answering
    i studied to find why you said schematic looks backward.
    so i find the correct one.
    in the first circuit the led is working perfect at night.
    now as i want to make , the ldr must make the pir work when it is activated at night. so in the second circuit i connect the pir. but i have a problem. i dont know where i make mistake but when there is light in the room the led stay on but very dim.when is dark the led work fine when pir take motion.
    thats why i make different connections in the main circuit i enter in the post , because when i connect them that way the pir and ldr work fine.
     
    Last edited: Feb 26, 2014
  10. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    So let's get this straight.

    You want the whole thing automatic ?
    You want the circuit to work or detect motion only at night ?

    If that is so.
    U want the LDR to keep the PIR off at day time and when it is dark the LDR should switch on the circuit (PIR) so any motion would light the LED. Am I right?
     
  11. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    thanks for answering
    sir i want to use the ldr in the circuit and pir too!
    So the LED's light with battery of 4.2V the way i want correct.
    first post circuit works as it is.when is dark and the pir take motion the leds turn on but dim! so , i think , my problem is that from the pir output + i must enter something ( boost regulator or npn 2n 2222 transistors) to amplify the volts so the leds turn on bright
    i added in my other answer 1 thumbnail , please check it!
     
  12. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    yes sir correct
     
  13. burger2227

    Member

    Feb 3, 2014
    190
    24
    Try this. Should work, but you may not need 2 transistors to turn on the PIR or the LED. Try one.

    [​IMG]
    Note that I use 100K on top of the LDR. That could even be 150K to cut down on current required.

    The LED can go where the meter is. You may be able to use all 547's instead of 2222 also.
     
    panayiotis likes this.
  14. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    dear sir i make the circuit as you told me!
    when there is no light it works perfect! when take motion leds on and bright!
    but when there is light leds stay on.
    i thought the ldr maybe has problem but i have more and i change it and still the same.
    i check 3 times the circuit if i make a mistake but all are ok.
    seems the ldr does not cut the power when there is light.
     
  15. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    The issue may be tht when you cut the GND the PIR out is floating.

    Try a 10KΩ resistor between Ground and output of PIR.
    Use the same circuit and just connect 10KΩ between output of PIR and ground
     
    panayiotis likes this.
  16. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    sir i try the 1KΩ because i do not have 10KΩ and it works!
    i also remove the one bc547 transistor as mister burger2227 told me and the circuit works only with one.
    thanks a lot. tomorrow i assemble the circuit in the lamp as it should be and i will message you.
    thanks again.
    just to confirmed something else , with two bc547 transistors as i have it at the first circuit , and now with one transistor the circuit get wicker? or it does not matter?
     
    Last edited: Feb 27, 2014
  17. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    Wicker ??
    What do you mean ?
     
  18. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    sir thanks for answering
    my english are very bad when want to explain. (sorry) .just advice me if it is better with one bc547 or with two , to connect the circuit for the ldr please
     
  19. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    If it works OK no change needed.
    If you need to cut cost, then just try with one and check.
    You already know how it is working, so I believe you can try the above options
     
  20. panayiotis

    Thread Starter New Member

    Feb 25, 2014
    16
    1
    dear sir
    i am very very thankful. you and mister burger2227 help me a lot!
    dont know how to thank you! i hope the best for you 2!
    and mister R!f@@ i will be around i will not leave the page!
     
    Last edited: Mar 5, 2014
    R!f@@ likes this.
Loading...