How can i amplify the pir output

Thread Starter

panayiotis

Joined Feb 25, 2014
16
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
 

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R!f@@

Joined Apr 2, 2009
9,918
What is the LED specification?
Are you connecting LED's in series or parallel ?
Did you use current limiting resistors for the LED's ?
 

Thread Starter

panayiotis

Joined Feb 25, 2014
16
What is the LED specification?
Are you connecting LED's in series or parallel ?
Did you use current limiting resistors for the LED's ?
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
 

Thread Starter

panayiotis

Joined Feb 25, 2014
16
About LED.
So far we know that they need 5 volts to turn ON.
What we need to know now is current for their normal operation. Too little current and LED will be dim, which you already noted. Too much current and the LED will "burn out" which is probably not desired since you want them to last for a long time.
So.
Measure current when LED are dim. Measure current when LED are bright (when you connected them directly to battery).
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.
 

shteii01

Joined Feb 19, 2010
4,644
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.
I said we need current. You measured voltage.
Good luck to you.
I am out of here.
 

Thread Starter

panayiotis

Joined Feb 25, 2014
16
I said we need current. You measured voltage.
Good luck to you.
I am out of here.

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
 
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burger2227

Joined Feb 3, 2014
194
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.
 
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R!f@@

Joined Apr 2, 2009
9,918
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.
 

Thread Starter

panayiotis

Joined Feb 25, 2014
16
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.
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.
 

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R!f@@

Joined Apr 2, 2009
9,918
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?
 

Thread Starter

panayiotis

Joined Feb 25, 2014
16
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?
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!
 

Thread Starter

panayiotis

Joined Feb 25, 2014
16
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?
yes sir correct
 

burger2227

Joined Feb 3, 2014
194
Try this. Should work, but you may not need 2 transistors to turn on the PIR or the LED. Try one.


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.
 

Thread Starter

panayiotis

Joined Feb 25, 2014
16
Try this. Should work, but you may not need 2 transistors to turn on the PIR or the LED. Try one.


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.
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.
 

R!f@@

Joined Apr 2, 2009
9,918
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
 

Thread Starter

panayiotis

Joined Feb 25, 2014
16
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
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?
 
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R!f@@

Joined Apr 2, 2009
9,918
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
 

Thread Starter

panayiotis

Joined Feb 25, 2014
16
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
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!
 
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