Can i create a electronic circuit to handle LED strips like this?

I am trying to create another electronic board that handles LED strips.  I am a newbie, and this is my second build. I tested the circuit but my 10 ohms resistor burnt out. Any advice or suggestions for resistor for this circuit? If i use any resistor 100 ohms + (100, 150, 225, etc) seems to dim the brightness of the LED strips. Should i leave my schematic the same and just use a higher resistor e.g.. 68 ohms or 82 ohms? My LED strips are :-

Working Input Voltage: 12VDC.
Working Current/meter: 0.4A.
Output power: 48W /5 Meter.

Picture of Can i create a electronic circuit to handle LED strips like this?
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iceng4 years ago
I would appreciate if you would Click me the best answer
if I helped you move

islandboii242 (author)  iceng4 years ago
Not a problem bro, i just did. We just made something i think others can take and kick it up to another level. :)
Yes we did !

200 people have viewed this thread and
maybe a few picked up some new info..


islandboii242 (author)  iceng4 years ago
yes yes :D next project soon begin, i already completed two prototypes.
It's Worth Knowing that if you do a Good job publishing your project
particularly in very clear explanation for beginners
then you may get your ible featured and
Then you will receive as a minimum a free three month PRO subscription..

Best Regards'

iceng3 years ago

You asked..

"My battery seems to not be holding charge. For example i left this
project without charge for 2 months and came back and it seems to be
completely dead..The Battery. How can i patch up that power leak?"

I assume the battery was hooked up with the LDR, transistors and diodes.

There will always be some current flowing ie leaking through the circuit.

The only way to stop current is to put a SPST switch in series with the battery.

The LDR is reacting to space particles always raining down on this planet and momentarily activating the transistor. Cover the LDR with black tape and you have a primitive Geiger detector.

SPST = Single Pole Single Throw

iceng4 years ago
You are in safe electronic territory .
Trial and result is what you need to do now,
discover what works best for you.

I would have to measure voltage drops to answer your detailed questions
don't be avers to trying three diodes.

  • BTW
  • 1N4002 is a 1Amp 100V version of the
  • 1N4004 1Amp identical 400V  diode version
The Fairchild diode factory makes a 400,000 lot of 1 Ampere diodes and
then tests their breakdown voltages.
  1. Putting those over 1000V into the 1N4007 bin,
  2. the remaining over  800V into the 1N4006 bin,
  3. the remaining over  600V into the 1N4005 bin,
  4. etc
The pdf is included, look at it please :-)
islandboii242 (author)  iceng4 years ago
ok i ran trials and still no luck with the led strips..but the same thing occurs..if i touch the positive lead from the battery and the positive on the LDR it i need to change my LDR? do you have skype? so i can show you what im doing to run the tests
Sorry no skype.

When you touch the battery + and the LDR  you are reducing the top resistance.

This is important because a very small increases in base current
has a corresponding higher amplified collector current pic2.

Can you measure the resistance of your LDR ONLY 
  1. with black tape over the sensor
  2. and no tape wit full light

IF the LDR is good.  
  • Would you also try to adjust the R & ?  with the LDR in the circuit and taped black, until the LED strip barely glows.. 
  • And then lower the resistor ? until the strip brightens up..
  • But never less then a total of 2k ohms !!!
  • Then remove the black tape and shine a light on the LDR
  • The LED strip should go out (LEDs off )

islandboii242 (author)  iceng4 years ago
Ok with 2 1/4watt 2.2k resistors and 2 1N004 diodes the LED strips turns off if i shine a single LED over the LDR..which is good but i need to make sure these LED strips are off during the day with little sunshine and on at thinking i MAY need another LDR. Ok i will send some pictures
islandboii242 (author)  islandboii2424 years ago
Ok LDR with no tape or not covered measures 45.7 on my multimeter at 200k ohms, with black tape over it it measures at 181.0
An LDR that changes from 46 ohms to 200,000 ohms is a very good range for a sensor.

Changing to another LDR is a mixed bag.
You could see some improvement or way worse performance.
In most changes you will have to re-adjust the circuit calibration.

The next step is to re-evaluate the the design limitations and do some engineerig.
  • A .higher voltage offers more choices using more transistors.
  • A CMOS NOR gate IC used as a compparitor is a sure way to get the go nogo switching action.
  • Of course an 8 pin uP ( requires software programming ) will do the best.


islandboii242 (author)  iceng4 years ago
Lol i have NO software programming skills...Didn't know this would go in-depth as i learn new things. What do you suggest someone like me do without no programming skills but basic electronic skills lol. My first prototype was simple using individual LED's.
islandboii242 (author)  islandboii2424 years ago
Ok i got everything to work now with some tweaking...My Version 2 of the controller board i will use the 8 pin uP or the CMOS NOR gate IC. Thanks for everything i will keep you posted!
islandboii242 (author) 4 years ago
do i need to increase the voltage by adding 2 more batteries?
islandboii242 (author)  islandboii2424 years ago
After adding more batteires then add a 650 ohms 1/2 watt resistor?
Get a 1 Amp = 1000 ma transistor  with a minimum DC gain of 25 hfe.

Try your circuit without the photocell or any other changes
it should light with the resistor touching plus
and then turn off with the resistor touching minus.

If that Works, add the photocell and try that.

When you raise the voltage  the base resistor needs to change also.
iceng iceng4 years ago
Do you know which NPN pin is the base, the emitter and the collector ?
islandboii242 (author)  iceng4 years ago
from the picture, the middle is the base. The right pin is Emitter, and the far left pin is the collector. The curve (front) or the npn transistor is facing the LED strips.
islandboii242 (author)  islandboii2424 years ago
Ok am i removing the photocell just to test the new changes? I will need the photocell to handle the on and off control. 1amp (1000 ma transistor w. DC gain of 25hfe)..i have no idea what a transistor with such configuration looks like. I'm a newbie, sorry. Can i get a picture of it please?
The ZTX450 NPN 1 Amp Transistor with a minimum gain of 100 (see the PDF)
Which means the resistor needs to be raised to 2.5K = 2500 ohms
to run your 0.4A LED strip.

This transistor has a range of gain 100 to 300 and your circuit depends on a delicate
balance to use the photocell consequently that resistor ma need to
be more then twice as large.

The TO-92 sized transistor is available from DigiKey Electronics for 67¢
You should buy 10.

What you call a photocell .... is it a LDR  (light dependent resistor) or a solar cell ?

As a "newbie" you should know most of us tech people help you for passing on what we know and the coveted best answer which you can click eventually.

BTW if you add more strips and increase the current load you will need a bigger transistor
probably a mosfet transistor.
islandboii242 (author)  iceng4 years ago
it's a light dependent resistor, which i have attached..yes yes thats why i do appreciate instructables and everyone on it. It's a inspiration to me. I will order the transistors. Thanks for the link and the help i am getting from you.

Would i need to change the LDR?
islandboii242 (author)  islandboii2424 years ago
10K-0.5K is what i see when i bought it.
First step is to use an $9 multimeter from Harbor Freight to verify the LDR
resistance change dark closet to bright room

Actually it is a good match for the ZXT450..
then play with resistor values but stay above 1K..
islandboii242 (author)  iceng4 years ago
I have received the new NPN Transistors and will have to get the new resistors or can I still use the 10ohms resistor.
Smoke the circuit if you like !

Power = Voltage × Voltage ÷ Resistance
Voltage = Battery - VBE = 10.8 - 0.4 = 10.4V
P =10.4 × 10.4 ÷ 10 = 10.8 Watts applied to a 1/8 Watt = 0.125 watt resistor.
THAT IS 100 TIMES the power of the 10 Ohm Resistor !

"The ZTX450 NPN 1 Amp Transistor with a minimum gain of 100 (see the PDF)
Which means the resistor needs to be raised to 2.5K = 2500 ohms
to run your 0.4A LED strip."I

I provide your circuit and a working one.

islandboii242 (author)  iceng4 years ago
the closest resistor i was able to get is a 2.2k which is 2200 ohms, so ill need to order these. thanks for everything :D
2200 is safe to use.

Resistor power 10.4^2÷2200 = 0.049 Watt

Base Current = V/I = 10.4 ÷ 2.2K  = 4.7 ma
At a min gain of hfe = 100 ... that can switch 0.47 Amps
islandboii242 (author)  iceng4 years ago
ok it works, i may have to change my LDR sensor because the LEDs doesn't turn off when light hits the sensor, but if the two wires for the LDR sensor touch, it turns off.
islandboii242 (author)  islandboii2424 years ago
LDR is 10K-0.5K
islandboii242 (author)  islandboii2424 years ago
i need to go higher to a 27-60kohm LDR instead?
NOT Higher !
Lower if anything (but then the LDR can easily fry like your resistor did)

The LDR is perfect o.5K  =  500 ohms low is as good as reasonably possible.

Try the two diodes (any small lead devices will do).
they make it easier to rob base current like when you shorted the wires.
Then add a second series resistor.......
islandboii242 (author)  iceng4 years ago
I used two 1/2 watt 2.2k ohm resistors, the LDR didn't work, i will have to purchase some diodes, i also have 1/4 watt 2.2k ohm resistors.
islandboii242 (author)  islandboii2424 years ago
Maybe my LDR no longer works lol
OMG and here I thought you were using the ohmeter function of a $9 multimeter from Harbor Freight to measure the LDRange.

You can try to use the 1/4w  2.2k  as a third resistor in series.
Get another  couple LDRs

When you do this,  TAKE CARE you watch (feel) the temperature of the transistor
if the LED strip only dims down.
If it burns skin ! .... Quickly pull power OFF
then remove the third resistor.
and try two or three signal diodes next

islandboii242 (author)  iceng4 years ago
i do have a multimeter with ohmeter function already, i have this one here Multimeter.

ok i just added the 1/4w 2.2k and the LED's dim once i place the LDR over the LED strips, but it doesn't completely turn them off.  With the third resistor the transistor seems fine, the transistor doesn't heat up. 

 Any particular type of diodes i need?
These 1N4004  are a good deal at 50¢ for 10 and can be used for other projects.
islandboii242 (author)  iceng4 years ago
ok i ordered the 1N4004 but i went ahead and purchased 2 1N4001 just to test the circuit. After adding the two diodes between the 2.2k resistor (single) and positive for the battery. The photocell (LDR) only works when i touch the positive wire where i connected the LED strips and the positive wire on the LDR, the LDR turns off when light hits the sensor and turns on when no light hits the sensor. I guess this is because of the Diodes correct?

islandboii242 (author)  islandboii2424 years ago
Ok so my question is about the diodes, do i use two diodes or a single diode for the 2.2k resistor because the LEDs doesn't shine that bright enough. But i guess i can play around with the circuit...i built a test sample. Will keep you posted.
  • Try putting those two diodes in series with the base
  • or try two resistors in series ( your transistor may have the high gain)