I'm using a 16F88 to accept the signal from the sensors, then to turn on the LED strips

16F88 PWM can control brightness of the LEDs. Are these LEDs strips pre-assembled? or you are building them?

MOD Note: Created your own thread for a parallel LED circuit.

 

I'm building them myself

If you want them to last, invest in some resistors, they are dirt cheap.
Wire them like this:

You'd have to know your LEDs Forward Voltage (Vf) and calculate resistor value for them

Edit: It doesnt matter if the resistor is on top or below the LED, as long as they are on top of the transistor Collector. I'd imagine placing the LED on top would look nicer and neater

 

hi Ing,
Change the 10K to 2k2 resistors, the 10k is much to high a value.
E

 

You need 1.6A to illuminate 8 LEDs in parallel. I’m making some typical assumptions here. 20mA per LED

20mA * 8 = 160mA = 0.160A

 

hi iim,
With modern high brightness LED's you should find that around 10mA operating current will give a good light output.

Ref your post #11..
You have a 24Vdc supply, the LED, if a White colour will drop about 3V, so that means you have to drop 21V at 10mA across the series resistor.
Using Ohms law that gives R= 21v/10mA = 2.1K.... the nearest preferred values of resistor are 2k or 2k2.

If you wanted 20mA, which I would not use, that would be 21V/20mA = ~ 1k or 1k2

E

BTW:
Assume that the transistor in saturation has a gain of 10 to 20, so with 8 LED's at 10mA that's 80mA, so the Base current into the transistor has to be approx 8mA.
From a 5V drive Base input voltage assuming a Vbe of 0.7v for the transistor, thats 4.3v/8mA = ~520R, so I would use a 470R to ensure a good Base drive current

 

If you want them to last, invest in some resistors, they are dirt cheap.

I was just suggesting wiring it in parallel method, wasnt hijacking the thread...

From a 5V drive Base input voltage assuming a Vbe of 0.7v for the transistor, thats 4.3v/8mA = ~520R, so I would use a 470R to ensure a good Base drive current

Right, my bad there i was using a 24v signal pulse for some reason

 

hi iim,
Not a problem.
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The LED circuit boards will heat with a lot of heat if the supply is 24V. Use 5V or 6V instead and re-calculate the resistor values.