In this post I have explained a 555 based PWM circuit which can be implemented as a 150 nos or more LED light intensity controller circuit. The idea was requested by Mr. Anil
The Circuit Request
I want to run 150 nos LEDs of 5mm with help of IC 555 on Pulse & continuous mode.
I want use 12V/5A DC supply
Thanks & early reply is highly appreciated.
Thanks & regards
Anil Rustagi
The Design
The figure shows a PWM based LED intensity controller circuit using the IC 555.
IC 555 are popularly used in most PWM based circuit applications due to their easy configuration and precise PWM generation ability which is adjustable right from minimum to the maximum.
In the shown design the 555 IC is configured in its standard PWM mode with a slight variation wherein it's discharge pin7 is used as the output instead of its usual pin3 which is rather employed for the discharge function here.
The above configuration makes the functioning a bit more efficient and allows the spaces of the duty cycles to be sharp and more accurate.
Pin7 becomes responsible for creating negative pulses only for the attached transistor, while the positive pulses are derived from the 10 k resistor across the base and positive of the transistor.
VR1 is used as the PWM control pot which almost provides a range from zero to the maximum supply voltage for the LEDs through varying ON/OFF duty cycles as determined by the setting of the 100k pot
TIP122 is rated to hold upto 5 amp with adequate heatsinking meaning more than 150 LEDs rated at 20 mA each can be included with the device as shown in the circuit diagram.
Comments
Hello sir..
You have firealarm curcuit. Using IC555 or any other for my school project.
Plzzzzzzzzzz suggest me as soon as possible .
Mr.Swagatham,
Thanks for prompt reply ,The solution mentioned by you is helpful but the thing is my psu will be having three output terminals (+),gnd,(-) and i was thinking of solution for switching off lm337 circuit from negative power supply it gets from rectifier bcoz i wont be using lm337 as often as lm317 so switching it off would lead to better temperature control and energy efficiency. Pls help me in this regard.
I would also like to build voltmeter featured in your blog using ICL7107 and MAN6910 led display are those both components readily available at shops in lamington road ?
Hello Mr.Swagatham,
I am in the process of building dual polarity psu featuring center tap transformer, LM317 and LM337 circuits sharing common ground line parallely but i would like to know how i can use it as either mono or dual polarity mode by switching lm337 circuit as per needed as i am doubtful about simply incorporating switch to negative line from transformer would do the trick or should i build seperate independent circuit for both ics and connected their ground lines to transformer gnd line ?
Hello Gururaj,
You can connect an SPDT switch across the output of the power supply for achieving the selection modes..
Use the center lead of the switch as the negative output, positive will be from the 317 positive out.
the other two leads of the switch could be hooked up with the (-) and the GND of the supply for the intended selection.