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7 CommentsDelhi, India
I am an electronics hobbyst, a DIY guy taking care of all the techinical stuff at home (and friends' homes!). I love to use the hammer, drill machine, screw driver (to screw anything that I can lay my hands on) etc. Profesionally, I own a manufacturing/production unit for professional quality PA audio equipment like audio mixers, digital echo units, amplifiers etc. My experience in electronics spans about 30 years.

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  • Power LED's - simplest light with constant-current circuit

    Congratulations on a simple but effective constant current circuit.The schematic symbol of the MOSFET shown in the circuit diagram is that of a P-Channel MOSFET, not N-Channel. Moreover, it is not a simple FET but a MOSFET.The power adapter voltage can be calculated as follows:V supply = 3.2 X n + 1VWhere 3.2 is the voltage drop across each led, n is the number of LED's in series.The 1V added in the end is to take care of any voltage drop that may occur in the power supply due to regulation errors. So a 6V supply can only feed one LED. A 12V supply can feed a maximum of 3 LED's. From the above rough formula we can say that 3 LED's in series will require:V = 3.2X3+1 = 10.6VSo a 12V supply will also work with 3 LED's, but to keep the power dissipation of the MOSFET at a minimum, it would ...see more »Congratulations on a simple but effective constant current circuit.The schematic symbol of the MOSFET shown in the circuit diagram is that of a P-Channel MOSFET, not N-Channel. Moreover, it is not a simple FET but a MOSFET.The power adapter voltage can be calculated as follows:V supply = 3.2 X n + 1VWhere 3.2 is the voltage drop across each led, n is the number of LED's in series.The 1V added in the end is to take care of any voltage drop that may occur in the power supply due to regulation errors. So a 6V supply can only feed one LED. A 12V supply can feed a maximum of 3 LED's. From the above rough formula we can say that 3 LED's in series will require:V = 3.2X3+1 = 10.6VSo a 12V supply will also work with 3 LED's, but to keep the power dissipation of the MOSFET at a minimum, it would be advisable to keep the power supply voltage as close to the calculated value as possible, thus 11V would dissipate less heat than a 12V supply. So if you have a 24V supply available, you can safely connect 7 LED's in series.

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  • Power LED's - simplest light with constant-current circuit

    Congratulations on a simple but effective constant current circuit. It is very wrongly mentioned in the article that Q2 is a N-Channel FET. It is actually a P-Channel MOSFET, you may check it from the data sheets. Moreover, it is not a simple FET but a MOSFET.The power adapter voltage can be calculated as follows:V supply = 3.2 X n + 1VWhere 3.2 is the voltage drop across each led, n is the number of LED's in series.The 1V added in the end is to take care of any voltage drop that may occur in the power supply due to regulation errors. So a 6V supply can only feed one LED. A 12V supply can feed a maximum of 3 LED's. From the above rough formula we can say that 3 LED's in series will require:V = 3.2X3+1 = 10.6V So a 12V supply will also work with 3 LED's, but to keep the power dissipation...see more »Congratulations on a simple but effective constant current circuit. It is very wrongly mentioned in the article that Q2 is a N-Channel FET. It is actually a P-Channel MOSFET, you may check it from the data sheets. Moreover, it is not a simple FET but a MOSFET.The power adapter voltage can be calculated as follows:V supply = 3.2 X n + 1VWhere 3.2 is the voltage drop across each led, n is the number of LED's in series.The 1V added in the end is to take care of any voltage drop that may occur in the power supply due to regulation errors. So a 6V supply can only feed one LED. A 12V supply can feed a maximum of 3 LED's. From the above rough formula we can say that 3 LED's in series will require:V = 3.2X3+1 = 10.6V So a 12V supply will also work with 3 LED's, but to keep the power dissipation of the MOSFET at a minimum, it would be advisable to keep the power supply voltage as close to the calculated value as possible, thus 11V would dissipate less heat than a 12V supply. So if you have a 24V supply available, you can safely connect 7 LED's in series.

    View Instructable »