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- chinmoy1955 commented on Dipankar's instructable LED TUBE LIGHT (AC)5 months agoView Instructable »
- chinmoy1955 commented on dan's instructable Power LED's - simplest light with constant-current circuit5 months ago
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.

View Instructable » - chinmoy1955 commented on dan's instructable Power LED's - simplest light with constant-current circuit5 months ago
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.

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