I only have a basic knowledge about electronics and need a little help with transistors.
For a project I need to drive 154 leds in 22 stings of 7. They would use a combined current of 440mA. Before every string is a resistor.
Now, what I need to achieve with the leds is to have two modes of operation.
1. I need them to automaticaly adjust to ambient light, they should be more dim when the room is darker. I want to do this with an LDR and a potentiometer for finetuning but I have no idea how I should choose the correct resistor values. I don't even know if that part of the circuit is correct, I just found it on the internet.
2. The second thing I would need them to do is to be able to mannually adjust them. I want to use a potentiometer for this and a resistor for a minimum value.
As far as i understand I can control how much current can flow trough the transistor by adjusting the voltage accross the base and the emitter. I think the voltage should be between 0,5V to "close" the transistor and 0,8V to fully "open" it? If this is correct how can I calculate the correct resistors with only the voltage?
thanks in advance
For a project I need to drive 154 leds in 22 stings of 7. They would use a combined current of 440mA. Before every string is a resistor.
Now, what I need to achieve with the leds is to have two modes of operation.
1. I need them to automaticaly adjust to ambient light, they should be more dim when the room is darker. I want to do this with an LDR and a potentiometer for finetuning but I have no idea how I should choose the correct resistor values. I don't even know if that part of the circuit is correct, I just found it on the internet.
2. The second thing I would need them to do is to be able to mannually adjust them. I want to use a potentiometer for this and a resistor for a minimum value.
As far as i understand I can control how much current can flow trough the transistor by adjusting the voltage accross the base and the emitter. I think the voltage should be between 0,5V to "close" the transistor and 0,8V to fully "open" it? If this is correct how can I calculate the correct resistors with only the voltage?
thanks in advance