N-Channel MOSFET

[R Y A N]

Hi all, I am new to electronics and need a bit of help locating what i think is a specific component.

I need a N-Channel MOSFET that only allows current above 4.5v to pass through. I am in the Midlands England if you can help me with a place to locate this that would be great.

Thanks in advance

Ryan

[Pauldf]

What current is it handling?

[R Y A N]

The circuit will be running on a 9v battery, sorry I cant be of more help lol I'm way out of my depth.

[Pauldf]

What is it running? Do you have a circuit diagram?
I'm taking it you are wanting something to happen the voltage in your circuit hits 4.5v? There are many ways of doing this, the easiest is probably just using a Darlington pair transistor (TIP110 is a 2Amp NPN), a zener diode and a few resistors.
Or are you after a constant voltage supply of 4.5v?

[piratepaul]

You are going to have to tell us what it is for, you are talking about apples(current) and oranges(4.5volts)
Current is Amps... force causing current to flow against a resistance is measured in volts... look up ohms law.
Tell us what it is for and we will see what we can do.

Tar&stuff.

[R Y A N]

Hi guys, sorry for late reply,

Unfortunately i wont be able to share a diagram with you at this time due to several reasons, but ill describe what i want to do.

The circuit include a light dependant resistor and there will be around 9 circuits all very close to each other. What i want the part mentioned for, is to make sure that there is definitely a led adjacent to the resistor and that light leakage will not cause the other circuits to activate. so i need something that will only allow power through when there is a considerable amount, and if there is some light leakage the other circuits wont be continuously on. i will then need the full power to flow through the circuit that the light is on.

This is probably the best i can do to describe what i want without showing you exactly what i am doing, i appreciate it may be hard to understand and if you cannot help me no worries.

I would like this part as it would be easier to replicate in many circuits.

Cheers

[Pauldf]

So you are in essence trying to make your own opto coupler? Why not just use opto coupler chips or solid state relays?

[R Y A N]

I would like to use a N-Channel MOSFET as this is what has been advised to me. It may be an american part as you guys don't seem to know what one is or may have a different name. i can find them with a google search but I don't know exactly what one I need and thought you could help me with that. I know this part would work but if its not possible to get or if no one can advise me on which one to get for my purpose i will begin to look at alternate ways to the same end.

Unfortunately I don't know what an optocoupler is and think its unlikely to be what I'm trying to make. All i need is a component that will only allow the energy to flow when it is supposed to, ie when the led is directly illuminating the resistor. i understand there will be light leakage and so only want it to work when there is a considerable flow of energy through the resistor.

Forgive my terminology as i said im no good lol

Thanks

[Pauldf]

An opto coupler is basically an LED and a photo transistor inside a chip, no light leakage problems etc. You apply voltage to the LED side and the output side switches on, you use the output side to drive a transistor and the transistor to drive the output, simples. With one of these you don't need to re-invent the wheel!
Have a look on google for an ILQ74 chip, this is a quad opto coupler. Plenty of data sheets out there for them.

[R Y A N]

The opto coupler wouldn't work in this case as i need the LEDs to be separated from the LDRs by a wooden timing disk allowing each circuit to be complete by a hole that allows the light through.