Is 3.3V enough to open either a IRF520 transistor or a bc547 transistor?

I have a problem that started when i changed the microcontroller of my project from an arduino uno with 5V logic to a nodeMCU board with 3.3V logic.
I have a problem now which i think comes from the fact that 3.3V isnt enough to "open" the transistor im using. The one i used when i used the arduino uno is a IRF520 transistor. But from what i've tried i cant get the nodeMCU to open the transistor... I wonder if it needs a higher voltage than 3.3V?

I also have another transistor which is a bc547. I dont know if that one will work instead. I tried looking at the datasheets but I didnt understand what i should look for really.. If anyone could let me know if it is possible to open the gate of any of these two transistors with 3.3V I would appreciate it very much.

I connected the circuit the exact same way as i had it when I used the arduino uno instead of the nodeMCU-board.

An IRF520 is not meant to be used directly with an Arduino, period !

The required gate voltage for proper usage with the IRF520 needs to be 10v.

I figure that it may. But what exactly do you have in mind?
-- Max. collector current is 100mA, a bit limiting. --

Oh ok, that is the one i got with the arduino starter kit that I bought a while ago though, it worked for me consistently when I used arduino, at least for what I was doing with it, which was oenig a solenoid valve which draws 300mA current at 12V. So i figured as those two are the only two i have right now i might try to use them

Okay thanks for the info, then I wont be able to use that one as I am trying to open a solenoid valve at 300mA

I could also buy another transistor which would work for my project if anyone has a suggestion. I need at least 400mA possible current draw and I need it to be able to open at 3.3V. But I would prefer to use the irf520 for now if possible even though it might not be perfect

What voltage will the IRF520 be controlling ?

You can use a circuit like E1 with an NPN BJT controlling the IRF520

The 5v on resistor R3 would be changed to 3.3v.

"open", are you saying turn it off, take it out of the case? The device needs just about 5V Vgs to start to turn on (it is far from fully enhanced). With what you are saying the MOSFET will remain off. It borderline worked with your previous version. You can turn the bc547 on with 3.3V but you need a resistor in series with the base. However since your load is 3X its current rating you will go through a lot of them. Try this link it will help you a lot: Recommended power Mosfets 3.3V to use with Arduino - #12 by Deous

12V with 300mA current draw.

Im sorry im pretty new to electronics and that seems too complicated for me, I dont think that is an option for me

I havent really understood the transistor-terminology but what I mean when I say open is that current can flow through two of the transistors pins.

It’s not really difficult at all.

You have the bc547 and the IRF520 already.

Add R3, R4, and R5.

The motor is replaced by your solenoid, place a reversed diode (1N4000-1N4007) across the load for protection.

Is q27 the bc547-transistor I this picture?



Here is a picture of the circuit i had earlier with the Uno that worked fine (The diode looks unconnected in the picture but It isnt really):

Okay thanks i will try this tomorrow. Although i think i still should get another transistor that is better suited for my use to tidy it up?

One more question about E1: D10, what is that wire supposed to be connected to?

D10 is any digital pin on the controller; in this schematic it is the Arduino digital pin 10.

An IRF3708 would be a MOSFET that should work directly with 3.3v logic levels.


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And that pin is used to open the bc547? I dont see how the bc547 isnt always on when it is powered with 3.3V constantly from the board as in the schematic E1

Well, you "open" a gate, but we are not using gates! :astonished:

You "close" a circuit to make current flow. :sunglasses:

Probably best to say you "turn on" a transistor or FET.

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Yes this is confusing but it makes sense :grinning_face_with_smiling_eyes: