How to design a transistor circuit that controls low-power devices

[Harald Kapp]

Why not simply use a piece of wire to turn on the motor?

It would not be easy to control the piece of wire, would it?
@Audioguru : that kind of answer is not helpful. Please show a bit more patience while we try to guide @stspringer to a viable solution.

 

[bertus]

Hello,

If you want to use a mosfet, have a look at the IRL520.
That is a logic gate fet, with a 10 A switching capability.
Or have a look at the logic gate version of the mentioned IRFZ44, the IRLZ44.

Bertus

 

[Audioguru]

1) He wants to turn on a 12VDC motor from a 12V "control" but he does not say what is the maximum allowed control current so maybe he should use a mechanical switch or a simple piece of wire.
2) He posted a video that wrongly talks about a PN2222A transistor with a hFE of 100 but its datasheet says its hFE is when it has a Vce of 10V (not used as a switch). The datasheets of all transistors show that a much higher base current is needed when a transistor is saturated as a switch.
3) The video and people on this forum did not mention that the solenoid in the video or the DC motor here has inductance that will produce a very high voltage when it is switched off so a flyback-arresting diode is needed to be added parallel to the motor.

 

[stspringer]

Look what I found on Amazon after looking at bertus post



Quote
"If you want to use a mosfet, have a look at the IRL520.
That is a logic gate fet, with a 10 A switching capability.
Or have a look at the logic gate version of the mentioned IRFZ44, the IRLZ44."

I will try my circuit first without this board, waiting for my mosfets now but this is interesting

https://www.amazon.com/WINGONEER-IR...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

[bertus]

Hello,

The shown boards use the IFR520.
That is a basic mosfet.
What voltage levels are you using to drive the input of the board?

Bertus

 

[stspringer]

Hello,

The shown boards use the IFR520.
That is a basic mosfet.
What voltage levels are you using to drive the input of the board?

Bertus

5 volt to turn on 12 volt motor

 

[Harald Kapp]

IRF520: 2 V < Vgs(th) < 4 V
Good for Ids = 1 A at Vgs = 5 V.
Should work with a 5 V control signal.

 

[majoco]

I don't know why this has turned out to be so difficult. Here is a simple schematic that I designed to run a small computer fan from a temperature sensor on the top of my Marantz tuner/amplifier - the fan gets a linear voltage to drive it from the sensor stuck on the top of the cabinet, the fan is mounted on a hole in the shelf underneath the cabinet. The fan starts to run at about 25 degs C and is going full blast at about 40 degs C. How simple can you get?

 

[stspringer]

I don't know why this has turned out to be so difficult. Here is a simple schematic that I designed to run a small computer fan from a temperature sensor on the top of my Marantz tuner/amplifier - the fan gets a linear voltage to drive it from the sensor stuck on the top of the cabinet, the fan is mounted on a hole in the shelf underneath the cabinet. The fan starts to run at about 25 degs C and is going full blast at about 40 degs C. How simple can you get?View attachment 46513

Thank you,
Maybe someday I will be at your skill level.

 

[majoco]

You will - the more you play, the more you learn!

 

[Electro Bro]

I am working on this too! Thank you for asking the question. It helps me a lot.