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

bertus

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Nov 8, 2019
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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
 

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  • irlz44n.pdf
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Audioguru

Sep 24, 2016
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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

May 10, 2019
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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

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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
 

Attachments

  • IRF520.pdf
    183.7 KB · Views: 0

Harald Kapp

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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

Nov 10, 2019
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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?fan controller.jpg
 

stspringer

May 10, 2019
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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.
 

Electro Bro

Nov 22, 2019
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I am working on this too! Thank you for asking the question. It helps me a lot.
 
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