Rpi Fan - Need an explanation

188

01:11:15

Simulating a fan for my Raspberry pi.
Fan is 5V, 0.15A and substituted here with a Lamp of 5v, 750mW as I figured they were equivalent.
Top circuit is the goal. Lamp is receiving 150mA.
The bottom three have an additional 3.33V source, one that will come from a GPIO and act like a control pin.
Why is the output so much better if I put the the transistor between Lamp and Ground instead of Lamp and 5v Battery?

published 3 years ago

mlira

3 years ago

With the transistor on the high side the gate current has to flow through the resistance of the fan (while also fighting for "bandwith" with the current flowing from the battery).

mlira

3 years ago

If you want high side switching have a look at https://everycircuit.com/circuit/6355143995686912

Thrum

3 years ago

Thank you mlira ! Was stumped but this makes sense. And thanks for the example!

mlira

3 years ago

No problem, glad to help.

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