Guide in designing circuit with Solenoid Valve (12VDC and 24VDC) interfaced with Arduino Nano

Projects General Guidance
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This is irrelevant if the transistor is used for switching, because hFE is given when there is still 2-4volt between collector and emitter.

For switching, you ideally drive the base hard enough to get collector voltage to drop below base voltage. At this point, gain drops to an even lower value. There is a switching graph in the datasheet that gives saturation voltage at a 1:10 base/collector current ratio.

If you're not driving the base at 1/10th of the collector current, then you should measure collector voltage and calculate dissipation. Not driving the base hard enough can quickly heat up the transistor to the point that it pops it's top.
Leo..

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23

thanks for this, but for further question, "not exceed 1.33W total power dissipation, which is VceIc*" from what I understood Ic is 375mA, what is Vce because if I use P=IV, that would mean Vce= 3.55?

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Measure it. If the transistor is saturated, it should be less than 1V.

Here is what I stated above:

Vce is the collector to emitter voltage measured when the solenoid is on.

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I'm sorry but I'm kind of lost at what you are trying to explain here.

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If you want to understand this material, I strongly suggest to do some more reading on transistor theory. There are plenty of outstanding resources on line, and in the bookstores.

Since this seems to be some sort of school project, be sure to credit Arduino forum members with designing your circuit for you, and explaining the design to you.

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Vce = Vbe + (Ic/hfe) = 0.7 + (0.375/20)
Vce = 0.71875 approximately

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Will surely do, thanks for answering my inquiries and being patient with me. Much appreciated.

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