Program launch: "Get Paid to Publish your Project!"

[Hero999]

How do did you calculate it?

I reckon I_B wil be between 17mA and 21mA, my calculations are shown below:

I_B(Q1) = ^{(VDD -  V_BE(Q2) - V_BE(Q1))}/_R3


With V_BE = 0.7V

I_B = ^{(3.3 - 0.7 - 0.7)}/₁₀₀ = 0.019 = 19mA

If V_BE is lower I_B will be higher and vice versa.

I didn't account for R4 because the current though it will be tiny, 0.6/1000 so won't effect the calculation.

Do you think I've gone wrong somewhere?

[H3LIO]

Hi Hero999,

I change R3 for 67 Ohm and I have ib of 24mA and vbe = 1.6V and it works with a min duty cycle of 3.13%.
I will send the file to Mixos.

Thank you for that it will have a faster switching time and it's cheaper to make.

[H3LIO]

Your calculations are Roth, I was using a different resistor 160 Ohm as R3 when I was doing I only notice now.

[Hero999]

What do you mean by Roth?

I'm glad you got it working but give 68R in the parts list as 67R will be hard if not impossible to get hold of because it's not a standard value.

I don't see why it should limit the minimum duty cycle though, the transistors should be able to turn off continuously, enabling a duty cycle of zero.

Does the fan draw a hight peak current when the duty cycle is low? You'd need a 'scope to measure it but that would make sense.

What transistors are you using?

[H3LIO]

I mean Right. I'm using the ones you told me BC338. I was think the same, that the specs in the fan would affect the way it works with dutycycle. It's working nice, but i will try different fans to know why it happens.


Thank you

[bogdanfirst]

Has the program been stopped?
I was checking new projects on the website and the add seems to be missing...

[mixos]

The program has ended. Stay tuned for future launch of this program.

[mojo_chan]

Any updates? I have a project read to go.