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Hi All,

I created a timer circuit (per below link) with a 555 chip, resistors, and capacitor which works fine when powering an LED. If I swap out the LED with a brushless DC fan, it doesn’t work. Is there some reason for this?

https://youtu.be/TjOykZsiEwE

Chris

A possible reason is that the output of the 555 is not rail-to-rail (not to ground and not to Vcc). Check the minimum required voltage for your motor.

I suspect the motor requires more current than your circuit can supply; however, it is very difficult to do any sort of analysis without a schematic diagram and motor data.

Did you also take out the LED series resistor? If this is still in I doubt that the motor would run.

I tried removing 2 of the resistors (except the one paired with the capacitor to set the timing) and still did not work. I will check the voltage and current reaching the fan to see what’s happening.

Don't forget you must replace the LED series resistor with a wire jumper to get a continuous circuit to the motor. Don't go randomly changing things without some plan of action and understanding of expected results.

Hi Foxx, thank you, that worked and the fan runs now. It runs much slower, however, then when connected directly to a battery. Per my DC supply, its only pulling about 150 mA but is rated for 300 mA. Based on franrungo's feedback, I did some googling and seems like the 555 may be limiting the current. Am I on the right track with article below?

https://electronics.stackexchange.com/questions/124112/how-to-get-more-current-from-555-timer

Preferable to place the load on the high side, with an NPN BJT. In the supplied example, the resistors R1 and R2 represent the "load", your DC motor and V555out, the possible output of a 555. You may get different current with different transistor, though, but the comparaison will likely hold for any NPN. Check the power dissipation for the transistor. Add a flyback diode for you motor.

(R3 represents the internal resistance of the source, and like the Amperemeter, they are not strictly part of the circuit.)

And note that a MOSFET canal N, or NMOS, is probably preferable. A little bit more expensive to buy, but more economical energetically.

Es probable que la salida del 555 no tenga suficiente potencia como para mover ese motor, si conecta un buffer mediante transitor y resistencia es probable que funcione