I have a 6v little fan that works with D batteries (4x1.5V). I want to replace the use of batteries or DC adapters, making a power supply that can be hidden into the fan case, in order to plug and use.
I copied a schematic from http://www.geocities.com/tjacodesign/index.html and I tried to design a 5V DC transformerless power supply applying my scarce knowledge about AC circuit analysis.
Before trying with the transformerless power supply I needed to know the fan motor resistance.
As I didnt know the current or resistance of the fan motor, I put a 10 Ohms shunt resistor in series with the motor and I powered them with a 6V DC power supply. With this I measured Vrshunt=2.5V and Vmotor=3.5V, I calculated that the resistance of the fan motor is 14 Ohms, and its current is 0,25 A.
Then, I tried to design a DC transformerless power supply that can manage the fan, something like 5V (0,25 A).
I attached the design and its calculus are:
Xc=120.5719
Z=120.5885
Iac=0.948 A, (120V-5.6V)/Z
Idc=0.474 A
I used an electronic circuits software simulator, and I saw that the 14 Ohms resistor load makes the Zener DC output to have too much ripple, I tried with various capacitor values but I saw that the problem only disappeared when the load was greater (1K and up), then I guess that ripple is not a problem in the implementation.
I ask for your help. I need to know if it is correct the analysis and design that I have made.
Now, Im going to see what componnent values I have in my benchmarck and if the analysis is right, to make the needed adjustments, i.e, I think to replace a 2 Ohms (2W) resistor with 4 resistors in series of 0.5 Ohms (0.5W each one).
I copied a schematic from http://www.geocities.com/tjacodesign/index.html and I tried to design a 5V DC transformerless power supply applying my scarce knowledge about AC circuit analysis.
Before trying with the transformerless power supply I needed to know the fan motor resistance.
As I didnt know the current or resistance of the fan motor, I put a 10 Ohms shunt resistor in series with the motor and I powered them with a 6V DC power supply. With this I measured Vrshunt=2.5V and Vmotor=3.5V, I calculated that the resistance of the fan motor is 14 Ohms, and its current is 0,25 A.
Then, I tried to design a DC transformerless power supply that can manage the fan, something like 5V (0,25 A).
I attached the design and its calculus are:
Xc=120.5719
Z=120.5885
Iac=0.948 A, (120V-5.6V)/Z
Idc=0.474 A
I used an electronic circuits software simulator, and I saw that the 14 Ohms resistor load makes the Zener DC output to have too much ripple, I tried with various capacitor values but I saw that the problem only disappeared when the load was greater (1K and up), then I guess that ripple is not a problem in the implementation.
I ask for your help. I need to know if it is correct the analysis and design that I have made.
Now, Im going to see what componnent values I have in my benchmarck and if the analysis is right, to make the needed adjustments, i.e, I think to replace a 2 Ohms (2W) resistor with 4 resistors in series of 0.5 Ohms (0.5W each one).
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