Can everybody direct me why I have a sine wave across my inductor when I connect it into 5V DC? The power supply is regulated so why my scope is showing more that 5 MHz across the inductor when the inductor is in parallel with the DC voltage?
I got almost 550 KHz when I joined a 483 cap across the inductor too!!
I know something about LC resonance, but not sure if it works with DC sources too!!
Resonance occurs when the Xl = Xc, so and in this cause the resonance freq of the L and C is equal
yea, the power supply is a switching power supply. but I don't have this problem when there is not inductor across the power supply. I have a pure DC voltage when the power supply is connected across the scope(i.e. without the inductor)
Is this possible the inductor starts resonating at the DC voltage? The frequency was exchanged when I put a ceramic caps across the inductor too!
Well I tried it with the secondary of a 15V transformer as an inductor. The inductor draws 500mA at 5V and I have a 454 kHz sine wave across it!
The power supply is able to give more than 6A at 25V
I am suspect to the power supply though!?
Is there anybody to direct me what I must expect of the output of an inductor when it is connected to a DC power source? I know that an ideal inductor is a short circuit at DC voltage but what about a real inductor? Can you let me know if I am seeing a fault on the scope due to the inductor across a DC power supply or I must expect so?
Well I tried it with the secondary of a 15V transformer as an inductor. The inductor draws 500mA at 5V and I have a 454 kHz sine wave across it!
The power supply is able to give more than 6A at 25V
I am suspect to the power supply though!?
Is there anybody to direct me what I must expect of the output of an inductor when it is connected to a DC power source? I know that an ideal inductor is a short circuit at DC voltage but what about a real inductor? Can you let me know if I am seeing a fault on the scope due to the inductor across a DC power supply or I must expect so?
How did you measure the 500mA? That implies that the resistance is 10 ohms, which is way too high for the secondary of a 15V transformer.
There is no good reason I can think of to connect an inductor directly across a DC supply. Why are you doing this?
yea, the power supply is a switching power supply. but I don't have this problem when there is not inductor across the power supply. I have a pure DC voltage when the power supply is connected across the scope(i.e. without the inductor)
Is this possible the inductor starts resonating at the DC voltage? The frequency was exchanged when I put a ceramic caps across the inductor too!
I tried the power supply using a 10 ohms resistor and yes I have that 454 kHz freq across the resistor to! So there is a problem with the switching powers supply.
I have bout it for 150$ so Why it has those ripples (the below pic) at its output?
Rolf,
My power supply showed me that current.
My ohmmeter shows 19ohms across the secondary of the 300mA transformer.
I just wanted to see the behavior of an inductor at DC and then put a large caps across the self and see the resonance freq via a scope.
Hayato
What do mean by this:
"ripple is exciting the natural resonance mode of the inductor"?
Well I tried it with the secondary of a 15V transformer as an inductor. The inductor draws 500mA at 5V and I have a 454 kHz sine wave across it!
The power supply is able to give more than 6A at 25V
I tried the power supply using a 10 ohms resistor and yes I have that 454 kHz freq across the resistor to! So there is a problem with the switching powers supply.
I have bout it for 150$ so Why it has those ripples (the below pic) at its output?
Much of your measured ripple could be due to equipment setup. Switchers generate a lot of EMI. What is your grounding like, how long is the ground lead on your scope probe? Keep your grounds short and solid. Use short scope ground leads.
A typical good quality switch supply usually has a 100mv of ripple. 50mv is better. You may be chasing a non problem depending on your application and setup.