I am just now starting to play with power supplies besides batteries or wallwarts.
For my first project I have acquired a few AC-DC Power Supply Buck Converter Step Down Module Chip 5V 700mA 3.5W
I am using home built unos that use less power than the standard ones and are easier to solder into a finished product. In the current project I have my simple uno reading the temperature, powering three 4 bit led displays and a relay. (Side note: First time with the displays, very impressed.) Anyway total power draw with the relay off is less than 20ma depending on what the displays reads it is normally drawing around 15ma. When the relay turns on total draw is ~170ma.
That is the set up.
My question the power supply I am working with makes a slight buzzing sound when there is no load hooked up, makes a lot of noise when running with just the uno and display(~15-20ma) and is silent when the relay is powered. Adding caps can change the noise with the small load some, but it is still there.
Tested the input at 119.5v ac.
Tested output at a solid 5v dc through the operating range that I use.
Also tested output at 10v ac through the operating range that I use.(dirty power?)
I do not have a scope to look at it with.
Any one else have any experience with this, is what I am describing normal? Everything seems to work and has done so for more than an hour at this point.
For this particular project the noise(audible noise) will not be a problem amusing it is not going to blow up or some such thing.
I can see some future projects where I am going to need a power supply that has no audible noise at the same range of draw 10ma-200ma. What do you guys use when you do not have the space for a wallwart and still need to power an uno type project from power mains?
Back to this one, should I be worried? Any ideas for cleaning it up some?
Thanks,
Brandan