Hello all, I have a osepp Uno R3 plus board
Microcontroller ATmega328P
Input Voltage 6-12 V
I'm trying to power it with a bridge rectifier. THis is my circuit below. I have the RED and BLACK leads attached to where I think I need to plug into my UNO. I think the red is supposed to go to the Vin pin, and the black lead is supposed to go to the GND pin on the UNO.
I'm reading 6.8v at the transformer secondary. However I can't seem to get the board to power on using this circuit! Can anyone understand what's wrong with it? It It should be noted that The capacitor is rated at 10uF.
The red wire takes the plus side of the transformer secondary, and the yellow wire goes from the negative side of the transformer secondary.
The picuture is attached below.
THank you all very much!
Vin. The input voltage to the Uno board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.
5V.This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.
6V is not enough for Vin pin (because of the regulator), and too much for 5V pin !
BTW, as far as I can see, the wiring on your picture seems .... weird, but it's difficult to see clearly
6.8v at the transformer secondary (as you indicated) or 6.8v where you have the test leads connected? If the 6.8v is at the transformer secondary, that is AC probably close to RMS so the output should be more like 7.5 across the cap or so. If it is 6.8 across the cap then that is DC. I do agree with Leo (Wawa) as to using a larger filter cap there but I would have expected something from your board if you connected it as you indicated you did.
Smoothing capacitors for mains frequency are LARGE. That's one reason we don't do this any more
but use high frequency switch-mode converters. (Having said that you still need smoothing
capacitance, but it only has to work for the small time when mains voltage is zero-crossing,
not last for 1/2 a cycle.)
The other reason is that mains frequency transformers are LARGE. Both capacitors and inductors
get larger for lower frequencies as they have to store energy for longer.
These days power electronics is marching to ever higher frequencies, up toward MHz now with
ultra-fast GaNFETs.
Which is why aircraft systems used 400hz instead of 60hz for their power systems - the weight savings in transformer and motor cores was very significant
