Arduino like circuit verification

Thread Starter

kshepitzki

Joined Nov 29, 2017
7
Because I am a software dude, I would like some help verifying this minimal Arduino based circuit which I designed with some changes.

It is single AAA cell operated (NiCd or Alkaline), needs to be very energy efficient.
Input:
4 push buttons, each can wake it up from sleep using Pin Change Interrupt on port D.
Once awake the circuit should read which switch woke it,
A visible light Phototransistor whose analog value can be read.
A tact switch whose on/off value can be read.
Output is done by blinking an LED using PWM.
The software (including Arduino boot loader) needs to be burned over SPI using USBTinyISP.
The FTDI port is for Arduino IDE debugging.

Are there errors in this design? Anything missing? Anything can be improved?
fi.png
 

DickCappels

Joined Aug 21, 2008
5,897
Is the ATMEGA328 in a DIP package? If so, I wonder about pin 4 (PD2) being tied to +5V and pin 3 (PD1) being labeled "Vcc" and "GND" respectively. It is probably not a good idea to tied I/O pins to the power supply rails. I think this also conflicts with the connections to your FTDI module.

Your LED will require between 2.0 and 2.2 volts when operated at its design current of 20 ma. With a 2.2 volt power supply you might not get much light out of your LED. Changing from orange to red will make it certain that the LED will light brightly. Even with a red LED you would probably want the very low value resistor in series with the LED would make me worry about the variation from LED-to-LED resulting in a large variation in luminance.

The note on the power supply circuit "2.2V @140ma" caught my attention. Note that the I/O pins are only rated at 50 ma each.
upload_2017-12-2_14-27-2.png

That's all I see here.
 

Thread Starter

kshepitzki

Joined Nov 29, 2017
7
Is the ATMEGA328 in a DIP package? If so, I wonder about pin 4 (PD2) being tied to +5V and pin 3 (PD1) being labeled "Vcc" and "GND" respectively. It is probably not a good idea to tied I/O pins to the power supply rails. I think this also conflicts with the connections to your FTDI module.

Your LED will require between 2.0 and 2.2 volts when operated at its design current of 20 ma. With a 2.2 volt power supply you might not get much light out of your LED. Changing from orange to red will make it certain that the LED will light brightly. Even with a red LED you would probably want the very low value resistor in series with the LED would make me worry about the variation from LED-to-LED resulting in a large variation in luminance.

The note on the power supply circuit "2.2V @140ma" caught my attention. Note that the I/O pins are only rated at 50 ma each.
View attachment 140640

That's all I see here.
Thanks Dick
It is ATMEGA328PB-MU in QFN. So pin 4 is Vcc (Pin 32 is PD2). In any case it is not +5V but meant to be +2.2v.
The DC booster actually allows me to go anywhere from +1.8V to +5.5v and so does the ATMega, so I could go +3.3v or whatever best.

Regarding LED, what is the minimal voltage that WILL provide much light from this LED and why red will shine brighter?
Thanks
 

DickCappels

Joined Aug 21, 2008
5,897
In general The longer the wavelength the lower the voltage for LEDs. Red is longer than orange.

What kind of current are you planning to apply to your LED?
 
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