# How to design the power supply for my project?

I just started my journey into electronics and have successfully built a 2 digit 7 segment counter (using IC 40110 and a pushbutton) on a breadboard. I used the 3.3V and ground pins of Arduino to power my breadboard.

I am trying to make a standalone circuit which can be powered by a battery. The goal is to increase the lifetime as long as possible while the circuit serves its function. Once I do this on my breadboard, I plan to design PCB for this circuit. But I feel stuck by not understanding the best way to power my circuit and need your help on this.

Q) How can I determine the power consumption of circuit? Should I measure the current and votlage across each of the 7 LED segments and sum their product?

Q) Is determining the input voltage of my circuit important? If so, how can I determine the minimum input voltage required? (I assume I should go for the minimum operating voltage so that I can reduce power consumption)

I researched online and found few ways of doing this:

A) Use 9V battery connected to this power supply module:

B) Use 9V batter and connect it to a down converter

Method A seems to be the easiest way but it uses linear regulatobrs which is less efficient than the buck converter. Q) Apart from simplicity, when/why would anyone use this?

I think Method B is the way to go because they are efficient than linear regulators but I don't know how much difference it will make. Q) How can I compute and compare these 2 methods?

• Why use linear regulators? Simpler, yes. Efficient, no. Do not create noise like a buck reg, yes. Rarely do you get a circuit that is ‘perfect’ - there’s almost always a tradeoff, so linear regs have their advantages and switch regs have a different set of advantages. You choose the one which gives the least compromise to your circuit. Sometimes you use both to capitalize on both their strengths. Jul 29 at 8:50