Reducing the power consumption

A project log for TIRO Vibrating Watch

TIRO (Time is Running Out) is a watch that vibrates every few minutes to remind the user that time in this world is quickly running out.

AccidentalRebelAccidentalRebel 02/28/2019 at 14:020 Comments

One of my main goals is for the circuit to find a way to lower the power consumption of the circuit as possible. I've made a couple of improvements that really helped a lot. Here are my findings:

So far this were the improvements that I did. Here's a table to give a better idea of the improvements that I did and how it affected the power consumption.

Internal Clock
WatchdogMotor Resistance
Motor Running Current Draw
Circuit Idle Current Draw
16 MHz
47 ohms
50 mA
7.75 mA
1 MHzNo47 ohms
50 mA
0.97 mA
1 MHz
No0 ohms
75 mA
1.38 mA
1 MHzNo100 ohms
45 mA
0.97 mA
1 MHz
Yes47 ohms
50 mA
4.00 uA

My concern right now is that the current draw of the motor when it is running is a bit high. But since the motor has a minimum operating current of 40 mA, it means I cannot go down any further if I wanted to. I may need to look for a less power hungry vibration motor, if such a thing exists. Here's what I'm using right now.

I'm open to hearing your thoughts if you have any ideas!