I'm making a solar based device but it needs to be aligned according to sun's position in sky , the whole assembly needs to move around 11 degree/hr. So I was thinking of using a timer circuit (low power) to power motor (stepper) after short time period. Now for powering the batteries I'm thinking of using wind energy as my project will be placed in open space (terrace etc). I need your help in suggesting switching circuit with low power consumption which remains in dead state when inactive.

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    \$\begingroup\$ Why not use a MCU that sleeps most of the time? \$\endgroup\$ Commented Apr 21, 2014 at 5:59
  • \$\begingroup\$ Why not use two light sensitive sensors that actually measures where the light is brightest and correct the assembly angle for that? \$\endgroup\$
    – jippie
    Commented Apr 21, 2014 at 6:11
  • \$\begingroup\$ Why not calculate the amount of power needed to drive the motors and then compare it to the power used for the timer? That may save you from over designing the timer. \$\endgroup\$
    – gbarry
    Commented Apr 21, 2014 at 6:21
  • \$\begingroup\$ You are going to need an MCU, such as Arduino, to control the steppers anyway, and the steppers will take considerable power (depending on the size of object you are movingm and especially if the stepper is required to hold the object in place) compared to the MCU... so as others have suggested, figure out the total power supply picture before optimizing the one part. You might also consider using a servo motor rather than a stepper... one or the other may be more appropriate depending on the size of object, and other mechanical properties. \$\endgroup\$
    – gwideman
    Commented Apr 21, 2014 at 9:53
  • \$\begingroup\$ If you have wind, PV wing force will exceed strength of motor and bracket unless very carefully designed. Consider windshield wiper motor with long lever control and high gear ratio. Then use 5 narrow PDs to measure strongest source angle an only move if significantly off angle with hysteresis. \$\endgroup\$
    – user38637
    Commented Apr 21, 2014 at 11:44

1 Answer 1


It seems you want to count hours, then look for RTC ICs (Real time clocks ICs). A common IC easy to use is the DS1307. But there are others ICs with better low power characteristics, here some suggestions:

UPDATED: For example the DS1375 is a RTC with alarm, you can connect the output SQW/INT to a darlington transistor and this to the switch (relay). The duration of the square wave output signal must be adjusted to get the 11 degrees pro hour that you need. In this case the device must be configured via external I2C and to prevent loss the configuration data use a small CR battery.

  • \$\begingroup\$ RTCs are notoriously incapable of controlling motors. \$\endgroup\$ Commented Apr 21, 2014 at 21:17
  • \$\begingroup\$ I not agree with you Ignacio. Some RTCs have "Programmable Square-Wave Output" and it can be used to control the motor (together with the alarm module). The output signal can be adapted with a darlington and a relay if necessary. \$\endgroup\$
    – Alf
    Commented Apr 21, 2014 at 21:59

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