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I am using this circuit as the automatic transfer switch where I am providing input from battery and solar panel and taking the output to run the motor.

Where AC/DC is written I am using the battery from this input where the motor is running slower and TIP127 is getting heated up and consuming extra energy.

As I have nearly no knowledge of electronics and took this circuit from a website.

It would be great if anybody could tell me why this is happening and how can I stop it?

As I want to make circuit very efficient and hence trying to reduce any kind of energy loss. Also when run via second input the motor is running extremely well.

Thank you.

  • \$\begingroup\$ What motor are You using? What current is it drawing? Why microcontroller tag? \$\endgroup\$ – fifi_22 Dec 26 '20 at 7:25
  • \$\begingroup\$ Using a bipolar transistor as a load management switch is a bad idea. a mosfet could do that more efficiently. look at this question : electronics.stackexchange.com/questions/283056/… \$\endgroup\$ – Tirdad Sadri Nejad Dec 26 '20 at 7:58
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    \$\begingroup\$ A lot of the weirdest and least efficient circuits posted here seem to come from that website... \$\endgroup\$ – user_1818839 Dec 26 '20 at 13:36
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    \$\begingroup\$ Scottky diodes from other answer will drop about 0.5V depending on current and diode rating. || In this cct - Take BC557 collector to ground via 1K. | Change existing 1K to 10K. | Place 1k between BC557 base and solar +. || Heating is probably due to slow change over between supplies with TIP127 dropping too much voltage. Hystsresis can be added but a better cct would be best. || The two x Schottky diodes will work OKish. \$\endgroup\$ – Russell McMahon Dec 27 '20 at 10:29
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    \$\begingroup\$ Your cct above is very badly designed by the "designer" and has little or no advantage over 2 diodes. The Shottky diode circuit here that you have mentioned powers the load from the highest voltage source. If the mains adaptor voltage is even slightly higher than the PV / battery voltage then the mains supply diode will conduct and the PV input diode will be reverse biased and will not conduct. You will lose ABOUT 0.5V voltage drop across a schottky diode - maybe slightly less. If you want almost zero drop a FET based circuit can be used. \$\endgroup\$ – Russell McMahon Dec 29 '20 at 7:37

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