I used this circuit to control the solenoid valve before, but I didn't pay attention after I took over. In a recent experiment, it was found that the temperature of the tiP122 tube rose sharply after it was turned on. The solenoid valve is 24v and the built-in resistance is 18 ohms. The measured Vce is only 0.9v and Ic is 1.1A. Why is it so hot? The board has come out, do you think it is saved?
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Florence Veröffentlicht am December 17, 2020
122 plus heat dissipation;

Adan Veröffentlicht am December 17, 2020
The solenoid valve uses a mos tube for such a large current. Triode can also be used for small current

Cruz Veröffentlicht am December 17, 2020
Use a 2A MOS instead of a triode,

Gary Veröffentlicht am December 17, 2020
First of all, good heat dissipation must be added to the three-connector, and secondly, the internal resistance of the three-connector is large, and it can work for a short time. It is recommended to change the field tube (internal resistance milliohm level) for long-term work.