Homemade air conditioner outdoor unit shutdown indicator

In the midsummer, air conditioners bring coolness, but I always have a knot in my heart, "I am afraid of catching a cold when I sleep at night" because I don't know when the refrigeration unit will start or stop. This year, I decided to make an "air conditioner outdoor unit shutdown indicator". After actual use, I have an intuitive feeling: I know that as time goes by, the shutdown time (light off) is gradually longer than the startup time (light on). This can roughly determine the power consumption. Now I recommend it to everyone.

This indicator does not change the original structure of the air conditioner. It adopts the current transformer detection method, which has no effect on the air conditioner and no additional power consumption. The materials used are: a waste semiconductor radio output transformer (core column section is 7mmx7mm/), a red light-emitting diode, a rectifier diode, and a 200Ω/8W resistor. The entire circuit composition is shown in the attached figure. Now we will focus on the production of the current transformer.

Remove the primary and secondary windings of the original semiconductor output transformer. According to the ultimate derivation formula of the current transformer; I1/I2=W2/W1. Where:

I1 is the working current of the outdoor unit of the air conditioner (the current of the indoor unit is ignored here). The actual working current of this air conditioner is 4A.

I2 is the working current of the light-emitting diode. Considering that the average value of half-wave rectification is 0.45mA, the value is between 10mA and 15mA.

W1 is the current detection winding. First, we need to consider whether the effective window area of ​​the core can accommodate it, and second, we need to consider the number of turns (too many inductive reactances will increase the partial pressure of the load, affecting the normal operation of the air conditioner, and too few turns will cause the core to heat up). Here, 8 turns are temporarily taken.

W2 provides the light-emitting tube current. Substituting the above three parameters into the above formula, W2=(4A/0.01)x8=3200 turns.

Choose from the wire diameters of W1 and W2; to avoid overcurrent heating of the coil, φ1 is considered to use 1.06mm enameled copper wire according to the current density of 3.5A. φ2 can use 0.09mm enameled copper wire. W2 is first wound on the original frame (its leads and phases are well insulated), then W1 and tape are wound on it, and the iron core is inserted to use a high resistance meter to measure whether the phase insulation is good. Finally, the rectifier tube, resistor, light-emitting tube and extended wire are welded to the W2 lead in sequence, and the w1 lead is connected in series to the phase line of the air conditioner socket. All components except the light-emitting tube are installed in the air conditioner socket junction box. Use adhesive tape to stick the light-emitting tube to the side of the indoor unit where it is easy to see and it can be put into use. This indicator is tested on Haier KC-35 window-type machine (its working current is about 7A). The light-emitting diode has a large brightness. At this time, the resistance should be increased to 820Ω.

In use, the AC voltage drop of W1 in the air conditioner circuit is measured with the voltage block of the multimeter, which is less than 0.1V, the DC voltage of the rectifier output is 1.7V, and the voltage drop of the resistor is 0.6V. From this, it is deduced that the current flowing through the light-emitting diode is 3mA and the voltage is 1.1V (the needle of the meter swings slightly when measuring the three data). After the outdoor unit is shut down, the rectifier output voltage drops to 0.4v, and the light-emitting tube is slightly bright (this is because the fan of the indoor unit is still working to blow away the frost on the evaporation tube). The light will disappear only after the machine is completely shut down.