- Distinguish the pins of the infrared receiver head
Set the multimeter to R×1k mode. First, assume that one of the pins of the receiver is the ground terminal, connect it to the black probe, and use the red probe to measure the resistance of the other two pins separately. Compare the two measured resistance values (usually in the range of 4-7kQ). The one with the smaller resistance is connected to the+5V power pin, and the other with the larger resistance is connected to the signal pin.
On the contrary, if the red probe is connected to a known pin and the black probe is used to measure the known power pin and signal pin separately, the resistance values will be above 15kΩ. The pin with a lower resistance value is the+5V terminal, and the pin with a higher resistance value is the signal terminal. If the measurement result meets the above resistance value, it can be judged that the receiving head is intact.
- Determine the polarity of unsigned electrolytic capacitors
First, short-circuit and discharge the capacitor, then mark the two leads with A and B. Set the multimeter to R×100 or R×1k, connect the black probe to lead A and the red probe to lead B. Wait for the pointer to stop moving before reading, and then short-circuit and discharge after measuring; Connect the black probe to lead B and the red probe to lead A. Compare the two readings, and connect the black probe with the higher resistance as the positive electrode and the red probe as the negative electrode.
