1. The wire of the DC power supply should be as thick as possible, generally, the wire thickness is more than 20mil.
2. The filter capacitor should be as close as possible to the VDD pin of the chip.
3. The pyroelectric infrared sensor and the chip should be as close as possible, and the signal line of the probe should be correspondingly short, so that the signal will be strong and the anti-interference will be good.
4. If the pyroelectric infrared sensor need to pass EMC certification and have good anti-static interference, you need to separate the signal ground from the power ground and connect them with a 0-ohm resistor.
(See which AVSS are the signal ground. When arranging, concentrate these devices with AVSS in the middle. Place a 0-ohm resistor in the nearest place of the power ground pin of the chip. The AVSS is covered with a layer of copper, and attention should be paid to make this layer of copper surround all the signal lines. At the same time, the back is also covered with AVSS copper of the same size, and the two layers of copper are connected together with vias.)
5. The power ground needs to surround the entire circuit board, except for the AC power supply board. For the application of AC power 220V, it should be noted that AC components (including relays) should be placed on one side, and DC components on the other side. Do not cover the DC power supply ground on the AC components to prevent the AC power from interfering with the DC power supply and signals of pyroelectric infrared sensor through the DC power supply ground.
6. The vias connecting the upper and lower power grounds should be as many as possible to make the two grounds fully connected.
7. The infrared sensor probe is made of the iron case, so it is necessary to avoid short circuit caused by the conduction of solder and iron case. If the inductive probe is installed close to the PCB, when PCB layout, the PCB on the same side under the probe should not be covered with copper, and the via should not be covered with copper. Moreover, the via should be small, only enough for the probe pin to pass through. Then it should be welded on the other side of the PCB. This can avoid the conduction of solder and iron shell.