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I have a SRD-12VDC-SL-C relay with this configuration: https://robu.in/product/1-roadchannel-relay-module-light-coupling-12v/ And I want to trigger it with PIR Motion Sensor Detector Module HC-SR501 https://robu.in/product/pir-motion-sensor-detector-module-hc-sr501/ The problem with direct connection to PIR is, when I connect PIR with 12v DC the Relay remains always ON, i.e. trigger from PIR does not switch it off. And when I connect it via 5V supply the Relay remains always OFF. The trigger output of PIR is 3.3V how can I rectify this problem? by adding some resistor/FETs, or something else.

Edit: The voltage at Relay-In(Green) is 10.5V and the relay is OFF it need to go below 9V in order to switch the Relay ON. When I connect it to PIR trigger it goes down to 2.7V (Thus Switching ON the relay, below 9V). And when the PIR trigger of 3.3V comes it goes up to 7.2V but because it is still below 9V) Relay does not switch. Configuration of the circuit

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    \$\begingroup\$ Isolate load effects from each load. PIRs need noise free Voltage. \$\endgroup\$ – Tony Stewart EE75 Aug 17 '20 at 21:37
  • \$\begingroup\$ Ah, your setup is a bit confusing. So you are connecting n PIR sensor to a relay, but it is not clear which is making trouble, or both are. First thing first is to do a structured analysis: I suggest to eat the big elephant byte by byte, in two bytes: PIR byte, and Relay bite. Now decouple (I mean, separate, or put one aside) the two modules and look at the PIR guys first. Only after making sure PIR is OK, then you eat your next byte. There is 90% chance you PIR is too sensitive, and 50% chance that your relay has the always-on-never-off problem. / to continue, ... \$\endgroup\$ – tlfong01 Aug 18 '20 at 2:36
  • \$\begingroup\$ For the PIR problem, you might find the first two of the following three links helpful. For relay, the last link should be helpful. (1) Why HC-SR501 PIR Sensor Always On? raspberrypi.stackexchange.com/questions/98371/… (2) Rpi PIR Motion Sensor HC-SR501 always reads high, why? [closed] raspberrypi.stackexchange.com/questions/113016/…, / to continue, ... \$\endgroup\$ – tlfong01 Aug 18 '20 at 2:37
  • \$\begingroup\$ (3) How to properly use a relay module (Appendix C - How come my replay is always on)? electronics.stackexchange.com/questions/505318/…. Hav a great locking down day. Cheers. \$\endgroup\$ – tlfong01 Aug 18 '20 at 2:38
  • \$\begingroup\$ I have added circuit diagram and readings please check. \$\endgroup\$ – Mohak Shukla Aug 18 '20 at 8:52

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