This has been very long since I left electronics but recently I restarted taking interest in it as hobby.

I bought some PIR sensors from Aliexpress and found it is very simple to implement if I have 5V DC supply on breadboard. I am not sure how I can hook it up to bulb (CFL or 230V LED bulb) as a complete unit.

Can some tell me, should I use 5v DC normal AC-DC step down power supply enclosed everything in small box and mount it near the bulb or is there any other way to do it. I will use 5V relay and relay driver using NPN transistor.

I am asking this because all the tutorials I have seen uses breadboard power supply or 12V DC adapter and 5V regulator IC. I did not come across with real life application using 5v drawn from mains supply.

  • \$\begingroup\$ Can you provide a link to the PIR sensor that you're using? The advantage of having a 5V regulator on board is that you can be sure that you're giving the PIR module a clean 5V supply. PIR's are often very sensitive to electrical noise which gives false triggering. And don't use the 5V regulator to power the relay - power that from 12V. \$\endgroup\$ – Steve G Mar 4 at 8:55
  • \$\begingroup\$ This is a link from where I bought the PIR Sensor \$\endgroup\$ – Silkograph Mar 4 at 8:58
  • \$\begingroup\$ And I may buy this power supply for this module. \$\endgroup\$ – Silkograph Mar 4 at 9:03

I can see that the Pir sensor can work from 5v to 20v. If your relays are 5v, I dont see any problem using an 5v power supply and power everything. You can use any USB charger that can provide enough current to power the whole circuit.

  • \$\begingroup\$ As I said, I know I can use USB charger but I can't pack that kind of power supply in a small enclosure and fix it near the bulb on a wall. I wanted use small AC-DC 5V DC normal full-wave rectifier. Have asked correct question. Is it quite simple, I can use? \$\endgroup\$ – Silkograph Mar 4 at 10:11
  • \$\begingroup\$ Yes, you can use it. \$\endgroup\$ – Mark3859 Mar 5 at 11:33

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