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jxmot / ESP8266-RCWL0516

An ESP8266 project that uses a RCWL0516 microwave presence sensor.
MIT License
43 stars 13 forks source link

Q: Why decoupling? #4

Closed PJaros closed 5 years ago

PJaros commented 5 years ago

I'm planing to build a ESP8266 RCWL0516 but didn't plan to decouple it.

Did you build it that way because you got errournous results with a different build? Have you tried a simpler variation before you concluded to build it like that?

jxmot commented 5 years ago

Hello,

Anytime I work with a module that is unknown to me I tend to play it safe. This is from previous experiences where a module should have been safe but wasn't. This was the primary reason for building it with an opto-isolator.

The decision was also driven by the cost of replacing the NodeMCU vs the RCWL01516 (if defective). For example, the cost of the NodeMCU is about $9 and the RCWL0516 is about $2, and the opto-isolator was less than $1.

In addition it seems that the RCWL0516 can accept 4–28 VDC for it's power supply. There was a time where I was going to experiment with supplying it with 12VDC to see if that had any effect on range or behavior. In that situation the isolation is a necessity to keep from damaging the NodeMCU in case there's a failure of the RCWL0516.

A future version of the project may replace the NodeMCU with an ESP-01. In that version I will probably still use the opto-isolator, and supply the 3.3v to the ESP-01S from a dedicated regulator (5v to 3.3v).

TIP : When using pre-built circuits that can be operated independent of support circuitry it's almost always a good idea to test them out before wiring them in. This was one of those situations. One of the RCWL0516 boards I bought was defective and output a constant 5v on the "OUT" pin.

chupocro commented 3 years ago

You can use 3V3 output pin of RCWL-0516 for powering it with 3.3 V and in that case even failure wouldn't damage the ESP8266.