### DESCRIPTION

I was asked to create 10 temperature sensors for a Blynk project. I designed to above board for it. For the code I am using the basic Blynk sketch they you can download from Blynk examples. I did not modify anything on that.

### TECHNICAL DETAILS / COMPONENTS

The circuit is using a HLK-PM03 mains to 3.3V power supply. For protection I added a 200mA slow blow fure and a MOV to clamp the transients. Since it will be installed in a workshop with a lot of heavy machinery, I thought the fure and MOV is required, but you can leave it out. 

On the low voltage side I have an ESP8266-01, DHT22 temperature and humidity sensor, 4.7k pullup resistor and a 47uF capacitor to smooth the power. I think it will work without the cap as well.

I used the following components:

85x58x33 enclosure: https://www.ebay.co.uk/itm/Waterproof-Plastic-Electronics-Project-Box-Enclosure-Instrument-Case-DIY-Screws/272438539904?ssPageName=STRK%3AMEBIDX%3AIT&var=571432144263&_trksid=p2057872.m2749.l2649

HLK-PM03 power supply: https://www.ebay.co.uk/itm/New-HLK-PM03-AC-DC-220V-to-3-3V-Step-Down-Buck-Isolated-Power-Supply-Module/272485432111?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Panel mount fuse holder: https://www.ebay.co.uk/itm/20PCS-Panel-Mount-PCB-Fuse-Case-Holder-With-Cover-For-5x20mm-Fuse-250V-6A-CF/272242518456?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Terminal blocks: https://www.ebay.co.uk/itm/10-50PCS-5-08mm-Pitch-Panel-KF301-2P-KF301-3P-Screw-Terminal-Block-PCB-Connector/272428154756?ssPageName=STRK%3AMEBIDX%3AIT&var=571414365701&_trksid=p2057872.m2749.l2649

DHT-22: https://www.ebay.co.uk/itm/1-2-5-10PCS-DHT22-AM2302-Temperature-Humidity-Sensor-Replace-SHT11-SHT15-Module/272484297869?ssPageName=STRK%3AMEBIDX%3AIT&var=571526067828&_trksid=p2057872.m2749.l2649

ESP8266-01: https://www.ebay.co.uk/itm/1-2-5-10PCS-ESP8266-Esp-01-Remote-Serial-Port-WIFI-Transceiver-Module-AP-STA/272498507465?ssPageName=STRK%3AMEBIDX%3AIT&var=571554361302&_trksid=p2057872.m2749.l2649

200mA slow blow fuse, 275V MOV, 47uF electrolitic capacitor, 4.7k resistor, various pin headers from local electronics store.

### LEARN / TOPIC / BUILD INSTRUCTIONS

I will solder a pin header for the DHT22, and run the sensor on a wire outside the case. I assume it would pick a lot of residual heat from the ESP and the power supply, so it is better to have it outside the case.

You can replace the DHT22 to any other sensor, e.g. BS18D20 or BME280 and modify the code. Check which requires the resistor and what value.