B4R Question What do I need to take care not to burn the house?

[hatzisn]

Hey everyone,

I bought this and received it from Banggood (when you open the link scroll down to download the manual/datasheet).

[US$8.99 18% OFF] 3Pcs SANMIN® AC 85-265V or DC 100-370V to DC 5V AC-DC DC-DC Isolated Switching Power Supply Module Step Down Buck Converter Module Board from Electronic Components & Supplies on banggood.com

3Pcs SANMIN® AC 85-265V or DC 100-370V to DC 5V AC-DC DC-DC Isolated Switching Power Supply Module Step Down Buck Converter

www.banggood.com

I am planning to power with it a WeMos D1 R3 Mini and a two relays module. As I have limited experience and knowledge in electricity safety do you think I should take care of something before connecting to the power? I mean both for High Voltage side and low voltage side...

This is the relays module:

[US$2.99 67% OFF] DC5V 2 Way 2CH Channel Relay Module With Optocoupler Protection Module Board from Electronic Components & Supplies on banggood.com

DC5V 2 Way 2CH Channel Relay Module With Optocoupler Protection

www.banggood.com

I also bought this to cool the whole construct if it is needed (Checking with a thermistor)

[US$2.99 63% OFF] 5v 30*30*10mm 3010 Cooling Fan with 2 Pin Dupont Wire for 3D Printer Part Office Equipment from Computers & Office on banggood.com

5v 30*30*10mm 3010 Cooling Fan with 2 Pin Dupont Wire for 3D Printer Part

www.banggood.com

Thanks

 

[rbghongade]

The circuit claims to have isolated output , hence no need to worry. Just use a good quality enclosure.

 

[agraham]

Having taken apart several Chinese USB mains adaptors I can confirm that cheap Chinese electronics and mains power are not always a good match. Their adherence to EU safety standards can be abysmal, any CE mark is often just that - a mark that means nothing. However that one doesn't look too bad, looking at the pictures there is proper isolation of high and low voltages with just an opto-isolator bridging them.

If you have " limited experience and knowledge in electricity safety" you should probably let someone who has hook it up for you. At a minimum put in a box so it cannot be touched and very importantly put a very low current mains rated fuse in the mains input side. For that unit a slow blow 50mA one looks about right. A quick blow one would need a higher rating as those switch mode PSUs can take quite a surge on switch on. I guess you are in Greece so I don't know how your country does electrical things but don't just connect it to a mains outlet without fuse protection

 

[hatzisn]

We have a 220V AC at 50Hz (don't know how many amperes). You mean I should add a fuse at the high voltage side line precedented by a switch to be able close it and to change it? Isn't 50mA fuse very low?

 

[hatzisn]

Please forgive my ignorance. Can you please tell me @agraham how do you choose the right fuse?

 

[agraham]

You mean I should add a fuse at the high voltage side line precedented by a switch to be able close it and to change it?

Yes - all protected from being touched accidentally

Isn't 50mA fuse very low? How do I select the right fuse?

From the link you posted the rated input current at 110VAC is 27mA and at 220VAC it is 14mA so 50mA should be fine. Just make sure it is rated for at least 220VAC - that is the voltage it must withstand across itself if it blows. The physical size doesn't matter, you just need the fuse and a matching fuseholder to put in the box with the PSU. Ideally put the switch on the box with an indicator of some sort to show when it is live - preferably wired before the fuse.