230V AC to 5V DC via phone charger

[MartinV279]

Almost every phone comes with a charger where you put your USB cable and charge your phone. This can put out up to 850 mA, as I can see on most of them. I want to use the electronics inside of the charger to power up a ESP8266 WiFi module (3.3V Vcc), a relay and/or an Arduino. Do you think that this is a smart choice? It's either this or a 9V battery. Also, this is meant to stay plugged in for long periods of time and without supervision. I want to know if it's a safe choice primarily.
Thanks!

 

[Gryd3]

Almost every phone comes with a charger where you put your USB cable and charge your phone. This can put out up to 850 mA, as I can see on most of them. I want to use the electronics inside of the charger to power up a ESP8266 WiFi module (3.3V Vcc), a relay and/or an Arduino. Do you think that this is a smart choice? It's either this or a 9V battery. Also, this is meant to stay plugged in for long periods of time and without supervision. I want to know if it's a safe choice primarily.
Thanks!

That depends on the charger...
There have been documented deaths caused by 'cheap' import chargers. A properly built charger will have no problem being powered 24/7 and a few members on here actually recommend using them for projects requiring 5V. It's usually a much safer reliable method than trying to build your own device. If you plan to remove the casing, great care should be taken to avoid potentially shorting the input and output side of the circuit. It would be a good idea to attempt to keep the case on the USB charger.

 

[Arouse1973]

Yep I second that. Leave it in its case. It means you can also plug it into the mains safely.
Adam

 

[MartinV279]

Well I'm trying to sort of make a prototype, which means leaving it in its case shouldn't be an option (I guess). But, I do agree with you both that it's the safest option. I have some experience with electronics, but mostly with lower current (not with socket for electrical grid for sure). I don't think there will be any damage on the circuit, but safety is first. Thanks for the responses

 

[Gryd3]

Well I'm trying to sort of make a prototype, which means leaving it in its case shouldn't be an option (I guess). But, I do agree with you both that it's the safest option. I have some experience with electronics, but mostly with lower current (not with socket for electrical grid for sure). I don't think there will be any damage on the circuit, but safety is first. Thanks for the responses

I am unsure on what your device is... but you could always put a USB socket on your prototype
More details will help, but we understand the want to keep secrets when developing new products.

 

[MartinV279]

No intention of keeping secrets haha I am making a budget friendly WiFi controlled wall socket. I need to power up the coil of a relay as you know. I was going to use a 5-9V battery, but I was thinking of using the power from the socket for that.

 

[Gryd3]

No intention of keeping secrets haha I am making a budget friendly WiFi controlled wall socket. I need to power up the coil of a relay as you know. I was going to use a 5-9V battery, but I was thinking of using the power from the socket for that.

lol, ok then. How big will it be?
Perhaps you can earn enough space with a power bar?
If you can make sure the entire thing is enclosed, and there is 0 risk of anything touching that should not, then you are welcome to open the phone charger... it just much safer if you dont.
See what you can make work.

 

[MartinV279]

There will be a case, a plastic but isolated one. I think I can ensure nothing touches it. I am still way more comfortable with using a battery, but I think I will try this. Probably in the laboratory at University at first, than on a real socket.

 

[Gryd3]

There will be a case, a plastic but isolated one. I think I can ensure nothing touches it. I am still way more comfortable with using a battery, but I think I will try this. Probably in the laboratory at University at first, than on a real socket.

If you do go the battery method, you should look at 'latching' relays. One pulse to turn it on, one pulse to turn it off... so you avoid the excess current draw from 'holding' a relay in the on position.
Have fun, and if you run into a snag, let us know!
(people do mains projects all the time. The usually get an enclosure and have high voltage on one side, and low voltage on the other. As long as everything is tidy and the sides are kept separate, you should be pretty safe.
If in doubt draw something and share it

 

[MartinV279]

I have honestly never heard of these latching relays, but I've always thought that would be a great idea. How great is this? I will definitely take a deep look in them, and most probably use one of them. Thanks a lot for this info. I'll be back if I have anything else comes to mind.