- Sun Aug 16, 2015 3:14 am
#26132
The esp8266 can draw a considerable amount of current at times. I wouldn't recommend a "low power" type linear converter (in TO-92 package, typically rated for 100 mA) and even not a "normal" converter in a TO-220 package, which generally can supply up to 1 A, still they get hot and several people have reported problems. I am using buck converters now, they don't get hot and don't waste a large amount of power into heat. They can be quite small nowadays, something like this: http://www.ebay.com/itm/5-x-Mini-DC-Con ... 3a918c05b2
- Sun Aug 16, 2015 6:46 am
#26147
Interesting question...agree with what RogerClark suggests about changing the zener in a usb charger, thats the cheapest and smallest thing i've found.
For example, this one, is the cheapest i've seen (they sell those in a 99p shop near me in London). The cover isn't glued it just clips on so its easy to pull apart and from what i can tell the circuit is similar'ish to this, so just replace that ZD 5V with a 3.3v zener.
Here's a photo of that with the cover off and the zener circled in red.
With the USB socket unsoldered there is enough space inside to include an ESP-01 and a small sensor too...
For example, this one, is the cheapest i've seen (they sell those in a 99p shop near me in London). The cover isn't glued it just clips on so its easy to pull apart and from what i can tell the circuit is similar'ish to this, so just replace that ZD 5V with a 3.3v zener.
Here's a photo of that with the cover off and the zener circled in red.
With the USB socket unsoldered there is enough space inside to include an ESP-01 and a small sensor too...
- Sun Aug 16, 2015 9:47 am
#26158
Wrong, it's a complete switching power supply (as it should).
Right behind the USB connector you see the transformer (which can be very small if the switching frequency is high - nowadays then go up to > 1 MHz). Behind that is the "switching" transistor, on the left you see the optocoupler to isolate high voltage from low voltage, in blue is the fuse (automatic, mostly NTC). I can't decipher the role of the IC on the far right, it may be part of the switching driver, which mostly is an IC with more pins than this. And then of course the black diode, probably schottky, which is probably a single phase rectifier. Or the unknown IC is a full two phase rectifier of course. The small diode is probably just an 1N4148, no zener.
Don't mistake a modern state of the art switching power supply with an abomination of a power supply! BTW if no transformer is used, it's UNSAFE.
Right behind the USB connector you see the transformer (which can be very small if the switching frequency is high - nowadays then go up to > 1 MHz). Behind that is the "switching" transistor, on the left you see the optocoupler to isolate high voltage from low voltage, in blue is the fuse (automatic, mostly NTC). I can't decipher the role of the IC on the far right, it may be part of the switching driver, which mostly is an IC with more pins than this. And then of course the black diode, probably schottky, which is probably a single phase rectifier. Or the unknown IC is a full two phase rectifier of course. The small diode is probably just an 1N4148, no zener.
Don't mistake a modern state of the art switching power supply with an abomination of a power supply! BTW if no transformer is used, it's UNSAFE.
- Sun Aug 16, 2015 10:34 am
#26172
It is probably a diode bridge, since it is very near of the AC wires ...
eriksl wrote:I can't decipher the role of the IC on the far right
It is probably a diode bridge, since it is very near of the AC wires ...
