Hi, I bought this logic converter because I only have 5V output from my Arduino, but I need a 3.3v output for other chips like the BME280 barometric chip.
http://www.ebay.co.uk/itm/172192184368?_trksid=p2057872.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AIT
unfortunately, reading it, it looks like I need to supply both a 5V AND a 3.3 v input for it to work.. can anyone tell me how to wire this up as I am confused?
The complete link for an Ebay item can be as short as this : http://www.ebay.co.uk/itm/172192184368
Which Arduino board do you use ?
In the middle you see GND and HV on one side and GND and LV on the other side.
The GND's are connected.
Arduino side : 5V to HV. GND to GND. There are four channels, but only two channels are needed for SDA and SCL.
Sensor side : 3.3V from Arduino or from module to LV. GND to GND, the other side of the selected channels to SDA and SCL.
If the sensor runs at 3.3V, you need to get 3.3V from somewhere to make the level shifter work. That is preferably the same 3.3V that the sensor uses, but if that is not possible, then you may get that 3.3V from somewhere else.
Some level shifters have a 3.3V voltage regulator on the board, but this one has only the 4 mosfets.
If your Arduino board is a Pro Micro (without 3.3V output) and your BME280 module has no 3.3V output, then you should get a 3.3V regulator as well, or get one of those level shifters with 3.3V regulator included : http://www.ebay.co.uk/itm/141742393893
Note the need to use some eBay-fu on this stuff.
Advertisers who specifically direct to regional markets such as UK or Australia, are often substantially more expensive despite being exactly the same Chinese supplier.
In this case, the devices are available at something like a third of the price from the ".com" listings (even allowing for currency conversion).
That is interesting, I didn't realize some come with a regulator. The 4-channel one appears to be a knock off of a Sparkfun design:
And schematic is available:
Do you guys know of a schematic that's available for the 2 channel converter with regulator? I'm sure I could figure it out but I'm a like-to-see-the-schematic sort of guy.
Whoops, I meant to talk about this one:
and its schematic:
I was not able to find a schematic for the one with 2 channels and a regulator, but I would like it.
I was also not able to find a schematic for the 2 channels with voltage regulator. But they are very simple. They have two level shifting channels with a mosfet :
And they have a voltage regulator of 3.3V with its input to 5V (connected to "HV" of level shifter) and output to 3.3V (connected to "LV" of level shifter). There is probably one or two capacitors added to the voltage regulator.
Since most sensors require very little current, the output of the small voltage regulator is more than enough for a number of sensors.
Sometimes the 3.3V is labeled as "3V", but it is always 3.3V.
Koepel:
Since most sensors require very little current, the output of the small voltage regulator is more than enough for a number of sensors.
I suspect it is even adequate for an ESP8266, perhaps with the help of a reasonably large capacitor.
Mind you, you apparently do not need the level converters for an ESP8266.
