I was experimenting with the my Arduino Mega 2560 and I think I must have done something terribly wrong because the 3.3v is no longer working. When I connect an LED and a resistor to it, it just flashes dimly for a split second and turns off. With the 5v output, there are no problems.
Ahh yeah, and there was this burning smell....
So, if I wanted to supply an SD card reader that takes 3.3V as a power input from one pin, would it work if I use a voltage divider circuit?
Also, any other options? I've tried to connect to the RX but it only seems to work momentarily. I don't need many 3v outputs, just one. I'd like to avoid an external power supply. Thanks
Daveste,
You could replace the 3.3 v regulator, if you like soldering SMT parts, that is.
If you need help finding it, then it is probably beyond the scope of your (present) abilities.
A TO92 LM33 regulator with a .1uf cap on the input, and a 10uf electrolitic cap on the output should run an SD card, but I would check. They can use a lot of current to write.
See the datasheet for the regulator for simple circuits to wire it up.
regulator: http://www.digikey.com/product-detail/en/LP2950-33LPRE3/296-31455-1-ND/3505910
TomJ
are you sure ur sd card thingy doesnt have a built in 3,3V regulator?
Where would u power it from otherwise?
Mine has a regulator but no level shifters (cheapest possible on ebay), means csi mosi and whats not r connected to 5V i/o of arduino. Using voltage dividers for these lines it works like a charm.
One of the more stupid ideas.
Why, because the current drawn by an SD card changes as it operates and therefor so does the voltage you are feeling it. Just because some crap design happens to function for a short time is no reasion at all to think it is fine. It will not work on other cards or when the card ages or over any great temprature range, or at any great speed.
ive seen people use those crap designs which use 3,3v for power, but only 5V for i/o and it works for them, so using a voltage divider to get into the 3,3V range for the i/o to arduino u still think its that problematic?
Changing a 5V logic output to 3V3 with resistors is fine because the load you put on the lower resistor is high impedance when compared to the lower leg resistor. It will slow down the signal edge but generally works well at low speed.
However when it comes to power it is another matter. Generally the lower leg should take at least ten times more current than you are drawing from the load. So if you want to use very low resistor values and burn a lot of current then at a push you can but I would not recommend it as a viable option in this day and age.
yea sorry, after i wrote that post i realized its wrong and modified the post before i read yours. all those cheap sd modules on ebay have a 3,3 Vregulator but no lvl shifter. Id believe davstes module has one too, otherwise how would you connect them on a regular basis to your 5V usb, if its not a arduino sd module.
Tumbleweed:
Daveste,
You could replace the 3.3 v regulator, if you like soldering SMT parts, that is.
If you need help finding it, then it is probably beyond the scope of your (present) abilities.
A TO92 LM33 regulator with a .1uf cap on the input, and a 10uf electrolitic cap on the output should run an SD card, but I would check. They can use a lot of current to write.
See the datasheet for the regulator for simple circuits to wire it up.
regulator: LP2950-33LPRE3 Texas Instruments | Integrated Circuits (ICs) | DigiKey
TomJ
I've just checked and locally, I couldn't find neither the regulator, nor the LP2950. ebay.co.uk don't seem to ship any either. If I can't get them from there I can't get them Sparkfun have exorbitant shipping to my location, and amazon have them available at $0.70 each with $60 shipping. Ugh, I might as well buy two new arduinos at that price...
I can't buy from digikey unfortunately. I wish I could but the shipping would cost me 100 times the part.
I also have my eye on this: http://www.amazon.co.uk/Alpha-Crucis-NCP1402-Step-Up-Breakout/dp/B008AS444W
I can use two AA batteries and extract 3.3v from them, that's great! Unfortunately it doesn't seem to be available. Is there anything similar?
Davste:
I can't buy from digikey unfortunately. I wish I could but the shipping would cost me 100 times the part.
I also have my eye on this: http://www.amazon.co.uk/Alpha-Crucis-NCP1402-Step-Up-Breakout/dp/B008AS444W
I can use two AA batteries and extract 3.3v from them, that's great! Unfortunately it doesn't seem to be available. Is there anything similar?
There's some on eBay but where would you get your input voltage from? You need 1-3V input for that, which is catch-22.
Sparkfun have exorbitant shipping to my location, and amazon have them available at $0.70 each with $60 shipping. Ugh, I might as well buy two new arduinos at that price...