Using a 5v pin to power a 3.3v volt device

Using Arduino General Electronics
1

Hey!

I need to power a 3.3.v component from my Mega using one of its 5v power pins as the ONLY 3.3v power pin on it is being used by a shield.

Whats the easiest way to achieve this?

Or is there another way I could get 3.3v out of the Mega to power this other device via another pin on the board?

This is the device http://media.wix.com/ugd/f7ab2a_19cf65df8854eea2ded14b2b37f8c671.pdf

Thanks

2

Page 17 of that guide shows one way to power from 5V.

Alas it doesn't seem to say how much current the module uses, so its not clear
it could be powered from the Arduino's 3.3V pin anyway which can only manage
50mA or something like that.

A 3.3V LDO regulator derived from the 5V supply would be one sensible method of
powering the device.

3

The manual states that ...

*The SMART WAV must always be powered with 2.7V-3.5V (Reset and RX pin are 5V
tolerant).

Im pretty sure it just means that the serial line can be 3.3 or 5v but the actual Vcc for the unit needs to be 3.3v in...

Can you link me to a small cheap product I can wire off a 5v pin to allow 3v3 ?

4

You need an external 3.3V regulator from the Vin or 5V pin.
SD/uSD cards need 200+mA, there is no way to power this module from the Mega's on board 3.3V regulator, which is only rated for 150mA,
and not from an IO pin, which are only rated to 40mA Absolute Max.

5

Ahh.. after looking again lol (at the wav player this time)

Forget the pass resistor!

3.3v ldo from 5v.

6

CrossRoads:
You need an external 3.3V regulator from the Vin or 5V pin.
SD/uSD cards need 200+mA, there is no way to power this module from the Mega's on board 3.3V regulator, which is only rated for 150mA,
and not from an IO pin, which are only rated to 40mA Absolute Max.

Would this be a good solution?

http://www.ebay.com.au/itm/1PC-New-DC-DC-4-5V-7V-to-3-3V-AMS1117-3-3V-Power-Supply-Module-Voltage-Regulator-/200963269245?pt=AU_B_I_Electrical_Test_Equipment&hash=item2eca58227d&_uhb=1

7

i see the device can tolerate 2.7~3.5v, if you just running out of regulators, connect 3 silicon diodes in series will get you 2.9~3.2v from the 5v input.

each diodes has a 0.6~0.7v barrier, 3 of them in series gives you 1.8~2.3v, so you get 5v - 1.8~2.3v = 3.2~2.9v, within spec.

but this is just a quick hack for convenience, don't do this if your project is going into production.

8

Yes, the e-bay device would be an acceptable solution.