5V down to 3.3V - AMS1117-3.3

Other Hardware General Electronics
1

Bough these on Amazon to enable me to drop 5V from a USB power supply down to 3.3V:

It uses a AMS1117 chip on it, I assumed this would be just a matter of putting the 5V from usb into the Vin and from Vout i would have 3.3V that i could use to power a ESP-01

However i must be doing something wrong as i am not getting anything close to 3.3v on the Vout and also when connected the power coming from USB also seems to drop.

Can only assume i need something else but am not sure what.

Be gentle am a developer so out of my comfort zone a bit.

2

do you have gnd connected? Post a picture of your wiring.

3

And the capacitors.

4

Yes i have GND connected to ground.

What capacitors?

Its wired directly from 5V source straight into the AMS module, just assumed that after than the output pin would provide 3.3v.

There isnt much to it the module has 3 pins Vin, Vout, GND i have 5v directly into Vin, GND connected to ground and expected 3.3V to be on Vout.

5

timuk:
What capacitors?

Ignore my post, I just looked at the link you supplied and see it is a module with the capacitors on the board.

6

Ok,

I have plugged in a 9v battery and get a steady 3.3v on the Vout.

So the next question is what is the problem with using an old USB cable from a 5v phone charger connected either into the wall or via a PC? On the multi-meter i can see i am getting 5v but as soon as connected to the voltage regulator the voltage drops.

Is there some clever circuity going on within the USB cable or socket?

7

What current output is the phone charger rated for? Maybe it cannot deliver enough current and the voltage collapses below the AMS1117 working voltage.

8

I have tried a few different ones now but all with the range output of 5V at 2A which i would have assumed would be plenty for what i am doing.

9

I have plugged in a 9v battery and get a steady 3.3v on the Vout.

If your battery was connected to one of your AMS1117 modules and it works but does not work using 5V from USB then you should suspect the USB cable (or something else) is dipping the voltage below the AMS1117 working voltage or the chips are out of specification.

10

timuk:
I have tried a few different ones now but all with the range output of 5V at 2A which i would have assumed would be plenty for what i am doing.

Only with a suitable USB cable - standard USB cables can drop voltage even at 0.5A even due to the wires being very thin. Its pretty common to only see 4.75V or so in practice through a USB cable

Since the 1117 regulator needs a large drop-out voltage (about 1.5V) this will matter much more than with
a really low-drop out regulator.

What current are you drawing? What input and output voltages do you see from the 1117 module?

11

timuk:
So the next question is what is the problem with using an old USB cable from a 5v phone charger connected either into the wall or via a PC?

An older USB cable may not be rated to provide. Get a few good quality, not the cheapest ones you can find, new modern USB cables.

12

Thanks everyone for your help, it looks like the 3 cables i was testing with are some sort of cheap ones. Tried a nice new one and 3.3V straight out the voltage regulator.

Never expected a cable to be the issue #suprised.

13

Glad you got to the bottom of the problem.