give external supply to nrf51

[nordicbeginner]

hello there,

i am giving external supply to nrf51. my external supply is usb 3.3 v. but when i connect it with nordic and then if i check it on multimeter , it shows me 2.12 v. can you tell me why??

[Roger Clark]

What are you using to supply the power ?

USB is 5V not 3.3V so whatever you are using must be regulating 5V down to 3.3V, or perhaps when you say its a USB supply, you mean something akin to a phone charger ?? but 3.3V ???

[nordicbeginner]

i am using LM1117 for regulating supply

[Sigurd]

You have to use resistors to set the output voltage to the desired value. So you have to use different values on the resistors to get the desired 3.3 V. Please read the datasheet for the regulator.

[nordicbeginner]

i am getting 3 v when it is not connected to nordic. but when i connect it to nordic it shows me 2.12 v

[Sigurd]

What is the supply voltage to the LM1117? 3.3 V ? or 5 V?