Pages: [1]   Go Down
Author Topic: Will the arduino Uno adc burn if the input voltage is around 5.25V?  (Read 953 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Full Member
***
Karma: 0
Posts: 213
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hey,

I am using 10k resistor in series with 2 schottky diodes which cuts of any voltage above 5.25V? So my question is will this voltage still burn the arduino ADC?
Logged

Offline Offline
Full Member
***
Karma: 3
Posts: 244
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

The chip is able to use 5.5 Volt supply. The data sheet said 0 to VCC

So if VCC is 5 volts then No i wouldn't use 5.25 on a ADC pin your reading would be off

I would use a 5 volt zener diode
Logged

Montreal
Offline Offline
Faraday Member
**
Karma: 27
Posts: 2556
Per aspera ad astra.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

All inputs, digital and analog  protected internally with diodes. You need only resistor to limit current < 1mA.     10k is capable to protect up to 15V :   15V - 5V / 10k = 1 mA
Logged

Washington
Offline Offline
God Member
*****
Karma: 38
Posts: 789
Firefox & Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

From the datasheet:
Quote
Voltage on any Pin except RESET
with respect to Ground ................................-0.5V to VCC+0.5V
Since the VIN should be around 5v, 5.25 < 5.5v.
Logged

Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

Austin, TX
Offline Offline
Faraday Member
**
Karma: 71
Posts: 6106
Baldengineer
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Funny how only pieces of answers are given when the question "Can I put XXX volts on an I/O pin?"

True, the spec sheet says:
From the datasheet:
Quote
Voltage on any Pin except RESET
with respect to Ground ................................-0.5V to VCC+0.5V

So consider your VCC source.  If using Vin, consider how stable your supply is and what it's ACTUAL maximum will be.  When using USB, realize that USB's spec allows Vusb to be between:  4.75V and 5.25V.  Keep in mind there is an on-board fuse (which nominally should be 0ohms, but could drop a small amount of voltage.)

So, if powered by Vusb there is the potential for VCC to drop down to 4.75V which means the Maximum to any I/O pin is now 4.75V+0.5V = 5.25V.

Will it burn the ADC?  No.  If anything did get taken out, it might be that particular input of the MUX going into the ADC.
Logged

Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Offline Offline
Full Member
***
Karma: 3
Posts: 244
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

He doesn't say if he using the pin as a I/O or analog   
Logged

Austin, TX
Offline Offline
Faraday Member
**
Karma: 71
Posts: 6106
Baldengineer
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

He doesn't say if he using the pin as a I/O or analog   

That doesn't matter.

From the datasheet:
Quote
Voltage on any Pin except RESET
with respect to Ground ................................-0.5V to VCC+0.5V

Notice the words "any Pin"?
Logged

Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 473
Posts: 18695
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I am using 10k resistor in series with 2 schottky diodes which cuts of any voltage above 5.25V?

In what way does a 10K resistor and 2 schottky diodes reduce "any" voltage to 5.25V? I'm just curious, I thought zener diodes were used in that way, but a quick Wikipedia search reveals:

Quote
Schottky diodes' voltage drop at forward biases of around 1 mA is in the range 0.15 V to 0.46 V ... which makes them useful in voltage clamping applications

So presumably it can be done, but how?
Logged

Pages: [1]   Go Up
Jump to: