View Single Post
  #4   Spotlight this post!  
Unread 02-02-2010, 16:38
RyanN's Avatar
RyanN RyanN is offline
RyanN
AKA: Ryan Nazaretian
FRC #4901 (Garnet Squadron)
Team Role: Mentor
 
Join Date: Jun 2006
Rookie Year: 2005
Location: Columbia, SC
Posts: 1,126
RyanN has a reputation beyond reputeRyanN has a reputation beyond reputeRyanN has a reputation beyond reputeRyanN has a reputation beyond reputeRyanN has a reputation beyond reputeRyanN has a reputation beyond reputeRyanN has a reputation beyond reputeRyanN has a reputation beyond reputeRyanN has a reputation beyond reputeRyanN has a reputation beyond reputeRyanN has a reputation beyond repute
Re: Wiring 3.3V Sensors to 5V Analog Breakout...

Any reason not to use a resistor connected to the 5V Analog Breakout?

Let's do the math.

V=IR
R=V/I

Voltage drop needed across the resistor will be 5V - 3.3V = 1.7V

From the data sheet, it uses 500μA typical. I'm not sure how the sleep current will work out.

So..
R = V/I
R = 1.7V/500μA
R = 1.7/500x10^-6
R = 1.7/0.0005
R = 3400Ω = 3.4kΩ

Now, the accelerometer has a bit of flexibility. You should be good with any resistor between:

V = 5V-2.2V = 2.8V
R = 2.8V/500μA = 5.6kΩ

and

V= 5V-3.6V = 1.4V
R = 1.4V=500μA = 2.8kΩ

I would stay away from either extreme, preferably lower since I'm not sure what will happen with the sleep current.

Before doing this though, let some of the more experience engineers take a look at what I provided before going with it. You could get a 3.3V voltage regulator, and it will work fine. Resistors seemed simpler and easier to acquire (@ RadioShack or in your shop).
__________________
Garnet Squadron
FRC 4901
Controls Mentor
@rnazaretian

Previous mentor and student from Team Fusion, FRC 364