Senior Member
Joined: 09/12/2009
Location: AustraliaPosts: 221
| Posted: 12:43am 17 Jun 2011 |
Hi Sparkey,
I havn't looked in any detail at the Maxi but the microcontroller appears to be running at 5V, and you shouldn't hook anything up to its input ports that could have a higher voltage than that.
That may sound like you've wasted your money, but you havn't. All you need to do is scale your input voltages to something the microcontroller can handle.
The easiest way to do this for voltages that may be higher than +5V is to use 2 resistors in series to form a voltage divider. For 48V max input (whats the peak output from your panels?) I'd use an 18k connected to the panel +V connected to a 2k resistor connected to gnd. This resistor ratio will give you 1/10th the input voltage at the junction between the two resistors - use this as the input to your maxi. That way if your panel voltage is 48V you'll have 4.8V on your maxi's input pin.
This to note:
- Build some calibration code into your program - all resistors have errors and that will effect the voltage. Calibration code will allow you to correct for this.
- Make sure you have a good margin for error between the maximum voltage of your input and the +5V the maxi can handle without smoking itself. To be honest the 2V margin on my suggestion above would make me nervous, however if your max voltage is actually 40V then it'd be plenty.
I don't know squat about the maximites - take my guesses about the +5V input with a grain of salt and look it up for yourself. it may be 3.3V or something