Converting float to char*

char array[10];
sprintf(array, "%f", 3.123);

sprintf: (from MSDN)

In Arduino:

//temporarily holds data from vals
char charVal[10];                

//4 is mininum width, 3 is precision; float value is copied onto buff
dtostrf(123.234, 4, 3, charVal);

monitor.print("charVal: ");
monitor.println(charVal);

char buffer[64];
int ret = snprintf(buffer, sizeof buffer, "%f", myFloat);

if (ret < 0) {
    return EXIT_FAILURE;
}
if (ret >= sizeof buffer) {
    /* Result was truncated - resize the buffer and retry.
}

That will store the string representation of myFloat in myCharPointer. Make sure that the string is large enough to hold it, though.

snprintf is a better option than sprintf as it guarantees it will never write past the size of the buffer you supply in argument 2.