field.h

00001 #include "mbed.h"
00002 /**
00003     Functions to control alternator field
00004 */
00005 
00006 
00007 /**void    set_pwm (double d)   {   Range 0.0 to 1.0
00008     This PWM used to limit max duty ratio of alternator field energisation.
00009     With R25=33k and C4=100n controlling ramp input to CS pin of MCP1630 (not MCP1630V),
00010     ramp terminates fet 'on' pulse after a max of approx 980 us.
00011     With const   int PWM_PERIOD_US = 2000    , duty ratio is thus limited to approx 50% max.
00012     This is about right when using 12V alternator on 24V systems
00013     A 1.225V reference (U7) is fed to the MCP1630 error amp which compares this to fed-back proportion of system voltage.
00014     This adjusts final PWM down to zero % as needed to maintain alternator output voltage.
00015 */
00016 
00017 class   FieldControl    {
00018     uint8_t     privatemadetab[440];
00019     uint64_t    t_on, t_off, measured_pw_us, measured_period, rise_count, fall_count;
00020     uint32_t    old_percent;
00021     PwmOut      pwm_osc_in;     //  Controller PWM driving MCP1630
00022     InterruptIn V_ext;          //  Connected to MCP1630 output to MOSFET
00023     void        VextRise ();    //  Handles - MCP1630 has just turned mosfet on
00024     void        VextFall ();    //  Handles - MCP1630 has just turned mosfet off
00025   public:
00026     FieldControl  (PinName pwmoscin, PinName vext)  ;   //  Constructor
00027     void    set_pwm (double);   //  What it says, 0.0 to 1.0 but inverts to suit MCP1630
00028     void    maketable   ();
00029     uint32_t    set_for_speed   (uint32_t rpm);
00030     double  get_duty_ratio  ()  ;
00031 }   ;
00032