Changes by last author:
Added:
| There is a preferred spark polarity (maybe for the ION current too). Anyone remembers ? If you find it while reviewing these (or other) papers, please answer here. |
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Another supply typology Push-pull type |
| Push-pull type DC/DC |
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uC controlled / standalone For the CDI / Ion, uC controlled supply might be simpler and cheaper (and better logistics). For uC main processor supply for the big display (with near-PC-performance, and a few Watts of dissipation at91rm9200+256 Mbyte SDRAM) power must be standalone. Standalone is usually made from SG3525 , SG3524 SOIC16 or similar chip (compatible chips available from other manufacturers). Standalone advantages * prevents "stuck in" output stage (that might blow a fuse) * suitable for the processor supply too (a processor can rarely control it's own supply, although it might be possible) Standalone disadvantages * higher cost the SG3525 is in the $0.6 range, logistics should not be too bad * bigger footprint * uC controlled has better flexibility (control supply voltage from software easily) ---- simple CDI implementation with v3.x Rather for experiment than production. * only works when injector PWMing is not used, since the PWMing duty is used to control (regulate) the CDI supply. * a FET activates the CDI flyback transformer (eg. 8:175 turns) primary side ** since freq is 15625 Hz (64usec), the transformer is a bit big (2cm2 should be enough). Ferrite core is needed (is toroid OK, or it must have a small air-gap to prevent magnetic saturation?). Maybe 32usec period would be better than 64usec. * when the FET switches off, the flyback voltage on the CDI transformer secondary side charges a cap through a diode ** diode is easy, ES2J can be fine ** 1..4.7uF cap, min 400V (electrolytic OK?). This cap will be charged to appr 300V. Not a small cap. * feedback voltage divider is needed from the 300V to a free mcp3208 input. * a control loop must be placed in firmware to regulate the CDI supply output voltage. Make sure the duty can go down to 0% (not 1/256 !) * ignition transformer primary+ is connected to 300V * ignition secondary switched with IGBT (as normal), but very low dwell (64 usec?). ** A flyback diode is needed (3xES2J in parallel?) towards the 300V trace * ignition transformer secondary- is connected to 300V through Rionsense (270 .. 510 Ohm?) resistor (the other end of the secondary winding is the HV wire to sparkplug, of course) ** this way the IonSense current becomes available. Possible to divide and GND-reference through a differential-input channel pair: available through midopa. Than record with AVR or with soundcard for analysis (not at 300V potential, but the GND-referenced signal) When CDI is active, the tip electrode of the sparkplug is either at +300V or +30000V (during spark) potential, so take care. ---- See also * http://fec.eng.monash.edu.au/challenge/ 30V to 230V DCDC inverter |