This is the one we are looking to achieve.ababkin wrote:a) MCU controlled: the intentional delay for various reasons before power is shut to the MCU and/or other devices
IMO this is a vehicle maintenance issue. If this is happening to you and you are getting a reset on each starting event then GET A NEW BATTERY!! :-) Seriously though, any battery that isn't well past its best and IS appropriately speced for the engine, compression ratio, and starter combo won't have a problem maintaining around 6 - 7V for the ECU to work from. This is a reasonable requirement to impose upon vehicle owners. If you have 5v available, injectors will be dozy and slow to respond, coils will take years to charge and fuel pumps will not be flowing well or at all.b) MCU uncontrolled: a protective circuit that will ensure there is power available for the MCU to react and prepare itself for the inevitable 'coming power-down'.
These circuits are tricky to implement properly.The latter is basically a brownout detection circuit with a largish cap that allows MCU to run for several milliseconds longer to save stuff and shut everything down properly.
Links please?I've seen some discussions on these circuits on forums discussing flash file systems on embedded devices (like EFSL).
It needs 8V to operate. That's too high for cranking on many vehicles unfortunately. A good LDO reg can work down to about 6V and with some inline protection an external input of 7V.- Not sure what power supply freeems is using (pardon ignorance, linear?), but i've discovered that a buck supplies like ones based on lm2678 (5A) or lesser current ones don't require much components, and give over 90% efficiency (free sample chips).
Good thought :-) Fusible links. beats the board frying, but then again, the board idea is free AND the wiring SHOULD be fused at the source anyway!- I would use one or two of those cute through-hole solder-in mini-fuses (look like 1/2W resistors) to protect the board. Easy to unsolder/resolder a new one and doesn't take up much space.
Fred.