Is there some ?cheap? IC solution that can hold a timer that count the minutes when enabled and then at power off saves the value and restarts counting again at next power on? It?s going to monitor on-time for various appliances so that in some kind of monitor mode one could read out the accumulated on-time.
I would like a solution that is connectable to a embedded processor.
Many embedded processors would be capable of doing the logging function but you should provide a little more detail about the appliance that you wish to monitor so that more specific help can be supplied. Such information should also contain details about available space, how intrusive the solution may be, and whether the solution is a one-off or part of an intended production run.
-- ******************************************************************** Paul E. Bennett ....................
a pcf8583 RTC can be used as an event counter, power it with a backup source and use a clock source powered from main power source, so the clock ( source ) is stopped when power is off
it has an i2c interface so it can be read from a micro
I think that maxim does some similar chip
"Mr Smith" wrote
restarts
various
A PIC could do this fairly easily. Power the PIC thru a diode using a cap on the PIC side of the diode to hold some extra juice. Tie an input pin directly to the power source on the other side of the diode. After the PIC powers up it can obtain the last saved value from the internal flash and begin counting seconds. When the PIC detects the input pin going low it should have plenty enough reserve power stored in the cap to save the current value in the internal flash memory and then go to sleep. Before going to sleep, the PIC could pull down the cap using an output pin and a current limiting resistor to finish the discharge quickly. Next time the device comes on, the PIC will do a power on reset and start the counting cycle again.
Yes.
You can also use the PIC's HLVD feature where available; this triggers an interrupt when Vdd crosses a programmable threshold (either rising or falling).
Or EEPROM.
input
After
internal
pin
Where available.
Is there really any difference anymore besides the terminology?
I thought EEPROM's lifecycle was several orders of magnitude shorter...
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shorter...
According to a PIC 16F88 datasheet, the EEPROM is specced at one order of magnitude more than the flash program memory (1,000,000 for EEPROM vs. 100,000 cycles for program flash). So there would appear to be some difference (at least in the specs) between the type of memory contained in the micro. The datasheet also claims >40 year retention for the EEPROM, but says nothing of the program flash implying a difference again. I'm sure that information is detailed in another datasheet that covers a series of devices.
I once used a Dallas RTC chip (DS-1339 ), it connects through I2C, and is quite cheap.
hope this helps
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