Hello,
I'm total EE newbie, apologies in advance for stupid questions....
I would like to build a simple stopwatch which counts from zero upwards. I found several ways how to do it and now I'm considering two:
- 32kHz crystal -> 4060 + 4040 -> 1Hz, and then some 7-segment LED displays driven by 4026.
- 32kHz crystal, some ATmega with clock divider set so it ticks at 1Hz, which in turns drives some LCD display (like HD44780)
Now, my questions are:
- which path should I take?
- the largest problem I have is I would the stopwatch to run for several years uninterrupted. That means, it might be a problem to power it from grid, so I tought I would run it on batteries as I saw some simple digital clocks to run for years on this small batteries. But when I did the calculations (here's when my lack of education kicks in) I realized batteries wont last enough. Please, do you have any suggestion for me?
The calculations were like this: one "D" battery has 12000mAh and if my LCD circuit draws 2mA (how does mA relates to mAh? what does it mean a ciruit draws 1mA? for what time?), it will run for 250 days. I would like it to run for 25000 days ( i.e. 100x). Not to mention LCDs (1st option) consume far more power.
(side node: 2mA * 60 sec = 120mAs/min = 7200 mAs/hour = 2mAh -- I found this on net too, not sure if it is correct. I never saw mAs/min before....)
Also, I was thinking about using solar power and super-capacitor but that might be too complicated for me..
Also, in 1st option, is it even possible to run that many LEDs off 4026s off batteries?
Anyway, thanks a lot for any help!
I'm total EE newbie, apologies in advance for stupid questions....
I would like to build a simple stopwatch which counts from zero upwards. I found several ways how to do it and now I'm considering two:
- 32kHz crystal -> 4060 + 4040 -> 1Hz, and then some 7-segment LED displays driven by 4026.
- 32kHz crystal, some ATmega with clock divider set so it ticks at 1Hz, which in turns drives some LCD display (like HD44780)
Now, my questions are:
- which path should I take?
- the largest problem I have is I would the stopwatch to run for several years uninterrupted. That means, it might be a problem to power it from grid, so I tought I would run it on batteries as I saw some simple digital clocks to run for years on this small batteries. But when I did the calculations (here's when my lack of education kicks in) I realized batteries wont last enough. Please, do you have any suggestion for me?
The calculations were like this: one "D" battery has 12000mAh and if my LCD circuit draws 2mA (how does mA relates to mAh? what does it mean a ciruit draws 1mA? for what time?), it will run for 250 days. I would like it to run for 25000 days ( i.e. 100x). Not to mention LCDs (1st option) consume far more power.
(side node: 2mA * 60 sec = 120mAs/min = 7200 mAs/hour = 2mAh -- I found this on net too, not sure if it is correct. I never saw mAs/min before....)
Also, I was thinking about using solar power and super-capacitor but that might be too complicated for me..
Also, in 1st option, is it even possible to run that many LEDs off 4026s off batteries?
Anyway, thanks a lot for any help!
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