Intervalometer with time of day constraints - Script Writing - CHDK Forum
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Intervalometer with time of day constraints

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Offline cygnusb

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Intervalometer with time of day constraints
« on: 19 / February / 2009, 22:30:03 »
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Kind of a strange request.  I tried searching the forum, but wasnt exactly sure how to word it.

Is there a script that would tell the intervalometer to only work from say, 7am-5pm?  I thought it possible since there is an internal clock.

I need to be able to take one photo every 30 minutes for 2 weeks, but only in daylight.   The camera is going to be outside in a field, but inside a Pelican case (for weather protection).  Kind of like a trail camera minus the extra pcb and IR bits.  I'm worried the batteries may not last two weeks  (roughly 20 exposures a day), but with no flash, no display, and no IS, it may make it.  I'm going to buy a PowerShot A590 if there is such a script.

Thanks!
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Offline reyalp

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Re: Intervalometer with time of day constraints
« Reply #1 on: 19 / February / 2009, 22:45:25 »
You can access the date in script. I doubt you can leave it on for 2 weeks even with turned down as much as possible, but I could be wrong. Even if that's true, building an external battery pack that uses the canon AC adapter plug should be pretty simple.
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Offline cygnusb

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Re: Intervalometer with time of day constraints
« Reply #2 on: 19 / February / 2009, 23:45:54 »
Have you seen any scripts that do it?  I'm a noob, and definitely not a script writer (i wish i were).  I've used the standard intervalometer on one of my older A series for indoor, AC powered fun, but nothing as advanced as time limits per day.
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Offline mattkime

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Re: Intervalometer with time of day constraints
« Reply #3 on: 19 / February / 2009, 23:49:45 »
it should be relatively easy to do but you'd need to get your hands dirty with scripting.
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Offline fudgey

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Re: Intervalometer with time of day constraints
« Reply #4 on: 20 / February / 2009, 03:47:16 »
You need external power.

The a590 is probably quite similar to my a570 in power consumption and supply. I've measured minimum power consumption of 330 mW in play mode (note that CHDK doesn't currently offer a way to switch between REC and PLAY, just giving you theoretical limits here), with lens in and backlight disabled, without av plug (it enables video driver), supplied at 3.15 V.

At 2.4 V it would have been slightly more than 330 mW, but that's not important here. What is important is that a set of two 2700 mAh, nominally 1.2 V batteries only has approximately 2 * 1.2 V * 2.7 Ah = 6.46 Wh of energy, meaning less than 20 hours of idle play mode operation at 0.33 W. In idle REC mode with backlight disabled that's reduced to less than 6 hours.

Your mileage may vary (and you have to shoot too) and I may have miscalculated, but you won't get 336 hours of uninterrupted operation without external power.

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Offline peabody

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Re: Intervalometer with time of day constraints
« Reply #5 on: 21 / February / 2009, 23:15:57 »
Fudgey, I've been thinking about the external battery pack for my A590 too.   I think I've found the right connector, but there's an issue of whether rechargeables can be used.  Do you know how low the voltage can go at the DC-In socket?  I know it says nominally 3.15V, but that doesn't mean it wouldn't work at lower voltage.  I was thinking may be a two-pack of C or D NiMH would be good, if I can find them (and a charger), but of course that's not going to provide 3.15V.



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Offline fudgey

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Re: Intervalometer with time of day constraints
« Reply #6 on: 22 / February / 2009, 06:01:00 »
My a570 shuts down at about 2,0 V from both AA batteries and the DC plug. Keep in mind that cable and connector resistances cause signiicant voltage drop during high peak currents, so an external battery won't last quite as long as the internal one (voltage wise).

A D-cell NiMH will only be 10 Ah or so (compare to 2.7 Ah for AA cells), which is still not nearly enough for your two week wish.
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Offline whim

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Re: Intervalometer with time of day constraints
« Reply #7 on: 22 / February / 2009, 06:44:03 »
I agree, 2 weeks would require at least 100 Ah capacity ...
If a mains PS is out of the question, that will probably mean rigging up (one or more) car batteries
with a voltage regulator, or - if you're good at networking - try to get sponsored by a fuel cell manufacturer  :D

cheers,

wim
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Offline fudgey

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Re: Intervalometer with time of day constraints
« Reply #8 on: 22 / February / 2009, 08:57:34 »
Well, if the average requirement is 1 W and requirement two weeks, 336 Wh of energy is required. A 12 V lead acid or gel battery is probably the most widely available & inexpensive (but very heavy) solution, but of course requires stepping down the voltage from 12 V to 3 V, preferably with a switching power supply to keep battery requirement to a minimum.

I have a 12 V, 3 A car cigarette lighter powered supply for my NiMH charger, it's perfect for this and cost like 10e if my mind serves.

Assuming 80 % conversion efficiency and 80 % discharge depth, a 55 Ah 12 V battery will be enough for at least 2.5 weeks.

In practice working with display turned off you may reach lower than 1 W input, efficiency is probably better and you can discharge the battery to 0% if you don't mind destroying it in a couple of years (and you have a good charger to service it). A car starter battery is not good for this sort of use since they're not meant to be discharged at all and sulphate quickly...but they are the cheapest way to start out. Marine/leisure and gel types are better suited as are agm.
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Offline cygnusb

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Re: Intervalometer with time of day constraints
« Reply #9 on: 22 / February / 2009, 12:44:56 »
Ok...lets take power out of the equation.  I am now hooked to the mains.   Power is no problem.   What I need is a solution for an intervalometer script with time-of-day constraints.  I haven't seen a script with this spec. 
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