Current Draw from timer causing battery drain

gizz

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The results from testing the current draw on my new digi multimeter show a problem. For reference I'm using MS20 w/RS Relay, OWL PF, 12V 1.2Amp battery. I got the circuit board plan a ways back and it consists of transistors and a capacitor as the main components. The results:

With the "timer board":
At idle  14.2 ma
Tripped with LED light on  62.0 ma

Same setup WITHOUT timer board:
At idle 1.65 ma
Tripped with LED light 34.0 ma

I checked several of the timer cams and get the same results.

I think I'm gonna have to go to the TLC555 setup or none at all. The board works great but the drain on my bat's is too much. Wish I would've known how to test this before but I guess this is how we learn.

Is the following correct?
1.2Amp gell = 1200ma
1200ma/14.2ma = roughly 85 hours or 3 1/2 days?
1200ma/1.7ma = roughly 706 hours or 30 days?
If this is right that's a BIG difference
 

Jaggermax

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Gizz, I just got the latest Digikey Electronics catalog and it lists life ratings for a lot of the batteries they sell.  They also have the same info on their website:  www.digikey.com.  

Do a search on batteries, and it will pull up a table with pull down menus where you can narrow you search by battery type, cell size, etc..  It will then pull up the page for that battery type and usually datasheet with it.  Most of the datasheets have the amp-hr ratings.  Check it out.  You would be surprised at the difference in the amp-hr ratings of a battery between the different venders.  
 

gizz

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Thanks jaggermax - I'll check it out.
I think my bat's at 1.2Amps are enough though I just need to reduce the intake from the transformer/cap board that I'm using to prevent camera shut-down. The one-shot TLC555 timer should do the trick.
The site sound neat nonetheless and I'll check it out. Thanks for posting.
 

gizz

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Tinhorn, yes it was the board I got from Marty. I didn't even know the difference between a multi-meter and a capacitor back then so it never got checked. If I'm careful I can de-solder the transistors and caps and keep for future work.

One question to help clear my confusion.
Does the 1200ma mean 1.2 Amps at 12Volts then as the voltage drops to 11, 10, 9 etc I still have some more capacity? I've tested the came down to around 10 volts on the batt's and it works fine so I'm assuming some where further down is when the cam will stop working.
 

Tinhorn

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Gizz

It's hard for me to say about the batt volts vs current.  I'm a little hazy on batterys really.  It seems wrong that the heavy rechargable batt's won't have as much capacity (ampcapacity) as the chemical batt's.  My old TI55 calculator I used in college had a 9v rechargable batt that would only last 4 hrs,    went dead on exams all the time.  One day I rigged up a 9volt tranisitor radio batt to it and it lasted "Days".....

I know that the CURRENT actually does the work and comparing it to water, Current is like a bigger water pipe and Volts is like the water pressure.

A squirt gun will have a lot of water pressure (Volts) but it won't fill the swimming pool very fast, no volume (current)

Some electronic components work is based on current, normal NPN or PNP transistors, or straight 555 timers and some components work on voltage, Cmos components, like the TLC555, and the old radio tubes, and these don't draw much current to kill the batt's.

I wish I could better explain your question on the batterys better but.........

Tinhorn
 

gizz

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No problem Tinhorn.
I was just trying to guestimate the number of days the 1.2Amp 12V will last. I would like to think that it has 1.2Amps at 12V and then the further the voltage drops the less amperage I have but maybe still enough to run the PIR a few more days. All in All though I'm gonna figure on a re-charge at least once overy thirty days to be safe. Maybe I'll set one on the bench and check it every day to see how long it lasts.
The new multi-meter works great by the way. $39.95 Pen Style from Radio Shack. Everything is auto ranging too which is nice. The ma's for current draw go down to .01
 

Jaggermax

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Let me guess Tinhorn, did you calculator have red leds in the display?  If so, I know just what you mean, I had to charge it up everyday after class in college!

Gizz, here is how I calculated the battery life of my cam.  I disconnected the negative lead of the battery and placed the probes in series to measure the total current draw.  I then turned my cam on and let it initialize for about a minute.  

My current draw was around 5 ma.  I then activated the PIR with my hand and watched to see how the current draw increased.  It went up to about 13ma max then down again.  Since my camera is in the wait mode 95% of the time (5 ma)  I just decided to use 8 ma as an average.  

I am using 4 "C" batteries in series so the rating is around 8000mah.  So I can expect the life of my batteries to be  (8000mah/8ma)/24hours=41days. I have had my cam in the woods now for about a month and the batteries are still fine.  

Use this formula to calculate battery life is:

(battery rating (in millamp-hours)/current draw of your cam (in milliamps)/24hours=X days.  

Hope this helps.  
 

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