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Circuit Power Consumption

Hello!

A few questions if I may. I realize this is probably basic Ohm's Law stuff, but I want to double check with some of you, if possible.

If it matters, the circuit in question would be this:

- One garden-variety 555 timer circuit that holds its output LOW for around 6 to 10 hours, then puts it HIGH for about 4 or 5 seconds.

- One garden-variety 555 oscillator circuit that (using a small switching transistor) gets 'powered on' by the HIGH state of the above circuit. When this circuit is powered on it pumps a square wave into a piezo buzzer. When the above circuit's output goes back to LOW, the transistor is biased off and power is interrupted to this circuit. I would use 2 separate timers instead of a dual timer just for the reason of leaving the second 555 powered completely off for the 6-10 hour duration.

So it's a circuit that will sleep for several hours, rudely but briefly 'buzz', then fall silent again for several hours. I plan on powering this all with a single 9V battery, with a voltage divider to cut it down to 5V. For longevity of battery life, should I:

1) Use 755 timer(s) for one or both halves? Will the 755 be able to drive a piezo buzzer?

2) Use very high value resistances in the voltage divider, i.e. V+-->40MegaOhms-->Vref-->50MegaOhms-->Gnd ?

3) Use a different timer or approach altogether? On data sheets, is it the "Power dissipation" field that indicates how current-hungry devices are (I realize it's depending on a lot of other factors, though).

4) This circuit will be exposed to outdoor temperature changes. Will that make a very large impact on its timing intervals?

5) Any estimate as what to expect for battery life? I realize that a precise answer is hard, but am I looking at hours, days, weeks or months, perhaps?

Any suggestions appreciated. Thankyou.

-phaeton

Reply to
phaeton
Loading thread data ...

--
No.  A 555 is a very bad choice for such a long timeout.  However,
the second one could be used to drive a piezo buzzer.
Reply to
John Fields 

--
Oops...
Checking Eveready\'s site gives 625mAH for their 9V alkaline, so with
a 100µA load that\'s 6250 hours, or about 260 days.
Reply to
John Fields

If 260 isn't enough, you can go even further by taking a small cheap MCU like a picmicro, use it's internal Watchdog timer to handle the timing, and then drive the peizo from the pic using a FET like the bss123.

The only tricky part is getting a low power Regulator to power the pic. I used the tps715xx from TI, although it's quite a challange to put them on your PCB by hand :). Maybe you can use a zener for this, but my personal experience with them is quite limited and the experience I do have usually involves needing alot more current then the 4uA from the LDO.

All this should not draw more then 4 to 5 uA when idle. So it could work for many years on a single 9V block. Assuming of course your piezo doesn't take up too much energy.

Goodluck to you.

Jasper

Reply to
Jasper Keuning

--- (and)

Ahh ok. is the "755" and "CMOS 555 Timer" the same thing? Jameco's 'search' function was giving me the same results for both searches, but IMHO it's not the greatest at times.

Good thing I asked. I had never heard of a CD4060 before ;) Does "CD" mean 'CMOS' or something?

It's pretty non-critical. The long 'wait' period could vary by a couple of hours, actually. I would prefer it to err on the side of longer, but either direction is ok. I bet that any variation would be in *minutes* at the most, huh?

However, when you say "what's being used to generate the timer's clock", do you mean 'which IC'? I'm assuming that the 4060 can be set up to just 'run' automatically once you apply power to it, like the 555 and things, right? No need for an external clock or trigger.

Thanks for this rundown on the time, or *specifically* how you deduced it. It's given me more stuff to google ;-) 260 days is entirely acceptable. The plan is to build several of these circuits with slightly varying 'wait' periods, and tape each one to a 9V battery. Then I'll randomly stash them out in my best friend's workshop and see how long it takes to annoy the bejeebus out of him >:-) I'll pretend like I don't hear them or something. After awhile I'll stick one under the seat of his truck and one under the lid of his toilet or something.

(We prank each other all the time, it's all great fun.)

Thanks for all the suggestions and help.

Jasper: If i were to use a uC then I'd have to make it play music or something. You know, "The Atmel Tiny Canon in Dbminor" or something :-) I'm already trying hard enough to resist using multiple buzzers and multiple 555s to play reciprocating tritones or something. :-D

-Phaeton, Stark Raving Mad Scientist

Reply to
phaeton

scrap the above, voltage dividers waste most of the energy they get, 9V batteries are over priced,

if 5V is enough for your needs use 4 AA cells, 1t's 6v but the 555 won't care.

a 555, 7555 etc will operate off upto 16V no problems

DYM a piezo speaker element or a piezo sounder?

do that an there'll be no power to run the 555

yes, use a 4096 for the delay, have it drive a transistor which switches a buzzer. By buzzer I mean a device that accepts 6vDC and produces a continuous tone.

depends on the parts you use.

the circuit you described will not work and with lower resistors in the divider will waste more than half the energy in the battery.

Bye. Jasen

Reply to
jasen

use a chip that'll run directly off the battery. (maybe use a 3v, or 4.5v supply)

--

Bye.
   Jasen
Reply to
jasen

AFAIK 7555 and 4555 are variuation on the CMOS based 555 theme

4060 is a cmos part number CD4060 is one variation on that part (R-C oscilator with 14-stage divider (divide the frequency by 4096))

you'll need to look at the stability of the capacitors you choose,

more the timing parts, resistor and capacitor.

I'm assuming that the 4060 can be set

yup.

:) polyphonic music is totally doable and the power consumption is less than

10 microamps.

Bye. Jasen

Reply to
jasen 

--
There are many CMOS variations of the 555, the 7555 being Maxim\'s
version.  I\'m not familiar with a "755" version of the 555.
Reply to
John Fields

I'd love one, if you have one handy. I've been reading over the datasheet for the 4060 and it's starting to make sense. Maybe a quick outline of one in practical use would help as well.

Otherwise, I'll figure it out eventually.. :-)

-phaeton

Reply to
phaeton 

--
I posted a schematic for you on alt.binaries.schematics.electronic,
but since you\'re hooked up to USENET through that goddam Google
Groups, you won\'t be able to get to it.  Email me a valid email
address and I\'ll send it to you there.
Reply to
John Fields

Hear Hear! Gaaddaamn Google is only a function of surfing Groups at work. At home I'll fire up Pan and grab it there. I'll toss you my email addy though, just for social development purposes.

You're the best!

-phaeton

Reply to
phaeton

On 28 Jun 2006 13:53:05 -0700, "phaeton" wrote:

--- Thanks!

Here's the simulation, using LTSPICE:

Version 4 SHEET 1 1092 680 WIRE -464 224 -464 -176 WIRE -464 368 -464 304 WIRE -464 416 -464 368 WIRE -304 -64 -304 -128 WIRE -304 32 -304 0 WIRE -304 96 -304 64 WIRE -304 224 -304 160 WIRE -304 368 -464 368 WIRE -304 368 -304 304 WIRE -272 -64 -304 -64 WIRE -272 0 -304 0 WIRE -272 96 -304 96 WIRE -272 160 -304 160 WIRE -160 -16 -208 -16 WIRE -160 -16 -160 -64 WIRE -160 16 -304 64 WIRE -160 16 -160 -16 WIRE -160 64 -304 32 WIRE -160 144 -208 144 WIRE -160 144 -160 64 WIRE 96 -128 -304 -128 WIRE 96 0 96 -128 WIRE 96 32 96 0 WIRE 96 96 96 64 WIRE 96 256 96 160 WIRE 96 272 96 256 WIRE 96 368 -304 368 WIRE 96 368 96 336 WIRE 128 -64 -160 -64 WIRE 128 0 96 0 WIRE 128 96 96 96 WIRE 128 160 96 160 WIRE 128 256 96 256 WIRE 240 -16 192 -16 WIRE 240 16 96 64 WIRE 240 16 240 -16 WIRE 240 64 96 32 WIRE 240 144 192 144 WIRE 240 144 240 64 WIRE 240 256 208 256 WIRE 240 256 240 144 WIRE 304 -16 240 -16 WIRE 304 208 304 -16 WIRE 368 64 368 -16 WIRE 368 144 368 64 WIRE 416 64 368 64 WIRE 448 144 368 144 WIRE 448 208 304 208 WIRE 560 -16 368 -16 WIRE 576 64 496 64 WIRE 576 192 512 192 WIRE 576 192 576 64 WIRE 640 192 576 192 WIRE 768 -16 624 -16 WIRE 768 192 704 192 WIRE 768 192 768 -16 WIRE 800 -16 768 -16 WIRE 912 -16 880 -16 WIRE 976 -176 -464 -176 WIRE 976 -64 976 -176 WIRE 976 96 976 32 WIRE 976 368 96 368 WIRE 976 368 976 176 FLAG -464 416 0 SYMBOL res 224 240 R90 WINDOW 0 -32 58 VBottom 0 WINDOW 3 -32 63 VTop 0 SYMATTR InstName R1 SYMATTR Value 10E6 SYMBOL cap 80 272 R0 WINDOW 0 -38 31 Left 0 WINDOW 3 -56 56 Left 0 SYMATTR InstName C1 SYMATTR Value 4.7e-7 SYMBOL Digital\\\\or 160 -96 R0 WINDOW 0 -30 14 Left 0 SYMATTR InstName A1 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 9v SYMBOL voltage -304 208 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(0 5 0 1e-7 1e-7 1e-6 0 1) SYMATTR InstName V1 SYMBOL res 512 48 R90 WINDOW 0 -29 58 VBottom 0 WINDOW 3 -28 61 VTop 0 SYMATTR InstName R2 SYMATTR Value 10K SYMBOL cap 624 -32 R90 WINDOW 0 -30 32 VBottom 0 WINDOW 3 -31 31 VTop 0 SYMATTR InstName C2 SYMATTR Value 1E-6 SYMBOL pnp 912 32 M180 SYMATTR InstName Q1 SYMATTR Value 2N4403 SYMBOL res 896 -32 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 1000 SYMBOL voltage -464 208 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value 9 SYMATTR InstName V2 SYMBOL res 960 80 R0 SYMATTR InstName R4 SYMATTR Value 90 SYMBOL Digital\\\\or 160 64 R0 WINDOW 0 -30 14 Left 0 SYMATTR InstName A2 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 9v SYMBOL Digital\\\\or 480 112 R0 WINDOW 0 -30 14 Left 0 SYMATTR InstName A3 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 9v SYMBOL Digital\\\\or 672 112 R0 WINDOW 0 -30 14 Left 0 SYMATTR InstName A4 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 9v SYMBOL Digital\\\\or -240 -96 R0 WINDOW 0 -30 14 Left 0 SYMATTR InstName A5 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 9v SYMBOL Digital\\\\or -240 64 R0 WINDOW 0 -30 14 Left 0 SYMATTR InstName A6 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 9v TEXT -458 386 Left 0 !.tran 30 uic TEXT -152 -40 Left 0 ;Q13 TEXT -296 -104 Left 0 ;RESET TEXT -280 192 Left 0 ;4060

-- John Fields Professional Circuit Designer

Reply to
John Fields

Oh well....I'll wait a day or two and repost if necessary.

-phaeton

Reply to
phaeton

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