Help with simple circuit please

Mr Sandman schrieb:

Hello,

and all electronics should be powered from an accumulator with enough capacity for at least one full day of operation. Of course the telephone should work also during a power off period. Not only the telephone of your house, but also of the neighbour.

Bye

the details depend on exactly how the dialer is triggered, but basically... Use a photocell to detect daylight. Use a wall wart charging a cap with enough discharge time to ignore short outages. If the solar cell is up and the cap is discharged, activate the dialer. Two hours is a stretch, but a lot depends on how long outages are. Around here, it it's out for more than a few seconds, it's out for good.

mike wrote in news:k5goa6$osa$ snipped-for-privacy@dont-email.me:

Since the O/P is an electronics novice, the use of an off-the-shelf 12V time delay relay for the two hour delay + a 240Vac coil relay to trigger it would probably be the best approach. Add a photocell module that inhibits the input to the time delay relay during the hours of darkness, a SLA float charger and a suitably sized SLA battery + the autodialler and the job can be done with no more than simple wiring.

As long as the photocell is before the time delay, it wont alarm till two hours after sunrise - otherwise it will be antisocially early in the summer. It may be better to use an off-the-shelf central heating control timer to implement the "not anti-social hours" function. Many have enough internal backup to keep time for over 6 hours without mains power.

However, by the time all that lot is obtained, it might well be cheaper and simpler to get a commercial mains failure and freezer monitoring module with GSM that will text you with mains failure and restoration or out of range freezer temperature events and ring the during civilised hours neighbour yourself!

snip

TheQuickBrownFox wrote in news: snipped-for-privacy@4ax.com:

No, that doesn't have a volt free relay output that is easily accessible. is a far better choice.

Ian Malcolm wrote in news:XnsA0ED9A306CA570xDEADBEEF@88.198.244.100:

... but it is ESSENTIAL to confirm that the module doesn't rely on mains power to operate the relay. Some small timer modules use a latching relay to save power and they would also work.

A convenient option would be this plus a netbook or some other computer that offers many hours of battery runtime:

Then it's all programmable and there is a light version of the necessary software that usually comes with these. At least it came with mine.

An interesting solution would use a palm pilot PDA.

If you're gonna use a laptop, just run BBS software on it and use the internal modem to do the dialing. And you could dial in any time to check status or download images captured by a webcam. There's probably freeware available to do just that if you have a data connection. Cobbling together some BBS software would save the cost of an ISP.

He could use either and a UPS and a battery bank. No solar, no worrying.

Just fire up the ups on the charge side long enough to top off the batteries a couple times a day, and whenever there is an outage on the controlled line, the UPS turns on and takes up the slack and sends a flag email.Check it for correct function and charge level once a month. Voila.

No, that doesn't have a volt free relay output that is easily accessible. is a far better choice.

Thanks, that looks like a good solution for the sociable hours side of the problem! I could program it so that it keeps the contacts closed during the night and run a power outage sensor circuit in parallel with it, so that if the power outage circuit has triggered(ie the power has been off for more than two hours and it has opened its contacts) it will trigger the auto dialler.

Sorted! Well now is just the design of a simple circuit that will trigger when the power has been out for two hours.....will a simple rc circuit have enough of a delay with a reasonable sized capacitor?

Steve

Mr Sandman schrieb:

Hello,

two hours are too long for a rc circuit. If you use a large resistor and a large electrolytic capacitor you will get problems with the leakage current of this capacitor.

Bye

Hi John, yes I'd love a schematic of your suggestion!

Many thanks

steve

--- Steve,

I've posted some files to abse for you:

news: snipped-for-privacy@4ax.com

a PDF schematic of something you can actually build, an LTspice simulation showing that it probably works in real life, and some support files for the sim.

Download all of the files into a single folder and click on the .asc file to view the sim schematic and later run it.

I'm assuming you have LTspice...

The PDF shows a 7555 astable running at about 1Hz for the clock, and another one - a one-shot - on the output. By selecting the values of Ct and Rt you can adjust the length of the output pulse in order to satisfy the dialer's requirements; T = 1.1RtCt.

Also, you may have to connect the 7555's output to a transistor if the dialer is looking for an open collector to drive it, or through a transistor to a relay if it needs contact closure.

If you need a circuit description, let me know and I'll write one up for you.

-- JF

Thanks john,

i want to be as sure as is reasonable that the power is off for good without someone's finger being introduced to flick a switch to get things back up and running, so yes at any time of the day if the power is off for 2 hours then i can be reasonably sure something has tripped off so the dialler needs to trigger. Storms in France tend to turn the power off for a few minuets before being automatically turned back on...presumably due to lightning strikes. If it happens to be night time then then it must wait until daytime before dialling out, if however, if by daytime the power has come back on by then, obviously there is no need to trigger the dialler.

A description of the workings will certainly help with my learning so yes please John!

Many thanks for taking the time to help us out with this!

Cheers

Steve