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I live in a place which is plagued by frequent power cuts (load-shedding). I have to design a circuit by which I can record the timings while power is gone or vice-versa. I also need an equivalent computer application which can be used to print daily/weekly/monthly reports of these power-cuts.

How should I go about doing this?

SamGibson
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A j
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  • This question appears to be off-topic because it is not a specific design question. – Leon Heller Sep 03 '14 at 06:57
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    Sir. Once I start designing the circuit I will raise "specific " queries too ! – A j Sep 03 '14 at 09:53
  • The interval timer of the DS1994 would have been rather nice as it had battery, counters and crystal but it is an end of life part. Using the replacement DS1904 you will need a u-controller to read the time and store it whenever the power is restored and again on a power fail before the PSU caps run out of power for later readout. The DS2417 needs batt and xtal but can interrupt your micro. DS1994 DS1904 DS2417 – KalleMP Sep 03 '14 at 09:57
  • A new device M41T62Q6F may be the basis for a logger design that will time stamp the power outages. – KalleMP Dec 07 '14 at 19:17
  • It occurred to me that almost any portable temperature logger could be used. Place it in close proximity to an plugged in and switched on incandescent lamp and have it log the temperature change. You may find it reacts in about 30 seconds giving you a easy 1 minute resolution. Such loggers usually come with some kind of download or visualisation software and batteries may last a year or more. – KalleMP Aug 03 '15 at 14:55

4 Answers4

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Use a microcontroller (For beginners, the arduino platform is very nice) and power it off a battery. Maybe an ATtiny is a good fit here, because it is small, simple and has low power consumption.

The device continuously monitors (directly via its ADC) the voltage of an AC-DC wall-wart (e.g. mains to 5V), and if it notices a drop to below some threshold, it saves a timestamp to its EEPROM (non-volatile memory). That's basically it. Reading out the device can be done in any way, e.g. Serial/USB. If you want precise timekeeping and don't want to sync the internal clock via the PC every few days, you'll also want an external realtime clock IC.

If you want it fancy you could make the wall-wart recharge the microcontroller's battery. But such simple circuits can usually work for a long time off a battery. You could also get a µC that can go into a very low power consumption sleep mode, and is wakened by a falling interrupt (not sure if that applies to the ATttiny). You might need to make a clear falling edge by throwing in a schmitt-trigger between wall-wart and interrupt pin.

DerManu
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    I like the "just monitor DC output from a AC/DC wall-wart", since it is safe to handle and simple. It may be required to put a slight load on the DC side, to discharge the internal capacitors. Going to high impedance, it could take some time for the DC voltage to drop below V_il. – Rev Sep 03 '14 at 13:00
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It's almost similar question from this thread How can I detect a power outage with a microcontroller?. Just put 100k resistor on transistor collector and 1uF cap across GND and collector and it should give you smooth signal. Just remember that signal will be inverted.

Edit: I thought my answer was clear but just to make it more obvious I've added schematic. Schematic

Edit: You absolutely must make sure that optocoupler has dual diodes inside. If it has only one, just add one external diode in reverse across it's terminals. Otherwise every other cycle full mains voltage will be applied across single diode in reverse. If it is not rated to that voltage it can emit magic smoke. In any case working with mains voltage is dangerous and you need to understand what you are doing.

Farid83
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  • The linked question provides a nice simple solution. However, I fail to see what you mean with "Just put 100k resistor on transistor collector and 1uF cap across GND and collector and it should give you smooth signal." This does not reflect the other answer. How exactly does your proposed circuit look like? What are the resistor and transistor requirements? It is dangerous if you have no mains isolation. – Rev Sep 03 '14 at 12:56
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Take a laptop with a good battery and run this tool: http://www.nirsoft.net/utils/battery_information_view.html

It logs when your laptop is disconnected from the power supply and re-connected again. And it can put this log into a file automatically.

Drawbacks:

  • The log is not event based, so with small time intervals it will get very large
  • If the power cut lasts longer than the battery time, some information may get lost
m.Alin
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mic
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  • How does this answer the "I have to design a circuit" question? Further it's impractical for longer logging, since you're always blocking (and running!) a laptop... – DerManu Sep 03 '14 at 20:24
  • A laptop (which can be a cheap one) IS a circuitry, PLUS it includes the requested "computer application" ;-) – mic Sep 04 '14 at 07:10
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Going old-school, a clockwork chart recorder sort of arrangement using a cheap battery-powered (or battery-backed) clock movement would remove the need for microcontrollers etc.

All you need is a drum (if you don't mind the recording looping) or roll of paper (EG a shop till receipt reel), some sort of indicator or marking device, and mains-powered solenoid or similar to move it so that when it's powered, it marks in one place, and when the mains drops it moves to another place.

It could be easily done using a dish of sand, where the hour hand of the clock sweeps a line in the sand (like a robot zen garden project I saw somewhere), that would give you 12 hours endless recording.

Adding features like timestamps etc. is left as an exercise for the user ;)

John U
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