Using RTC on its Own

Hi,

The DS1337 Datasheet says "Access is obtained by implementing a START condition and providing a device identification code, followed by data. Subsequent registers can be accessed sequentially until a STOP condition is executed".

Regards, Nick

I do not see why not - provided the Vcc supply to the RTC is not interrupted, and the SDA/SCL lines are pulled up - the RTC will not know if the processor is physically there or just not speaking to it any more... Easy enough to try.

Geo

I have done this with a Xicor RTC a few years ago and it does work. Just ensure you leave the pull-up resistors connected from SDA, SCL and INTA/B* to VCC and that VCC is not interrupted during or after removing the micro. You also need to leave the resonator / crystal in place. Your micro will need an I2C interface to talk to the RTC to set the alarm time, I generally use an ATMEL AVR ATmega16 for tinkering around with this sort of circuit. What is your application? A timer of some sort? If anyone is monitoring these groups you might get 'looked at' if you do not state an appropriate application.

Alan.

Precisely what are you trying to infer by that?

"Anthony Fremont" schreef in bericht news:MulFf.28145$ snipped-for-privacy@tornado.texas.rr.com...

Risk of getting reported to the authorities, for preparing a timer for a bomb or something. Totally insane of course, because such timers always need the 7-segment LED display showing the count down. And it needs a bunch of wires, of which you have to cut one to make it run 5x faster, and cut another to make it stop at 00:00:01. I know that, I've seen that in countless movies.

I think he's helpfully suggesting that if the OP is looking for information on how to build, say, bomb timers or unjammable remote IED triggers he should come up with some kind of fake "appropriate application" in order to avoid undue attention from the authorities.

Best regards, Spehro Pefhany

Hmm. If he *were* using a RTC for that purpose, would he be expressing concerns over the ultmate fate of a cheap micro. One suspects not.

Steve

Hi,

I am using it for Maintanence purpose (Machine Lubrication). My machine needs lubrication after 500hrs hours of working. Earlier i thought of using an electronic timer but that would cost too much. Hence i thought of using the RTC without Microcontroller.

Thanks and regards, Nick

Which RTC chip did you say you wanted to use ??

If its for machine lubrication, then it must be plus/minus 5% or 10 hours.

Any microcontroller will get that and better.

So whats the problem ???

The problems you are looking at trying to avoid (cost) will bite you soon enough.

I do not understand why this is being discussed.

Donald

Nick,

Perhaps you think microcontrollers are too expensive? It looks like they may be cheaper than the RTC you're using.

Atmel's ATtiny11 8-pin microcontroller would probably do this fine for US$0.54 in quantity-1, and it has built-in clocking. Or ATtiny13 for about US$1.40 each if you require NVRAM - see

Also, if the machine stops and starts, how will your RTC timer allow for this? With NVRAM, you could save its timer periodically to survive power-down. With a 16-bit counter, 512-bytes of NVRAM, and 100,000 write cycles, you could save the timestamp every 5 minutes and run the machine for 25 years before exceeding the NVRAM specs. And/or detect power failing and save to NVRAM then. (You'd need a scheme to write in a loop to level the wear on the NVRAM, and scan NVRAM for the highest value upon restart.)

Regards, Richard

Hi, I have to retain the hours counted at power cut, which cannot be achieved using a controller as timer will stop totally or remain in running state if provided with battery backup. And using a RTC, allows me to save the counted hours in case of power fail. I can use a microcontroller, but the controller has only the work of seing the RTC alarm and giving it to the output. If the use of RTC alone does work out i will use the microcontroller.

Thanks and regards, Nick

Why don't you just keep track of the time with a microcontroller running at 32kHz and forget the RTC?

Nick, You seem to know a lot about what micros can and can't do, but do you really? You are making assumptions about the micro yet forgetting that the RTC requires power all-the-time to maintain it's count. Don't you think that a micro could operate in the same fashion? I'll tell you now that it can and yet it doesn't have to. You only need a capacitor to hold up the power long enough for the micro to commit the count to eeprom. What a lot of the in-the-know people have been saying to you is correct, "use a micro", it's cheaper yet more importantly, far more flexible for your application.

You don't even need to run it at low-frequency or low-power as it only needs to run when the machine is working and for a fraction of a second thereafter. I have done very similar things maintaining run-time for warranty and service issues, and I certainly didn't use an RTC.

Of course you can use an RTC without the micro, what's the big deal, it's not even really a question. The options have been put before you and they point in the favor of a micro but somehow you still seem determined to use an RTC. However, all being said, you decide for yourself.

Nick wrote:

be cheaper than the RTC you're using.

Perhaps he never used them before and prefers a fully HW solution without the need to write any SW?

"SioL"

without the

Maybe so, but it's going to be pretty challenging talking I2C to the RTC with pushbuttons. ;-)

Yep, that's true. :)

How he is going about all this is strange indeed.

Siol

------------------------------------------------ Rather than a heartless beep Or a rude error message, See these simple words: "File not found."

Let's face it, this is a public forum on the subject of electronics intended for genuine queries that may be answered by helpful peers, which is great. It may also be used by not very bright nutters trying to build nasty things as described above. I'm just making sure people are fully aware that it wouldn't take a lot for any authority to generate a program to search these threads continuously and automatically for keywords and flag messages and their comentators for review. I am not implying that you cleverly mask your application if it is dodgy, I am however saying that genuine users be vigilant for this type of activity so as not to give the nutter the information they want, or unwitingly get themselves on some sort of 'list'.

Alan

Unh, okay. I have this legitimate application wherein I would like to photograph "deer". These "deer" are quite skittish and I'd like to station myself some distance from the "camera" so they don't detect me. There can be quite a bit of electrical interference so I've decided a strong IR LED will give me the best chance of getting the perfect shot. I know there are many "hobbyists" who would like to build this circuit, so it should be made from easy-to-find parts such as consumer IR receiver modules and so on. Maybe a wireless camera link would allow me to be out of the line of sight of the "deer" while I'm waiting patiently to trigger the "shutter" (Bambi sipping from a babbling brook or something). Can anyone suggest a schematic?

Best regards, Spehro Pefhany

Excellent example, that's exactly what I mean! ;)

Alan