I'll start by saying that I have no idea what I'm doing, and I'm hoping you guys can give me some direction. I'm a software developer but have minimal experience with electronics.
My father runs a small Campground and has 15 individual kWh meters (luckily contained within the same enclosure) that are each hooked their own electromechanical counter:
Kubler K46 Electromechanical Micro-Counter @ 10 Hz count frequency
According to the documentation from the meters, the voltage into these counters is 12VDC.
Right now my father has to go and note the values of each of the meters at 3 points in the day... every day. He has never complained, but I feel this can be somehow automated.
Now my question is, what kind of board would I need to accept these pulses as input for logging purposes? It seems 12V is within the input range of the Duemilanove, so would this be able to do the job? If so, how many pins on the board could I use for this pupose? 14?
Sorry for the amateur questions, and would appreciate any suggestions/direction I can get Thanks!
We probably dont wanna send a software guy to scout out how these 12v pulses are generated and whether they are isolated, or have a common ground, etc. So I will base an interface solution on opto isolators.
If youre not into soldering you can buy standard industrial grade "DC Input Modules" which are the same opto-isolators with the other curcuitry already packaged. http://www.opto22.com/site/pr_details.aspx?cid=4&item=IDC5D They cost $10 to $15 each, or if you prefer we can help you "roll your own" for about half or less.
Theres some more details, depending on your specific pulse width and the amount of lightning / surge protection you need. The opto-22 modules could be used instead, they have pretty good protection built in.
There are mcuh cheaper ways to do this using just a few resistors, but I went this way for emphasis on rugged and long-term reliable in what could be a nasty electrical environment.
You'd save about $50 to $150 going the cheaper way. Gotta be sure all counters share one common lead that can be grounded and tied to Arduino ground, then use resistors, capacitor and diodes to DIO pins.
Wow, thanks for the quick and informative replies.
I'll try to find out more about the meters when I have access to them again.
As for the duration of the pulses, I'm going to guess that they are 0.1s since the counters claim they work at 10Hz.. EDIT: It sounds like there are multiple counter outputs on these meters (10 kWh, 100 kWh, 1000 kWh), that give different levels of accuracy. I'll see if I can find more about these pulses and get back to you.
If the rate is low, as it probably is, we can "stretch" a narrow pulse with a capacitor. That gives you more time for polling or interrupt servicing if you need it.
You can put a LED and 1k resistor across a counter to see if the flash duration is near the counter minimum or several seconds long. Mind the polarity !
Thanks!