Detecting AC current

Did a quick search and didn't see anything that really stood out. What I would like to do is sense when my sump pump turns on and off. One way I was thinking of doing this is by sensing when the current draw on the AC line went up and down.... something like an AC clamp meter (out of the AC circuit and non-distructive). Is there a device out there that I can do this with and be able to interface to a pic? Don't need a high resolution output, just something to indicate there is current draw past the idle threshold... assuming there is a small amount of current draw in the idle state. Any enlightenment would be appreciated. Voltage = 120V 60 Hz .Thanks

Current transformer in serie with the load is the way to go. You can easily built your own with few feets of wire.

The simple Way : use three power Si diodes in series with the line to create a voltage loss. Three other diodes anti-paralled will allow full wave transmission.
Or two diodes and a small value resistor, if there's an offset.

Then use this loss to power on the led of an opto-coupler ...an have the looked-for info from the opto's transistor.

plus a free zero voltage detector for synchro-switching !!!

so simple ...

Have a look to slave supplies sold for powering computer accessoiries ...

Alain

Thanks for your enlightenment. I went the route of a current transformer, just to keep out of the high voltage circuit. Did a google seach to read up some more on it. Snagged one of those iron donughts you see on computer cables for the core. When I get to the point of filtering the signal, I may also incorporate the opto as Acetronics suggested. Seems to work pretty good. I have to play around some more with the # of turns on the secondary to get the right voltage. Built it last night while watching TV... my kids thought it was pretty cool when I explained the operation. Thanks again!

Yet another problem solved. I did many things with current transformer as now without any opto isolator wich are working really great. But i guess it's still a good practice... safer but not cheaper ;)

Many more turn on te secondary will cure the problem but you can also use an opamp to raise the voltage and filter the signal in the same package too. Voltage comparator could be another way and will act as a buffer.

As always... endless possibility are in your hands :o]

Hello Rhino,

I notice you are working on a sump pump project...

I know this is "off the wall", but it may be worth checking into..

they have a "Water Sump Pump"... NO electricity at all...It relys on your water provided by the city/town. The only way this would not work, is if you have well water, and use a electrical pump to pump water from your well...

DWayne

I have seen those types of pumps (or are they siphons?).... and they're a great solution if you're worried about power outages and such. Haven't checked all of the dimensions to see if two pumps would fit in the pit, but I also thought about getting one of those battery powered pumps that you plug in and it trickle charges the battery when there is power. For this project, I am trying to collect some data on how much the pump runs, then figure out based on the flow rate of the pump, approximately how many gallons of water we pump out each day. I'm kind of a data freak. In the grand scheme of things I eventually would like to pump that water to a drum or tank, then use that water on dry summer days to water the lawn. I gotta tell you guys though... it's nice to be able to come to a forum like this with people that like to do stuff like this. My wife and friends all think I'm some kind of geek to play with this stuff as a hobby. I appreciate your feedback...Thanks!
- Ryan

Hello Rhino,

Rhino>>I have seen those types of pumps (or are they siphons?).... and they're a great solution if you're worried about power outages and such.<<

They are a water pump, operated by water. They can be in co-existance with a regular pump.

Rhino >>
Haven't checked all of the dimensions to see if two pumps would fit in the pit, but I also thought about getting one of those battery powered pumps that you plug in and it trickle charges the battery when there is power.<<

And when the power is out for days??? <grin>... I was out for 7 days once... I woke up by the sun, went to sleep with the sun...And sweated with the sun. <g>. But you know??? It was rather enjoyable...


Rhino >> For this project, I am trying to collect some data on how much the pump runs, then figure out based on the flow rate of the pump, approximately how many gallons of water we pump out each day. I'm kind of a data freak. In the grand scheme of things I eventually would like to pump that water to a drum or tank, then use that water on dry summer days to water the lawn.<<

Humm.. the old gravity fed Water system.... and when a squirrel decides to drown in the tank... and you find your water tasting just a little bit funny.....
But hey... thats progress right??? <g>.


Rhino>> I gotta tell you guys though... it's nice to be able to come to a forum like this with people that like to do stuff like this. My wife and friends all think I'm some kind of geek to play with this stuff as a hobby.<<

GEEK?? I don't know of any Geeks around here....(cough)

Rhino >> I appreciate your feedback...Thanks!<<

No sweat... Just trying to help, just in case the alternative may provide a little more security and peace of mind.

DWayne

The idea that I had for the holding tank was just to plumb a pump to it, and once it was full, pump it out to the sprinklers. I've already plumbed the sprinklers and tested it with the sump... but sumps are low pressure, high flow, so I didn't stick with that setup. Didn't want to burn up the sump... that would be bad. Probably just get a 55 gal plastic drum, pump from the sump to that. Have a float on the drum. When that fills up, kick on the other pump, and run it out to the sprinklers. Ran into some cost constraints with this setup though. Figured I'd need a directional valve to divert the flow of water to the holding tank when it got full to somewhere else. Those can't be cheap... I haven't even sought out for one. I guess I could rig up something like an Asco valve that could do the trick. And the cost of another pump that will output ~ 40 psi (which I think is about our city water pressure) to run the sprinklers was another inhibitor. You're right though, a water sump pump does offer peace of mind in case of power outages, and with a newly finished basement, I'll have to seriously consider one. Guess I'm looking to see how much water I pump out on average to get a good idea on how often my lawn could be watered.