I came up with a concept while reading a book a few days ago about computer engineering. I'm not going to get into how that interface works too much, but basiclly heres what i hope to do. I can make an interface and software on my computer that can monitor 5 (five) inputs. The inputs can have two states, either GND or +5vdc. So heres what i hope to do with it, i want to run at my cottage a software i will design that can monitor 5 inputs, i want to be be able to monitor things like
In well pump Furnace blower fan Security (motion) lights
I'm trying to think of a good way to trigger a two position relay ( i forget the short terms right now ), on that is normally on one position, and then when power is applied, switch to the other position until power is lost.
Would the best way to do this to be to find some relays that are powered by 120 or 220 volts, or to use transformers to power the relays, i was thinking maybe 12v or 24v relays that are used to control "zone valve" relays in hydrological heating systems.
Or if there is another soltion, basiclly have to change the on off 120volts to 5vdc or GND depending on if i have 120 or not. (In the case of the well pump, it's pure 220 volts, so unless i can find a 220 relay for that i'll need to figure out how to get myself a neutral)..
I hope this is sort of clear, i'm not there much and i want to know everytime my well pump, furnace blower, etc get power and for how long.
SSAC makes a solid state relay that uses a 5Vdc input(actually 3-32Vdc) to switch a 120Vac output. I know they make a 10A and a 30A. They are pretty reliable with no moving parts to wear out and are very small.
I don't follow your end goal. Are you trying to control devices(pump, fan, lights) with your outputs or just trying to monitor the devices when they are on?
Re: Looking for advice on the "smart home" project#17944 12/06/0211:49 AM12/06/0211:49 AM
You have three ways (I don't exactly know what products would be suitable), but one would be to sense current on the load, and report that to the computer, the other would be to sense if power is being applied to the load (usually by a lamp of some sort, optically coupled to a phototransistor which the computer reads), or detect the effects of the device being on, such as airflow in the furnace, or light from the MS lamps.
Re: Looking for advice on the "smart home" project#17945 12/06/0207:43 PM12/06/0207:43 PM
Actually it's not a very expensive project, i had to buy a buffer IC that cost me $1.50 and a parallel port connector. Seems you guys are interested in the how it works parts a bit too. There are 8 possible outputs and 5 possible inputs for a computer's parallel port, yes they are usually programmed in qbasic, however it's rather easily used in Visual Basic, so i can make a windows application with this stuff.
The relays will be the only real cost here, and yes i just want to monitor when voltage is applied, not control.
"SSAC makes a solid state relay that uses a 5Vdc input(actually 3-32Vdc) to switch a 120Vac output. I know they make a 10A and a 30A. They are pretty reliable with no moving parts to wear out and are very small."
Actually, i just need relay that works on a 120 or 220 input and switches a dc load, it needs to have two positions, not on and off because to a parallel port, ground and off are two different things. Nothing at all isn't a state and it will think it's not connected. The dc load current is next to nothing, it's in the single digit miliamps i believe.
I've already thought of dreaming up extentions to this project, although i haven't gotten the relays to finish the first part. I'm trying to think of a way to get my computer to run the thermostat, i just don't know how to get a temperature reading into my computer, otherwise i could monitor and set the temperature over the internet
Re: Looking for advice on the "smart home" project#17947 12/10/0204:26 PM12/10/0204:26 PM
Most motherboards these days have the ability to connect a temperature sensor, meant for detecting case temp, using an inexpensive thermometer. The motherboard collects the data in real time and you can capture this in a windows app.
Also, in physics in college I conducted experiments using all sorts of peripheral devices...thermometers, motion sensors, timers, photo cells, etc. I don't remember where we got them, but these were part of a complete system of devices that connected to a peripheral scsi-based junction box. HTH, and I'd sure like to hear more about this. I'd love to extend the capabilities of my PC and get more out of it!