PLC weather station DIY project

[fischb22 0]

I'm thinking about trying to design and implement a PLC based weather station at home, just to see if i can do it more then anything else. Here is what i was thinking parts wise(some parts i have, some i'd have to pickup) SLC 5/04 CPU DC Input card Thermocouple card Analog input card couple of prox switches and some aluminum tape. for windspeed: i was thinking of getting 2 pcs of PVC pipe that slide over each other, the outer peice of PVC i was thinking of attaching some strips of aluminum tape, and mounting a prox switch on the inside of the other peice of PVC. questions about this part: how fast can a prox switch change state? if i have a 1/2" gap(or perhaps 1/8" bigger gap then the head on the sensor) in the alum tape, would the prox switch be able to change state fast enough to measure wind speeds pretty accurately? I understand at a fast wind speeds the prox would propbably not be able to keep up with changing states. My reason for not using an encoder on this, is 1) cost, 2) i think the encoder would provide to much drag to get an accurate reading. wind direction: for wind direction, i was thinking of using alum tape only, running a common wire to the turning part, and having 4 'patches' of alum tape on the station part of the PVC pipe, (north, south, east, west). Rain gauge: For a rain gauge i was thinking of using another prox switch, along with some plans i found on the internet for making a tipping bucket type deal, again using a prox switch to check the state on the bucket. Temperature: Simple, just use a thermocouple card, and i was thinking of using more then 1 sensor location, and getting an average reading. Light brightness: Using a resistive photocell, and calibrating it for 4-20ma, to provide precentage of light. again, i would probably have 2 or 3 of theses scattered about to get a more accurate reading. Edited 9 Jul 2008 by fischb22

[Ken Moore 23]

http://www.inspeed.com/anemometers/Vortex_Wind_Sensor.asp 1 pulse per 2.5 mph wind speed, max speed of 125 mph would be 50hz. Shoud be able to detect that with a standard I/O card.

[leonuce 0]

We need more details about this project, there parts that you do not describe clearly. With respect to the proximate switch you can pick keyance with fiber optics, I do not have the part number handy, these switches have the ability of picking objects moving at very high speed from 1/32" to 8 ". As soon as you start putting parts together let me know I have a couple of these switches available in the shop that I send to you.

[panic mode 246]

proxy sensors easily do 500-2000Hz, tipically smaller sensors are capable of higher switching speeds and normally faster than standard PLC input. but how precisely you want to measure it? you could try different things and maybe use small DC motor as generator and just measure voltage, diy encoder etc.

[fischb22 0]

not a bad idea, and much cheaper that i expected, however using something like this would i need to use a HSC card? or do you think that it would be fairly acurrate using a counter and a 1 second timer?

[fischb22 0]

anyone have any suggestions on reading humidity?

[paulengr 44]

Check out Texas Weather Instruments. Interface is very simple and the stuff is professional grade and very modular.

[OkiePC 14]

You might want to rethink the aluminum part, most inductive prox switches don't do well with non-ferrous metals. Maybe a photocell and some reflective tape would work better.