Remote sensor reading from desktop ...

[john1]

Hi,

Is it possible to get a microprocessor to wake-on-lan, and then to output an HTML page ... ?

If it can't output an HTML page, then maybe it could present some temperature values, and i can insert or map them into a locally drawn page.

I want to use my downstairs desktop PC to access some sensor signals which i intend to fit up in various places on my water heating arrangements.
They would show up in various places on a sort of water-diagram.

I feel sure this sort of thing has already been addressed,
any help or advice would be welcome.

Cheers, John

 

[kchriste]

Microchip has a free TCP/IP stack for their ethernet controller and PICs with built in controllers.
**broken link removed**

 

[john1]

Hi kchriste,

Thank you for your reply.
I have visited that site, and spent some time reading and re-reading various pages there.

It seems that using the ethernet system to interact with remote devices is a well known established arrangement. However, i could not find any mention on that site of the 'wake-on-lan' facility.

As i'm sure you know, the 'wake-on-lan' facility is partly a function of the ethernet card, and partly a function of the motherboard, or the supporting electronics for the ethernet card.
I found the whole site difficult to read and understand, but there some parts which were easily understood.

I want to access the remote ethernet card from my small LAN, so it will have to have a run of cabling over to it, which is fine. I also want the ethernet card to respond to the wake-up and provide power to a simple set of sensors for temps, and maybe for flow sensors arranged on my water pipework.

I dont really want the ethernet card to be housed in another computer, mainly because of the start-up time, but i would imagine a microprocessor unit could manage to feed the ethernet card with the signals from the sensors without a problem.

I would also imagine that the time taken for the ethernet card to respond to the wake-up, and start its local power supply, and to interact with the sensors would be a very short time.
But i can only guess at that, i have no experience along those lines.
My guess would be less than two seconds. Maybe less than one.

If its difficult or unreasonable to get the microprocessor to output an html page with the sensor figures shown in a picture of the pipework, then the picture of the pipework could be done on my PC which would be accessing the remote ethernet card.
Then hopefully just get the sensor figures from the remote ethernet card, to be shown on the picture.

Or maybe there is a completely different way to do this.
There may be another way to access remote sensors that i have not thought of.

Thanks for any comments or suggestions, John

 

[kchriste]

It seems that using the ethernet system to interact with remote devices is a well known established arrangement. However, i could not find any mention on that site of the 'wake-on-lan' facility.
As i'm sure you know, the 'wake-on-lan' facility is partly a function of the ethernet card, and partly a function of the motherboard, or the supporting electronics for the ethernet card.

I may be misinterpreting what you need, but an 18F4620 and a ENC28J60 Ethernet chip don't need to go to sleep as they draw very little power. So little, that you won't notice the 115VAC current draw difference between the loaded and unloaded wallwart powering them! No need for an ethernet card except in the computers on your network. Below is a fully functional web page server which I built on a breadboard. You can read the ADC inputs & turn on LEDs etc, via a web browser, all with code downloaded from MicroChip. The only thing not shown in the picture is the RJ45 network plug connected to the VALOR pulse transformer:

 

[john1]

Hi kchriste,

I don't think you are misinterpreting in any way, although you don't mention what it is you think i am looking for. I've seen other postings from folk trying to do something, in a way that is not appropriate, simply because they dont know the various ways to do what they want.

In this case, i did not know that an arrangement such as you show here in the image, could operate without an ethernet card.

In my first post i wondered if it may be possible, but i was also thinking about the wake-up, so i thought that it may as well have a card to use the wake-up.

But as you point out, the current draw is so small that it can simply be left on.

The arrangement you have shown certainly looks as though it would meet my (comparatively) simple task, namely to be accessed from my lan like an ethernet card, and present the user with an html page showing the pipework layout, and of course the sensor readings in their appropriate places on the pipework.

From your text, you say you can 'turn on LEDs etc' I dont need any control over stuff from my PC, just information from the sensors. But i am impressed that this facility is there. Maybe in the future, i might use something of it.

I am very impressed with that layout, and i want to do something similar.

Just to re-cap, will this present the user with an html page, picture of pipework, live temp readings, maybe two or more extended pages for detail ... ?
Will it be accessible via the ethernet locally, from any PC on the lan (just like normal)

How many sensors could it handle ? . For the time being i'm only thinking of four or five.

Thank you very much for the picture, and the encouragement.
John

 

[kchriste]

I am very impressed with that layout, and i want to do something similar.

Thank you. It's not an example of my tidiest work but it was quick and easy to assemble.

Just to re-cap, will this present the user with an html page, picture of pipework, live temp readings, maybe two or more extended pages for detail ... ?
Will it be accessible via the ethernet locally, from any PC on the lan (just like normal)

That's exactly what it does. There are about 4 small pages of HTML with simple graphics in the MicroChip example. I was able to access it with two computers at once on my network. It will bog down if too many computers try to log on to the mini web page at the same time due to limited memory and processing power. A DOS attack would only take 5 computers.

How many sensors could it handle ? . For the time being i'm only thinking of four or five.

You can use different 18F series chips. I used the 18F4620 in a 40 pin dip with 64K of flash memory. The MicroChip example serves up 26Kb of web content, but you can add more. There are 8 analog inputs free for measuring voltages with the ADC. There are 18 pins of digital IO left over for whatever task you want to assign them.

 

[john1]

Hi kchriste,

Well, as you say its not the tidiest job, but i am sure it would look fine if it were transposed on to vero-board.

I dont know how 26Kb works out for a web page, but it hardly sounds enough for a reasonable picture.
The text parts on an html page could probably be done with less than 2Kb.

Maybe if the picture is only half the page, with text alongside or underneath it would do it OK.
If the pipework picture is monochrome with no grey scale, just black and white drawn, then maybe it could be done with minimum kilobytes.

I know that a server can only serve a limited number of PCs before becoming overwhelmed, but i have never really grasped why the output falters, especially in the case of a single html page, where the output would be the same for any PC looking in.

I will have to look at the various microprocessors available.
John

 

[kchriste]

I will have to look at the various microprocessors available.
John

I've never played with them, but you could also look into the NET+ARM microprocessors.

I dont know how 26Kb works out for a web page, but it hardly sounds enough for a reasonable picture.

26Kb isn't the upper limit. It is just what was used for the demo and you could add external eeprom for more data. Attached are the files used to create the web pages. I modified them a little as an experiment when I was testing it out. It'll look a little funny in your browser because the CGI script won't be running:

 

[john1]

Couldn't get anywhere with that zip, maybe it got corrupted, could you send it again please

John

 

[kchriste]

I just used XP's built in zipper. I downloaded it and it unzipped for me OK. It's nothing much to look at so don't worry if you can't open it, but here it is in RAR. Crud, I can't upload RAR so here it is again in zip but created by WinRar:

 

[john1]

Thanks, got that.
Downloaded it alright, 11 files.

Haven't looked at it yet, i have to go out.

Will be getting a microprocessor for this job soon,
will be back when i have made a start.

This focus on the water system has been brought about by the unreasonable rise in the
price of "house gas" which is used widely over here for heating and cooking.
Its piped in from the street to the houses, and metered like electricity.

The government have sold our "house gas" companies to foreign concerns, and now
prices have climbed beyond the reach of many. Last months increases were around
forty per cent, with more increases to come. It is expected that many here will be very
cold come the winter.

There is loads of stuff on the internet about gas prices. (i'm not talking about petrol.
Gas is what Americans call petrol, or gasolene. We call petroleum petrol, and we call
gas, Gas.)

So i will be monitoring my water heating system very carefully.

Cheers, John