Logtemp, alarms and relay control

[dinitro]

Dear All

I've been looking at Logtemp, the hobbyboards site (8 relay board) and was wondering if anyone has used the alarm function on Logtemp to control a relay via one wire.

The idea I have is if the solar return climbs above 60 degrees it causes a relay to power and stop the boiler from firing.

Additional features that could be utilised is for heat dump and emergency boiler firing eg if outside temp drops below a certain temp.

I found on odd occassions I get a short or something causing readings of 127.69.  Messes up the graphs, however found a prog called text crawler cleans up
the logtemp data files..

also does anyone have any experience in plotting yearly readings on logtemp?

dinitro

[ericw]

I think that LogTemp only supports DS2405 & DS2406 and not the DS2408 used in the Hobbyboards 8 channel board.

http://www.audon.co.uk/tai8555.pdf describes a 1 wire switched relay but it is not rated for mains voltages so would need to drive another relay.

Alternatively http://www.homechip.com/catalog/product_info.php?products_id=138&osCsid=0562253984440eaa24abfa735c is another one but you have to add your own output circuitry.

It would also be worth keeping an eye on the 1 wire slave thread, something useful might turn up there.

[dinitro]

Hi Eric

Many thanks for the reply

...you saved me from purchasing the 8 channel relay!

Probably should ask the writers if they will support the 8 channel relay!

many thanks

dinitro

[dinitro]

I've has a reply from the Mikko Rintala writer of Logtemp. 

He says the DS2408 support is coming...... Yipeee!

Better get planning with the solar, boiler, thermal store, wind factor, room temperature configured heating controller!

dinitro

[ericw]

Dinitro
It looks as though you are in business then
I just programmed up a psuedo DS2405 and gave it a try and it seems to work.

[dinitro]

The only thing is I have logtemp running on an Acer Revo with win 7 although it only consumer 21-29 watts, the PC has crashed
a couple of times and so I would want to incorporate a failsafe.  I think I could do this with a SPDT relay.
However I am unsure how the relay board would work (latching or not) with loss of signal on the one-wire network.

dinitro

[ericw]

Dinitro,

I think if the computer crashes then the the relays are likely to remain in their last set states.
However the DS2408 has a reset pin which forces all the relays to the open state. This is get-at-able in the Hobbyboards kit.
So you need to do two things
   1) make sure that the all N/O state is a safe failure state.
   2) detect lack of activity on the 1 wire bus to indicate a computer crash.

 I can help you with 2) by giving you a 1 wire slave that would operate the reset if it doesn't detect bus activity for say 1 minute (or rather longer than whatever your sampling time is).

The current rating of Hobbyboards relays is fairly small, is 0.25A (62VA) good enough for your needs?

[dinitro]

Dear Eric

Many thanks for the offer of help.  I will take you up on it once the Logtemp software is updated and I receive the Hobbyboards relay board.

I also asked Mikko whether there are any future updates that will plot year data and plot energy use and temp on the same graph.  Unfortunately he says it will be too heavy for the program and it would be better to go down the mySQL route, however my lack of experience (failure) for installing it on my SLUG means I will probably go for the windows msi route.

The 0.25A rating does not matter since I would use the relay to drive another relay.  This offers greater flexibility in terms that the hobbyboard relays can switch 12v or so and the mains relays can be positioned closer to where the appliance is.  Also a 2PDT can be used to drive neon indicators/ zone valves etc.

The state of the relays NO/ NC really depends on what I want to achieve.  The current system has a system boiler that heats directly a thermal store under timer control and restricted by tank stats on the top, bottom and return pipe of the boiler.

The rads and a slave tank are driven directly from the thermal store.  The pump to drive them is controlled by a BEM5000 danfoss weather compensator + programmable room stats/ tank stat + timer.
A shower and DHW coil also tap the store.

I was also looking at Virtual sensors and this seems the ideal way to react against weather events ie subtraction of two sensors.

The logtemp/ hobbyboards adjunct will make up for the following difficiencies;

1) solar return looks promising ie above a certain temp ... therefore will stop boiler firing
2) top of the tank / bottom of tank differential increases above a certain point, boiler fires overriding timer.
3) the top tank/ bottom tank differential decreases below a certain point plus top of tank greater than 55, stops boiler firing
4) a room temp drops below a certain level indicating increased heat demand.

This list is from the top of my head but the permutations are endless..

However this adjunct needs to function so that if I pull the plug/ system crash of the 1-wire system, the system reverts to its solid state function.
Kind of like those cars which will get you home limping but none the less get you home.

dinitro.

[KLD]

" (...)  the mySQL route, however my lack of experience (failure) for installing it on my SLUG means I will probably go for the windows msi route. "

Dinitro, just on this one point: SleepyB runs MySQL on his unslung SLUG. Mine runs Debian, and I use SQLite3 without any problem. If you run the slug off a flash memory stick, it'll probably take up less then 1W, quite an incentive to get it going :-)
Mind you, one of the drawbacks of the slug is that it needs a hardware modification to make it reboot automatically after a power failure.

Klaus

[dinitro]

Hi

I've tried to install MySQL about 5 - 10 times on my unslung SLUG but fail each time
... I also have problems with cherokee executing perl scripts

...its probably that i'm a dinosaur but I find getting things working on my SLUG tiresome.
I struggled with OWFS, OWW, Digitemp.  If it wasn't for logtemp I think I would never monitor anything!

I wish when apps are written that they install and operate in a similar fashion on all platforms.
I found that some help articles tell you to type eg cherokee-admin at the prompt.
I went as far as copying it to /bin/ but then found out that typing /opt/bin/ suffices.

dinitro

[KLD]

Dinitro,
Sorry to hear about all those troubles you've had with your slug. Do you use it for other things, or did you just want it for low-power data recording?
If you like I could send you a memory stick with Debian installed and all the Digitemp, sqlite, lighttp etc software running. Of course, that would still require that you re-flash the slug with the Debian firmware. OTOH you seem to have found a way to solve your control issue from within Windows and logtemp.

Oh well, following the k-i-s-s principle you'll probably best stick with what works for your. Shame about that that involves M$ software 

Good luck!
Klaus
 

[dinitro]

Dear Klaus

Running it from a USB stick .... isn't that dangerous due to limitation of write cycles on the memory?

My SLUG at the moment is my webserver and a NAS drive ... a bit of a waste really.

I thought unslung was debian albeit one with the linksys front end.

Although the offer of a working solution certainly has wet my appetite.... naturally I would pay you for the privilege!

I also have a clean linksys SLUG ... probably I should try your solution on that!

dinitro

[KLD]

Dinitro

A spare slug, that sounds like an ideal "playground". WRT to flash memory as a system drive: you probably read the same pages as I did; so, it seems do-able, and with a few tweaks you can lower the number of read/ write events. All that said, I had the same worries, and am now using a small 2.5inches harddisk.

So, I found a link to the Debian Lenny firmware image (about half way down the page). Since I've installed Debian using the "installer" method, I don't actually know whether this image will work together with my files.

I could either burn a DVD for you, with iso images of the "/boot" and the "/" filesystems. You could then copy these onto a flash stick or a spare hd. Or, if I can find a suitable usb stick in on of those boxes you could have that one.

Do you want to give it a go?

Klaus

[dinitro]

Dear Klaus

Have to have a think (sorry dither mode has kicked in)... I'm wondering if I should use the UnSlung box and
reflash it rather than losing my other slug which functions as a NAS.

memories of redboot? are coming back.... I wonder if its worth trying this?

dinitro

[KLD]

Dinitro,

Did you have problems with flashing the unslung firmware onto the slug? I did mine quite a while ago, but seem to remember that once I found the upslung program, everything was easy. Go on, give it a go. 

Klaus