Hi. I use some similar relay circuits myself, mostly for controlling large heaters on a home brewery setup. I do worry about the failure modes that could occur during use, moreso that the startup state. In particular, some time ago, I had trouble with my 1-wire network that would result in owfs hanging, and an inability to send the appropriate "relay off" command. Now and then, I still lose communication with individual devices. Even with the best of communications, I don't particularly trust my computers or software to fail safely either.
I've toyed with timer circuits to shut off the relay if not reset, by, say toggling the device state. I also have a couple of Pascal Baerten's 1-wire microcontrollers that can make it easy to combine this functionality. Where heaters are involved, separate, mechanical thermostats can help. Overall, though, I haven't really settled upon a protection mechanism that I really trust, and is convenient enough to simply use with every relay. What do others do about this? Thanks. ~Jacob On Wed, 14 Dec 2011 08:56:13 +1100 Nathan Hurst <[email protected]> wrote: > On Tue, Dec 13, 2011 at 06:53:29PM +0000, Mick Sulley wrote: > > Yes that is pretty much the circuit I have used. The thing that feels > > wrong to me is that the relay is energised until you turn the DS2406 > > output on. > > Yes, use a pnp transistor instead, emitter to v+, base to ds2406 via a > suitable resistor, collector to the existing relay portion with diodes > etc. That would also result in much less power dissipation when the > device is off. Something like figure 3 here: > http://www.rason.org/Projects/transwit/transwit.htm > (but I wouldn't bother with the biasing 47k resistor) > > njh > > > > > Mick > > > > On 13/12/11 16:49, Zoff wrote: > > > Hi! > > > > > > you can take a look at my 1wire relay. maybe its of some use to you: > > > > > > http://1wire.zoff.cc/2010/09/18/31 > > > > > > it uses a DS2406 and a normal relay to switch high power loads > > > it can easly switch 220V loads, but i take no responsibility if you > > > house burns down! > > > > > > i have 2 of those in use 24/7 since Sept. 2010, but only with low Watt > > > loads for now. > > > > > > > > > cheers, > > > Zoff. > > > > > > Mick Sulley wrote: > > >> Hi Jerry, > > >> > > >> Your system sounds interesting. I also have a control system based upon > > >> 1-wire and Python which controls a solar (hot water) heating system > > >> heating the domestic hot water and a swimming pool. My plan is to > > >> extend it to control the whole of the central heating system as well. > > >> > > >> Reliability is key to this sort of project and each time I have had a > > >> failure (there have been a few!) I have tried to identify the root cause > > >> and prevent it happening again, but this is an ongoing task. > > >> > > >> I use a mix of home brew outputs based on DS2406, and X-10 to drive > > >> valves and pumps. X-10 seemed the easy way to go but has not proved to > > >> be very reliable and so I am moving to the DS2406 solution. What do you > > >> use for driving outputs? It seems to be quite difficult to get > > >> something that is fail safe, i.e. fails to off rather than on. > > >> > > >> In terms of timing, my system reads all the temperatures, currently 26 > > >> sensors, then sets the outputs according to the logic and logs all the > > >> data to a MySQL database. This takes around 20 seconds and it then > > >> loops round again. > > >> > > >> User interaction is by a local web page in PHP which reads and writes to > > >> the database. > > >> > > >> It runs on a server built from an old PC, located in the loft. I have > > >> also built a second similar server, so that I can easily swap the plugs > > >> over if the first server fails. > > >> > > >> I have notices that many people use hubs to split their 1-wire networks, > > >> currently mine is a single network with everything on it. I would be > > >> interested to hear views on the use of hubs, do they improve reliability > > >> or speed? Are there other advantages? > > >> > > >> Cheers > > >> Mick > > >> > > >> On 12/12/11 22:19, Jerry Scharf wrote: > > >>> Hi, > > >>> > > >>> I'm finally finding some time to write the next generation of my home > > >>> control system. I have had a number on control ideas I have wanted to > > >>> try out, and it is time to give them a try. The control and sensor > > >>> plant > > >>> in my house is close to ridiculously complex. > > >>> > > >>> One fun thing is that I am getting rid of the ability for users to set > > >>> the room target temperature. Instead, there will be buttons that say > > >>> "I'm cold" and and "I'm hot". Push once if you are a little so, push > > >>> more than once if you are really so. The rest is figured out by the > > >>> control system. > > >>> > > >>> This comes from my belief that 72F is a random control knob that has no > > >>> real meaning to a person in a room. If you want to prove this, go to > > >>> the > > >>> supermarket, pick up a room thermometer from the housewares aisle, then > > >>> go and stand in the section where the frozen food is. How cold do you > > >>> feel, what's the temperature say. Odds are you feel colder and the > > >>> temperature says it's higher... > > >>> > > >>> > > >>> I am building this in python/django (ruby on rails for python) an a > > >>> linux box. There is a database at the center of things and I want to > > >>> make the various parts to be independent processes. I want this so I > > >>> can > > >>> do things like replace the heating controls without impacting the > > >>> ventilation and cooling code at all. > > >>> > > >>> The 1 wire reading is pretty easy, I create a process for each bus and > > >>> each process pulls the list to read, finds which ones are on its bus, > > >>> reads them and stores them into the database. Each process is self > > >>> scheduling (easy pieces built into python for this.) > > >>> > > >>> I am having more trouble deciding on partitioning the controller and > > >>> driver parts. Part of this comes from how to make things stable and > > >>> simple, part comes from needing to decide where different functions > > >>> should be done. > > >>> > > >>> I don't think each process should be accessing the control points > > >>> directly, these are mostly done via a mport box interfacing RS485 nudam > > >>> controller pods. Having each one setting up telnet sessions and writing > > >>> whenever they think it's reasonable does not seem like the path to > > >>> reliability. > > >>> > > >>> I also want to be able to do things like: > > >>> Almost all controls are variable, and I want to use this. So when a > > >>> zone > > >>> calls for heat, it wants to open the water valves in a particular > > >>> stepped pattern, go to an higher than final flow rate for a period of > > >>> time (based on the lag of the zone) and then return to the final flow > > >>> rate until the temperature reaches the target. > > >>> > > >>> This means that a single valve may be getting new position commands > > >>> every 10 seconds or so during the startup phase. I have plenty of > > >>> signalling bandwidth and there is plent of slow in the control > > >>> system, I > > >>> just don't want to swamp either the database or the cpu by having lots > > >>> of processes polling every second. I also don't want t be waiting 15s > > >>> for something to happen that was only supposed to be there for 10s. > > >>> > > >>> > > >>> I would like opinions on two things: > > >>> Do you think that things like start-up patterns should go in the > > >>> heating controller or the driver? > > >>> > > >>> What method makes a reasonable balance of simplicity, > > >>> efficiency and > > >>> response for passing actions between the controllers and drivers? > > >>> > > >>> All other kibitzing is also welcome. > > >>> > > >>> jerry > > >>> > > >>> > > >>> ------------------------------------------------------------------------------ > > >>> > > >>> > > >>> Learn Windows Azure Live! Tuesday, Dec 13, 2011 > > >>> Microsoft is holding a special Learn Windows Azure training event for > > >>> developers. It will provide a great way to learn Windows Azure and > > >>> what it > > >>> provides. You can attend the event by watching it streamed LIVE online. > > >>> Learn more at http://p.sf.net/sfu/ms-windowsazure > > >>> _______________________________________________ > > >>> Owfs-developers mailing list > > >>> [email protected] > > >>> https://lists.sourceforge.net/lists/listinfo/owfs-developers > > >> > > >> ------------------------------------------------------------------------------ > > >> > > >> > > >> Systems Optimization Self Assessment > > >> Improve efficiency and utilization of IT resources. Drive out cost and > > >> improve service delivery. Take 5 minutes to use this Systems > > >> Optimization > > >> Self Assessment. http://www.accelacomm.com/jaw/sdnl/114/51450054/ > > >> _______________________________________________ > > >> Owfs-developers mailing list > > >> [email protected] > > >> https://lists.sourceforge.net/lists/listinfo/owfs-developers > > > > ------------------------------------------------------------------------------ > > Systems Optimization Self Assessment > > Improve efficiency and utilization of IT resources. Drive out cost and > > improve service delivery. Take 5 minutes to use this Systems Optimization > > Self Assessment. http://www.accelacomm.com/jaw/sdnl/114/51450054/ > > _______________________________________________ > > Owfs-developers mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/owfs-developers > > ------------------------------------------------------------------------------ > Systems Optimization Self Assessment > Improve efficiency and utilization of IT resources. Drive out cost and > improve service delivery. Take 5 minutes to use this Systems Optimization > Self Assessment. http://www.accelacomm.com/jaw/sdnl/114/51450054/ > _______________________________________________ > Owfs-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/owfs-developers
signature.asc
Description: PGP signature
------------------------------------------------------------------------------ Systems Optimization Self Assessment Improve efficiency and utilization of IT resources. Drive out cost and improve service delivery. Take 5 minutes to use this Systems Optimization Self Assessment. http://www.accelacomm.com/jaw/sdnl/114/51450054/
_______________________________________________ Owfs-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/owfs-developers
