Thanks for all the replies, I have made some progress!!! The problem was indeed caused by volt drop, the thing that confused me was that as I said I have separate supplies for sensors and relays. What was happening was that the relay circuit was causing the Gnd connection at the far end to come up by a couple of volts, so I had a good +5 to the sensors but with Gnd at +2 or so I only had 3v powering the sensors. I have today connected the Gnd to the earth of the mains wiring at each relay box, and the system seems to be running fairly well. I have had a few no-reads so I think it is still a bit too close to the edge for comfort due to the volt drop in the +5 relay line, and so I will probably change to 12v for the relay circuit to make it a bit more robust. This will half the current and therefore volt drop, which on double the voltage gives a four fold improvement.
Regarding the components, obviously I need to change the relays but do I need to change any other components? When I was at college they taught me about thermionic valves as transistors had only just been invented, so I would appreciate guidance from people whose knowledge is a little more current than mine. The current relays are 5v 400mW Matsushita ALE12B05 and I will probably replace them with the same but 12v Thanks for your help, it is greatly appreciated. Mick On Mon, 2011-03-21 at 21:05 -0400, Ziggy wrote: > How are you getting the relay power to the relay? Along the same cable as the > 1-wire network? It kind of sounds like it. > > It would be useful to know how long the wire run is, what gauge wire is used, > and what the relay coil specs are (resistance, voltage, current, etc.). > Generally speaking, with one wire devices that use any amount of power, there > are two ways that power is delivered: > > 1) A higher voltage is provided on the same cable as the 1-wire. Often this > is 12V or more. Then a point-of-load regulator is provided where this power > is used. In your case, this would be at the relay. > > 2) Provide the (regulated) power required directly at the point of load - at > your relay. Do not use the 1-wire cable as an auxiliary power bus. > > I also kind of wonder if you're really turning that 2N2222A on hard enough. I > would have thought a 4.7k more appropriate than 10k for the pull-up (and not > sure I understand the need for the 1k base resistor). Again, what are the > relay coil specs? If we assume something like 40ma and 125 ohms, then we know > we can safely drive the transistor fully into saturation with no current > limiting collector resistor. If the beta of the transistor is 100, then we'll > need 400ua of base drive. The 11k that you have when the circuit self biases > as the output of the 2406 floats barely provides that. > > Also, have you considered a BSS110 as a high side FET switch (or maybe a > 2N7000 as a low side switch)? Then you are pretty much just dealing with the > gate voltage and no biasing issues. > > Caveat: It's been a while since those ET classes in college, so I could well > be talking nonsense. But hopefully this is of some help. > > On Mar 20, 2011, at 6:26 PM, Mick Sulley wrote: > > > Hi, > > > > I have expanded my network to about 20 DS18?20's and all was fine. I am > > now trying to add some I/O using Embedded Data Systems D2P modules which > > use DS2406. I need to switch mains voltage so built circuits to switch > > relays with the D2P units. > > > > The network is basically Cat 5 cable with some spurs off in 4 core phone > > cable. I had some concerns over power requirements a while back and > > decided to use 2 separate 5v power supplies, one for the sensor circuit and > > one for the relay circuits. > > > > I added one of the D2P units and it seemed OK, I then added a couple more > > and the network crashes. Using owfs and looking at the directory structure > > I see various things, maybe no devices at all then refresh and see a couple > > of the temperature devices, refresh again and see nothing, etc. > > > > The D2P unit that caused the crash was at the far end of the network, I > > unplugged it and plugged it in half way down and it worked. I put it back > > at the end and unplugged the relay +5v supply and it works (but obviously > > the relays don't work). Not sure if this diagram will get through, the > > circuit I have used is - > > > > > > <unknown-BFUOSV.png> > > > > I am really stuck here, I don't know what to do next. Can anyone help > > please? > > Thanks > > Mick > > ------------------------------------------------------------------------------ > > Colocation vs. Managed Hosting > > A question and answer guide to determining the best fit > > for your organization - today and in the future. > > http://p.sf.net/sfu/internap-sfd2d_______________________________________________ > > Owfs-developers mailing list > > Owfs-developers@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/owfs-developers > ------------------------------------------------------------------------------ Enable your software for Intel(R) Active Management Technology to meet the growing manageability and security demands of your customers. Businesses are taking advantage of Intel(R) vPro (TM) technology - will your software be a part of the solution? Download the Intel(R) Manageability Checker today! http://p.sf.net/sfu/intel-dev2devmar _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
