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JamesF

JamesF's observatory build

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7 hours ago, DaveL59 said:

An earth spike (4ft) is relatively easy to do so long as the ground isn't littered with rocks under the surface. A 4lb hammer should drive it in ok, maybe easier if the ground is wet. Then fit the clamp on the end and 10mm earth wire back to the consumer unit to bond that to earth and the obsy should be fine.

Around here earth spikes are minimum of 2m or 2.2m long. Galvanized or copper coated.

There are several ways of getting them down into the ground:
Manual hammering.  Needs a stepladder and a helper to hold the spike straight.
Hammering with a contractors large hammer drill and hollow driver socket.
Keep adding water around the spike as you bang it in. It is supposed to run down around the spike.
Using water pressure from a hose to a long pipe to make the hole and replace the pipe with the spike.

I used two lump hammers followed by a sledge hammer as the resistance increased.
Clay soil and no rocks until nearly full depth @ 2.2m.
I was lucky and only hit a rock at full depth.

You couldn't get a 6" nail in where I once lived in Wales on an ice age moraine.
The local board replaced an old and wimpy pole transformer for us while we were there.
The earths for that were several, absolutely massive, stranded cables spread out on the field and buried for probably 50 yards each.

A serious cable clamp on top of a domestic earth spike, under a protective cap, ensures a long life connection.
The job is strictly for an authorized electrician over here. As is all outside electrical work and most inside.
I did the job while they were here, fitting new sockets indoors.
The sparks watched happily as I hammered the spike in for over half an hour.
Then nodded through my 2.5mmm earth cable connection to a single row of 3-Pin sockets indoors for my UK Hifi. Hum gone!

 

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hehe yeah has gone that way here for the most part where apart from "repairs" you're supposed to get someone who is part-P certified to do the work or have them check and certify your work afterwards. Back way back when, I've rewired houses from the meter, laying in new rings and main RCD/MCB distribution board etc. Ran the earthing down into the basement where I installed said spike as it was just a few turns of bare wire around a metal supply pipe (water or gas) in the old setup. Even installed galv trunking to protect the cabling that ran from the distribution board in the garage that was all earth bonded between sections etc. So a couple years after I left the ex had builders in doing other works and to see how they left it all was shocking, just trailed wires around, opened the trunking and didn't bother to re-cap it etc., what a mess. No wonder I'm usually reluctant to get a "professional" in to do works where I know I can do it at least as well myself 😉

 

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At the risk of starting an endless argument:

Modern piping is often plastic. Rural homes are almost certainly fed by miles of plastic hose.
Connecting the indoor metal pipes, if any, as an earth, will be lethal and based on a lack of basic electrical knowledge.

Discussions on forums, which have US members, suggests that the rules for earthing are as varied as the soils on which the building stands.
I claim absolutely zero knowledge and nobody should ever follow anything suggested on a forum.
Your "expert" advisor might be a trolling, psychopathic, serial killer!

ALWAYS seek EXPERT advice from a local, fully qualified electrician with experience of your local conditions.

Your having moved on from your own installation leaves those who follow on in a very precarious position.
Which through their own ignorance, of what they only think they should trust, might easily kill them.
This doesn't even begin to deal with the matter of lightning and adding extra earthing rods to an existing electrical system.

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8 hours ago, JamesF said:

I'm sure it won't do the job either.  Makes me quite uncomfortable.  That's what was there when we moved in though, and I've been wanting to replace it for years.  I think it's off an MCB on the main distribution board, though I have to admit that since we had everything reorganised last year I've lost track a bit (we had a modern board put in last year when we had the cellar made usable, to replace the old one that used cartridge fuses).  We should have Western Power in very soon to deliver a second phase to provide power for the barn conversion, so I'll get everything sorted then.

I'm reasonably convinced that a local earth spike should do the job ok.  The ground around that area tends to be quite damp.  That's one for the electrician when he visits.

James

If there are no extraneous metal parts in the out building 2.5 is ok, depending on load and distance.
If there are extraneous parts then 6 or 10mm will be needed for bonding depending on you supply type.

What is your supply type btw?

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49 minutes ago, Rusted said:

At the risk of starting an endless argument:

Modern piping is often plastic. Rural homes are almost certainly fed by miles of plastic hose.
Connecting the indoor metal pipes, if any, as an earth, will be lethal and based on a lack of basic electrical knowledge.

Discussions on forums, which have US members, suggests that the rules for earthing are as varied as the soils on which the building stands.
I claim absolutely zero knowledge and nobody should ever follow anything suggested on a forum.
Your "expert" advisor might be a trolling, psychopathic, serial killer!

ALWAYS seek EXPERT advice from a local, fully qualified electrician with experience of your local conditions.

Your having moved on from your own installation leaves those who follow on in a very precarious position.
Which through their own ignorance, of what they only think they should trust, might easily kill them.
This doesn't even begin to deal with the matter of lightning and adding extra earthing rods to an existing electrical system.

I don't disagree re getting expert advice, that's generally a good way to go if planning some new works and esp so if you've no relevant expertise yourself.

In terms of my past installations, they were all done to building code at that time and in some aspects to industrial above domestic at that, so I've no worries on that front. They all passed inspection by the relevant authority on hand-off or you wouldn't be able to connect to the main supply into the building 🙂 I have however seen several dodgy installs that have been inherited when buying another property too, like main power and lighting cross-connected, regular ring wiring run to outbuildings in garden hose just inches under the edge of flower beds etc, scary the way some have done installs and a new unsuspecting owner is put at risk...

 

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50 minutes ago, wxsatuser said:

If there are no extraneous metal parts in the out building 2.5 is ok, depending on load and distance.
If there are extraneous parts then 6 or 10mm will be needed for bonding depending on you supply type.

What is your supply type btw?

I'm very sure there will be loads that exceed the maximum capacity of a single run 2.5mm T&E.

The supply type is an interesting question.  It definitely used to be TT, and there's an earth rod next to the house wall where the supply comes in.  At some point it was changed to TN-C-S (I think), the earth being provided by conductors buried in the field above our house (which is also where the transformer is).  However, the earth rod may still be connected.  The cabling is a bit obscured and I can't see exactly where it goes.  When they eventually turn up to provide the additional phase I'll make sure it's properly documented and if the earth rod isn't being used I'll probably remove it so there will be no confusion in the future.

James

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2 hours ago, Rusted said:

At the risk of starting an endless argument:

Modern piping is often plastic. Rural homes are almost certainly fed by miles of plastic hose.
Connecting the indoor metal pipes, if any, as an earth, will be lethal and based on a lack of basic electrical knowledge.

Discussions on forums, which have US members, suggests that the rules for earthing are as varied as the soils on which the building stands.
I claim absolutely zero knowledge and nobody should ever follow anything suggested on a forum.
Your "expert" advisor might be a trolling, psychopathic, serial killer!

ALWAYS seek EXPERT advice from a local, fully qualified electrician with experience of your local conditions.

Your having moved on from your own installation leaves those who follow on in a very precarious position.
Which through their own ignorance, of what they only think they should trust, might easily kill them.
This doesn't even begin to deal with the matter of lightning and adding extra earthing rods to an existing electrical system.

We had a professional survey done of our electrics.

He said the best bit was my workshop, which I wired up myself - ring main, spur lighting + spur for the heater, all off a dedicated distribution box with RCB.

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3 hours ago, JamesF said:

I'm very sure there will be loads that exceed the maximum capacity of a single run 2.5mm T&E.

The supply type is an interesting question.  It definitely used to be TT, and there's an earth rod next to the house wall where the supply comes in.  At some point it was changed to TN-C-S (I think), the earth being provided by conductors buried in the field above our house (which is also where the transformer is).  However, the earth rod may still be connected.  The cabling is a bit obscured and I can't see exactly where it goes.  When they eventually turn up to provide the additional phase I'll make sure it's properly documented and if the earth rod isn't being used I'll probably remove it so there will be no confusion in the future.

James

You should be able to tell if its TN-C-S as the main coming in should be two wires and an earth wire should come out of the neutral in the cutout.
The TN-C-S cutout may have a sticker on it that points out it's a PME system, the company neutral is earth staked multiple times in it's run to the consumer.

If the main is /was TT then out buildings would need earth rods and RCDs as fault current might not be large enough to blow fuses.

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1 hour ago, wxsatuser said:

You should be able to tell if its TN-C-S as the main coming in should be two wires and an earth wire should come out of the neutral in the cutout.
The TN-C-S cutout may have a sticker on it that points out it's a PME system, the company neutral is earth staked multiple times in it's run to the consumer.

If the main is /was TT then out buildings would need earth rods and RCDs as fault current might not be large enough to blow fuses.

I'm not 100% sure what's coming in because the positioning of all the components means it's not absolutely clear what wiring actually enters the cut-out.  I know there's at least one four-core cable that they don't need to replace to provide us with a second phase from the transformer and it presumably already carries live, neutral and earth.  That earth may also be connected to the earth spike, but I just can't tell.  There's no earth on the distributor's side of the transformer at the end of our field however; that's all hooked up from multiple earth stays under our field.

James

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When we came to France house-hunting, I quickly started to focus on the power distribution - whatever anyone thinks as a poor installation is nothing comapred to what we have seen here...

James, if you are having a second phase commissioned, please be aware across the phases will be over 400 volts.

From memory of my higher education, where I did a years' module on three-phase power transmission, the supply is distributed on three wires, one per phase. At the step-down transformer, the three phase windings change configuraiton to make a 4-wire system. Three for the phases, the fourth a Neutral. Think about the shape of a Y with the centre being the neutral. This is then grounded at the transformer and this is the ground reference.

Ideally, the current in each phase is the same and if so, then no current would pass down the neutral wire (Kirchoff's law) Any difference in current will lead to current flow through the neutral and some offset in Neutral voltage to earth.

I would guess the four core cable you have would be the three phase supply and two of them have been isolated at some day.

Please make sure your electrician explains what you end up with before they leave.

My house has a three phase supply with it distributed around the house with at least 30mcb's as France does not do ring mains.

Take care.

Gordon.

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Took a detour via Screwfix after swimming today to collect about 20m of trunking for the internal cabling and got on with installing some of it this evening.  I didn't get as far as I wanted, but I do at least have a plan of where all the sockets etc. will go now, and how I'm going to connect up the 12V supplies to the piers.

James

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19 hours ago, JamesF said:

Took a detour via Screwfix after swimming today to collect about 20m of trunking

It's definitely cheating when your trunks stretch the whole length of the pool.

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2 minutes ago, Stub Mandrel said:

It's definitely cheating when your trunks stretch the whole length of the pool.

I shan't be wearing those knitted woolly ones again.

James

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4 hours ago, Stub Mandrel said:

It's definitely cheating when your trunks stretch the whole length of the pool.

Brilliant!!  Laughed so much it brought tears to my eyes!

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Well, it's been over a month since my last posting, largely down to holidays and other stuff going on.  Things haven't come to a grinding halt however.  A little progress has still been made and I hope the pace will pick up again over the next few weeks.

The electrics have been the main focus recently.  At the moment pretty much all of the electrics in the warm room are done.  The only major item outstanding is the consumer unit which isn't yet fitted.  In the scope room I have three weatherproof double sockets around the walls, but the boxes for the power etc. to each pier are not yet installed.  That's probably the next step.  Once those are done and the consumer unit installed I can re-fit the desk (temporarily removed to make working on the cabling easier) and make some shelving to go underneath it to hold the 12V power supply and a network switch.

Whilst the weather is dry I really must take the opportunity to get the EPDM glued down and finish off the last length of cladding on the sides of the roof, too.

James

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Great to see you are on the final leg of your Obsy build James. Unfortunately it's heavy rain here at the moment and it's curtailed any outside work for me today :(

Steve

 

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1 minute ago, sloz1664 said:

Great to see you are on the final leg of your Obsy build James. Unfortunately it's heavy rain here at the moment and it's curtailed any outside work for me today :(

Hmmm.  A look at the wider picture for the weather shows a huge band of rain stretching from London to Northern Ireland :(  None of that is forecast to come our way -- we have bright blue skies at the moment, but perhaps I shall have to keep some "rainy day" jobs in mind in case things change later.

James

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Just reading through the last few pages - some great progress made!

While getting an electrician in is definitely the way to go, on grounding I'd just throw conductive concrete out there as a thing that exists - at work, we (and many other telcos) use http://www.cubis-systems.com/uk/conductive-concrete-landing-page/ underneath our concrete pads for utility cabinets that have electronics in. It's basically a carbon-concrete matrix which bonds to a copper electrode cable laid within the concrete that comes up to provide your earth. It can be poured dry without needing water or mixing - it'll absorb enough from the surrounding earth. The huge benefit is that it doesn't corrode, so lasts absolutely ages, and the conductivity is actually much better than an earth rod - so you can do a relatively small and shallow installation and get a very good ground. Worth considering if you've got challenging material 50cm+ down that makes getting a rod in hard or makes the rod less effective!

Also, if you're planning to run Ethernet back to your house, consider using fibre optics. If you're running off different supplies or phases or just have a different ground, there is a risk that you put more volts across your Ethernet cable than are tolerable from either end; I've seen someone cook a very expensive network switch (~£80k if memory serves) by doing this across two racks fed off different phases at a trade show booth. You can get pre-terminated 30m LC patch cords for £10 or so, and TP-Link and others make media converters to go between a fibre SFP and a copper RJ45 on each end. Fibre SFPs for 1G again around the £10 mark for short distance stuff. So it's not a huge outlay, and you really can't end up with any ground loop excitement via glass 🙂

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10 hours ago, discardedastro said:

Also, if you're planning to run Ethernet back to your house, consider using fibre optics.

This is something that has been nagging at the back of my mind for some time.  I had no idea the kit had become so cheap though.  It's certainly worth considering.

James

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1 minute ago, JamesF said:

This is something that has been nagging at the back of my mind for some time.  I had no idea the kit had become so cheap though.  It's certainly worth considering. 

James

fs.com are a very cheap retailer, but do good parts - plenty of professionals and big networks in the UK running off some of their optics etc. My advice:

  • Stay single-mode. Multimode is cheaper, but comes with many more headaches. Single mode (OS2) is also more widespread. The cost differential is not significant, and the longer range gives you more margin of error.
  • You'll need a pair of SFP modules, and either switches that accept SFPs (Mikrotik and Ubiquiti both do 'em, some cheap Netgears even do now) or media converters (which are transparent, from a network perspective)
  • Those SFP modules will have LC UPC connectors and need two fibres to work (one for transmit, one for receive). You can do single-fibre working and an SC connector using different wavelengths (so-called bidi) but two-fibre working is easier to work with. You will therefore need cables that are terminated in LC UPC duplex pairs - this is very common. UPC just means "Ultra polished contact" and is distinct from "angled polished contact" APC connectors. UPC is blue, APC is green. Avoid APC.
  • You can daisy-chain patch cords if you need more length, but having a continuous run is preferable. Joints outside will need to be in waterproof boxes with rubber seals that don't put too much pressure on the cable. Consider getting a cable made to length if you need >50m; it's usually pretty cheap, and the cost of fibre is all in the ends until you get into very large cables (we do 864 fibres in a 20mm cable at work - that's fun to work on). Otherwise, you just need couplers to join cables together - they're cheap as anything, just plastic to push the two cores together.
  • Get pre-terminated cables unless you know someone who does fusion splicing for a living. And even then, get pre-terminated cable.
  • If you're pulling cable any appreciable distance, tension can kill fibre - use a pulling sock and be gentle. Be mindful of bend radii.
  • Cleanliness is king. You can be pretty abusive to fibre cables, especially newer G.657.A1/A2 cables which will bend quite severely, but if you get dust or dirt on a connector you'll have a Bad Time - it can damage connectors or transceivers. Just keep dust caps on everything until you're ready to plug it together, tape up before pulling through duct, and buy a one-click cleaning pen (~£20) which you can use a few times before mating any connectors. In short runs, so long as you don't lick them/clean on your t-shirt, you'll be fine. Treat the ends like telescope optics and it'll all be alright.
  • If it doesn't work, swap the transmit and receive cables on one end - the most common "I plugged it together and nothing works" cause is inverted polarity.

 

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Mostly sorted out the power to the piers today.  The first one took a while just making sure it was all going to work as I intended, but after that it went pretty well.  I almost didn't finish the last one though.  It was around dusk and dozens of gnats descended on me, clearly looking for a meal.  I decided there were just too many to fight off and called it a day.

James

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22 minutes ago, discardedastro said:

fs.com are a very cheap retailer, but do good parts - plenty of professionals and big networks in the UK running off some of their optics etc. My advice:

  • Stay single-mode. Multimode is cheaper, but comes with many more headaches. Single mode (OS2) is also more widespread. The cost differential is not significant, and the longer range gives you more margin of error.
  • You'll need a pair of SFP modules, and either switches that accept SFPs (Mikrotik and Ubiquiti both do 'em, some cheap Netgears even do now) or media converters (which are transparent, from a network perspective)
  • Those SFP modules will have LC UPC connectors and need two fibres to work (one for transmit, one for receive). You can do single-fibre working and an SC connector using different wavelengths (so-called bidi) but two-fibre working is easier to work with. You will therefore need cables that are terminated in LC UPC duplex pairs - this is very common. UPC just means "Ultra polished contact" and is distinct from "angled polished contact" APC connectors. UPC is blue, APC is green. Avoid APC.
  • You can daisy-chain patch cords if you need more length, but having a continuous run is preferable. Joints outside will need to be in waterproof boxes with rubber seals that don't put too much pressure on the cable. Consider getting a cable made to length if you need >50m; it's usually pretty cheap, and the cost of fibre is all in the ends until you get into very large cables (we do 864 fibres in a 20mm cable at work - that's fun to work on). Otherwise, you just need couplers to join cables together - they're cheap as anything, just plastic to push the two cores together.
  • Get pre-terminated cables unless you know someone who does fusion splicing for a living. And even then, get pre-terminated cable.
  • If you're pulling cable any appreciable distance, tension can kill fibre - use a pulling sock and be gentle. Be mindful of bend radii.
  • Cleanliness is king. You can be pretty abusive to fibre cables, especially newer G.657.A1/A2 cables which will bend quite severely, but if you get dust or dirt on a connector you'll have a Bad Time - it can damage connectors or transceivers. Just keep dust caps on everything until you're ready to plug it together, tape up before pulling through duct, and buy a one-click cleaning pen (~£20) which you can use a few times before mating any connectors. In short runs, so long as you don't lick them/clean on your t-shirt, you'll be fine. Treat the ends like telescope optics and it'll all be alright.
  • If it doesn't work, swap the transmit and receive cables on one end - the most common "I plugged it together and nothing works" cause is inverted polarity.

Interesting.  If I have any problems with WiFi, I'll seriously consider this.  I did have a run of CAT6 UV resistant cable running to my observatory but with a Ubiquiti AP I find WiFi quite adequate.

Edited by Gina

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25 minutes ago, discardedastro said:

fs.com are a very cheap retailer, but do good parts - plenty of professionals and big networks in the UK running off some of their optics etc. My advice:

Thanks.  I wasn't aware that daisy-chaining was possible, though I don't think I'd want to do that anyhow.  More pain than it's worth if something goes wrong, especially given that I'll probably be burying it in ducting.  Need to give it some thought.  Unfortunately the last time I worked with fibre was over twenty years ago and I've forgotten pretty much everything.

James

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22 hours ago, JamesF said:

Thanks.  I wasn't aware that daisy-chaining was possible, though I don't think I'd want to do that anyhow.  More pain than it's worth if something goes wrong, especially given that I'll probably be burying it in ducting.  Need to give it some thought.  Unfortunately the last time I worked with fibre was over twenty years ago and I've forgotten pretty much everything.

James

Passive daisy-chaining is very safe using standard singlemode SFPs (10/20km optics) - you typically have -9dBm launch power (worst case) and a receiver sensitivity of -22.5dBm (worst case), so a link budget of 13.5dB. Assuming a 30 metre patch cord (~0.009dB loss in fibre) and a typical connector (0.5dB) you can put 25*30m patch cords + couplers in (750m) and have room left over for a patch panel at each end! In practice -9dBm launch is worst-case so you'll get another 3dB or so atop of that. But if you're burying in duct, I'd definitely stick to pre-terminated runs of the appropriate length. fs.com will make you up cables for £100 or so for ~100m, last I checked.

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I'm pleased to be able to relate that all the mains wiring in the observatory is now complete and it is connected up to the existing supply from the house.  I no longer have extension leads and trailing sockets all over the place which is a big improvement, to say the least.

Yesterday I had quite a big tidy up to get rid of most of the stuff that's been hanging about "in case I need it" which has also improved things by making much more space.  I also refitted the desk (previously removed to make it easier for the cabling to be done) and got most of the trunking finished.

Today I made up a shelving unit to go under the desk so I'd have somewhere to put the 12V PSUs in the warm room and then cut up a discarded length of twin core cable with nice fat conductors (it was on a cement mixer until someone managed to break one end) to feed 12V from the PSUs to the cabling running under the floor.  Once that was done I made up the connections at the pier ends.  All this whilst repeatedly rolling the roof on and off due to random showers.  I could have just left the roof closed, but it was unpleasantly humid here today (I think it was about 90% RH at one point) and I wanted all the ventilation I could get.  After that I undertook a ridiculously paranoid level of testing as I was very keen not to feed the wrong polarity to a NEQ6, before powering a mount up and using the handset to point it at whatever objects I thought might be in the afternoon sky (all obscured by clouds, sadly).  Apparently Mercury, Venus and the Moon were all there somewhere and Jupiter was just creeping above the eastern horizon.

Finally I took down one of the computers that I intend to use on the piers and connected it up inside the box on one of the piers.  It's all a bit scruffy at the moment, but it might allow me to do a bit of testing later in the week.

At this point I think all that remains in terms of cabling is finshing the network cables (putting the RJ45 plugs on, basically) and deciding on the final routing for the cabling for the power supply for the scope room lights.  They're powered from a 24V PSU that I intend plug into a standard 13A socket in the warm room.  I just need to come to a decision about routing the cable between the two and get it sorted.  There's probably no major rush for that though, as I can feed them from one of the IP66 sockets on the warm room wall for the time being.

This evening it occurred to me that temporarily I could perhaps use one of my old ADSL/wifi routers as a wireless bridge between a wired network in the observatory and the network in the house.  I'm never going to use it as an ADSL router again because it isn't supported any more and may have security issues that won't get fixed, so this seems like a better idea than binning it.  It won't be a brilliant, but is perhaps the best I can do until I sort out a permanent connection.  Unfortunately I couldn't get it working after a brief test whilst I went out to shut the chickens up for the night, so additional configuration may be required at the house end.  I'll look into that this week.

Other than that I think I'm going to try to get some of the other computery/networky-type stuff done this week so I can actually start using it all.

James

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