A Little Ladder Logic

Ladder logic program. © Eugene Brennan

Just found this among documents I was going through after getting the oil boiler serviced last week. I had forgotten all about it. The electrician made a minor cockup when wiring the controls for the dual oil/solid fuel heating system 9 years ago. So I had to go off and look for a CAD package to draw a ladder logic diagram for him, showing how it should have been wired. (He had his own ladder logic diagram, but it made more sense for me to draw a new one, rather than trying to explain the error in English). Ladder logic is a schematic system for showing the wiring in an electrical/electromechanical system, input devices such as switches and sensors and output devices, e.g. motors and relays being shown as symbols on a diagram. It has evolved into a graphical programming language, the graphical program used to control programmable logic controllers (PLCs). These are basically modular, industrial control computers, built into a box, with terminals for connecting inputs and outputs. A computer can be connected for programming and they can be linked-to by various computer networks.

I'm rusty on this stuff. It's a shame when you learn stuff, and then forget it all if you're not applying the knowledge on a daily basis (I never really used this practically, even though I studied industrial automation).

See if you can understand what this does. Hint: MV1, 2 & 3 are zone valves, R1 & R2 are relays. SF is solid fuel.

Heritage Week Sunday Cycle

Historical buildings in Ballitore and Calverstown.© Eugene Brennan

My Sunday cycle this week was supposed to be to Kilkea Castle, but it was 4 pm by the time I set out and I changed plans midway. (Sometimes I make up the route as I go along and let the bicycle decide). Usually on the steep road out of Crookstown heading west towards the Athy road direction, I turn left for Mullaghmast at the top of the hill. I travel cross country to Kilkea this way, crossing the new N78 Athy Link Road at the bottom of Mullaghmast Hill, and then take a right just before the Moone Inn. On Sunday, I took the second turn after the Mullaghmast turn on the Crookstown road. This leads to the Burtown area on the new N78. I travelled a few miles east on the N78, and then exited for Ballitore. In the village I took some photos of the historic Quaker buildings including the Meeting House and Mary Leadbeater's house, now a library and museum. Leadbeater (1758 - 1826 ) was a Quaker and author who lived in the village and documented events during the 1798 rebellion. 

Mary Leadbeater's house, now a library and museum. © Eugene Brennan

A school established in 1726 by Abraham Shackleton. It's now a Quaker meeting house. © Eugene Brennan

Next I headed to the outskirts of the village and the location of Ballitore Mill. This a large, ruined structure, built in the early 19th century. An EPA hydrometric station that monitors water level and flow is located on the River Griese, which runs alongside the mill. The Griese in addition to powering this mill also powered a second mill in Ballitore, located down a cull-de-sac in the village. I headed back on the old section of road towards Crookstown. This was the original Carlow road before it was replaced by a wider section several decades ago. It's amazing how the ditches of a road that's no longer used begin to creep inwards and the accumulation of leaves and other debris begin to return it to nature, obscuring the tarmac. 

Ballitore Mill. © Eugene Brennan

Ballitore Mill. © Eugene Brennan

EPA hydrometric station. © Eugene Brennan

From Crookstown, I headed back towards Calverstown via Narraghmore Bog. I took the road that runs alongside Crookstown Millview AC's track and then turned off that to pickup up the Narraghmore - Calverstown road. I've always intended to visit Blackhall Castle, and I've passed the entrance multiple times over the decades, so I decided to investigate it on Sunday. A long, wooded lane leads down to the castle, situated in the grounds of an old farmhouse, probably dating to the Georgian period and owned by Jeffrey and Naomi White. The owner, Naomi, and a barking Cocker Spaniel greeted me and Naomi explained some details about the ruin. The four story castle was built by the Eustace family in the 16th century and appears to have a large , impressive fireplace on the fourth floor. Unfortunately half of the castle collapsed in 1999, due to instability in the structure. Naomi told me they had secured a grant to stabilise the structure, but it's a shame the collapse happened before this work could be done. There's also a "Sheela na Gig" carving which was luckily recovered from the rubble after the collapse and is now mounted in a ground floor wall. More information on Blackhall Castle is available on the Irish Historic Houses blog here.

Blackhall Castle. © Eugene Brennan

 

Blackhall Castle. © Eugene Brennan

 

Sheela na gig carving. © Eugene Brennan

 

My cycle route. © Eugene Brennan

I Present to You for Heritage Week

Items found in the garden. © Eugene Brennan

.....my archaeological discoveries from the garden. Found while digging and doing construction work over the last few decades. Probably nineteenth century stuff. My theory is that rubble from the demolition of the Carlow Stables was spread out to level the ground during construction of the Nicholastown housing estate and that's where some of these fragments may have came from. During the era when a Bianconi coach service ran from Dublin to Cork, via Clonmel, horses were replaced at intervals along the way. The Carlow Stables in Kilcullen was one of the relay sites. The building was located just before the first turn into the estate, heading south. Some of the fragments I found were rough pottery with glaze, so these could be pre-nineteenth century and not manufactured in moulds or by machine. One piece has shallow grooves, possibly made by finger marks when the pottery was turned on a wheel. The top of a flagon came from outside the wall of my house, dug up when the council was fixing a broken water main almost 20 years ago. It's embossed with the text "Price Bristol". That grass bank outside the house probably contains a treasure trove of items, lost and discarded over the centuries since the road and the trail which probably preceded it has been in existence. I also found a piece of red brick, three feet under the ground, when I was digging a soakaway in the front lawn, but there were no houses in the area before the estate was built. The triangular tile-like objects were found when I was digging the foundations for my gate piers a few years ago. Not sure what they are.

Painting Tip Related to Science

Cleaning a paint brush in white spirit. © Eugene Brennan

I've been painting my front door, something I've been putting off for a couple of months. Painting requires preparation and then there's all the cleaning up to do afterwards. The trend now is towards the replacement of oil-based paints for wood and metal by water-based formulations. Presumably this is an eco-driven thing, to reduce emissions of volatile organic compounds (VOCs) into the atmosphere or landfills when paint containers are discarded. I'm not convinced water-based paint is as durable as oil-based types, however it does make the cleaning of brushes easier. Cleaning oil paint off brushes requires the use of a solvent such as turpentine, white spirit or kerosene. Here's where the science comes in, but first some background knowledge on the subject of mixtures. When two or more substances are combined together, the result is known as a mixture. There are several different types of mixtures. A solution is a mixture of a soluble solute, e.g. sugar or salt in a solvent, e.g. water. The solvent doesn't have to be water: another example of a solution is light oil or fuel additive in a solvent such as petrol. Atoms in a mixture don't combine chemically, they just closely intermingle, but don't bond with each other. Another type of mixture is a colloid such as milk or paint or a suspension such as muddy water. The only difference between a colloid and a suspension is the size of the solid particles and the time it takes for them to settle out, if they ever do. Mixtures don't have to be combinations of a solid and liquid; they can also consist of two or more solids— such as sugar and salt, or stones and sand. Gasses also combine to form mixtures. So air is a mixture of nitrogen, oxygen, carbon dioxide and small traces of inert gasses such as neon, argon and xenon.

Often in a lab, it's necessary to separate the individual items in a mixture. The processes used are also employed in industry. Filtering is one technique, but that only works for non-solutions. You can't remove salt from salty water for instance by filtering the solution. That's because the salt exists as individual molecules of sodium chloride in the solution and they would just pass through any filter medium. So to extract it, evaporation of the solvent, water in this case, is the separation technique used, leaving the salt behind. If the mixture is a colloid or suspension, the particles are much larger and so filtering can be used. In a lab, this can be done using a funnel and filter paper. On an industrial level, e.g. in a water treatment plant, muddy water is filtered through sand beds. Hence the colloquial term for the Ballymore Water Treatment Plant, the "Filter Beds". Distillation is another separation technique used for example to separate a solution of alcohol and water when making spirits. Alcohol and water boil at different temperatures: 78.5°C, for alcohol, while water boils at 100°C. Heating a mixture of alcohol and water above 78.5°C causes the alcohol to boil off, leaving the water behind. A condenser or "still" is used and cold water circulating in the condenser cools the evaporated alcohol, creating a condensate, which is then collected. Yet another separation technique is decanting. The principle is simple, give a suspension enough time and the suspended particles will settle out. That's what happens in the BWTP and muddy water from the reservoir is given sufficient time for the suspended mud particles to settle out in tanks. The clearer water from the top is pumped off and filtered through sand. That initial treatment removes material that would quickly clock the filter beds. And that's what I do with the white spirit that I use for cleaning my paint brushes: instead of discarding it, I collect it in a 5 litre container and after 6 months or more, all the suspended solids settle out, leaving a reasonably clear solution. Then I can decant off the white spirit as necessary to fill bean tins for washing paint brushes. The decanted white spirit isn't perfectly clear, but good enough for cleaning brushes.

© Eugene Brennan

Attacking the Brasses With Acid

Shiny fittings on the newly-painted front door, the result of hours of polishing. © Eugene Brennan

Painting is something I tend to procrastinate on and life is too short for cleaning brasses regularly. I do a good job of cleaning the hardware on the front door every two or three years when I paint it, but then I only polish the brasses a couple of times before I lose interest and have more pressing chores to attend to. After three years of non-cleaning, a thick layer of oxide builds up on the fittings which takes several hours to remove with wire wool and Brasso. (Brass is an alloy of copper and zinc, so the tarnish is zinc oxide and copper oxide). There may be other compounds making up tarnish such as acetates (The green patina on domes of public buildings and the Statue of Liberty, known as verdigris, is copper acetate. This forms naturally or is created artificially by using acetic acid on the copper sheeting, pre-construction). Anyway to cut a long story short, from my school chemistry I knew that acid dissolves oxides and turns them into salts. Someone gave me half a 5 litre container of Ecokem phosphoric acid they didn't want. Phosphoric is used for cleaning rust (iron oxide) off iron and steel and descaling lime build-up from sanitary fittings. So I tried the stuff and it did a reasonable job of quickly removing the tarnish. 

Phosphoric acid, a product used for descaling. © Eugene Brennan

This is a faster method than using wire wool or Brasso, but I'll use the latter to further clean and polish the brass (Brasso contains a mild abrasive). I noticed the brass had turned pink and suspected that the acid had reacted to a greater extent on the zinc in the brass alloy, dissolving it and leaving the copper behind. My suspicion was confirmed by Grok. After washing the acid off, the brass turned black and brown when it dried. Not sure what produced that chemical reaction. Will have to ask Grok for a follow up.

The acid dezincified the brass, leaving copper behind. © Eugene Brennan

Edit: Grok said it's copper oxide, formed by the rapid oxidation of porous copper after dezincification by oxygen in the air or rinse water. It transpired that the dezincification was superficial and I used Brasso to finish the job, leaving the fittings perfectly shiny.

Grok confirmed the dezincification. © Eugene Brennan