No connection - maybe

Mum's driving! At the wheel of RRS Discovery

 Today we are leaving this wonderful place here in Scotland and heading for Berwick-upon-Tweed for the second week of our holiday. I have no idea when or if I will be able to get a good connection down there, so if it all goes quiet for a while you will know why!

Ralph

On the road - Dundee...

The recycled fridge, luggage and three humanoid figures arrived in the land of haggis and bagpipes late yesterday afternoon and after avoiding boarder patrol we eventually, 449 miles later, we arrived at the cottage we had booked after an internet search. This can be a bit of a risky business – not this time.   What a place! The instructions of how to get here casually described following the drive to the top and then… Well, what a drive, it must be a mile long! At the top of the drive we found our cottage, part of a converted stable complex, complete with everything you could possibly need including Wi-Fi.

Under the covered part of the yard I found something of interest to a workshop owner with the start of withdrawal symptoms, a circular saw, I wonder if they will let me have a go? This petrol driven monster is obviously used for chopping logs for the open fires. There is a lot more to explore here, we are in 100 acres of private woodland and gardens and we have free run of most of it. I’ll post a few more pictures over the next few days.

Today we went to Dundee, 12 miles up the road and managed to catch the Olympic torch relay, while dodging showers in the town centre. Tomorrow we will be going back to visit RRS Discovery which is on display in a purpose made dock. I remember Discovery being moored on the Thames in London as a training ship. It had no engines as they had been stripped out and used as scrap to help the 39–45 war effort, and as far as I know they were never replaced. Her journey from London to Dundee was made in a transport ship.

Ralph.

On the road – well, almost…

Every now and then, there comes a time when the workshop has to be locked up and left under the careful watch of the neighbours. For the next couple of weeks the tools will be dormant, the waft of solvents and flux will subside and the resident colony of arachnids will be free to build a great metropolis of silk, dust and insect carnage. Yes, it is time for a HOLIDAY!

There comes a time when the tables are all reversed. As a kid I used to look forward to the summer holiday, bucket and spade in hand, ready to rearrange the sea defences at Dymchurch and build a castle to help fight of all invaders. These plans were usually thwarted by the incoming tide or one of the’ big kids’ who’s idea of fun was ruining mine…

Happy days! How things change. Now I am sitting here typing this on a Sunday morning and the schedule is as follow:

1000 hours – Tune in to Radio 4 to catch up with The Archers

1115 Hours – Collect together ‘important’ items ready for holiday and check oil and tyre pressures on the recycled fridge.

1230 hours – Lunch!

1300 hours – Depart to collect Mum.

1400 hours (approximately) Arrive at Mum’s

1430 hours Bundle (Sorry, help…) Mum into car and return to London ready for tomorrow.

… Monday, 0500 hours leave The Smoke and head North attempting to beat the morning rush.

There is a theme developing here and for the next couple of weeks it is our turn to look after Mum and entertain her, just like she and Dad did for me all those years ago. 

That's the essentials packed. Have you worked out what is there...

While Mum is packing her bucket and spade, I have been busy sorting out the essentials. No I am not talking about all the clothes, wash things and other incidental stuff. That seems to look after itself and ends up in the cases. My only job regarding all that (other than lifting it into the back of the car) is to inspect the contents on arrival and then spend the next couple of weeks moaning about the fact that my favourite pair of socks was left behind. You just can’t get the staff these days.

No, I am taking about the really important stuff. They say a change is a good as a rest and, for me, it is. I am not one for taking token bits of my hobby on holiday, no, that can have a holiday too. For the next couple of week I will be on the lookout for prototype inspiration. We are off to Scotland and North East England so I will be armed with survey tape, pens paper cameras etc. with an eye on the world around us. Not having an accent myself (born and lived in South East London my entire life) I usually find it hard to understand the locals, but I will have a go. What I don’t get is they keep asking me to repeat what I have just said – strange…

I will be collecting prototype information on everything from the colour of the dirt to the form of the trees. I particularly like studying the grotty bits, especially the accumulations of rubbish, overgrown and neglected areas, graffiti and the general decay. All of this is seldom modelled and can really add to the scene.

For the next couple of weeks, as long as I can get on line, I will post my adventures and show you what we have found in the way of relevant material. Now what did I do with my knotted handkerchief? 

Ralph

Messing with LEDs

LED specifications. Don't you just love a good chart?
All this information is readily available on the internet, just Google it!

I have never been interested in electronics for electronics sake. Perhaps I should have been, as I would know a lot more about the general stuff now. For me, the electronics were a means to an end. I would build a kit or follow a diagram without really understanding how it worked, being satisfied in the knowledge that it did what I wanted it to do.

Way back in the days of rebuilding and tinkering with my old 1970 Ford 1600E Cortina (remember those?) I wanted to add intermittent wiper control. I could have just bought a unit and screwed it in place. In those days there were car accessory shops and/or motor factors on every corner. There was very little in the way of electronics built into a car then, even a top of the range model like my 1600E. The systems were mostly, if not totally, electro-mechanical. The wiper control had two speeds, too fast and too slow! Most cars of the period were similar so aftermarket bolt-ons were readily available and popular.

Not being one to go down the bolt-on-goody route I saw a project in Practical Wireless on building one. It looked simple, and it was, just a few components soldiered to a printed circuit board (supplied by PW) and it was done. The parts were duly acquired; the unit was built and installed. It worked fine and was still in the car when I sold it some years later. Yes, I had built it, and installed it but I had not bothered to find out how it worked. It probably explained all that in the original article but I would of skipped that bit at the time being more interested in improving the performance of the wipers than understanding how it worked.

Forty years on my attitude and interest has changed somewhat. For a start our vehicles are very different today. There are few places to buy car parts or accessories as most cars come with everything under the sun including hot and could swinging doors! And, they are full of electronics. The net result being, in the past I could strip down and rebuild a car (every last nut and bolt) and be confident that it would start when the key was turned. Not any more. Even the van has all sorts of electronic engine management systems incorporated and buried in the most inaccessible places. I now leave the automotive stuff to others and concentrate on the model making – much cleaner! These days I have the time and the inclination to try and understand what is going on, hence my revived interest in electronics.           

The LDR is located in the frog's mouth

Do you remember that pound-shop croaking plastic frog? I decided to have a go at using the croak output to drive an LED as had been suggested by someone on the EEV blog forum. I ‘extracted’ the PCB, battery box and speaker from the frog and discovered the LDR in its mouth was hard-wired and needed the application of the wire cutters to remove it. To test the theory, I set up a little experiment on a piece of breadboard to see what, if anything, would happen. A pair of leads were soldered to the speaker terminals and the other ends are plugged into a couple of tracks of the breadboard with an LED places across them.

Snip! that could almost make your eyes water!

I had already cut the LDR from the circuit while extricating the guts of the frog. I replaced the LDR trigger with a read switch, that just happened to be handy, as any movement was causing the LDR to trigger the frog into making three double croaks, driving me nuts! The read switch made it much more controllable. I could of used anything that would ‘make’ the circuit. The LDR has a minimum resistance if full daylight of approximately 100 Ohms and maybe I should have incorporated a 100 Ohm risister in series to the reed switch but it seemed to do the job without.

This is what a frog's croak looks like! I know, I must sort out some video...

 I should also of added a resisters to limit the current being supplied to the LED but I think the IC under the ‘blob’ must have provided some current limiting as it too seems to work OK. Measuring the voltage being applied I get an approximate maximum voltage of around 4V. A red LED of this size (5mm) is happy to operate at around 20mA (.02A) and has a forward voltage about 2V. All this information is available from data sheets or charts, readily available on the web, like the one illustrated at the top of this post. The voltage across the LED is Vs – Vf (supply Voltage – forward voltage) in our case this is 4 – 2 = 2. Using Ohms law (V=IR) transformed to R = V/I to work out the value of the resistor required:

R = (Vs - Vf) / A  =  (4-2) / .02  =  2/.02  =  100 Ohms

Now all I need to do is find a use for my discovery… Glowing embers, or a dodgy flickering light in the station’s waiting room.

LEDs and Meccano

Moving away from the model railway applications, Sue has always been keen on lighting our Meccano models. Suggesting she uses her 1935, boxed and strung, lighting kit may lead to a cries of “How could you?” and result in me having to cook my own tea for a week or so. Better look at a more 21st century solution. 3mm LEDs will, with a bit of persuasion, mount in a Meccano hole using a 3mm plastic LED clip. This is intended to fit into a 4.4mm hole but a spot of ‘percussive maintenance’ (to use a Dave Jones, of EEV blog, phrase) will get the thing seated. With this in mind, I decided to get the Arduino and breadboard out and have a go at prototyping the electronics. My mate Tim (chief programming nerd and all-round techie-geek) was here last week messing with stepper motors and we had the Arduino out to drive them – but that is another story – When he had gone the stuff was still sitting there next to the computer so I refreshed myself with what was going on and saved the ‘sketch’. Why Arduino insist on calling programs ‘sketches’ has passed me by. Maybe I am just getting old…

Four LEDs running light only needs one resistor

The Arduino software comes with several example sketches (Grrr!) one of which is an array of LEDs. The example sketch was written for six LEDs and the run is supposed to reverse, lighting the LEDs in a 12344321 sequence but I wanted to use two groups of four to simulate a simple running light by running in a 12341234 sequence. Having messed with the Arduino for about 36¾ minutes in total, I now consider myself an expert and duly modified the sketch to suit my needs – Confirming my total understanding of the subject the modifications worked first time – Nobody was more surprised than me! I now had my little experiment working using four LEDs and one resistor as only one LED is lit at a time.

Running lights working wired in parallel - not the best solution

Next, I need to expand the idea further. Initially, to extend the LED run I added the extra four LEDs in parallel to the existing array. Although this did work, as I discovered later, it is not the correct way to do it. Further reading illustrated that wiring LEDs in parallel is not a good idea. I am not going to try and explain the ins and outs here, as I am only a beginner on this subject myself. If you want to know more take a look HERE at The Electronics Club. This is a really good website for just telling you the basic facts and pointing the reader in the right direction.

That's better now wired in series pairs - works a treat!

A simple bit of rewiring and a recalculation of the resister value gave me four pairs of LEDs wired in series with a 68 Ohm resister. Calculating LEDs in series is simply a matter of adding the Vf of each LED and deducting it from the Vs. This figure, in this case  5 – (1.9 x 2) = 1.2, is then divided by the preferred current of 20mA (0.02A) giving a resultant figure of 60. As there is not a standard resister value of 60 Ohms the next higher value (68 Ohms) is used. I plugged it back into the power and off it went.

One more small step forward and some more knowledge gained has given me a sense of achievement. That’s enough electronics for now, time to get back to the modelling!

Ralph.

My leg fell off!

A nice day to mend a horse - better do some weeding too!

Not my leg, you understand, but the leg of my ancient saw horse. One of a pair a friend and fellow wood mechanic left behind some 20 years ago. after lending a hand to refurbish the staircase in our Victorian house that we were converting back to a house after it had been converted into flats in the early 70s.

New piece glued in place

Although I have built several horses over the years this pair have spent their entire life with me, here at Laughton Towers. The tops are sacrificial lumps of MDF screwed to the horses through deeply recessed counter-bored holes. Spending most of their time outdoors, at best protected from the elements by a folded tarpaulin they are prone to rot and insect attack. After being used last week while building the stand for the Chelsea Flower Show. one of the horses developed a wobble. The rot had got at one of the legs, so it was out with the saw, a scrap of wood suitably sized on the bandsaw, and some type III glue. A careful bit of cutting and fitting, a period in the cramps and the leg was as good as new.

There is something very satisfying about fixing something that has been around for a while. These horses get used for all sorts of jobs and it would have been a real shame to just discard them. They should go on for a few more years now.

Ralph.

 

Frogs, rollers and don’t you love eBay!

But first, here is a good reason for not being in the workshop much this week! this was 10 o'clock tonight!

More frog...

Having stripped the guts from the frog there were still two wires connected to the Light Dependent Resistor (LDR) fitted in to the mouth of the frog. A quick snip with side cutters and the whole lot is free. The black mount/shield is easily prised from the frog’s mouth. The intention is to build this silly little bit of electronic fun, as it is, into a model at a later date to entertain the kids.

The little circuit board has a few through-wired components and a black-blob that covers the naked IC providing the timing and ‘croak’. This is a common method of mass-producing cheap circuitry for all sorts of gimmicky gifts and novelties such as this and musical greetings cards etc.  I also found the same method being used on the circuit board in a pound-shop USB hub that I was dismantling for the bits. I must admit at the time I was not at all sure what these black blobs were as I am only now reviving my interest in electronics. Having not built anything electronic for over 20 years, until recently, I have a bit of catching up to do. A post on the EEV Blog forum regarding these black blobs soon returned some sound answers and some other interesting facts that have got me thinking. Some of the flickering light novelties utilise the musical greetings card electronics to power LEDs instead of miniature speakers rendering a rhythmic but apparently random flashing. I wonder what croaking frog would look like?

Plate bending rollers

Rolling bars are screwed down when in use

Now look here people, you are supposed to be looking at what I am showing you in the pictures that accompany my ramblings, NOT LOOKING AT WHAT IS LAYING ABOUT ON THE BENCH!! I have received several e-mails asking about the sheet rollers mounted to the bench while I was bending the Meccano to build the crown for the Chelsea Flower Show exhibit. They were purchased from a chap who was selling them on e-bay a couple of years ago. Unfortunately I could not find them when I looked tonight. I think he may just make a batch and list them intermittently. If you do find a listing let me know and I will post a link. Bending the longer, heavier gauge, perforated Meccano strips proved a bit much for my Meccano built bender. You will find some more information on Meccano built bending machines on our Meccano website HERE.

eBay

Love it or hate it eBay is a fact of life and if you play nicely it can be a very useful tool. If you need a particular part or a left-handed what’s-it to fit a 1935 widget there is a good chance that someone will have one for sale. If you are selling the afore mentioned what’s-it, there is bound to be some one who wants to buy it. OK, you do get the odd idiot but they are fewer than the stories will have you think.

This week has been a case in point. I was looking for a middle of the range (sorry about the pun) auto/manual ranging digital multimeter with a micro-amp range. Spending three figures on meters is restricted to work. I can’t justify spending Fluke-like prices on something that is a hobby tool and is never going to pay its way. So. There I was skipping through the listings on eBay and there on a buy-it-now listing was a Extech 430 for £14.95. Halfway through a double take and I hit the ‘BUY’ button – Result!

The meter had only been listed a few minutes earlier and for once I was in the right place at the right time. A couple of days later and the postie was knocking on the door. Grubby and looking used it was looking a bit sorry for itself but it was working and had a battery with a full charge. While Sue set to work with the good old kitchen cleaner and MR Muscle bathroom cleaner (wonderful stuff) I got to work with the screwdriver and took it to bits (as you do!) to get at the clear plastic LCD display cover. This was badly scratched and just generally grubby. Liberal application of Auto-Sol chrome cleaner cleaned off all the dirt, polished out the light scratches and cleaned up the deeper scratches making them far less obvious.

Stripping the meter gave all the connections between the plug together boards a workout and subsequently improved the sound of the continuity tone. Great value for money, a decent meter for less than the price of a round of drinks!

Ralph.  

       

Frogs and powersupplys and Circuit Cellar

The £1 frog croaks as you get near to it - got to be something interesting in there!

Now all that Chelsea stuff is over I have just got back into the workshop. You can't beat the smell of flux and glue. On firing up the workshop's IT system, it collected all the e-mails it has missed for the last few days and among them was a note from Circuit Cellar magazine to let me know they have mentioned my workshop blog on their website. See, somebody must read it! You can see what they had to say HERE

Frog guts!

Meanwhile, on a trip to the local High Street on Saturday Sue managed to pick up one of the frogs mentioned by Dave at the bottom of HSBH 3, which you can read HERE. I have not had a chance to have a look at this thing so I was about to use some 'percussive maintenance' to open it when I discovered the works can be pulled out without damaging the frog. I am not sure what we have here but I will get onto it tomorrow. The small circuit board is just loosely stuck in place and there is what looks like a light censer in its mouth. Looks like this could have lots of uses and for just a pound it even comes complete with batteries!

Putting the frog to one side for now, I decided to take a closer look at an unused AXT computer switched power supply I have had laying around for a few years. These things make a good bench top power supply, if you can only get then to power up. After a bit of head scratching it occurred to me that there might be a bit of a clue in the name. When you connect your computer to the mains supply the power supply does not start until the start button on the front of the computer is pressed. After a bit of a Google search I found a pin-out diagram for all the plugs attached to the huge harness HERE. I should say at this point, unless you know exactly what your are doing, DON'T DO THIS AT HOME.

Don't play with this unless you really know what you are doing. Even when it is off there
is likely to be some stored power in those large capacitors

Pin 14 (of the 20 pin motherboard connector) usually has a green wire attached to it and the pin is marked: PS_ON which means Power Supply ON. If you connect this wire to a ground pin, of which there are several on the plug (Pins: 3,5,7,13,15,16 & 17 are all ground pins) the Power supply will run continuously. If you connect the green cable to ground via a switch, you will be able to turn the supply on and off. I intend to use this as the basis for a bench power supply. I will let you know how I get on in due course.

Ralph.