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Processor Control of Lineside Items - The Lineside. - Getting You Started. - Your Model Railway Club
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 Posted: Wed Oct 7th, 2020 03:14 pm
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Dave C
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Thanks Nigel.

On my last layout I did play around with reed magnets and the 555 timer chip but found the reeds to be a little unreliable (maybe it was me and my fumble fingers in mounting them correctly!). Not only that but they only detected where the magnet was, presumably under the belly of the loco (or wherever the magnet got fitted). I'm looking at detecting the entire train. The reeds were also a bit obtrusive and noticeable in that they lay along the track and were somewhat difficult to "hide". But for those that use them, great, as long as it does the job for you.

And to you Chris, again, thanks for the comments.

I did have a look at the Arduino, mostly the Uno, but found that it had a limited number of ports to which you can connect things - am I right in thinking only 20 digital and 8 analog? Maybe there are add-on boards to increase this number of ports but that then adds to the complexity of it. Having said that, I guess my idea of using the PICAXE processors is just as complex in that I only have the bare, naked processor to start with, and it along with everything else has to be mounted onto a piece of board. Swings and roundabouts, I guess. But the PICAXE 40X2 has up to 32 ports for connectivity and even for my needs I have found it limiting when trying to sort the signalling out.

For instance to save ports, I have to generate a three-aspect signal from two outputs and a two-aspect signal from just one output - plus a couple of logic chips to make up for the deficiency and the missing aspects - more on this when I get round to the next instalment, coming (I hope) shortly. Presumably the Arduino is as capable of only driving a limited amount of current from each port (and overall) as the PICAXE. Therefore, if you want to run the layout signals as well as duplicating them on a mimic board then other add-on chips to increase the current capability would also be required.

Don't get me wrong, I'm not trying to put you off the Arduino. In some respects I'm trying to make a comparison about the Arduino of which I know very little about. Like the reed switches/magnets mentioned above, it's horses for courses. You run with whatever you feel is right for yourself.

I'm not sure about making videos.....I only recently found out I have a YouTube channel by way of the GMail account, I think that's how come I got it. Never even thought about videos. Maybe one day. At the moment there's not enough hours in the day to do much on the layout (same old story, I know). Can't recall the last time I actually ran some trains.

Anyway, glad you're enjoying the series, Chris

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 Posted: Thu Nov 12th, 2020 11:14 am
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Dave C
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Thought I ought to give an update on the automation of the signalling as it's been a long time a-coming.

Well, life over the past few months has certainly been getting in the way of all things railway. But there is progress, slight though it might appear. The circuit board has finally been completed and the inter-connections checked and double and triple checked - it's not been supplied with power yet so there is still a chance I may have missed something along the way. Once I start checking the board it will be very slowly, slowly, bit by bit.

Then I can start to connect up the sensors and signals and the associated layout mimic/track diagram. But even some of the signals and sensors are not yet in place - so there's still a lot to be doing before it all gets up and working.

But to give an indication of where we are, the following is a preliminary shot of the circuit board - on standard stripboard.



Note the two large processor sockets and small add-on board for the "master" processor - not enough room to squeeze it onto the main board - and the use of two 7805 regulators (just to make life easier on having just one of them). It's still a bit cramped though.

So, as you can see, there IS life at the end of the tunnel - if only someone would turn the light back on! .... more to come in the next few weeks as and when I can get the time together to spend in "The Train Room".

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 Posted: Sun Nov 22nd, 2020 05:06 pm
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Dave C
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Another quick update - not that much has been happening.

The signals are now installed and connected up to the (new) main patch-panel - there are over 120 individual wires to connect through. The sensors are also getting there. The original sensors in the hidden track area were all initially run from +12v - which is of no use what-so-ever for feeding into a processor that only likes +5v. So they are in the process of being updated and modified for +5v. They all need updating as there will be an overall layout track diagram complete with (pseudo) signals in the hidden section (only visible on the track diagram) and the sensors are needed for controlling them. The signals also need to be wired essentially back-to-front with a permanent +12v to the anode of the LEDs - it's the negative side (the cathode) that gets switched to ground (via the limiting resistors) which lights the light, so to speak.

When I started this layout I didn't really have a long term plan of what I wanted to finally achieve. And processor control of the signalling was far from being in my mind at that time.

If only I had made a plan! How many times has that been said amongst us all? And signalling didn't come into it.

Ah well, that's life I guess. At least I'm trying to keep everything written up and making notes of wire colours and where they start and finish and their purpose in the grand scheme of things. Which is helpful - until you look at the masses of wires strung all over the place under the boards and at the few circuit boards fitted wherever there was space to fix them. Plan? Nah!

I can certainly appreciate looking at other layouts and can only assume there is neat and tidy wiring under the layout. Or am I kidding myself? Mine started out relatively tidy, but then more and more wires were added and it become more of a jumble.

More to follow in due course.

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 Posted: Sun Nov 22nd, 2020 09:23 pm
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Sol
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Dave, Plans are like Rules - for the guidance of wise people & for fools to follow ( so one of my Engineer masters told me but heaven help me if I stuffed things up by not following plans/rules).
Of course with DCC you only need two wires.......



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 Posted: Sun Nov 22nd, 2020 09:57 pm
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Petermac
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When you say the sensors need updating Dave, does this mean replacing or can you just re-programme a change in voltage ?



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 Posted: Mon Nov 23rd, 2020 08:43 am
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Dave C
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Thanks Sol
But, as you say "Of course with DCC you only need two wires.......",  even then, two wires can still get mixed up and get you into a pretty pickle. Beats the two wire system of DC though, every day!

And PeterMac, yes thanks for the query. When I said the sensors needed modifying, I have taken it to mean all the sensor circuitry - i.e. the sensor parts (emitter and receiver) and the voltage comparator, all taken as a whole unit.

Fortunately it's just a change in the voltage to the LED that gets fed to the comparator output (see the diagram in my post #16). It's this connection between the LED (and it's current limiting resistor) and the comparator output (LM339 in this case) that gets fed into the processor's input. So while the comparator itself (and the actual sensors) are still working from a +12v supply, it's the switched-off state of the comparator that matters at its output - the output being open-collector and needs a supply voltage to make the LED work - and this switched-off state can be no more than +5v.

Hope that clarifies the situation for you.

Cheers all.....

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 Posted: Mon Nov 23rd, 2020 09:06 am
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Petermac
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Hmmm .........

I'm sure you know how to do it Dave - I'll just continue watching from the sidelines if you don't mind.... :???: :shock:

As I said to Bill (Longchap), electrics are for those with 17 eyes and antennae sticking out of their heads .............. :roll:  Do you have 360 deg. vision and a couple of antennae ?



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 Posted: Mon Nov 23rd, 2020 09:22 am
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Dave C
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I couldn't possibly comment Peter :lol:

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