Electronics SIG Zoom meeting Wednesday 18th January 2023

[Graeme Dunbar]

Iain has booked a Zoom meeting for us - thanks Iain! -


Topic: Electronics SIG - Graeme Dunbar

Time: Jan 18, 2023 20:00 London

Join Zoom Meeting

https://us06web.zoom.us/j/84491374182?pwd=MlI5WXhOcENaakhXdm5zVTBuRXdXQT09

Meeting ID: 844 9137 4182

Passcode: 099771

[Stephen Rainsbury]

I have a scout meeting that should be over by 8.30, but dont wait for me.
SR

[Graeme Dunbar]

I have a scout meeting that should be over by 8.30, but dont wait for me.
SR

Thanks Stephen. I've got a couple of things on the go. Does anyone have any thoughts of track circuit detection (for DC)?

[Stephen Rainsbury]

I have managed to move my scout meeting so should be there OK :-)

[Stephen Rainsbury]

Thanks Stephen. I've got a couple of things on the go. Does anyone have any thoughts of track circuit detection (for DC)?

I remember a system from Railway Modeler (Or Constructor?) in the 1970s that took a section of track, joined with insulating fishplates at each end.

The power to this section was fed from its neighbours, using a 22 Ohm resistor. An op amp monitored the PD across the resistor, which when there was nothing on it would be almost zero, but as soon as a loco ran over and took its feed through the resistor the PD increased and so the op-amp knew something was going on.  I cant remember the exact circuit but I think it was arranged open loop and was used to illuminate a bulb.

I also recall that he had two such circuits, one for each direction of the current, each feeding its own bulb so on teh control panel it would be one colour for one direction and a different one for the other.

Nowadays I would just use a PIC, and for 009 use a smaller resistor.
;)

[Hugh Norwood]

Opto isolators?

[Graeme Dunbar]

Thanks both. I am inclining towards an electrical track circuiting approach, though the extra cuts in the rails and soldering to them does not fill me with glee.

I think I would go for the opto isolator (photo interrupter /  light gate) approach in off-scene areas. I think they offer a good combination of reliability and ease of placement and adjustment. It is just that I am not convinced about the reliability of upward facing detectors hidden between sleepers in scenic areas.   Fine I think at home where the ambient lighting is known factor, but less so in an exhibition hall. It is probably no longer an issue with the move to LED lighting, but traditional incandescent studio/theatre type lighting is a nightmare for anything involving IR sensitive detectors.

Another aspect is that track circuiting operates over a whole section whereas optical sensors are general spot detectors. Good for spot detection but not so much for occupancy within a block.

There are reliable track circuit detectors for DCC, but many traditional designs for DC work with older locomotives but there can be issues with newer ones - the locos are just too sensitive and react to them either slowing down or creeping along if stopped. I have a possible solution, but it is complex and was hoping for other ideas. There is an ancillary benefit of my idea though that may sway things. Many electrical track circuit designs are polarised and have to be repeated for up and down running whereas my idea is independent of track polarity.

Tune in on Wednesday to find out more!  ;D Plus an update on the box file layout revealed at the last ScOONs meeting!

[Hugh Norwood]

I wasn't thinking along those lines, rather an opto isolator in series with each track section (i.e. in the power circuit) it would then give a signal if track power was being drawn in that circuit....

[Graeme Dunbar]

I wasn't thinking along those lines, rather an opto isolator in series with each track section (i.e. in the power circuit) it would then give a signal if track power was being drawn in that circuit....

That sounds interesting and with bipolar/AC opto isolators it could work with track set for either direction.

[Dave Cooper]

I have a scout meeting that should be over by 8.30, but dont wait for me.
SR

Thanks Stephen. I've got a couple of things on the go. Does anyone have any thoughts of track circuit detection (for DC)?

I think I saw a club-type group at an exhibition in Bristol. They specialize in (DIY) electronics for model railways and I seem to remember that train-track sensing was one of their modules. Think I picked up one of their leaflets at the time. I'll see if I can find it...
ps sorry to have missed the Zoom (again !), I'm trying to fix a guitar special effects processor at the moment - main suspects are a group of 20+ year old electrolytics.   

[Graeme Dunbar]

I have a scout meeting that should be over by 8.30, but dont wait for me.
SR

Thanks Stephen. I've got a couple of things on the go. Does anyone have any thoughts of track circuit detection (for DC)?

I think I saw a club-type group at an exhibition in Bristol. They specialize in (DIY) electronics for model railways and I seem to remember that train-track sensing was one of their modules. Think I picked up one of their leaflets at the time. I'll see if I can find it...
ps sorry to have missed the Zoom (again !), I'm trying to fix a guitar special effects processor at the moment - main suspects are a group of 20+ year old electrolytics.

Thanks. That sounds like it could be MERG, the Model Electronic Railway Group. https://www.merg.org.uk/

I'm a member. They have a range of 'TOTI' (Train On Track Indicator) modules, but I'd like to look for other ideas.

[Dave Cooper]

Hi Graham,

Yes, I think that was the one. They had a small layout running with some of their kit-based modules in action. I'm thinking of building some of their kits as a way of learning more about electronics....

I have an Arduino 'starter' set, but am stuck with the software part - ie what 'C' components does one need /how to download /access the libraries etc, etc.

Best regards,
Dave

[Graeme Dunbar]

Hi Graham,

Yes, I think that was the one. They had a small layout running with some of their kit-based modules in action. I'm thinking of building some of their kits as a way of learning more about electronics....

I have an Arduino 'starter' set, but am stuck with the software part - ie what 'C' components does one need /how to download /access the libraries etc, etc.

Best regards,
Dave

I know I did bit on Arduino in an earlier SIG Zoom meeting, but if you like I could do a 'get you started' session. The last one was a bit 'theoretical' and dealt with comparisons with other systems. We could arrange a one-to-one Zoom if you like.

Which version do you have? I guess a 'Uno'.

[Dave Cooper]

Hi Graham a 'one-to-one' would be great. I have a new Windows 11 laptop now.

The Arduino kit is called "Super Starter UNO R3 Project" (I think the chip is actually an 'Elegoo' clone). There is a CD with it but the instructions are a bit 'Chinese'....

I would probably need some instructions on how to get the laptop going on Zoom as well if that's OK ? Time and date to suit you.

Best regards,
Dave

[Graeme Dunbar]

Hi Graham a 'one-to-one' would be great. I have a new Windows 11 laptop now.

The Arduino kit is called "Super Starter UNO R3 Project" (I think the chip is actually an 'Elegoo' clone). There is a CD with it but the instructions are a bit 'Chinese'....

I would probably need some instructions on how to get the laptop going on Zoom as well if that's OK ? Time and date to suit you.

Best regards,
Dave

Hi Dave,
Perhaps we could take this onto 'PM' or email as I imagine there could be a bit of too-ing and fro-ing ins getting things set up. My PM and email links should be displayed if you click on my name to the top left of the message or you can contact through the Electronics SIG mailbox I set up: 009electronicssig@gmail.com.

If set up a Zoom call and email you the link to join the call all you should have to do is click on the link. Windows 11 might even install what is necessary at the time you click on the link, though I'm not certain of that.