Any Question Answered

[Crosland]

3 hours ago, Donw said:

The MERG circuits for frog juicers include two which are innovative.  Julian Coles designed one that rather than look for an excess current looks instead for a colapse of the voltage across the track when a short occurs. This enables a quicker response.

 

A short is a short and detecting voltage drop is no faster then detecting current, all other things being equal.

 

Julian's circuit biasses the frog voltage somewhere between the two rails (with resistors) and looks for a direct connection to one rail or another. The resistors ensure there is never a short circuit between the two rails. It needs some fairly clever monitoring in the PIC that controls it. I claim the credit for suggesting this idea to Julian (which he acknowledged)  

[A. Bastow]

36 minutes ago, queensquare said:

The tie bar on a point has to be physically thrown by something, doesn't matter what, so why not just use that movement to work a microswitch at the same time. All this frog juicer stuff just seems to be a very complicated way of solving a very simple problem. Somebody once told me that the advantage of them is that you can run through a point that set against you without it shorting - presumably the train then falls off the track so I can't see much advantage.

jerry, a great believer in the KISS principle.

Hi Jerry,

 

I am reluctant to use microswitches because I have had bad experiences in the past, albeit 10 years ago now. 

Might be time to revisit with higher quality equipment? 

[Donw]

1 hour ago, Crosland said:

 

A short is a short and detecting voltage drop is no faster then detecting current, all other things being equal.

 

Julian's circuit biasses the frog voltage somewhere between the two rails (with resistors) and looks for a direct connection to one rail or another. The resistors ensure there is never a short circuit between the two rails. It needs some fairly clever monitoring in the PIC that controls it. I claim the credit for suggesting this idea to Julian (which he acknowledged)  

 

The current has to rise sufficient to be recognised as a short rather than say a starting load of a big loco. Whereas the voltage drop would not occur for any other reason I think. Certainly  from the oscilloscope  screens Julian posted it seemd very quick and the current didn't reach such a high value. Perhaps that was due to the idea of using the resistors my comment was based on Julians original post.

 

Don

[Donw]

1 hour ago, queensquare said:

The tie bar on a point has to be physically thrown by something, doesn't matter what, so why not just use that movement to work a microswitch at the same time. All this frog juicer stuff just seems to be a very complicated way of solving a very simple problem. Somebody once told me that the advantage of them is that you can run through a point that set against you without it shorting - presumably the train then falls off the track so I can't see much advantage.

jerry, a great believer in the KISS principle.

 

You make a good point here but I do know people who find using a juicer simpler. The wiring up is the same for a microswitch or a juicer but the juicer doesn't need any adjustment. Convenience over cost. 

It surprised me to find that a lot of people seem to regularly drive against turnouts so it is a problem for them. I think learning to operate properly would be a good idea although with cramped micro layouts it can be easy to just stray over an insulated join. With DCC it will shut the whole system down so is a bit of a pain. Of course signals interlocking and working trap points will fix that.

 

My interest comes from finding crawling under baseboards less welcome these days. I can fit a tortoise or a servo with a flexible operating arm that will take up any slack so they only need rough adjustment when installed. I do not mind an extra bit of electronics to save trying to adjust a micro switch. So I am going to try some.

 

Don

[nick_bastable]

1 hour ago, A. Bastow said:

Hi Jerry,

 

I am reluctant to use microswitches because I have had bad experiences in the past, albeit 10 years ago now. 

Might be time to revisit with higher quality equipment? 

If you use a DPDT switch with servos one side operates the servo the 2nd side energies a relay  ( suitable relay boards for ardunio are cheap )

 

Nick B

[Donw]

4 hours ago, A. Bastow said:

 

I plan to throw tie-bars with wire in tube (with the Mercontrol system).

 

I could be convinced to use servo or stall motor though I have no experience of them. 

 

Adam

 

 

With wire in tube it is usual for both ends to be on the same baseboard so you can have a switch as part of the human end and run wires out to the turnout. Nice and fairly simple unless you do what I have done on one layout (7mm) and saw through a turnout so the tiebar is on a different  board to the frog  which means having to have a link across the join. I  was looking to a juicer as another option to minimise cross baseboard links.

 

I am less in favour of mechanical means I built a 7mm exhibition layout  but found the slack in the mechanical system took up some of the operating movement and operation was not reliable. I had seen adverts for the Tortoise in Model railroader and bought some. It solved all my problems in that only rough adjustment was needed it self adjusted for themal changes and I never had any trouble with the microswitches.

It also had a more profound effect. I was able to put the switches into a small box which I attached to the back of  the handheld controller taping the leads together. My fellow operators found this meant they could pass the two under the layout and operate from out front where is was easier to do the three links. It also proved to be a much better way of interfacing with the exhibition viewers.

You may well feel very different. There is no right/wrong /best way other than what works best for you.

 

Having had the pleasure of operating Bob Harper's Maristow  which had a interlocked lever frame  that is something I would very much like to have but the link from Frame to the turnouts and signals will be electric.

 

I thoroughly recommend operating as many other layouts as you can it is the best way to find out what you like. It  is also a way to find things that do not work for you. People have been kind enough to let me loose on their layout and I am gratefull to them all.

 

Don

 

[justin1985]

19 hours ago, Donw said:

The MERG circuits for frog juicers include two which are innovative.  Julian Coles designed one that rather than look for an excess current looks instead for a colapse of the voltage across the track when a short occurs. This enables a quicker response. The other by Tim Coombs leaves the frog disconnected and uses a low voltage to spot a connection from the Frog to either stock rail and then connects the Frog to that stock rail should both stock rails get connected to the frog in perhaps a derailment the frog is left disconnected. This circuit can be used with DC.

Boards are usually available from other members or you can order them yourself.

 

Hi Don, could you clarify how Julian's circuit is available? I don't remember seeing it in the kit locker when I was briefly a member last year. 

 

One of the things I couldn't get my head around was why MERG kits were only available as kits. All the electronics tinkerers at my local Makerspace seem to go straight from breadboard to ordering ready made surface mount versions of their designs from Chinese "Shapeways" type services (even for one off or small quantities), which seemed cheaper than buying the equivalent through hole components from Farnell etc, let alone getting custom PCBs etched on their own!

 

J

[Donw]

10 minutes ago, justin1985 said:

 

Hi Don, could you clarify how Julian's circuit is available? I don't remember seeing it in the kit locker when I was briefly a member last year. 

 

One of the things I couldn't get my head around was why MERG kits were only available as kits. All the electronics tinkerers at my local Makerspace seem to go straight from breadboard to ordering ready made surface mount versions of their designs from Chinese "Shapeways" type services (even for one off or small quantities), which seemed cheaper than buying the equivalent through hole components from Farnell etc, let alone getting custom PCBs etched on their own!

 

J

 

I suspect that a lot of people enjoy putting together the kits gives them more satisfaction that jusst buying the ready made item. This is true of a lot of modelling. 

Julians design is available in that the design has featured in the journal and on the forum where it was discussed. The details are in the MERG knowledge base  including the Gerber files for the PCB, the schematic and the hex file for the code. I got some auto reverser PCBs from another member who had some spare and some PCBs for Julians current detecting TOTI  from another. 

 

Don

[Caley Jim]

You and me both, Jerry! 

 

Jim

[A. Bastow]

14 minutes ago, Caley Jim said:

You and me both, Jerry! 

 

Jim

 

I thought I was keeping it simple but it seems like I've opened a can of worms! 

 

I was just going to worry about the physical motion of the tie-bar and let the technology take care of the polarity on the frogs! It's given me so much more to think about than I initially intended! 

 

I think I'll stick with my 4ft test track for now, haha.

 

Adam

[Izzy]

On the keep-it-simple theme and if you are wary of micro-switches then perhaps this design might be another(!) idea to consider. My latest batch of hacked servos for point control. These were intended until recently for 'upgrading' Priory Road but have been re-assigned this week to a project currently in the works - a micro roundy-roundy.

 

 

 

Based on the design I have used before with complete success and reliablity, the servos are Tower Pro MG90's - an alternative metal geared version of their SG90 - coupled to a DPDT switch. this controls the servo movement in conjuction with either a SPDT or DPDT on a panel (depends if you want any electrical inter-locking) provides frog polarity changeover, and sets the servo movement. The power is provided by a 4-pack of re-chargeable AA's, so totally independent of whatever control system is used, DC or DCC.

 

Cost is minimal. The servos were £2 each (e-bay) while the switches come from Expo Tools - the micro ones are needed - at again £2 each, so £6 in total plus wire etc and some time and effort.

 

How you connect them up to whatever tie-bar system you use is up to you. Action is fast as they need the full voltage to ensure the DPDT throws properly but I have not found it an issue. Still much better than a solenoid.

 

As an aside these MG90's are much better being metal geared, no wrecked gears if anything goes pear-shaped at any time as there are no limit stops so with the electronic bits pulled out 360 degree rotation can be obtained if needed.

 

 

Edited August 16, 2022 by Izzy
restore images

[justin1985]

20 hours ago, queensquare said:

The tie bar on a point has to be physically thrown by something, doesn't matter what, so why not just use that movement to work a microswitch at the same time. All this frog juicer stuff just seems to be a very complicated way of solving a very simple problem. Somebody once told me that the advantage of them is that you can run through a point that set against you without it shorting - presumably the train then falls off the track so I can't see much advantage.

jerry, a great believer in the KISS principle.

 

But that depends on what "complicated" or "simple" are to you, Jerry!

 

For me (I'm in the minority amongst 2mm modellers, I know) anything mechanical is "complicated". Cranks, cams, working out throw distances, how much slack or flex in a mechanical linkage, are BAFFLING to me! "Just" use a microswitch? I've wasted HOURS trying to get microswitches aligned to reliably "click" from the tiny throw of a 2mm turnout, while not getting in the way of other things, or stopping the tiebar from moving freely.

 

But, for me, electronic systems are "simple". Something like a Frog Juicer might be complicated circuitry inside, but if it is a "black box" that can be plugged in and trusted to do its job, then that is "simple", for me. I might not know the precise details of what goes on in the "black box", but if it just does it, then its "simple"!

 

I totally get it that a (commercial) frog juicer is a "dirty" solution to a problem that can be solved more elegantly in engineering terms, but if it does the job, then surely it is a horses for courses question? Dare I wonder if this might even be a generational difference? Or at least a difference between those who had a proper education in engineering type issues at school, and those (like me) who didn't?

[Donw]

1 hour ago, Izzy said:

On the keep-it-simple theme and if you are wary of micro-switches then perhaps this design might be another(!) idea to consider. My latest batch of hacked servos for point control. These were intended until recently for 'upgrading' Priory Road but have been re-assigned this week to a project currently in the works - a micro roundy-roundy.

 

 

 

 

Based on the design I have used before with complete success and reliablity, the servos are Tower Pro MG90's - an alternative metal geared version of their SG90 - coupled to a DPDT switch. this controls the servo movement in conjuction with either a SPDT or DPDT on a panel (depends if you want any electrical inter-locking) provides frog polarity changeover, and sets the servo movement. The power is provided by a 4-pack of re-chargeable AA's, so totally independent of whatever control system is used, DC or DCC.

 

Cost is minimal. The servos were £2 each (e-bay) while the switches come from Expo Tools - the micro ones are needed - at again £2 each, so £6 in total plus wire etc and some time and effort.

 

How you connect them up to whatever tie-bar system you use is up to you. Action is fast as they need the full voltage to ensure the DPDT throws properly but I have not found it an issue. Still much better than a solenoid.

 

As an aside these MG90's are much better being metal geared, no wrecked gears if anything goes pear-shaped at any time as there are no limit stops so with the electronic bits pulled out 360 degree rotation can be obtained if needed.

 

 

 

I presume with no limit stops you are just taking the power off when the turnout has operated, or does the DPDT cut the power off  when it operates sufficiently.

 

Don

 

 

[Donw]

7 minutes ago, justin1985 said:

 

But that depends on what "complicated" or "simple" are to you, Jerry!

 

For me (I'm in the minority amongst 2mm modellers, I know) anything mechanical is "complicated". Cranks, cams, working out throw distances, how much slack or flex in a mechanical linkage, are BAFFLING to me! "Just" use a microswitch? I've wasted HOURS trying to get microswitches aligned to reliably "click" from the tiny throw of a 2mm turnout, while not getting in the way of other things, or stopping the tiebar from moving freely.

 

But, for me, electronic systems are "simple". Something like a Frog Juicer might be complicated circuitry inside, but if it is a "black box" that can be plugged in and trusted to do its job, then that is "simple", for me. I might not know the precise details of what goes on in the "black box", but if it just does it, then its "simple"!

 

I totally get it that a (commercial) frog juicer is a "dirty" solution to a problem that can be solved more elegantly in engineering terms, but if it does the job, then surely it is a horses for courses question? Dare I wonder if this might even be a generational difference? Or at least a difference between those who had a proper education in engineering type issues at school, and those (like me) who didn't?

 

I think there is rather more to it that just education. I have an engineering background and am capable of lots of things from making replacement windows through brick and masonary work to rebuilding a hipped roof. One thing I found difficult was adjusting relays. I knew how to do it but getting the right contact pressure was difficult I was not good at fine adjustments. undertanding electric circuits writing code are all much simpler to me. We all have differing levels of natural skills and to spend your time doing something that may irritate rather than being a pleasure is not my idea of a hobby. For you I suspect the cost of a juicer would be well worth it and spend your time doing things that are more satisfying. The commecial juicers work well many find them a fit and forget solution.

 

Don

[Izzy]

On 25/03/2021 at 12:41, Donw said:

 

I presume with no limit stops you are just taking the power off when the turnout has operated, or does the DPDT cut the power off  when it operates sufficiently.

 

Don

 

 

 

The DPDT acts as the limit stop as well as cutting the power. The small Expo switch is required since the handle end sits in the servo arm to accomplish this, and larger switches have handles too big in diameter. A larger hole needs making even for the small one.

 

Edited August 16, 2022 by Izzy

[Caley Jim]

2 hours ago, Donw said:

....We all have differing levels of natural skills and to spend your time doing something that may irritate rather than being a pleasure is not my idea of a hobby.

For me, the simplicity of the mechanical approach is that if something goes wrong, it's fairly simple to work out where the fault is and fix it.  Perhaps the fact that I have been endowed with the gift of enough patience (or is it dogged determination?) to fiddle about with something until I get it to work.   I can understand basic electrics, current, voltage, resistance, but beyond that is beyond the comprehension of my little brain (believe me, I've tried!).  Fit and forget is all very well until it goes wrong (Sod's 1st law - If something can go wrong it will!) but if it's part of some complex circuitry, what bit has gone wrong?

 

I've used wire in tube for 50 years and the main things I've learned are 1) you need excess throw at the operator's end with omega loops taking up the remaining excess at the 'working' end and 2) you need the tube to be well secured to the baseboard at frequent points along its length in order to avoid losing throw through it flexing.  This is especially the case with the MSE wire-in-polythene tube which I have on Kirkallanmuir.

 

As @Donwmentioned above (why don't we have post numbers any more?) it's down to what you find easiest to understand and make work.

 

Jim

Edited March 25, 2021 by Caley Jim

[-missy-]

2 hours ago, Donw said:

 

I have an engineering background and am capable of lots of things from making replacement windows through brick and masonary work to rebuilding a hipped roof.

Don

 

I have a few engineering qualifications but I can say I have never touched any bricks, windows, etc throughout my engineering life! I think I have missed something somewhere...

 

Julia :p

[Ian Smith]

2 hours ago, justin1985 said:

 

But that depends on what "complicated" or "simple" are to you, Jerry!

 

For me (I'm in the minority amongst 2mm modellers, I know) anything mechanical is "complicated". Cranks, cams, working out throw distances, how much slack or flex in a mechanical linkage, are BAFFLING to me! "Just" use a microswitch? I've wasted HOURS trying to get microswitches aligned to reliably "click" from the tiny throw of a 2mm turnout, while not getting in the way of other things, or stopping the tiebar from moving freely.

 

Personally I wouldn’t put the micro switch at the turnout end of a linkage - the amount of throw at a 2mm tie bar (or even a 4mm one) is probably far too small to reliably throw the micro switch.

 

I would generally put it at the panel end of a linkage where the throw will be much greater or at least somewhere in the movement that provides sufficient throw, be that a panel switch or within the movement of the point motor/servo before any reduction to the small amount of tie bar throw.

Ian

[Donw]

53 minutes ago, -missy- said:

 

I have a few engineering qualifications but I can say I have never touched any bricks, windows, etc throughout my engineering life! I think I have missed something somewhere...

 

Julia :p

 

Hi Julia  I statrted out as an Apprentice Telephone Engineer  but  among the various things I learnt about included building Manholes and joint boxes, laying ductswork. I could have sat back and said not interested in that stuff. But if we were working alongside people I took an interest in what they were doing.

A lot of things I did was because we wanted to live in an old cottage in a nice area but didn't have the money to employ builders so we ( that incudes Marion)  found out how to do things and did them. But although I aquired a lot of skills over the years fine adjustments is really not my forte. 

 

Don 

[2mm Andy]

3 hours ago, -missy- said:

 

I have a few engineering qualifications but I can say I have never touched any bricks, windows, etc throughout my engineering life! I think I have missed something somewhere...

 

Julia :p

Having seen some of your woodwork I can believe that!  I do look at your mechanical engineering wizardry with considerable envy though.

 

Andy (another professionally qualified engineer).

 

[Crosland]

On 25/03/2021 at 08:06, justin1985 said:

 

Hi Don, could you clarify how Julian's circuit is available? I don't remember seeing it in the kit locker when I was briefly a member last year. 

 

One of the things I couldn't get my head around was why MERG kits were only available as kits. All the electronics tinkerers at my local Makerspace seem to go straight from breadboard to ordering ready made surface mount versions of their designs from Chinese "Shapeways" type services (even for one off or small quantities), which seemed cheaper than buying the equivalent through hole components from Farnell etc, let alone getting custom PCBs etched on their own!

 

Julian posts his designs on the MERG Forum and in the Journal, for which you need to be a member. Only designs that are adopted by MERG become kits ion the kit locker. There are simply too many different member developments for them all to become MERG kits. Some members supply their own kits or bare PCBs.

 

Kit supply by MERG is seen as a way around CE marking rules, and maybe other issues, which would apply to selling finished items. It's completely different to makers making a few for their own use or selling a few to friends within the £1000 tax free trading allowance.

 

There's a continuous debate within MERG about using more surface mount or having the "heart" of modules manufactured as SMD assemblies but unless members step forward and actually do something to make it happen, it will not happen. 

[garygfletcher]

is there a standard hight used from the ground to the very top of a platform?

[2mm Andy]

8 minutes ago, garygfletcher said:

is there a standard hight used from the ground to the very top of a platform?

 

There is a standard height from rail level to platform level. It is shown on this diagram;

 

http://2mm.org.uk/standards/loadinggauge.htm

 

It is a standard that changed over time though - early railways had lower platforms, and some stations kept those platforms until they closed, so the answer depends to a large extent on the period and location you are modelling.

 

Andy

 

 

[garygfletcher]

2 minutes ago, 2mm Andy said:

 

There is a standard height from rail level to platform level. It is shown on this diagram;

 

http://2mm.org.uk/standards/loadinggauge.htm

 

It is a standard that changed over time though - early railways had lower platforms, and some stations kept those platforms until they closed, so the answer depends to a large extent on the period and location you are modelling.

 

Andy

 

 

 

Thats exactly what I was after, thanks Andy!

[Valentin]

Is it safe for a mill to be used as a saw? As in cutting, with a slow, constant X / Y movement, 0.7mm P/B sheet.

 

 

Edited March 28, 2021 by Valentin