Frog Juicers - Light Loco Problem

[Bufferstop]

Geoff I can see where the switch rails are cut before the crossing on the second point, are they similarly cut on the first one. It looks as though the two juicers are interacting the multiple IRJs should hopefully do it. I'd have given up on them by now and searched my parts boxes for a couple of microswitches, or even slide switches at the operating end of the rods.

[Dad-1]

Hi Bufferstop,

I don't like to be beaten by a few bits of metal & plastic !!
All rails are cut as required and in both theory & practice all works as it should - ONLY
when a second loco is on the tracks.
I was thinking last evening about the platoon of troops on a light bridge, break step, OR
break the bridge …….. This had me thinking (I know a bad habit).
I have both juicers connected in the same way, each driven by black onto the left pad,
with red onto the right pad. It shouldn't make any difference because they work both
ways. However all it takes is a few minutes to change them around on one juicer.
Nothing to loose, it'll take more time removing stock & locos than changing the wires.

I don't have the required ceramic capacitors, or 100-150 Ohm 2-3 watt resistors to make
a terminator which should remove ripples without damaging the AC wave form. So back
to that 'Thinking' lark - IF a decoder fitted locomotive doing nothing other than sitting on
the tracks smooths out enough for the problem to be hidden, would a spare decoder wired
somewhere between my black & red tracks do the job ? Being AC I always struggle to
explain which 'polarity' is which.
The only difference would be the damping mass of the parked locomotives wheels and
pickups, which in theory shouldn't be enough to make any difference ?
The advantage of that method would be that I do have spare decoders knocking around.

The only other 'fix' I could try would be lifting the track, grinding off enough from that
25 mm long spacer piece to add IRJs at all 4 corners. That would completely separate
the two points - except that they are all fed from the same underboard Bus power supply.

Where is Flashbang when you want him ?

I suppose being more or less confined to home for at least another 2 - 3 weeks ? It keeps
my rather sluggish brain working.

Just in case anyone starts claiming problems are made worse by using Hornby decoders I
shall get my two Roxey Mouldings locos out, both are fitted with Lenz best quality mini
decoders and I'm certain the problem will be there just the same.

Geoff T

[Bufferstop]

I always refer to the rails and the wires connected to them as feed and return, works for DCC and DC as even on analogue the rails aren't dedicate pos and neg. Analogue supply is just an irregular alternating wave of extremely low frequency.
At this stage I'd go with anything that works. Solving what is happening, even by suck it and see methods is going to involve isolating that bit of track. To save lifting it I'd go in with the slitting disc, then fill the gaps later with Araldite and grind it to shape.

[RAF96]

Rather than think of DCC as polarity think of it as phasing.
If you get your phasing out of synch - i.e. one waveform rising when the other waveform is falling then its the same as crossing + & - polarity.

[Dad-1]

Hi RAF96 & Bufferstop,

Ahh, sorry about the identifications, main thing is I know what I've done, but getting others to understand can
be difficult, although I don't always know what I'm doing !!
So a change of wires into the Frog Juicer made no difference, didn't expect it to, but it was easy to try.

What I'm currently doing HAS worked, there was a spare new unused small 'N' decoder that No.1 son
had obtained on Ebay a year or so back for a tenner. He bough 4 if I recall correctly, he must have used the others.
This has been soldered onto the ends of my headshunt track, red onto right, black onto left as usual DCC practice.
The result is a perfectly working layout using the Sentinel at minimum speed, slower than I would normally to load
the system, well at least make the Sentinel's decoder have to work hard.

A Question : What is that doing ????????? Apart from making it work !!

I don't have spare auto bulbs and if I have to purchase anything I expect the DCC Concepts 'Terminator' would do
the job, hidden neatly under the layouts boards.

Never had a problem like this to solve before.

Geoff T

[Bufferstop]

Terminators are something that has come from communication systems. When you send a pulse down a cable you get reflections coming back from any significant joints or changes in the conductor, and you get one heck of a reflection back from the open end, so they put across it a resistor of the same value as the theoretical resistance of the cable at it's working frequency. The cable used in comms is usually 50ohms, for TV systems it's 70. The terminator is just a connector with the appropriate resistor across it. DCC terminators aren't quite the same, they are more like a spark or spike quench that is used across contacts to absorb any spike coming back from disconnecting a reactive load. Disconnecting a decoder and a bit of trackwork and rapidly reconnecting it the opposite way round is going to send back a spike of opposite polarity to the waveform, which looks to the other juicer like a short circuit, so it flips and then flips back, chopping up the supply. The load across the bus ensures that enough current is flowing to overwhelm the spike. The relatively short lengths of track involved mean there is less capacitance to absorb any spikes, so they are going to go anywhere they can and the frog juicers are the only place available. The redundant decoder is providing the spike quenching that a terminator would, it probably puts across the line a bridge rectifier with a capacitor on its output, needed to power the decoder's various functions.

[Flashbang]

Hi

Im here!!!

Make your own DCC filters - Cost around £0.50 - £0.60p per filter! They are nothing more than a series resistor and ceramic capacitor connected across the rails or DCC bus pair of wires. Resistor wattage ideally try to get 2 or 3 watt ones and a Ceramic capacitor of 0.1uF with a voltage rating rating of 50v or more will be fine. My website shows how to make them here >>>> https://www.brian-lambert.co.uk/DCC_Pag ... Bookmark16 Components needed and their part numbers are shown and I get mine from Bitsbox, but of course there are many other suppliers. I these days of shop closures internet sales are still possible in most cases and even ebay can be used

[Dad-1]

Thank Heavens for that Flashbang !!

MMMmm that cheap to make, so difficult to resist that option.

I wonder if you've come across this problem before ? I've only used one Frog Juicer before and that on a single
point application which works fine. What really confused me was that another 'resting' loco cured it, just seemed
very strange to me.

Oh and thanks as ever for you expertise. I do sometimes muddle my way through and find an answer, just wish I KNEW what I was doing !!

Geoff T.

[Flashbang]

Hi Geoff
I don't use Frog Juicers or any similar other makes.
I prefer to use a physical change-over switch operated normally by the point motor moving over to set the points frog polarity.
Items that detect short circuits occurring then as the short current increases flip the power to correct, are really relying on a fault current to be generated to operate and IMO are not really the best method. The so called fault should be removed before it ever becomes a fault!
The same applies to a DCC reverse loop module. There are now some that work on Infrared detection or other detection means than the short occurring. But many will use the conventional RLM as they are simple to use devices.

[Bufferstop]

Hi Flashbang, you seem to share my feeling that relying on a fault to start an operation isn't good practise. Frog juicers and reverse loop modules rely on being able to detect a short circuit before the main supply does. My reaction to the first one I saw was that if that unit can spot a short circuit first what happens when you use a similar circuit in the power unit to spot short circuits. It's bound to happen someday.
Switching the polarity when it's under load is bound to create a spike whereas mechanically switching it when the route is set up avoids the problem. Geoff chose a rather unusual combination of mechanically operated points and frog juicers, a couple of microswitches against the ends of the operating rods, or slide switches with the end of the rods hooked into the dollies would, I think, have met his aim to be unbustable.

[Flashbang]

<SNIP>
..... a couple of microswitches against the ends of the operating rods, or slide switches with the end of the rods hooked into the dollies would, I think, have met his aim to be unbustable.

Absolutely

With any point frog polarity switch it needs to be of the 'Break before Make' type, then there is a clean cut off before power restoration.

[Dad-1]

Had Flashbang not given the product codes I'd never have found them !!
Now on order.

I had used a home made polarity switch before, but too vulnerable for general
club knock around use.



A neo magnet between 2 screws, you get a super loud snap as you change polarity !!
Fully adjustable as well.

Geoff T.

[Bufferstop]

No problem working out which wire goes where Geoff. I bought a packet of these little fellas from Squires at one of the exhibitions.

[gppsoftware]

Yes, unfortunately, these 'frog juicer' devices are one of those things, like terminators, designed to part the unwary from their money!
With the exception of turntables, return loops and perhaps, triangle junctions, juicers are really not necessary.

The OP mentioned that two turnouts were involved. With such a small number of turnouts involved, why not just wire the turnouts correctly using the time-served method of wiring live frog turnouts: http://www.mrol.com.au/Pages/Vu/LiveFrogWiring
Do this and you'll find 'juicers' are completely unnecessary.

I am also of the view that relying on a fault (short) is bad practice.

[Dad-1]

Ahh gppsoftware,

If you had read the whole saga you would have noted that the points were fully bonded, in fact exactly
as per best practice. However using manual point operation there was no simple incorporated frog
switch opportunities, unless one used separate micro switches and devised some under board mechanical
operation for them.
Frog juicers offered a suitably simple answer for total track power reliability as needed in a 48" long shunting
layout where speeds are always at a crawl. Now with a suitable quench circuit introduced it runs as required.
I'd agree not good practice, but this needs the minimum of moving parts as I know the layout will suffer a
degree of abuse when different club members take out to exhibitions.

Geoff T.