high frequency track cleaning for DCC

[Pete the Elaner]

Thanks. I wasn't trying to be argumentative; I was just trying to understand how it works.

Explains why I got a nasty kick once or twice from my friend's relco-equipped DC layout causing me to shout loud expletives at an expo. I am convinced he did not wire them properly , so that probably didn't help.

 

So the previously mentioned method of mixing them 'safely' effectively reduces the voltage?

Isn't that defeating the object of having the HF cleaner in the first place?

[bertiedog]

Relco operation depends not on an ultra high voltage, in fact about 40 VAC is the lowest that track cleaning circuits will work with, but Relco does generate higher spikes. My own designed circuits are limited to about 100 VAC, I do not know the upper limit for a Relco, offhand, but I seem to remember testing on a scope with spikes of about 200 VAC peak at very, very low ampage.

 

The air is ionised in the gap, just like in a spark plug in a car, and voltage applied causes a small current to flow, which being AC breaks the insulation properties of the air further and reconnects the current flow. The unit does nothing if the contact is OK, and stops as soon as contact is restored, in milli or micro seconds.

 

The new US HF "cleaning" units work with voltage limitation, and fast clamping of the signal, and do not interfere with the Digital signal to the chip, and should not cause any breakdown in the chip or the board.

 

Note very carefully the bad use of the word cleaning, as I mentioned before the last thing these units do is clean the track!!! They just maintain a circuit, that's all, they do not remove, destroy, vaporise, or teleport the dirt away!!!!

 

The track and wheels must be clean to start with, and the Relco and equivalents maintain contact if the dirt gets in the way, that's all.

 

Stephen.

[Ron Solly]

Reading all of the above especially this piece about the new unit

The Electrak works by generating a high voltage, high frequency signal that is current limited to about 2 mA.

Due to the current limit, almost anything that is attached to the rails (e.g. a motor in DC or a decoder in DCC) will act as a short circuit to the Electrak. Thus, loads on the rails normally short the generated signal. Current flows from the generator, out one wheel set, across the rail load, into the other wheel set, and back to the generator.

Due to the low impedances involved, there is very little voltage in this loop (hence its safety and compatibility with DC and DCC). When the Electrak encounters a spot in the track that does not provide a good connection to the Electrak wheels (i.e. a dirty spot), the full 216 volts of the generator appears across this high impedance.

This high voltage acts to break up the contamination, and thus clean the track.

 

Now as I read it, as soon as a bit of dirty track is found & the short circuit created by the load being a decoder disappears, the unit reacts & off goes a high voltage spike cleaning track - I am lost to understand this as surely if the dirty spot was 2" long & the loco was a large 6 axle diesel that picks up on all whels, the short will still be there so the unit could never fire! Am I wrong? What good is the unit then? Would Relco on DC be any better in this situation?

Edited December 27, 2009 by Ron Solly

[bertiedog]

Reading all of the above especially this piece about the new unit

The Electrak works by generating a high voltage, high frequency signal that is current limited to about 2 mA.

Due to the current limit, almost anything that is attached to the rails (e.g. a motor in DC or a decoder in DCC) will act as a short circuit to the Electrak. Thus, loads on the rails normally short the generated signal. Current flows from the generator, out one wheel set, across the rail load, into the other wheel set, and back to the generator.

Due to the low impedances involved, there is very little voltage in this loop (hence its safety and compatibility with DC and DCC). When the Electrak encounters a spot in the track that does not provide a good connection to the Electrak wheels (i.e. a dirty spot), the full 216 volts of the generator appears across this high impedance.

This high voltage acts to break up the contamination, and thus clean the track.

 

Now as I read it, as soon as a bit of dirty track is found & the short circuit created by the load being a decoder disappears, the unit reacts & off goes a high voltage spike cleaning track - I am lost to understand this as surely if the dirty spot was 2" long & the loco was a large 6 axle diesel that picks up on all whels, the short will still be there so the unit could never fire! Am I wrong? What good is the unit then? Would Relco on DC be any better in this situation?

Inserted Edit I think you may be mixing up terms for a "short" , with a "break", which is what sets off Relco. I do see that you see the decoder and motor load as a "short", and this goes as the break occurs, I agree, quite right, the lack of flow is the set off point.

 

Covered before in the replies, if many contacts are made the unit will not work, but then the loco is running fine,so it is not needed at that point.

 

Most of the time it does nothing, it only fires when needed, when run right, all is all right!!

 

It does not clean 2 inch strip of dirt, it does not clean at all, it gets the current flowing only in the micro second the current vanishes, breaks the gap, and then microseconds later the normal operation returns.

 

It's normal operation is too "not be operating", just like a fire brigade, always there, but you hope never called upon, so to speak.

In practice it does fire up all the time, randomly and it does indicate this with the cleaner wheels evidence, although again it does not clean them off as such, it keeps clean wheels cleaner.

 

Stephen.

[Ron Solly]

Thanks Stephen.

[Oakydoke]

I was once told that it was a myth that Relco's and other similar devices cleaned the track. It was suggested that I should think of these so called track cleaners as an electronic hand from the sky, which helped push the trains along when the current was affected by dirty sections of track.

Bertiedog seems to be confirming that view.

[Simon_R]

I had a relco on my first layout when i was a kid. I was mostly old Hornby stell track and was a constant battle to clean hence being draw into the Relco idea. It never really did anything and i got rather sick of the electric shocks i used to get when touching the track.

One thing i did notice was that if i left the layout powered up by accident my dad would go mental because the relco would put out that much HF interferance that he couldn't get Radio 4 in the kitchen! It seems the track was acting as an antenna and the relco a short range HF transmitter!

[bertiedog]

I had a relco on my first layout when i was a kid. I was mostly old Hornby stell track and was a constant battle to clean hence being draw into the Relco idea. It never really did anything and i got rather sick of the electric shocks i used to get when touching the track.

One thing i did notice was that if i left the layout powered up by accident my dad would go mental because the relco would put out that much HF interferance that he couldn't get Radio 4 in the kitchen! It seems the track was acting as an antenna and the relco a short range HF transmitter!

 

More notes for poster and other users.....use advice as relevant....

 

I am afraid the results you got were typical, as Relco did not supply the clearest of instructions, and modified the unit to two ways of operating, one being in series with the whole lot, which gave the interference, and powering with a separate feed with suppressing capacitors and RF chokes, which was the later way now adopted by other makers. The capacitors and the correct fitting, preferably with RF chokes as well are vital, and all locos have to have fully working suppressors and RF chokes as well.

 

Most users are not electrical Engineers, and Tri-ang and other makers barely helped in the old days with decent suppressors.

 

Steel track never worked well with Relco, the chance of a bad contact was more, and the unit fires up all the time. The voltage being felt is in the hands of the Gods, some people are very sensitive to any voltage.

 

The shocks were an indicator the track and loco pick-ups were bad, and the unit was working overtime!! As can only be repeated, first clean everything, and then the Relco keeps it going,(as does DCC on it's own in similar way)

 

People forget the wheel pick-ups being out of contact also made the unit fire up, any loss of contact did, so and an old Tri-ang loco with steel wheels on steel track with slack pick-ups was a very poor recipe for success, the Relco unit must have been running all the time.

 

Quite how an "out of action, but power connected on" track would trip the Relco into continous operation is very difficult to understand, it's impossible in theory, as the Relco shuts off when there is no load, but attempts to apply a high voltage, but it has nowhere to go, unless the track was in some way so corroded that partial current could flow and kept tripping the unit. The proper capacitors and choke in the power feed cures this sort of situation occurring.

 

This condition will not occur on any normal modern track like Peco. Oddly fine scale track with pc sleepers can have trouble, the gaps can conduct if dirt builds up. Make absolutely sure the capacitors are fitted and RF chokes as well.

 

Stephen

[Owen Edis]

What voltage output can be expected from HF track cleaners to check they are functioning correctly 

[Suzie]

Enough to light a neon testing screwdriver.