Electronic Boosters

[Dagworth]

Also suggestions of using a latching relay was made, but the cost is as much as the the DCC chip!, they are expensive devices.

 

http://uk.rs-online.com/web/p/electromechanical-relays/0515511/ £3.05 Hardly expensive. The whole kaboodle would only be a fivers worth of bits.

 

Andi

[bertiedog]

But the rating is 12volt,surely it will need to be a far lower rating to operate in a practical circuit? They don't actually quote a minimum operating voltage, so it looks like the full 12 volts to get it operating. The circuit would still work, but the loco would have to run at a fixed higher voltage level, with a steady voltage the operation would be easy, say a round track,steady speed and a missing or insulated section!!

 

There are other circuits that would meet these conditions to act as a simple "no stall", even a simple floating battery in the loco across the motor would meet the simpler steady speed restrictions, with a steady load,, and no reverse operation. If the speed range is all right at 6 volts, then puting a 6 volt battery across the motor will act as a power source, It would be charged all the time by the 6 volt track voltage, allowing for loses.

 

Also if the loco had a 2 volt motor, a very low current coreless type, then simply putting the power cap across it would work........in theory..

No reverse without a duel circuit., and also not one to try without a precision power supply, as the power caps do not like any over rating voltage, they explode! It would need a regulator, and the circuits already exist, as constant lighting units for LEDS, so find a motor that runs on about 2 volts at 20 ma!!!!!!

 

Stephen.

[bertiedog]

http://uk.rs-online....relays/0515511/ £3.05 Hardly expensive. The whole kaboodle would only be a fivers worth of bits.

 

Andi

 

I may be miss reading it, but the quoted relay appears not to be a latching relay,, but an ordinary relay type,,... power on, it switches,.... a latching relay is a type that changes from one state, off, to an on state, and remains on when power is removed, and that type are £30 upwards. They re-set on resumption of power, or by reversal of power in other types..

An ordinary relay can be wired to keep itself set, latching on with a signal pulse for instance, but needs power to maintain the condition.

 

Stephen.

[Dagworth]

But the rating is 12volt,surely it will need to be a far lower rating to operate in a practical circuit? They don't actually quote a minimum operating voltage, so it looks like the full 12 volts to get it operating. The circuit would still work, but the loco would have to run at a fixed higher voltage level, with a steady voltage the operation would be easy, say a round track,steady speed and a missing or insulated section!!

A 5 volt relay would be an option instead of 12volts, but you would need to add something to stop it being overdriven at full power. The only thing this relay does is change the polarity of the output to the motor, it DOESN'T switch the circuit into or out of use

No reverse without a duel circuit., and also not one to try without a precision power supply, as the power caps do not like any over rating voltage, they explode! It would need a regulator, and the circuits already exist, as constant lighting units for LEDS, so find a motor that runs on about 2 volts at 20 ma!!!!!!

 

Stephen.

Eh? You clearly haven't actually read my description of how the circuit works! The power from the track is rectified but then fed back to the relay contacts which feeds it to the motor, the latching relay is purely a reversing switch that reads the polarity on the track and locks into that state. The cap could be something as simple as a 25v 10uf electrolytic, (pence) as all it has to do is drive the transistor gate to let power out of the battery into the motor in the instances when the cap charge is higher than the track voltage. PLEASE READ THE CIRCUIT DESCRIPTION!

 

Andi

[Dagworth]

I may be miss reading it, but the quoted relay appears not to be a latching relay,, but an ordinary relay type,,... power on, it switches,.... a latching relay is a type that changes for one state, off, to an on state, and remains on when power is removed, and that type are £30 upwards. They re-set on resumption of power, or by reversal of power in other types..

 

Stephen.

 

From my link

I know exactly what latching relays are, I use them a lot in my own layout elecctronics, single coil versions exist that fire one way when power is fed to the coil in one direction and the other when the power is reversed, and hold that state when powered down.

 

Andi

[bertiedog]

The other comments about low current operation were absolutely nothing to do with the suggested circuit, but refer to direct constant lighting style operation of a very low voltage motor

Please note I had already said the circuit should work,

The other comments.were about the rating of the relay and then another different way of just using a capacitor....not your circuit at all.

Stephen.

[Dagworth]

The other comments about low current operation were absolutely nothing to do with the suggested circuit, but refer to direct constant lighting style operation of a very low voltage motor

Ok, but it would have been helpful to have quoted the post you were referring to. Low current motors etc. are going wildly away from what the topic was about and are not really helpful.

 

Please note I had already said the circuit should work,

Yes, but with numerous comments about test tracks, motor draw etc. all of which were completely irrelevant as the circuit will work at any required speed or load.

The other comments.were about the rating of the relay and then another different way of just using a capacitor....not your circuit at all.

Stephen.

And then back to discussing my circuit again in the same posting. As my postings are the only ones mentioning relays it was fairly logical that you were referring to my circuit.

 

Andi

P.S. an apology about the link would be nice...

[bertiedog]

Yes I am sorry about the latching reference, the second link makes it quite clear.

 

I am still not sure about the relay is operating as intended, as it appears to be a cam latching type, a pulse,(AC or DC), arrives,(or a steady voltage),and the relay flips on and another pulse arrives, (or a steady voltage), and it goes off, or a reversal of the contacts occurs in the same conditions.

 

If the original circuit for the relay to control reversing it would have to be a polarised latching relay, where a pulse of positive DC,(or steady DC) latches or changes it, and a then a pulse of negative, (or steady negative), flips it off or makes the change over.

 

The second type of latching relay can be imitated by diodes and two relays of the cam type.

 

Which type is intended in the circuit? I can see the rest of the circuit working, but the operation of the relay seems problematic.

 

Stephen.

[Dagworth]

Yes I am sorry about the latching reference, the second link makes it quite clear.

 

I am still not sure about the relay is operating as intended, as it appears to be a cam latching type, a pulse,(AC or DC), arrives,(or a steady voltage),and the relay flips on and another pulse arrives, (or a steady voltage), and it goes off, or a reversal of the contacts occurs in the same conditions.

 

If the original circuit for the relay to control reversing it would have to be a polarised latching relay, where a pulse of positive DC,(or steady DC) latches or changes it, and a then a pulse of negative, (or steady negative), flips it off or makes the change over.

 

The second type of latching relay can be imitated by diodes and two relays of the cam type.

 

Which type is intended in the circuit? I can see the rest of the circuit working, but the operation of the relay seems problematic.

 

Stephen.

My experience of these relays is that they will change state if the polarity is reversed, I've not come across a pulse on-pulse off version. Every latching relay I've ever seen has worked as I would expect, even twin coil ones will function like that with a pair of steering diodes.

 

This section from the datasheet from the relay linked would suggest that they would work as I would expect.

Andi

[bertiedog]

 

What I think happens is the relay receives power and operates, but this would surely be irrespective of the polarity, the polarity makes no difference unless the relay is a polarised latch type, able to detect the polarity, which a plain cam latch cannot do.

Is this what is intended?........... also as it stands surely turning off the power manually and then re-applying the power would cause a reverse, unless the polarised latching relay is used, as if a plain cam latch is used it responds to either AC, DC or pulses, each application causing a reverse.

 

Stephen..

[Dagworth]

See my edit to my previous reply, the relay is polarised and will switch dependant on track polarity and so would only change when the direction of the controller was changed..

 

Andi

[Dagworth]

I've noticed an error in my original circuit... the cap as shown wouldn't allow the transistor to come on at all, this is it corrected

 

 

Andi

[bertiedog]

It appears then that these relays contain circuitry to give polarisation, cam latch types do not. By a can latch I mean a rotary cam that is nudged by the ciol attaching the arm and causing a rotation each time it operates, this is a plain cam latch, common on PO relays etc They work on AC, CD or pulses.

 

It will certainly work if these relays are polarised, power on would trip, further power or pulse will do nothing till the power polarity is reversed, and then any pulse or steady voltage does nothing more......and so on as each cycle occurs.

 

Polarised types that were mechanical were very complex, I suspect these are simply chipped to do the same job.

 

But I still can't see how the circuit works at lower voltages, the trip voltage of the relay must be important, in other words at lower speeds reversal can't be done, the power will not trip the relay. the power will come from the battery till power is restored, but if the loco is stopped and power put back on in reverse, surely it will still go forward till the relay operates and then go into reverse?

 

Stephen.

[bertiedog]

My comment in the previous post would be wrong if any voltage at all tripped the relay long before the motor moved, so what sort of voltage is the minimum to trip these miniature latched relays? if it tripped at say 2 volts then it would work...I think.,, but if it trips at say 6 volts then the motor sets off in the wrong direction before the relay trips, giving strange operation.

 

Stephen.

[Grovenor]

Andi,

Its going to be very difficult to do a slow start with that circuit when reversing, the relay will need close to its rated voltage to latch up and that voltage will be instantly applied to the motor, which will already have started in the wrong direction before the relay latched.

For this to be successful the controller needs to be modified with a reversing button in the Maerklin style, so you reverse polarity press to latch the relay then start to speed up.

 

Which gets us back to latching relays with a pulse on. pulse off action, these were the standard reversers with AC trains, Maerklin, Lionel etc. often referred to as 'E units'. Trix twin had a modified version to get round the patents, that needed 2 pulses to reverse, one pulse just turning it off.

 

And Bertiedog, while you are going back and reading the datasheets for latching relays before commenting it would be a good idea to go and read the Lenz manuals for their USP system and then tell us where your description is wrong.

 

Regards

Keith

[Dagworth]

If a 5volt relay is used then it will trip at 3.5 volts. The bridge rectifier and the other diode will eat 2.1volts of the track voltage so the motor would only see 1.4volts before the relay fired. Very few loco motors will turn at 1.4 volts.

 

As to the low speed operation of the circuit, the voltage at the base of the transistor is derived from the capacitor. This cannot be higher then track voltage in normal operation. The transistor will only allow power through it from the battery proportional to the voltage applied to its base connection, so in low speed use the voltage available from the battery would be low too. Note that when track voltage and capacitor voltage are the same then no current flows from the battery as the diode above the transistor is reverse biased and won't conduct, all motor power comes from the controller. Now when the loco hits a dirty spot the track voltage drops instantly to zero, the transistor output voltage is then higher than track power (which is zero), so the diode becomes forward biased and conducts, allowing battery power to reach the motor keeping the loco moving. If track power is not very quickly restored then the capacitor discharges through the transistor, reducing the voltage available from the battery as the capacitor and hence transistor base voltage drops. The same happens when the controller is turned down, the cap - transistor - battery kicks in but only for as long as it takes for the charge in the cap to drop to track/controller voltage. With a low value capacitor this would only be a couple of seconds, just long enough to get the loco over the dirty patch as desired.

 

Andi

[bertiedog]

Andi,

Its going to be very difficult to do a slow start with that circuit when reversing, the relay will need close to its rated voltage to latch up and that voltage will be instantly applied to the motor, which will already have started in the wrong direction before the relay latched.

For this to be successful the controller needs to be modified with a reversing button in the Maerklin style, so you reverse polarity press to latch the relay then start to speed up.

 

Which gets us back to latching relays with a pulse on. pulse off action, these were the standard reversers with AC trains, Maerklin, Lionel etc. often referred to as 'E units'. Trix twin had a modified version to get round the patents, that needed 2 pulses to reverse, one pulse just turning it off.

 

And Bertiedog, while you are going back and reading the datasheets for latching relays before commenting it would be a good idea to go and read the Lenz manuals for their USP system and then tell us where your description is wrong.

 

Regards

Keith

The description is simpler than the specification, there are several versions published and it is only an outline. Lenz did notpublish any details for a long while.

[peach james]

The idea of using the “gold caps†surfaced in one of the last issues of MRC. (May, 1986, if I am right). The author of that article used a 1 F /6V capacator to provide power for a Lima pancake motored diesel, and a Hornby HST. In order to reverse the diesel, he used a dpdt switch mounted on the buffer beam. There almost certainly are electronic ways to do so, but they mostly mean that you end up with as much circuitry as a DCC chip.

 

 

The rate of discharge for the caps are usually quite high, such that a 500ma draw should be able to be sustained but the voltage will be dropping towards 0 on a log scale.

 

Here- the Panasonic formula is

 

T=C (Vo-V1)/I+I(leak)

 

Where C=Capacitance in F

V0= Original Voltage

V1=Finish Voltage

I=current draw

I(leak) =.2 uA

 

So, lets plug them in

 

T= 1*(6-3)/(.5+.000002)

=6 seconds for a farad.

 

The 6V limit is quite common for the larger caps. I am not sure if 12v caps are available, but the insulation is a problem. From memory of the article referenced above, the 1F caps above could have had several of them put in series in the body of a HST.

 

 

http://www.panasonic.com/industrial/components/pdf/about_gold_capacitors.pdf

 

 

Note, in my view, a big mechanical flywheel may be preferencial. But, it certainly has possiblities to add capacators. I think, that the easiest route would be to add either a Lenz, or DCC Specalties chip and go down the DCC route, but if you are willing to do your own electronics work, then it should be possible to set up your own DC version. I just would not see it being as small of a solution, given the use of SMT for DCC. Certainly, any mechanical solution is likely to take conserable volume to execute, and require that volume in a relatively unforgiving alignment. Cap's would at least be able to be squeezed into less useful space onboard.

 

Best solution: It's your engine. Off the shelf, would be Lenz and Power 1/3 module. Requires some little work: DCC Specalties. Requires lots of mechanical work: Flywheel. Requires lots of electronics work: DC Cap/battery drive.

 

James

[bertiedog]

And Bertiedog, while you are going back and reading the datasheets for latching relays before commenting it would be a good idea to go and read the Lenz manuals for their USP system and then tell us where your description is wrong.

The area you probably mean is the uninterrupted control signal getting through, which is different to the power not getting through. This is done by high Frequency (but not radio frequency) signals that will get through due to any remaining, even single wheel, contact with the track, or Lenz claim, by close proximity to contact.

 

. As far as I know they have not published the exact circuits used, they are closely patented. No power is transmitted by this signal, the power comes from the capacitor storage unit.

 

Reversal and stop can be commanded despite the break in the circuit,

 

Demonstrations are done by them of a loco running on paper over the track,all wheels out of contact and the DCC command signal still operates the chip, but if the entire loco is lifted bodily from the track it looses the control signal , but continues running till the capacitor power runs out.

 

Stephen.

[Dagworth]

The area you probably mean is the uninterrupted control signal getting through, which is different to the power not getting through. This is done by high Frequency (but not radio frequency) signals that will get through due to any remaining, even single wheel, contact with the track, or Lenz claim, by close proximity to contact.

I've always assumed that USP (uninterrupted signal processing) works by using the capacitance effect of the minute gap to pass the DCC signals across. A capacitor will conduct AC, DCC is a square wave AC so a capacitor will conduct it. The piece of paper trick is simply using the paper as the dielectric of the capacitor, it still conducts DCC signal.

 

Andi

[bertiedog]

The idea of using the “gold caps†surfaced in one of the last issues of MRC. (May, 1986, if I am right). The author of that article used a 1 F /6V capacator to provide power for a Lima pancake motored diesel, and a Hornby HST. In order to reverse the diesel, he used a dpdt switch mounted on the buffer beam. There almost certainly are electronic ways to do so, but they mostly mean that you end up with as much circuitry as a DCC chip.

 

 

The rate of discharge for the caps are usually quite high, such that a 500ma draw should be able to be sustained but the voltage will be dropping towards 0 on a log scale.

 

Here- the Panasonic formula is

 

T=C (Vo-V1)/I+I(leak)

 

Where C=Capacitance in F

V0= Original Voltage

V1=Finish Voltage

I=current draw

I(leak) =.2 uA

 

So, lets plug them in

 

T= 1*(6-3)/(.5+.000002)

=6 seconds for a farad.

 

The 6V limit is quite common for the larger caps. I am not sure if 12v caps are available, but the insulation is a problem. From memory of the article referenced above, the 1F caps above could have had several of them put in series in the body of the HST

 

If 6 volt or 12 volt are available in the smaller sizes needed for small OO models it will work, the trouble until recently was the working voltage of the tiny power caps was too low 1.5 and 2.2 volt being common,, and anything above the rating blew them.

 

Stringing them in series was not advised, as when the voltage is applied it took time for the charge to even out, along the string of capacitors, and the first capacitor blew before the voltage settled down. Tolerances have got wider though, and maybe the current types can stand a bit more temporary overload than before.

 

There are certainly larger voltage super caps versions but they jump in size and cost, not a type to fit to smaller OO models., as mentioned by Kenton.

 

Stephen.

[bertiedog]

I've always assumed that USP (uninterrupted signal processing) works by using the capacitance effect of the minute gap to pass the DCC signals across. A capacitor will conduct AC, DCC is a square wave AC so a capacitor will conduct it. The piece of paper trick is simply using the paper as the dielectric of the capacitor, it still conducts DCC signal.

 

Andi

 

Got it exactly ...Lenz were very close indeed about whether it was inductive, capacitance or partial contact, they simply would not reveal the method at first, but the NMRA did get an explanation given to the Technical Group.and they reported capacitance, which would explain the cut off on complete removal,but still getting control when very close to the track.

Lenz did once show an RF unit as well, this attempted to transfer limited power and the DCC signal, but proved difficult to get reliable operation, and would have involved licensing it in the States and the UK as a radio system, with associated frequency allocation.

A full radio control system is simpler, and often used in Garden Rail situations..

 

Stephen..

[bertiedog]

And by the way, the whole idea came from thoughts by the DCC designers about the old Relco track cleaner units.......the idea, not the method, which was HF ionisation of the gap. but the germ of the idea of being out of contact and still getting a control signal stuck in the mind, and developed from there. In the late 1970's there were several US experimenters and companies who dabbled in HF signals to transmit power, but this was before DCC settled down.and provided a framework around which the ideas worked.with the control signal....and then came super capacitors......

Stephen.

[Kenton]

Andi

Thanks again for the input i am finding the debate over your solution very interesting.

Despite again the wandering off topic into the mire of DCC during the last few posts

 

I think I have the same miscomprehension as Stephen though regarding the continued operation.

Considering for now only the forward motion through two points. The power is applied in the forward direction sufficient to sense direction and trip the relay and charges the cap. At the insulfrog of the first point power is lost. The cap discharges activating the transistor to allow the battery to drive the motor. All well so far.

When power is picked up as normal the relay remains unchanged and the transistor is turned off taking the battery out of circuit.

 

Does the cap recharge at this point, thus being ready when the insulfrog of the second point is reached? Or is this a one shot, until such time as there is a reversal.

 

I think we have clarity that on reversing the track polarity at any position the voltage taken to revert the relay polarity will be less than required to power the motor, therefore there will be no weird movement.

[Dagworth]

Does the cap recharge at this point, thus being ready when the insulfrog of the second point is reached? Or is this a one shot, until such time as there is a reversal.

 

Yes, as soon as track power is restored the cap will charge again almost instantly ready for the next frog.

 

Andi