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Heljan 7mm Class 20


brian daniels
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Hi.

 

I did think this but messaged Ben Jones before attempting to use the Combi. I also have a meter monitoring the current during the running in and each motor only draws 0.3 amps. However given the fact that the Combi is only rated to 1 amp, that's why I though a motor stall caused by the resistance would temporarily push the drawn current above the 1A and cause the loco to cut out.

 

I will be chipping the loco for DCC but just wanted to check the resistance I've experienced isn't a sign of a possible current or future problem.

 

Thanks,

PJ10 

Edited by PJ10
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  • 3 months later...

It has been a while.  I put the loco to one side while working on other aspects.  I got in the mood to complete the wiring today and, hooray, the lights now work.

 

One final issue is the fan.  The circuit board seems to have two possibilities:

 

1) There's a 1.5/5V output.  I tried this connecting the other wire to Common but nothing happened.  I would assume the output is constant so no need for functions.

 

2) FO4.  The function sheet has "Function 4 Fan" listed under Function 22.  Tried this but nothing.  In fact I ran through all the functions and got nothing besides some surprising sounds.

 

Can anyone point me in the right direction on this?  Not that big a deal really, I'm chuffed that I have everything else working.

 

John

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John,

 

Refer back to my post of 03/02/2021.

 

The project's Function List is correct, FO4 is assigned to F Key 22

 

However, on an MX644C, Function Outputs 3 and 4 are Logic Level only, and your wiring attempts are for 'Open Collector' (aka Full Power) so it's not surprising that the fan does not spin.

 

The output must be amplified in order to provide sufficient power. Heljan does not provide this, so you will need to add a small circuit including a transistor.

 

This is all a result of the confusing variations on the '21MTC' so the sooner this obsolescent interface disappears form our models, the better.

 

The PluX22 interface is superior and removes the anomaly of Open Collector/Logic Level function outputs completely. More and more UK models are now being designed for PluX22.

 

If you intend to use MX 'Small' decoders in future projects like this, I would suggest MX645P22 decoder and ADAPLU adapter, then all FOs will be Open Collector and this problem will not arise.

 

Best regards,

 

Paul

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Thanks as always for responding Paul.  I am delighted with the lights - controllable and look good.

 

The fan is kind of a nuisance, I had hoped it would be simple.  I have no idea what a transistor circuit would look like.  As I mentioned the fan is not a big deal so, unless someone comes up with a simple circuit, it will remain dead.

 

Thanks

 

John

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Hi Brossard,

 

I’m at a similar point with my own 20 after having to strip one bogie down several times to address the resistance/tightness I mentioned in a previous post. I’ve actually ended up removing the motor and all gears from that bogie and using just one motor and one driven bogie. Fine for my plan for a small shunting plank.

 

Anyway, back to the fan. I did think about using a function to control the fan with a driver circuit but concluded that this would mean the fan was either off or running at full speed. Probably not realistic for my plank. I did think about using the function dimming option to reduce the speed but as I’ve decided to use some of the functions for independent lights, I’m now using this to dim the lights to an acceptable level. If I recall correctly, I have cv 60 set to 15. This has the effect of reducing the voltage of the function outputs by using Pulse Wave Modulation to reduce the effective voltage seen by the lights or whatever is connected to the outputs. 

 

I’m a relative newbie to DCC and there may be a way to combine the two options but I’ve decided to leave the functions and dimming for lights. This may not be an issue for you depending on how you have the lights connected and how you want the fan to run

 

Instead, and to give a little more “play value”, I’m currently considering using an old Bachmann chip I have no use for configured with a different address to the loco sound chip and wiring this to the track feed. In this way I will be able to set the fan to run at any speed I want using my controller independent to the loco speed. I’m not sure if the fan on a real 20 runs at variable speed but it could be fun. Well for a few minutes until I get fed up with the feature. Whether I eventually decide to go down this route or not, time will tell.

 

PJ10

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Hi PJ.  I have decided to keep both motors for now but depending on how things go I may do as you did.  My layout is a fairly short BLT.

 

As for the fan, your approach is interesting.  However, I can live without it if I have to.

 

Cheers

 

John

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On 02/07/2021 at 11:03, pauliebanger said:

John,

 

Refer back to my post of 03/02/2021.

 

The project's Function List is correct, FO4 is assigned to F Key 22

 

However, on an MX644C, Function Outputs 3 and 4 are Logic Level only, and your wiring attempts are for 'Open Collector' (aka Full Power) so it's not surprising that the fan does not spin.

 

The output must be amplified in order to provide sufficient power. Heljan does not provide this, so you will need to add a small circuit including a transistor.

 

This is all a result of the confusing variations on the '21MTC' so the sooner this obsolescent interface disappears form our models, the better.

 

The PluX22 interface is superior and removes the anomaly of Open Collector/Logic Level function outputs completely. More and more UK models are now being designed for PluX22.

 

If you intend to use MX 'Small' decoders in future projects like this, I would suggest MX645P22 decoder and ADAPLU adapter, then all FOs will be Open Collector and this problem will not arise.

 

Best regards,

 

Paul

2 questions. I'm confused why a 21 pin chip has been used for an 0 gauge class 20 installation that requires hard wiring, and how is it Heljans fault that Zimo only offer logic level outputs?

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It's a 21 pin decoder installed into a circuit board.  (See previous posts above for more detail).  This board replaces the Heljan board. The board has screw terminals for the wires for track power in, DCC power out (to two motors), speaker and the various lights.  This does make things more convenient.  This particular model is dated.  More recent models are supposed to be DCC ready.

 

I think Paul was being critical of Zimo.

 

John

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12 hours ago, blueeighties said:

2 questions. I'm confused why a 21 pin chip has been used for an 0 gauge class 20 installation that requires hard wiring, and how is it Heljans fault that Zimo only offer logic level outputs?

 

Hi Lee,

 

Your 2 questions answered:

 

1. John has answered why he has chosen this route. The Heljan model was supplied as an analogue model with no provision for DCC, so each end user makes a choice on how to instal a decoder. Hard wiring the decoder directly is one solution, others prefer to hard wire an adapter which replaces the Heljan PCB but still allows the decoder to be easily removed/relaced without de-soldering or unscrewing of internal wiring.

 

2. It's not 'Heljan's fault' that this specific decoder (MX644C) has Logic Level only Function Outputs on AUX3 and 4, and I have not suggested otherwise.

 

Best regards,

 

Paul

 

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14 hours ago, brossard said:

 

 

I think Paul was being critical of Zimo.

 

John

 

John,

 

I was not being critical of ZIMO (or Heljan for that matter).

 

My criticism is that there is confusion regarding FO types with 21 pin decoders.

 

There is a solution for your fan 'problem'  - I'm busy with something which will not wait at the moment, but I'll get back to you asap.

 

Best regards,

 

Paul

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Sorry if I put words in your mouth Paul.:scared:

 

Good to know you are working on something but please don't go to too much effort on my account.

 

I will leave things be for the time being and see what develops.

 

John

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On 04/07/2021 at 13:38, brossard said:

Sorry if I put words in your mouth Paul.:scared:

 

Good to know you are working on something but please don't go to too much effort on my account.

 

I will leave things be for the time being and see what develops.

 

John

 

Hi John,

 

The info I gave you earlier regarding FO types remains true for the decoder.

 

However, I thought a bit more about the ADAMTC 15 adapter board which you have fitted. I looked at the components on the board and came to the conclusion that the additional circuitry I mentioned to amplify the Lofic Level outputs were probably already included on the adapter.

 

Although it is possible to infer this from the written description of the ADAMTC family of adapters, it was not specifically highlighted as one of its features.

 

One of my contacts at ZIMO has confirmed that the Logic Level Outputs are indeed amplified by the ADAMTC adapter, thereby converting the output from FOs 3 and 4 to 'Open Collector' type which can be used as normal.

 

This all goes to reveal that there is something else which is preventing the fan from operating with F key 22.

 

It may be that you have a version of the sound project where FO4 is not mapped to F key 22.

 

So we need to identify the exact version you have to know what should be happening.

 

Can you tell me the version number from the User Notes you had from Digitrains and whether it mentions the gauge (0 or 00), please? The version number may also be read from CVs 105 and 106, so if you can tell me what you find there we should be able to narrow it down.

 

Once that's established we can explore possible reasons for FO4 not operating the fan. Re-mapping may be required, but I can give you the CVs and values to enter.

 

Best regards,

 

Paul

 

 

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Hi Paul.  Exciting that there may be something to be done.

 

My sheet says"  ZS20ASL Class 20 Active Drive SL V17.07"

 

A contact here on RMweb has the same configuration (because I copied off him) but Digitrains installed his system.  He has confirmed that the fan works via F22.

 

John

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John,

 

OK, there's discrepancy. I'll need to contact Digitrains. Can you tell me when you bought this decoder, please?

 

(The Class 20 sound project is one of my most regularly updated projects, and Digitrains also add their own features).

 

You mentioned earlier that you tested all F keys and go some odd sounds - do they agree with the Functions List in the User Notes?

 

Best regards,

 

Paul

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I ordered the decoder in Aug 2020.

 

I was being flippant about the sounds, functions in the tens and 20s are not accessed very often.  TBH, I haven't gone through the sounds.  After the fan is sorted that's a job to do.

 

John

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John,

 

Understood, but it will help to ensure we are talking about the same version of the sound project if you can agree the sounds and functions to the list in the User Notes you have, or if you can point out any differences.

 

One reason that your decoder is not behaving as you expect is that you may have a different version of the sound project than the User Notes supplied. It's only a small possibility that this has happened, but there's a chance of spending a lot of time trying to sort a problem which arises because of this. Best to be sure at the start.

 

You have identified that F key 22 is not operating your fan as expected, what I would like to establish is whether the actual project you have is set up for the fan on F key 22, regardless of what it says in the User Notes.

 

Please check the F Key responses to the Function List and let me know what values are in CV105 and CV106.

 

If the feature is included in your project on F key 22 (it's not in the 00 version, for instance, since there are currently no Class 20 models aviailable with operating fans in this gauge) you should connect the positive of the fan to the Common Positive terminal, and the negative to the screw teminal for Function Output 4. (probably marked 'FA4').

 

Best regards,

 

Paul

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Ah OK, Paul, I will run through the functions today and let you know.

 

My problem with F22 is that I couldn't find anywhere on the sheet where it describes the connections for the fan.  I will try connecting FO4 and see what happens.  The sheet does say that cab lights (which this model does not have) should be connected to FO4.

 

John

 

 

 

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Paul, I have run through all the sounds and they appear to be correct. 

 

I connected the fan wires as you indicated but nothing happened.  I soldered the blue wire to the Common + pad (the board in the loco does not indicate + or - so that is a guess) and connected the brown wire to FO4.

 

Wondering if the 1.5V/5V terminal is relevant.

 

John

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No, the low voltage connection is not relevant to this issue. Use one of the 'Plus' connections, either at the screw terminal or the separate solder pad for the positive, and FA4 for the negative.

 

From what you say, F key 22 will be the control key for FO4

 

Does the fan have a separate small PCB to which the fan is connected?

 

If so, there is usually a small potentiometer (variable resistor) which can be adjusted with a small screw driver blade. It's possible that the resistance is set so high that the fan motor will not turn. Try adjusting this. (It might also be a good idea to test the fan in isolation with a DC source to confirm that the fan motor actually works).

 

Also, 'cab lights' provision in the project may be  direction dependent, so check that 'nothing happens' applies in both directions.

 

Best regards,

 

Paul

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Thanks for the clarification on the low volt output Paul.

 

Yes there is a board on the roof associated with the fan. I assumed the potentiometer was set correctly because the fan did work on DC. 

 

Glory hallelujah!, tweaking the pot did the trick, so that's all sorted.  Feeling a bit embarrassed.  The lid can go back on now and job done.

 

I had the cab off to add a driver.  There is no light.

 

I hope all those lurkers watching this found it helpful.

 

I'm grateful for your patience on this Paul.  You will have guessed that this sort of thing is outside my comfort zone.

 

John

Edited by brossard
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Well done guys for sorting it out together. 

 

This will come in useful for someone else too, so hopefully it can be quickly resolved again.

 

Paul 

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I would describe current Heljan locos as ESU ready rather than DCC ready. It's not entirely their fault because with the larger locos with 2 motors there is no standard interface suitable to fit either ESU or Zimo.  Heljan have decided to fit a DCC socket suitable for ESU decoders and that's not suitable for a  Zimo decoder. 

Norman

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