Schaudt DT201 Display Circuit Diagram anyone?

[Alanb]

Stuart,

 

The Omnistep on our PVC is a slideout version. The limit switch is an internal cupboard door style switch, over which one of scissor operating arms slides at the end of the closing movement.

 

Have you checked for continuity through the step switch, with the step extended? Your connection point for the replacement step would be an obvious testing point.

 

My apologies if you have already carried out this test, and perhaps making a short at the same point towards the DT201.

 

Sometimes the obvious eludes all of us.

 

Alan

[Brian Kirby]

StuartO - 2021-05-31 9:10 PM

 

Hymer seem to get Schaudt to design their electrical installation, based on using Schaudt components. Hymer also buy in other accessories as necessary but will then “Hymerise” them if appropriate, as for example with the Omnistor electric double step, re-badged as a Hymer step. Schaudt incorporate the step (now sold under the Thule brand name) into their circuit design for Hymer, in this case using a Schaudt controller/relay. The Thule step can be used in two basic ways, either automatically retracting the steps if the vehicle’s engine is started or not, in which case a warning buzzer can be triggered. The current Thule step is virtually the same as the Omnistor step of 20 years ago and the circuit options are also unchanged.

 

My 2006 Hymer had an Omnistor 440 step, since replaced with a Thule 440 which is effectively the same, down to the colours of the electrical cables. It was installed as a direct replacement using the same cable connections and the new step worked responded to the same control switches in exactly the same way. The warning buzzer has developed a fault, initially intermittent, now persistent, and the buzzer used to sound from the direction of the DT201 display unit, over the habitation door. The fault has been narrowed down to the DT201 as described above.

OK. Further wild card. :-) Since in essence the set-up is simple (albeit somewhat complicated by Hymer's desire to adapt it to their preferences), why not abandon the buzzer on the control panel and obtain a replacement Thule buzzer, and wire that direct from the step contacts - in line with Thule's wiring diagram - in lieu of the non-functioning Schaudt, PCB mounted, buzzer? It could more easily be tested before finalising the installation, and you could then site the new buzzer in whatever location is a) convenient and b) clearly audible at the driving seat. You would, of course, have more wiring to do, which would admittedly take time, but it should prove a fair chunk cheaper in cash terms! The obvious drawback would be if the Schaudt panel needs inputs from the step for other, not presently apparent, reasons.

[StuartO]

Brian Kirby - 2021-06-01 10:17 AM

 

StuartO - 2021-05-31 9:10 PM

 

Hymer seem to get Schaudt to design their electrical installation, based on using Schaudt components. Hymer also buy in other accessories as necessary but will then “Hymerise” them if appropriate, as for example with the Omnistor electric double step, re-badged as a Hymer step. Schaudt incorporate the step (now sold under the Thule brand name) into their circuit design for Hymer, in this case using a Schaudt controller/relay. The Thule step can be used in two basic ways, either automatically retracting the steps if the vehicle’s engine is started or not, in which case a warning buzzer can be triggered. The current Thule step is virtually the same as the Omnistor step of 20 years ago and the circuit options are also unchanged.

 

My 2006 Hymer had an Omnistor 440 step, since replaced with a Thule 440 which is effectively the same, down to the colours of the electrical cables. It was installed as a direct replacement using the same cable connections and the new step worked responded to the same control switches in exactly the same way. The warning buzzer has developed a fault, initially intermittent, now persistent, and the buzzer used to sound from the direction of the DT201 display unit, over the habitation door. The fault has been narrowed down to the DT201 as described above.

OK. Further wild card. :-) Since in essence the set-up is simple (albeit somewhat complicated by Hymer's desire to adapt it to their preferences), why not abandon the buzzer on the control panel and obtain a replacement Thule buzzer, and wire that direct from the step contacts - in line with Thule's wiring diagram - in lieu of the non-functioning Schaudt, PCB mounted, buzzer? It could more easily be tested before finalising the installation, and you could then site the new buzzer in whatever location is a) convenient and b) clearly audible at the driving seat. You would, of course, have more wiring to do, which would admittedly take time, but it should prove a fair chunk cheaper in cash terms! The obvious drawback would be if the Schaudt panel needs inputs from the step for other, not presently apparent, reasons.

 

I have been considering installing an independent buzzer and it could be done near the DT201 because the necessary feeds are likely to be available there (step out signal, ignition on status and earth return and this was mentioned earlier in the thread. However my DT201 is giving indications of other faults and it’s fifteen years old so May it needs changing anyway. I have also just learned from Martin Bushnell (who runs Alan Evans former business) that a buzzer fault is usually a processed fault, so that needs repairing in Germany by Schaudt. I need to decide whether to replace my DT201. I’m not currently seeing that your contribution is helping.

[Brian Kirby]

StuartO - 2021-06-01 11:10 AM...............I’m not currently seeing that your contribution is helping.

OK, that's me told!

[StuartO]

No “telling” intended Brian I think it might have been useful if you read the earlier part of the Thread so you’d have had a better idea of the context.

 

Another twist to the story. DT201 units are no longer available from Schaudt and nor do they have any continuing capacity to repair them. Presumably they have exhausted their stock of spare PCBs and will be having no more made. It is said that you can replace with a DT203, at a stiffer price. I was lucky and bought a new DT201 (presumably old stock) from Apuljack Engineering, so I will have that up my sleeve. I think I will still pursue the idea of an independent DIY step buzzer circuit so that my original, faulty DT201 will still be useable too.

 

Incidentally Martin Bushnell, who continues to run the late Allan Evans’ business was very helpful with advice, even though he couldn’t help with stock of a DT201. The website is still http://www.aandncaravanservices.co.uk/ and the Trust Fund to support the education of Allan Evans’ young children is still open to donations. We will all remember how helpful Allan was on this Forum and with his highly informative website. There are instructions on how to donate (and a picture of Allan and his children) on the website.

[Brian Kirby]

StuartO - 2021-06-03 1:10 PM

No “telling” intended Brian I think it might have been useful if you read the earlier part of the Thread so you’d have had a better idea of the context. ...................

I had, but you had seemed to abandon the idea while the solution via repair of the Schaudt equipment appeared to be getting more and more complex and costly. So, it seemed the abandoned work-around might after all offer a quicker, simpler, solution. Sorry it didn't prove helpful.

[StuartO]

I'm further along the learning curve but have yet to find a solution. I'm still pursuing the "DIY circuit" option, to install an independent buzzer (from the Dt201 panel buzzer) but that will require help from an electronically competent friend, so in parallel with that I have also being making more enquiries to diagnose, or at least confirm, the fault which stopped the Dt201 buzzer sounding - because it did once sound reliably, although in recent times it seemed to become intermittent and then stopped completely.

 

I had the opportunity to buy what is supposed to be a "new" DT201 from Apulyard engineering and prior to installing that I went very carefully through resetting the dealer-only Options Menu on the DT201, to make sure I was on the correct setup, to enusre the buzzer fault was genuinely on the original DT201 panel. On the old panel the correct graphic image of a Hymer with steps out was showing when the steps were out and this graphic disappeared when the steps were retracted. Both swithes for operating the steps (up or down at the habitation door and up-only at the driving position) worked perfectly. The only fault was that when the ignistion was turned on the buzzer should sound if the steps were out and this wassn't happening. Hoepfully when I installed the "new" DT201 panel this fault would disappear.

 

But it didn't. I was careful to swap the panels over with the 12v system shut down at the EBL as well as on the DT201 and I took care to make the connections correctly. I set the Options Menu on the new panel to the correct configuration for my MH (step alarm active and solar current page active) and the new panel behaved exactly the same as the old one during this process. Unfortunately the step warning buzzer remained silent with the new panel installed, so either both panels were faulty or neither of them were. Obviously it would be nice if both were serviceable because I would then have a working panel and a spare; I was happy to have paid £290 for the replacement because I seemed to be buying the only new DT201 anywhere and replacing with a DT203 would cost nearly twice as much.

 

So far I have no explanation for why the DT201 panel buzzer doesn't sound when it should. It used to sound and there have been no changes since it did stop sounding apart from installing a new electric step, during which the electrical connections were remade like-for-like and the new steps then worked perfectly. So far I have not found any damaged wiring or poor connections and the 5v positive voltage from the step microswitch is arriving correctly at the DT201 panel and the panel displays the correct graphic image of steps out when the steps are out. I haven't sidcovered where in the circuitary the signal that the igition switch is live reaches the DT201 and there is nothing relevant as far as I can see on the Schaudt 12v wiring diagram for my B674 model. I have yet to visualise the EMS02 control/relay part of the circuit so that's my next job.

 

Any further thoughts, even from over-sensitive Brian, will be most welcome. :-D

[Robinhood]

..are you absolutely convinced that the buzzer is actually in the control panel?

 

I know it has visual step indication on it, but the step connection at the rear is a single, simple one, and it appears to be supplying the correct signal to the visual function so it's questionable as to whether the buzzer is actually there.

 

Hymer practice and control panel fitment has varied over the years (and still does from model to model) but it has been common to find the step buzzer installed under the driver (or passenger) seat.

 

https://www.ebay.co.uk/itm/184325875530

 

Mine, under the driver's seat, is similar to this (though, I think, black). It can be difficult to identify the source of the sound without knowing where it is, dropping the front seat flap on mine confirms its location and type. (It is located on top of one of the various small Schaudt "control boxes". I can't identify this because of its position, but I wouldn't be surprised if it is the latest version of the step relay box (it would be logical)).

 

The buzzers themselves are known to sometimes fail, and patently there might be a wiring issue to it if it isn't mounted in the control panel.

 

I think I would consider looking elsewhere other than the control panel; earlier versions may have the buzzer wired separately, but I would possible expect back to the step relay.

 

I think I'd be looking

[StuartO]

I spoke to Martin Bushnell (of aandncaravanservices.co.uk) and he talked about a buzzer being on the DT201 PCB and it certainly looks like there is a buzzer on the PCB and that’s where I remember the sound coming from.

[Robinhood]

OK.

 

The DT201 is certainly likely to have a buzzer on-board, as it can audibly alarm for other reasons (e.g. fresh water empty). This should at least give you the opportunity to test for the functioning of the buzzer (if, indeed, the step uses the same one - and I agree, the manual might lead one to believe so).

 

Though it's possible, I wouldn't have expected a replacement panel not to be working, so a test of that alarm (with empty water or likewise) would be good (and I'd expect it to work).

 

Assuming the step alarm is in the panel, and the second one isn't faulty:

 

In order to activate the step alarm, the panel would have to know that the step was extended, and that the engine was running. As you are getting the correct graphic, then I would assume the former is OK (driven by a negative and positive step connection, only, no other input, at the panel rear).

 

As far as the latter is concerned, I can only assume the panel receives that via the D+ signal connection on the rear, shown on a different connection block. (I can't, offhand, think of another DT201 panel function that would require that connection). It would make sense to test that D+ function at the panel input and source, though it isn't clear where it is supplied from. (My suspicion would be from the EBL - which model have you got?).

 

Edited to Add.

 

On the DTxxx capable EBLs I've looked at, the panel does appear to be supplied with D+ from one of the EBL to panel connections.

[StuartO]

My EBL is a 101. I can’t I have understood the activation method of the Options Menu and all I’ve been able to achieve has been to input a single parameter figure of 5, the sum of 1 for the step and 4 for the solar current page. The Options Menu is supposed to present the individual activations in sequence but all I’ve seen (after inputting the Code) is a display in which all the option graphics are flashing at once. Hence my resorting to inputting a total figure for the parameters. This does seem to work, and to yield the correct activations, but I could be getting the Options Menu completely wrong.

[snail]

Hi Stuart just in case you are not aware there is a very good and knowledgeable Facebook group called hogs

Hymer owners group

They also get discounts on some suppliers

I'm sure someone will help you free to join just need to register

[Robinhood]

StuartO - 2021-06-06 6:42 PM

 

My EBL is a 101.....

That EBL appears to supply a D+ signal to the DTxxx control panel via Pin1 of block 9. (the corresponding connection on the control panel is detailed in the manual).

 

If that isn't present, or (properly) connected, then I would surmise that the step buzzer wouldn't work, as it would have no way of knowing the engine was running.

[StuartO]

Robinhood - 2021-06-06 7:02 PM

 

StuartO - 2021-06-06 6:42 PM

 

My EBL is a 101.....

That EBL appears to supply a D+ signal to the DTxxx control panel via Pin1 of block 9. (the corresponding connection on the control panel is detailed in the manual).

 

If that isn't present, or (properly) connected, then I would surmise that the step buzzer wouldn't work, as it would have no way of knowing the engine was running.

I’ll look into that. Could you explain what D+ means? I have got the necessary manual etc but “D+” has puzzled me.

[Alanb]

Robinhood - 2021-06-06 7:02 PM

 

StuartO - 2021-06-06 6:42 PM

 

My EBL is a 101.....

That EBL appears to supply a D+ signal to the DTxxx control panel via Pin1 of block 9. (the corresponding connection on the control panel is detailed in the manual).

 

If that isn't present, or (properly) connected, then I would surmise that the step buzzer wouldn't work, as it would have no way of knowing the engine was running.

The only other functions on Block 9 are pin 6, solar charge to starter battery and pin 7, solar charge to habitation battery. Worth checking?

 

Alan

[Keithl]

StuartO - 2021-06-06 7:51 PM

 

I’ll look into that. Could you explain what D+ means? I have got the necessary manual etc but “D+” has puzzled me.

The D+ signal means 'Engine running'. It is named after the old fashioned Dynamo's D+ terminal. On modern cars it is often computer generated by the engine control module.

 

Keith.

[Robinhood]

StuartO - 2021-06-06 7:51 PM

 

I’ll look into that. Could you explain what D+ means? I have got the necessary manual etc but “D+” has puzzled me.

The D+ signal is created from the Alternator D+ output, which is only present when the engine is running, and thus the alternator is charging.

 

The EBL takes the signal (present on all/most alternators) and augments and distributes it to any function that needs to know when the engine is running (fridge, etc.). The D+ signal (not just ignition on) is generally also used to invoke the warning for the step.

 

Your control panel patently knows that the step is down (the icon is illuminated) but would appear not to know when the engine is started, which would invoke the buzzer.

 

The EBL101 outputs a D+ to the control panel from Pin1 of block9 (but only when the engine is running), this is passed to Pin1 of connection X6 on the back of the Control Panel.

 

As I said above (though someone else may identify something) I can see no function that would require such a signal at the control panel other than to work the step alarm (Pins 1 and 2 on X9 on the control panel are simply the live and ground associated with the step being down, and used to light the indicator - the additional logic to sound the alarm - in conjunction with that indicator being powered - must come from the presence, with the engine running, of the D+ signal (at c12V))

[StuartO]

Mystery solved, I have a working step alarm and an explanation for why it went wrong when it did.

 

I had been testing the step buzzer simply by turning the ignition on but without starting the engine, not realising the significaance of needing the D+ signal from the engine actually running. With the engine started up, the step alarm buzzer was working promptly and reliably every time. The step buzzer was not intended to work unless the engine was actually started. Silly me.

 

The original fault was the step switch in my old set of Omnistor electric steps which depended on a rather crude switch with brass contacts inside the motor casing but otherwise exposed to the elements. These contacts had stopped making,probably as a result of the long period of winter/covid storage outside, hence I had destroyed the steps by leaving them out as I moved the MH back into our side garden past the heavy iroko gateposts. I replaced the steps and the new, microswitch based, step switch worked perfectly from the outset; I was simply not testing the step alarm properly.

 

I have therefore bought a replacement DT201 panel unnecessarily but that's OK; I learned that these panels are no longer available or repairable by Schaudt, so having a spare is no bad thing. Of course I also had to buy a replacement set of electric steps but that was no bad thing because the original ones were badly worn (because the grandchildren had used them as a toy, riding up and down while standing on them) and we now have a shiny set of steps which no longer lean down markedly to the left.

 

As many things in life, you eventually discover you got something wrong because you did something which was perhaps a bit stupid - but it all came out right in the end and I am most grateful for the expert advice I've had from contributors to this Forum. I shall never again fail to see the difference between merely switching the ignition on and triggering a proper D+ signal.

 

By the way I have been a contributor to Facebook's HOG Page for quite a while but I doubt I would have had the penny drop for me any quicker than by asking on here.

[Thai Bry]

StuartO - 2021-06-07 8:23 AM

 

Mystery solved, I have a working step alarm and an explanation for why it went wrong when it did.

 

I had been testing the step buzzer simply by turning the ignition on but without starting the engine, not realising the significaance of needing the D+ signal from the engine actually running. With the engine started up, the step alarm buzzer was working promptly and reliably every time. The step buzzer was not intended to work unless the engine was actually started. Silly me.

 

As many things in life, you eventually discover you got something wrong because you did something which was perhaps a bit stupid - but it all came out right in the end and I am most grateful for the expert advice I've had from contributors to this Forum. I shall never again fail to see the difference between merely switching the ignition on and triggering a proper D+ signal.

Hi Stuart

 

Like you, I too now feel a bit foolish, after the supposed help that I tried to give you.

 

I've only just realised - after having my van from new in 2007- that the step alarm only gives out an audible sound if the engine is switched on.!!! Just tried it out!!!!!

 

Egg on face time for me, but I'm also happy to have learnt from much wiser people than I on this forum.

 

Regards

Brian - Thai Bry

[Alanb]

Robinhood - 2021-06-06 8:15 PM

 

The D+ signal is created from the Alternator D+ output, which is only present when the engine is running, and thus the alternator is charging.

 

The EBL takes the signal (present on all/most alternators) and augments and distributes it to any function that needs to know when the engine is running (fridge, etc.). The D+ signal (not just ignition on) is generally also used to invoke the warning for the step.

Robin,

 

I cannot agree with the inclusion of the word "augments" in your second paragraph above. The EBL 101 uses the D+ signal to operate the "Battery cut-off" (split charge) relay, and its internal refrigerator relay. The D+ signal is distributed by being made available at Block 8, pin 15. There is no relaying, or amplification of the inputted signal.

 

I am sorry if the above may seem to be nit picking, but I do not want other readers to be misled.

 

For general information.

 

On earlier vehicles, without a computer generated D+ signal, the Schaudt system uses the true D+, or alternator field terminal node. If too many devices are connected to the D+ point, the alternator will be reluctant to start generating. This is what Allan Evans referred to as "lazy alternator syndrome", but I am not sure that he understood the cause.

 

Alan

[Thai Bry]

Thai Bry - 2021-06-07 9:21 AM

 

StuartO - 2021-06-07 8:23 AM

 

Mystery solved, I have a working step alarm and an explanation for why it went wrong when it did.

 

I had been testing the step buzzer simply by turning the ignition on but without starting the engine, not realising the significaance of needing the D+ signal from the engine actually running. With the engine started up, the step alarm buzzer was working promptly and reliably every time. The step buzzer was not intended to work unless the engine was actually started. Silly me.

 

As many things in life, you eventually discover you got something wrong because you did something which was perhaps a bit stupid - but it all came out right in the end and I am most grateful for the expert advice I've had from contributors to this Forum. I shall never again fail to see the difference between merely switching the ignition on and triggering a proper D+ signal.

Hi Stuart

 

Like you, I too now feel a bit foolish, after the supposed help that I tried to give you.

 

I've only just realised - after having my van from new in 2007- that the step alarm only gives out an audible sound if the engine is switched on.!!! Just tried it out!!!!!

 

Egg on face time for me, but I'm also happy to have learnt from much wiser people than I on this forum.

 

Regards

Brian - Thai Bry

Or should I explain that I never once associated the step alarm going off if the ignition was on.

[StuartO]

We who have become self-taught fettlers of cars etc may do quite well at fixing many thingsbut because we never did any formal education in the subject,i.e. we never went to night school or whatever mechanics do as part of their apprenticeship, we are never taught things like what "D+" means in the context of a circuit diagram, so we are prone to suffering the consequences of our patchy knowledge. So it was ignorance rather than stupidity which led me into error and all I needed was for a proper engineer, who presumably did go to college, to explain D+, which turned out not to be anything complicated at all.

 

I've been basking in the joy of a solution to my step buzzer problem this morning but I also know that I remain ignorant of one useful aspect of all this DT201 stuff in that I just haven't hoisted in at all how the Options Menu is supposed to operate. Once you've entered the secret code to let you in you are supposed to get a sequence of flashing graphics to show the order in which the options may be activated or not but what I got (on both my serviceable DT201 panels) was a single screen on which all the graphics were flashing at once, so I had to fiddle about for ages trying to work out how to enter the requisite "parameter" values. There was some vague recollection from some dark episode in my own education from which I vaguely remembered that computer-type processors add up the activation numbers to store what they need to know. The step alarm had a parameter of 1, the solar current display had a parameter of 4, so I tried inputting 5 for both and it worked, but goodness knows why.

 

If only we motorhomers could rely of all caravan and motorhome dealerships to have on their staff trained mechanics who would know these things but sadly they don't and were it not for this Forum I would be really stuck. So thanks to the clever, proper engineers who understand these things and share their knowledge on this Forum; it's really useful and much appreciated.

[Brian Kirby]

StuartO - 2021-06-07 8:23 AM

Mystery solved, I have a working step alarm and an explanation for why it went wrong when it did........................

Excellent news!

 

Now for the $64,000 question. :-D Did you discover in the process where the buzzer is, actually, mounted? Should it fail in future you'll still need to know where it is, and finding it after it has failed will be much more difficult than finding it when it's making a noise!

[Thai Bry]

Brian Kirby - 2021-06-07 3:29 PM

 

StuartO - 2021-06-07 8:23 AM

Mystery solved, I have a working step alarm and an explanation for why it went wrong when it did........................

Excellent news!

 

Now for the $64,000 question. :-D Did you discover in the process where the buzzer is, actually, mounted? Should it fail in future you'll still need to know where it is, and finding it after it has failed will be much more difficult than finding it when it's making a noise!

Hi Brian

Don't know about Stuart's Hymer, however after testing mine, the buzzer is definitely emitted by the DT201.

I just thought there was also a repeat buzzer by the dash. As I can raise the step- if we've forgotten to raise them - from the dash.

 

I also sent Stuart a copy of the parameter values as received from Allan Evans when he sorted out faults on our DT201 many years ago.

[Robinhood]

Alanb - 2021-06-07 10:34 AM

 

Robin,

 

I cannot agree with the inclusion of the word "augments" in your second paragraph above. The EBL 101 uses the D+ signal to operate the "Battery cut-off" (split charge) relay, and its internal refrigerator relay. The D+ signal is distributed by being made available at Block 8, pin 15. There is no relaying, or amplification of the inputted signal.

 

Alan

True for the EBL101, Alan, and I agree, the wording might have confused. I was simply trying to be "generic".

 

On my later 'van, the Schaudt electronics effectively take input and distribute an amplified/augmented D+ signal, albeit by an add-on unit (AD 01) external to the EBL. (largely, I assume, to avoid the alternator D+ overload you mention). My understanding was that, in certain more sophisticated implementations, similar function was natively incorporated into certain EBLs themselves.

 

Nonetheless, the overall description seems to have (magically) resolved Stuart's problems. ;-)