Omnistor Omni-Step Double inoperative on Hymer 644B 2005

[Alanb]

Whiskeymac,

 

Is this diagram any use? I do appreciate that what is required is an internal schematic.

 

 

[Whiskeymac]

Alanb - 2019-07-17 9:40 PM Whiskeymac, Is this diagram any use? I do appreciate that what is required is an internal schematic.

Are you referring to the diagram from pwlsm?

I'm hoping that pwlsm is able to tell me the procedure for testing relays in situ that he alludes to.  Awaiting reply.  I have a career solderer who is happy to try to fit a replacement if she can remove a relay without removing the solder pads from the board in the process.

[Alanb]

Alanb - 2019-07-17 9:40 PM

 

Whiskeymac,

 

Is this diagram any use? I do appreciate that what is required is an internal schematic.

 

[Whiskeymac]

[Whiskeymac]

Trying to attach photo of EMS 02 board Photoshoped to less than 200k using attach after posting

[Whiskeymac]

Trying to attach photo of EMS 02 board Photoshoped to less than 200k using attach after posting. Had a message that files must be less than 100k!  Also file not selected so trying with different browser.

Using Chrome instead of Firefox enabled Select to add a file but seems I fell foul of next to useless 100k limit.  Will try to reduce size, perhaps B&W image if I can work out how to get that.  This may have to wait for the weekend.

[Whiskeymac]

Trying to attach photo of EMS 02 board Photoshoped to less than 200k using attach after posting

[Whiskeymac]

Trying to attach photo of EMS 02 board Photoshoped to less than 200k using attach after posting. Had a message that files must be less than 100k!  Also file not selected so trying with different browser.

Using Chrome instead of Firefox enabled Select to add a file but seems I fell foul of next to useless 100k limit.  Will try to reduce size, perhaps B&W image if I can work out how to get that.  This may have to wait for the weekend.

[Whiskeymac]

At last.  Apologies for all the trash

[Keithl]

Whiskeymac - 2019-07-18 9:21 AM

Trying to attach photo of EMS 02 board Photoshoped to less than 200k using attach after posting. Had a message that files must be less than 100k!  Also file not selected so trying with different browser.

Using Chrome instead of Firefox enabled Select to add a file but seems I fell foul of next to useless 100k limit.  Will try to reduce size, perhaps B&W image if I can work out how to get that.  This may have to wait for the weekend.

The error message still says 100 kB but I believe the limit has been raised to 200 kB.Keith.

[Alanb]

Alanb - 2019-07-18 8:37 AM

 

Alanb - 2019-07-17 9:40 PM

 

Whiskeymac,

 

Is this diagram any use? I do appreciate that what is required is an internal schematic.

 

 

Sorry folks, that did not work twice, firstly because I could not get my drawing into the correct format, and secondly because my attempt at editing timed out.

 

Alan

[Whiskeymac]

The error message still says 100 kB but I believe the limit has been raised to 200 kB. Keith.

I'm in unknown territory but I reduced a 1.5M about 140k and it still wouldn't go, but after a bit of googling and video tuition I got it down to 75k and it worked, so it seems that the 100k limit is still there, unless 200k is accepted via some other process. 

Anyway, there is what the top of the board looks like.  I'll try to get a clar and meaningful image of the circuit side. It might then be possible to identify relay terminals and then test, once I know how.

[mgnbuk]

https://www.reichelt.com/gb/en/de/en/high-current-relay-fra2c-s2-12-v-1-changer-30-a-fra2c-s2-12v-p101959.html?r=1

 

Might help ?

 

Nigel B

[Whiskeymac]

Alanb - 2019-07-18 10:34 AM

Alanb - 2019-07-18 8:37 AM

Alanb - 2019-07-17 9:40 PMWhiskeymac,Is this diagram any use? I do appreciate that what is required is an internal schematic.

Sorry folks, that did not work twice, firstly because I could not get my drawing into the correct format, and secondly because my attempt at editing timed out.Alan

I feel for you!!  Thanks for trying.

[Whiskeymac]

mgnbuk - 2019-07-18 11:38 AM https://www.reichelt.com/gb/en/de/en/high-current-relay-fra2c-s2-12-v-1-changer-30-a-fra2c-s2-12v-p101959.html?r=1 Might help ? Nigel B

Yes, thank you.  There seems to be no sign online of the FRA2C-C2, only the -S2, assumed to be an alternative, and maybe what my relays should have been labeled.  First I want to fault test what I have if possible, but I need help to do that.  Then if faulty, the culprit needs to be removed without losing the soldered connection tabs on the board, so that a replacement can be fitted.  If not, it's £72 from Brownhills fo a complete unit.

[Alanb]

Whiskeymac,

 

I will try again with the EMS 03 connection diagram, using a different method. Follow this link and you should see the external connection diagram. You should be able to drag and drop into a word processor or other programme, rotate and print in landscape format. This is where I went wrong, as it is not the a jpeg file.

 

SPECULATION ONLY.

 

As your last operation was to lower the step, and it subsequently failed to raise, you would appear to have a low resistance fault in the EMS. Prime suspect would the last used "lowering" relay. The relay could have welded or whiskered NO contacts There is also the possibility of a diode failure.

 

Diode testing is the easiest, so start with that. I case I am stretching your knowledge of electronics the diodes are the black cylindrical objects with a white band. There seem to be two different sizes involved.

 

Start with the larger (power?) diodes. Use the diode test facility on your multimeter, and test in both directions. You should see about 0.6V in the forward direction (positive lead remote from white band on diode) and about 3V in the reverse direction. Be suspicious of low readings in both directions, but without a schematic it is difficult to confirm.

 

I have yet to think of a viable method for identifying which is the "lowering" relay, as the relay coil supply appears to be taken from the motor power supply. Perhaps tracing the PCB tracks, rather fiddly but sometimes necessary.

 

Regarding relay type, I see no absolute need for a sealed relay inside the MH. The "S" model should suffice. Many automotive style relays are not sealed.

 

Alan

 

[Keithl]

Alan,

 

I have saved the drawing you linked to as a .jpg

 

Keith.

[Whiskeymac]

Some great info here and very interesting diagrams.  Well found.  I will have to study this info and suggestions at the weekend as I have a very long day away tomorrow.  Thanks for all the help.  I think this will be a definitive thread in time.

[Alanb]

Hi,

 

While spending the last hour trying unsuccessfully to remove the brake pedal switch from my x244, I have given some thought as to what the function of the transistor resistors, and diodes might be on the EMS circuit board. A time delay is a non starter due to the abscence of a capacitor. The only other possibility that I can think of at the moment is a motor stall current operated release for either or both of the relays. (For the less technically minded the motor current will rise sharply when it stalls at the end of the step travel.) I believe that Thule market a control box that offers a single button operation of the step, and may which use the rise in current to switch off the motor.

 

Alan

[plwsm2000]

From the Schaudt info, there is a big difference between the EMS02 and EMS03 modules although they look very similar and have similar connectors. The EMS02 is a fairly simple unit with two relays and the EMS03 has extra circuits to monitor the motor current and has a timer function. The EMS03 is just for controlling steps whereas the EMS02 can be used for steps, shutters and roof hatches (examples given by Schaudt).

 

The photo that was posted earlier looks like the EMS02 with just two relays and a few extra components.

 

The EMS02 has an extra feature that prioritizes the retract/close function in the event that both switches (the one in the cab area and the one by the step) are pressed at the same time. I am guessing that the extra transistor and resistors etc. perform this prioritization function by disabling the "out/open" relay if the retract/close button is pressed.

It might be that one of the relays has failed but it is also possible that this prioritise function is faulty. If you were to swap the motor polarity, the open and close functions would be reversed and the priority would now be on the "open" operation. If this has been done (either on purpose or wired incorrectly), it is possible that this transistor has failed (so not enabling the relay that closes the step).

 

Without having the extact schematic, it would not be wise to test the relays in situ, but it is still possible to check the unit "on the bench" with just a 12V power source and a DMM. The following steps might help -

1) Connect 12V power to ST2 pins 2 & 4 as per the sketch that Keith posted.

2) Connect DMM set to measure DC VOLTS on ST2 pins 1 & 3 (in place of the motor wires)

3) The DMM should read 0V in this state (nothing connected to ST1 yet)

4) Temporarily short pins 1 & 2 on ST1. You should hear one of the relays click and the DMM should now read either +12V or -12V (I don't know what the polarity will be).

5) Remove the short on 1 & 2 and now short 1 & 3. Again you should hear a relay click and this time, the voltage on the DMM should be the opposite polarity to the previous step (ie change from +12V to -12V or vice versa).

6) Repeat 4 & 5 using the other switch on ST1 pins 4,5 & 6

Obviously the relay contacts are not taking much current with just a DMM "load" so you could add a 12V lamp to increase the load.

[Alanb]

Hi,

 

I am looking at the photo of the PCB, while enjoying my breakfast cuppa, and have come up with some more ideas.

 

The four small diodes probably of the IN400x series (about 3mm dia) seem to be either polarity protection diodes in series with the four control inputs, or more likely steering diodes linking the four inputs to the drive the single transistor, which could control both relays.

 

Reading towards the left are what appear to be two resistors, the right hand resistor appears to be discoloured, which is a sign of overheating. Is it possible to read the colour code bands on this resistor?

 

Between the resistors and the lower relay are two more diodes. These could be supression diodes in parallel with the relay coils. These diodes would only pass current when the associated relay coil is de-energised. Such diodes are commonly used to protect transistors controlling relay coils.

 

I can now suggest another possible failure mode. If the diode associated with the step "lowering" relay failed when taking surge as the relay was de-energised, it would take the transistor with it, and is possibly cause the overheating of the resistor.

 

Investigation.

 

Check both diodes adjacent to the relay, using diode test facility. If my deductions are correct there be a relay coil in parallel with each diode, but it should be possible to see a difference in reading, according to polarity of test. If no difference, that diode is suspect.

 

Can you read the type number of the transistor with a magnifying glass. Googling that will reveal the connections, e = emitter, b = base, c = collector. Use diode test facility again and test as two diodes, emitter to base, and base to collector.

 

A further observation. The single resistor on the LHS of the PCB appears to be a low resistance device, possibly used to detect the motor current.

 

Well there you are two possible lines of investigation. Perhaps the reality lies somewhere?

 

Alan

 

 

 

 

 

[plwsm2000]

Alanb - 2019-07-19 9:50 AM

 

Hi,

 

I am looking at the photo of the PCB, while enjoying my breakfast cuppa, and have come up with some more ideas.

 

The four small diodes probably of the IN400x series (about 3mm dia) seem to be either polarity protection diodes in series with the four control inputs, or more likely steering diodes linking the four inputs to the drive the single transistor, which could control both relays.

 

Reading towards the left are what appear to be two resistors, the right hand resistor appears to be discoloured, which is a sign of overheating. Is it possible to read the colour code bands on this resistor?

 

Between the resistors and the lower relay are two more diodes. These could be supression diodes in parallel with the relay coils. These diodes would only pass current when the associated relay coil is de-energised. Such diodes are commonly used to protect transistors controlling relay coils.

 

I can now suggest another possible failure mode. If the diode associated with the step "lowering" relay failed when taking surge as the relay was de-energised, it would take the transistor with it, and is possibly cause the overheating of the resistor.

 

Investigation.

 

Check both diodes adjacent to the relay, using diode test facility. If my deductions are correct there be a relay coil in parallel with each diode, but it should be possible to see a difference in reading, according to polarity of test. If no difference, that diode is suspect.

 

Can you read the type number of the transistor with a magnifying glass. Googling that will reveal the connections, e = emitter, b = base, c = collector. Use diode test facility again and test as two diodes, emitter to base, and base to collector.

 

A further observation. The single resistor on the LHS of the PCB appears to be a low resistance device, possibly used to detect the motor current.

 

Well there you are two possible lines of investigation. Perhaps the reality lies somewhere?

 

Alan

 

 

 

 

I took a closer look at the photo and tried to work out how they implemented the "prioritization" function on the relays. (sorry this is a bit technical and may only be of interest to one or two members).

Maybe what they have done is to use the transistor to switch the 12V on the "open" relay. The transistor is arranged to be off IF the retract button is pressed (so if the open button was also pressed, it would not operate its relay).

What follows is pure speculation just based on the photo. It would be nice to know what the component part numbers are and a photo of the PCB tracks on the other side to be certain of how it works.

My guess is that the transistor is something like a BC184L (cheap and cheerful NPN transistor) connected as an emitter follower (the right most pin looks like it goes to the base on the "L" version). It could also be a P-MOSFET but these are a bit more expensive. This lead seems to go to the anodes of the top 2 diodes and the cathodes of these diodes go to the open/close connector pins. Basically when the button is pressed, this will pull down the base of the transistor and so cause the 12V relay supply to switch off.

 

The 4 "fat" diodes on the circuit seem to be arranged as suppressor diodes and are connected in series across the 12V supply with the motor connected to the anode/cathode junctions. If these are just normal rectifier diodes, I think it is highly likely that the transistor mentioned above has failed and not the relays. The problem with this design (if this is correct) is what happens if the fuse blows due to excessive motor current? In this condition, there will be a lot of energy stored in the motor windings that has to go somewhere. If the fuse is now open circuit, you will get a very high voltage from the back emf of the motor (because it cannot be dumped back into the 12V battery). Since this tiny transistor is probably rated at about 30-50V it is almost guaranteed to fail since it is also connected to the same 12V (or now 100's of volts from the back emf). I would be tempted to replace the two diodes on the 0V side with some TVS diodes (something like 1.5KE18A) to protect the circuit if this happens again.

The other potential cause of failure would be a surge voltage picked up on the control button wires. These would go straight to the base (or gate) of the transistor as there doesn't seem to be any over voltage protection on it. Another TVS diode (or zener) would help.

 

Alan, the resistor on the left hand side looks a bit like a zero ohm link to me. As the PCB is only single sided (to keep the cost down), the PCB designer probably could not get all the tracks on one side so used a link to bridge another track. Having one or two of these on a single layer board is probably still cost effective.

 

The other point I would like to make is that adding this complexity is totally pointless IMO. The relays could have been wired as in my earlier sketch (without any prioritisation) to control the step. If someone was to press the "open" button" while someone else was pressing the "close" button, both relays would be energized and the motor would just stop as there is no voltage across the motor (both sides at 12V).

 

 

[Whiskeymac]

Back on the job after 2 days of commitments.

The transister is BC337 - 40. Also says S2 (unless it's S7, hard to be sure).

I realise that my photo was well below par, using the size reduction method recommended on line.  This morning I spent some time searching for a better method and came up with the delightfully simple and effective, free PIXresizer.  This needs to be published as a recommendation, which I'll do.  I have shot 5 photos showing:

The PCB from the underside.

The PCB looking through from the top side, plus much better image of components.

Edge connectors.

Edge connectors with plugs inserted.

View of plugs to show wire connections.

Note that the outside blue and brown wired pins show zero resistance when metered, as do the two brown wired pins.  My simple mind suspects that this is a short circuit caused by a faulty component, but I'm prepared to be wrong.

Hopefully these pics will help with your spendid analysis.

Right now to send the photos for which I think will necessitate a post for each.

[Whiskeymac]

I've discovered the diode testing position on my meter, which is a revelation.  All 4 small diodes test ok, but one of each pair of large ones gives a warning screech both ways so is open circuit.  The other two are fine.  In both cases it the the diode that is closer to the centre of the board that is faulty.  They are IN5402.

The transistor tests out ok.

[Whiskeymac]

I forgot to aswer the question on the value of the resitor.  You will see from the new photo that it's not discoloured, merely a slightly darker colour.  The left resistor tests at 3.9 and the right at 10.  You can probably see the colours better than I can describe them, not being used to this. The left from bottom to top is purple, purple, black, white, orange (or is that pink?) (And what I've called purple could be mauve!)

The right one is (let's guess) Mauve, blue, blue, purple, mauve.

Hope that's clear enough.

I haven't tested with 12v attached as I kept blowing fuses when testing from the electroblocend and the short would just result in the same would't it?