Glow Worm (Valliant) UltraCom 30cxi schematic

[Whitespirit66]

The second one would look great on my lounge wall. Interesting use of colours.

Looks like the night map on my sat nav

I'm still on a dog-eared A to Z, but to us, art can appear in the most unexpected places.

 

[underwurlde]

Well I'm impressed.
Did you start off by photocopying the board?

Yes. Photographed the bottom of the PCB & mirror imaged it. Using a 2 monitor setup, that image was always on one monitor. Then I visually copied the top tracking and at the same time making the schematic - if the schematic did not match the tracking then an error would appear, hence IF my PCB tracking fully matches the original PCB then the schematic should be correct. This was also confirmed using a continuity tester.

Took me a while but kept me off the streets I suppose.

A

 

[underwurlde]

It helped me to replace a 50p capacitor instead of spending £100 on a new PCB and now my water is hot, house warm. Also I was bored, stuck in doors with man-the-fk-up flu. No, I'm not an RGI and hence no Gassy type things were touched.

...except, of course, the small issue that the PCB controls the gas valve, and the fan (which affects combustion) and the flame rectification etc etc, so technically gassy type things were most definitely touched

True, but I did not change the inherent design of the controller. I have only copied it (out of sheer boredom).

 

[underwurlde]

cannot get the image up on the lap top ? but

Is this one of them in-famous symsi pcb's an example of carp electronics dumped into boilers by some manu

Symsi is probably some word that translates or means "Turkey" ???

power cut symsi can go t*ts up , turn the fuse spur off symsi can go T*ts up

Breathe on it symsi can go T*ts up etc etc

Gloworm should get an award the "electronics turkey award" along with Johnson & Starley for the Reno carp & the legendary potty suprima pcb

What stood out about this design after completing the schematic was the utter lack of ESD protection. A lot of processor pins are simply tracked straight to connectors thus wired to the outside world, snaking off to wherever! AND the design has an on-board ESD generator, the circuit used to fire the spark electrode! So, IMO, this design could be improved upon really.

A

 

[johnplumb]

Impressed

So how did doing the drawing help you find the fault. Did you know the logic of the board, what does what and when, to enable you to find the fault. How did you test it.

 

[picasso]

potterton have had about 20 ? design changes to their suprima board and still cant get it right, If I were cynical I would suspect they were making a lot of money from the poorly designed boards

 

[underwurlde]

Impressed

So how did doing the drawing help you find the fault. Did you know the logic of the board, what does what and when, to enable you to find the fault. How did you test it.

A picture is worth a million words... or rather a schematic. Having a schematic to hand is a must for fault finding beyond the obvious.

What I see is:
Mains filter -> switched mode PSU -> 24V -> Regulator -> 5V.
Loads of connectors -> filters & level shifters -> processor I/O.
Mains voltage presence detectors -> opto isolators -> processor inputs.
Dual H-bridge -> Actuator drive of diverter valve with over-current detect.
Astable multivibrator -> EHT generator <- ION flame detector.
Gas valve stepper motor driver with lots of monitoring thereof (safety stuff).
eBus line driver comms.
5V level full duplex Tx & Rx comms.
5V level half duplex TxRx comms.

Not fitted stuff guessed at, 95% sure of (just out of interest)
Neutral Feed (to relays) current monitor.
Solid-state mains relay.
Quad buffered outputs.
8 way connector for extra AtoD inputs via multiplexor.

Weird stuff I see:
Use of an ISOLATED switched mode power supply which is then bridged: Neutral connected to GND.
Lack of ESD or I/O protection to processor pins.
Reset capacitor miles away from processor input pin < PROBLEM FOUND!

I know (or strongly suspect) what every pin of every connector does & what it is connected to, even for those connectors that are not fitted.

In the image below I identified the most important test-points. From the schematic I know what levels etc they should be at.


Yes, I was bored.

 

[johnplumb]

Well that me fooked then.

 

[transam]

very good

what is your back ground i.e do u work in electronics or ??

interested

 

[underwurlde]

very good

what is your back ground i.e do u work in electronics or ??

interested

Electrical & electronics engineering, man & boy.

 

[sooey]

So, given your obvious experience and ability in electronics design what's your opinion on these boards, considering the cost of them and the cost of the boilers they're fitted in?
Would it cost the makers much per board to bring them up to a reasonable spec in your opinion, or do you think that most boiler repairers suspicions that they have been designed to fail are not too far off the mark?

 

[DP]

OP, well done. Very impressive, deserve a gold star

 

[underwurlde]

So, given your obvious experience and ability in electronics design what's your opinion on these boards, considering the cost of them and the cost of the boilers they're fitted in?
Would it cost the makers much per board to bring them up to a reasonable spec in your opinion, or do you think that most boiler repairers suspicions that they have been designed to fail are not too far off the mark?

Very good question! My field is not designing of boiler controllers, but the stuff I design IS safety critical, designed for manufacture and RELIABLE.

Also, this is not the first boiler controller I have reverse engineered: I did the same for 3 versions of PCB used on Baxi Solo boilers. See here: //www.diynot.com/forums/viewtopic.php?p=1789359

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Those Baxi Solo boards are basically analogue computers. Clever design but (as in a previous heated discussion on this forum) cheap - no reason AT ALL why they shouldn't cost the manufacturer more than £10 to make.

Ditto the design on this thread, although the design uses a larger PCB and TWO ( ) processors, one of which is a custom design (from Elmos) I for the life of me cannot see why it would cost more that £15 to make. Hell, there is no enclosure, it is not IP rated, there are no heatsinks or expensive cabling to go with it etc.

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As for the design - they do seem to be always on the limit. A LOT of these boards, under NORMAL working conditions exhibit burn marks where certain components are just simply underrated.

I see on this design a string of small surface mount components slapped straight across the mains! I also see TWO processors! WTF. I think this design has evolved from a basic one processor system to include two processors, probably due to ever evolving safety standards.

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Also as mentioned, considering the moderately extreme conditions these boards are meant to work in (hot & potentially wet, with mains and EHT floating about), there does NOT seem to be much consideration for this employed within the design to protect the 'inner' components (i.e. processors) - it's not that difficult or indeed expensive to add a scatting of components to provide good levels of protection.

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To sum up then, what I generally see is on the limit, cheap designs that lack adequate protection. None of these control boards should cost more than say £10 to £15 to make in volume (>50K p.a.). That said, I could say the same about the automobile industry. So, yes, this has to be where considerable £££££ are being made. I guess they're a business at the end of the day that exist to make ££££££.

Andy

 

[Gasguru]

The series string of resistors across the mains is to short out cap C3 when the boards powered off....otherwise 340 VDC would make the repair eng jump a bit

I would guess that Elmos ASIC chip might be to stop pcb copying. Much of the design may well be employed on the other Vaillant/Glowworm/Saunier Duvall boards. Some of the older Glowworm/Saunier Duvals have a stepper driver on the gas valve (directly modulating burner pressure). Nowadays the higher spec Vaillants have a stepper on the gas valve for trimming the mix.

The diverter driver often fails....the Vaillant Group diverters have been hopeless...often leaking despite relatively clean systems. If left, then eventually the actuator can't cope and the H bridge drivers burn out on the board. Gets a very expensive repair.

Despite your board retailing at relatively low cost (for the boiler industry) the similar Vaillant and Glowworm SYMSIs can be anything up to £300 Still, someones got to pay for all the design faults repaired under warranty.

IMHO the the boiler manufacturers are pretty incompetent...so you get some terrible pcb design. Some of the peripheral components eg. DHW Hall flow sensors have CMOS buffered outputs....with absolutely no protection, just fitting the part could destroy it.

Whenever you touch any pcb or other modules, brushless fans, flow sensors etc ALWAYS earth yourself first.

 

[underwurlde]

The series string of resistors across the mains is to short out cap C3 when the boards powered off....otherwise 340 VDC would make the repair eng jump a bit

Indeed. My point was that it consisted of a string of SURFACE MOUNT components across 350V. A failure in any one of them would avalanche them all to fail. In other words I do not see much consideration for failure modes in these designs as you have also pointed out - leading as you say to catastrophic failure in some instances.

A