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      09-11-2013, 03:46 PM   #45
Mick70
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I am not sure if that could really happen - afaik the security circuits and end switches are "hardwired" and not affected by a smarttop module.

Anway, at least the issue of the German forum has another impact: Removing the module (if you can) will remedy the problem and bring all canbus devices back to work.
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      09-11-2013, 04:48 PM   #46
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That's interesting info. According to that post (and I'm using Google translation here):

Quote:
the smart module has an input protection circuit, consisting of a Verpoldiode, a Polyfuse (PTC) and suppressor. - The Verpoldiode at the entrance protects the module, if the operating voltage lines are reversed during installation. - The Polyfuse is no fuse in the classical sense, which simply "blows"
I would think that with the newer style plug-n-play connectors, it is not possible to connect the lines wrong. So I think this scenario perhaps only applies to the older style where you have to splice wires.

Just to add, the only problems I've ever heard is with the earlier BW1 module. I haven't actually read any problems with the current BW3 module.
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      09-12-2013, 02:57 AM   #47
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Quote:
Originally Posted by morfinx View Post
I would think that with the newer style plug-n-play connectors, it is not possible to connect the lines wrong.
I am not an electrician, but in my understanding of the explanation, wrong polartity should have not been an issue in the older module's circuit:

- The "Verpoldiode" prevents damage due to wrong polarity but has never shown any issues.

- The "Polyfuse" is not exactly a fuse but a kind of a resistor that increases its value if the current sent through it is too high. This will prevent the circuit from high currents (so it's normally not necessary to replace the Polyfuse in case of malfunction). However, the Polyfuse of course cannot stand unlimited load and will blow ("burn") under certain currents nonetheless.

- The "Suppressor Diode" is a transient voltage suppressor diode in order to prevent the module's circuit from high and transient voltage peaks. Such peaks are simply grounded to the chassis as the diode is placed between + and - of the module's power supply. If the diode fails (as some did), not only the peaks but all current of the power supply is sent to ground = shortcut. This is the moment when even the Polyfuse dies.

- So the module is simply "switched off" - this is the same situation as with some of the older modules without connector harness if they are not properly connected to +/- 12V.

Therefore I do not believe that only the newer design with the connector harness will avoid the failure issue. As already mentioned, a newer circuit design (or at least a better suppressor diode) is necessary. It appears that the new circuit design has been introduced on 19/01/2011 (serial numbers starting with 110119-xxx). Smarttop had a notice on their website with this serial number, so I believe this number is a quite good indicator for "safe" modules.

Last edited by Mick70; 09-12-2013 at 03:25 AM..
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      09-12-2013, 03:42 AM   #48
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Quote:
Originally Posted by Mick70 View Post
I am not an electrician, but in my understanding of the explanation, wrong polartity should have not been an issue in the older module's circuit:

- The "Verpoldiode" prevents damage due to wrong polarity but has never shown any issues.

- The "Polyfuse" is not exactly a fuse but a kind of a resistor that increases its value if the current sent through it is too high. This will prevent the circuit from high currents (so it's normally not necessary to replace the Polyfuse in case of malfunction). However, the Polyfuse of course cannot stand unlimited load and will blow ("burn") under certain currents nonetheless.

- The "Suppressor Diode" is a transient voltage suppressor diode in order to prevent the module's circuit from high and transient voltage peaks. Such peaks are simply grounded to the chassis as the diode is placed between + and - of the module's power supply. If the diode fails (as some did), not only the peaks but all current of the power supply is sent to ground = shortcut. This is the moment when even the Polyfuse dies.

- So the module is simply "switched off" - this is the same situation as with some of the older modules without connector harness if they are not properly connected to +/- 12V.

Therefore I do not believe that only the newer design with the connector harness will avoid the failure issue. As already mentioned, a newer circuit design (or at least a better suppressor diode) is necessary. It appears that the new circuit design has been introduced on 19/01/2011 (serial numbers starting with 110119-xxx). Smarttop had a notice on their website with this serial number, so I believe this number is a quite good indicator for "safe" modules.
Ah, thanks. I didn't actually read the whole post for some reason. Is the person who made the post affiliated with mods4cars? I'm an electrical engineer, although I haven't dealt with analog circuits for quite some time, so my knowledge is a bit rusty. I've never heard of verpoldiode, but it sounds just like a regular diode, which allows current to flow in only one direction. Your description of polyfuse and suppressor diode (TVS diode) are spot on. The TVS diodes can usually handle quite a bit of current. But if that fails, a short circuit can certainly kill the polyfuse. I'd be interested in hearing what caused the failures and what modifications were made to fix the problem.
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      09-12-2013, 05:39 AM   #49
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Quote:
Originally Posted by morfinx View Post
I'd be interested in hearing what caused the failures and what modifications were made to fix the problem.
Yes, a "Verpoldiode" is just a regular diode to prevent damage due to "Verpolung" (= wrong polarization).

Unfortunately, the thread ends without detailed indications - apparently, the TVS diodes just failed without a certain reason (bad batch?).

Another forist in the thread says that, to his impression, the new circuit design may show "less diodes" but that "an additional diode is now soldered flying to one of the IC's legs". Of course, this is not a sufficient description for the remedy (I would personally just change the TVS diode for a good batch).

I am not sure if "42w203" is indeed an engineer but all his posts on zroadster.com are very elaborated and afaik always proved to be correct. A link to Smarttop is very unlikely.

BTW: Some of the German forists - including 42w203 - still do not trust the new modules. They have simply extended the canbus cables and now placed the module behind the glove box or above the ski sack (not possible with hifi pro)...

Last edited by Mick70; 09-12-2013 at 06:15 AM..
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