Why does this washing machine have microprocessor pins directly connected to the main AC power?

Clash Royale CLAN TAG#URR8PPP

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I'm studying the attached washing machine partial schematic at the point in which the main microcontroller activates 2 water elecrovalves.
I would ask:

1. It seems the microcontroller pins 36 and 40 are connected by the 1k resistor to the main AC "ground" (which means phase or neutral). How is it possible that the 230V phase, and not the neutral, could be connected to the pin? From my experience an optoisolator is the correct choice.


2. The triac is not provided by a snubber. It is correctly designed?


3. Why does one of the triacs have a voltage divider with 560 Ohm resistor and not the other?

Thanks a lot

control triac

share|improve this question

edited 13 mins ago

Blair Fonville

2,4462826

asked 4 hours ago

daigs

61

New contributor

daigs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  "main AC "ground" (which mean phase or neutral)" does it? Or does it mean PE? Around here washing machines are required to have PE. This thing seems to be russian, if its something older it can also mean "we don't care about safety"
  – PlasmaHH
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  If all inputs and outputs of the microprocessor are referred to the same ground potential it is no problem if this ground potential is actually the phase. But all keys and LEDs connected to the microprocessor should be isolated the same way as a wire conected to the phase should be to guarantee users safety.
  – Uwe
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  From my experience an optoisolator is the correct choice. In general opto isolators are needed in devices that have a mains connection and a low voltage, safe to touch connector. Example: a phone charger. Without the opto isolator there would be a direct mains connection so the output would be unsafe to touch. But if there aren't any connections to the outside and the metal case is grounded, then there is no need for an opto isolator.
  – Bimpelrekkie
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Hi plasma, this machine is not old and not only dedicated to the russian market.
  – daigs
  4 hours ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

favorite

I'm studying the attached washing machine partial schematic at the point in which the main microcontroller activates 2 water elecrovalves.
I would ask:

1. It seems the microcontroller pins 36 and 40 are connected by the 1k resistor to the main AC "ground" (which means phase or neutral). How is it possible that the 230V phase, and not the neutral, could be connected to the pin? From my experience an optoisolator is the correct choice.


2. The triac is not provided by a snubber. It is correctly designed?


3. Why does one of the triacs have a voltage divider with 560 Ohm resistor and not the other?

Thanks a lot

control triac

share|improve this question

edited 13 mins ago

Blair Fonville

2,4462826

asked 4 hours ago

daigs

61

New contributor

daigs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  "main AC "ground" (which mean phase or neutral)" does it? Or does it mean PE? Around here washing machines are required to have PE. This thing seems to be russian, if its something older it can also mean "we don't care about safety"
  – PlasmaHH
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  If all inputs and outputs of the microprocessor are referred to the same ground potential it is no problem if this ground potential is actually the phase. But all keys and LEDs connected to the microprocessor should be isolated the same way as a wire conected to the phase should be to guarantee users safety.
  – Uwe
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  From my experience an optoisolator is the correct choice. In general opto isolators are needed in devices that have a mains connection and a low voltage, safe to touch connector. Example: a phone charger. Without the opto isolator there would be a direct mains connection so the output would be unsafe to touch. But if there aren't any connections to the outside and the metal case is grounded, then there is no need for an opto isolator.
  – Bimpelrekkie
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Hi plasma, this machine is not old and not only dedicated to the russian market.
  – daigs
  4 hours ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

favorite

up vote
1
down vote

favorite

I'm studying the attached washing machine partial schematic at the point in which the main microcontroller activates 2 water elecrovalves.
I would ask:

1. It seems the microcontroller pins 36 and 40 are connected by the 1k resistor to the main AC "ground" (which means phase or neutral). How is it possible that the 230V phase, and not the neutral, could be connected to the pin? From my experience an optoisolator is the correct choice.


2. The triac is not provided by a snubber. It is correctly designed?


3. Why does one of the triacs have a voltage divider with 560 Ohm resistor and not the other?

Thanks a lot

control triac

share|improve this question

edited 13 mins ago

Blair Fonville

2,4462826

asked 4 hours ago

daigs

61

New contributor

daigs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

I'm studying the attached washing machine partial schematic at the point in which the main microcontroller activates 2 water elecrovalves.
I would ask:

1. It seems the microcontroller pins 36 and 40 are connected by the 1k resistor to the main AC "ground" (which means phase or neutral). How is it possible that the 230V phase, and not the neutral, could be connected to the pin? From my experience an optoisolator is the correct choice.


2. The triac is not provided by a snubber. It is correctly designed?


3. Why does one of the triacs have a voltage divider with 560 Ohm resistor and not the other?

Thanks a lot

control triac

control triac

share|improve this question

edited 13 mins ago

Blair Fonville

2,4462826

asked 4 hours ago

daigs

61

New contributor

daigs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 13 mins ago

Blair Fonville

2,4462826

asked 4 hours ago

daigs

61

New contributor

daigs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

share|improve this question

edited 13 mins ago

Blair Fonville

2,4462826

edited 13 mins ago

Blair Fonville

2,4462826

edited 13 mins ago

Blair Fonville

2,4462826

2,4462826

asked 4 hours ago

daigs

61

New contributor

daigs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 4 hours ago

daigs

61

asked 4 hours ago

daigs

61

61

New contributor

daigs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

New contributor

daigs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

daigs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  "main AC "ground" (which mean phase or neutral)" does it? Or does it mean PE? Around here washing machines are required to have PE. This thing seems to be russian, if its something older it can also mean "we don't care about safety"
  – PlasmaHH
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  If all inputs and outputs of the microprocessor are referred to the same ground potential it is no problem if this ground potential is actually the phase. But all keys and LEDs connected to the microprocessor should be isolated the same way as a wire conected to the phase should be to guarantee users safety.
  – Uwe
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  From my experience an optoisolator is the correct choice. In general opto isolators are needed in devices that have a mains connection and a low voltage, safe to touch connector. Example: a phone charger. Without the opto isolator there would be a direct mains connection so the output would be unsafe to touch. But if there aren't any connections to the outside and the metal case is grounded, then there is no need for an opto isolator.
  – Bimpelrekkie
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Hi plasma, this machine is not old and not only dedicated to the russian market.
  – daigs
  4 hours ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  "main AC "ground" (which mean phase or neutral)" does it? Or does it mean PE? Around here washing machines are required to have PE. This thing seems to be russian, if its something older it can also mean "we don't care about safety"
  – PlasmaHH
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  If all inputs and outputs of the microprocessor are referred to the same ground potential it is no problem if this ground potential is actually the phase. But all keys and LEDs connected to the microprocessor should be isolated the same way as a wire conected to the phase should be to guarantee users safety.
  – Uwe
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  From my experience an optoisolator is the correct choice. In general opto isolators are needed in devices that have a mains connection and a low voltage, safe to touch connector. Example: a phone charger. Without the opto isolator there would be a direct mains connection so the output would be unsafe to touch. But if there aren't any connections to the outside and the metal case is grounded, then there is no need for an opto isolator.
  – Bimpelrekkie
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Hi plasma, this machine is not old and not only dedicated to the russian market.
  – daigs
  4 hours ago
  

  
  
  
  

1

1

"main AC "ground" (which mean phase or neutral)" does it? Or does it mean PE? Around here washing machines are required to have PE. This thing seems to be russian, if its something older it can also mean "we don't care about safety"
– PlasmaHH
4 hours ago

"main AC "ground" (which mean phase or neutral)" does it? Or does it mean PE? Around here washing machines are required to have PE. This thing seems to be russian, if its something older it can also mean "we don't care about safety"
– PlasmaHH
4 hours ago

If all inputs and outputs of the microprocessor are referred to the same ground potential it is no problem if this ground potential is actually the phase. But all keys and LEDs connected to the microprocessor should be isolated the same way as a wire conected to the phase should be to guarantee users safety.
– Uwe
4 hours ago

If all inputs and outputs of the microprocessor are referred to the same ground potential it is no problem if this ground potential is actually the phase. But all keys and LEDs connected to the microprocessor should be isolated the same way as a wire conected to the phase should be to guarantee users safety.
– Uwe
4 hours ago

1

1

From my experience an optoisolator is the correct choice. In general opto isolators are needed in devices that have a mains connection and a low voltage, safe to touch connector. Example: a phone charger. Without the opto isolator there would be a direct mains connection so the output would be unsafe to touch. But if there aren't any connections to the outside and the metal case is grounded, then there is no need for an opto isolator.
– Bimpelrekkie
4 hours ago

From my experience an optoisolator is the correct choice. In general opto isolators are needed in devices that have a mains connection and a low voltage, safe to touch connector. Example: a phone charger. Without the opto isolator there would be a direct mains connection so the output would be unsafe to touch. But if there aren't any connections to the outside and the metal case is grounded, then there is no need for an opto isolator.
– Bimpelrekkie
4 hours ago

Hi plasma, this machine is not old and not only dedicated to the russian market.
– daigs
4 hours ago

Hi plasma, this machine is not old and not only dedicated to the russian market.
– daigs
4 hours ago

add a comment | 

2 Answers
2

active

oldest

votes

up vote
5
down vote

The two pins you mention drive the gates of triacs. Obviously the ground that the cathodes of the triacs are connected to is the same ground that the micro is connected to. One way or another, a low voltage supply is created somewhere to run the micro from, and the negative output of that supply is tied to the system ground.

share|improve this answer

answered 4 hours ago

Olin Lathrop

278k28331781

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks Olin, but the pin 36 "sense" about 220 V from the 1K resistor, regardless it is in high state (220-5v in this case) or low. Don't this voltage destroy the pin circuitry? Thanks.
  – daigs
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @daigs: Your comment makes no sense. Pin 36 is going directly to the gate of a triac, with the cathode of the triac grounded.
  – Olin Lathrop
  4 hours ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

The schematic is only partial but it looks to me like they are using the mains neutral as "system ground". To add to the confusion it looks like they are using the "earth ground" symbol to represent system ground.

In designing an electronic system with logic controlling mains there are essentially two options. One option is to refer the electronics to the mains supply (either live or neutral) and put safety isolation between the logic and the user. The other option is to have the logic either floating or reffered to mains earth and put safety isolation between the logic and the mains.

In large volume the former approach is often more economical as it avoids the need for a bunch of isolation components. Yes it means your buttons and displays need to have safety isolation but that can often be done at very little cost through careful design of the front panel.

share|improve this answer

answered 21 mins ago

Peter Green

10.9k11837

add a comment | 

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

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active

oldest

votes

active

oldest

votes

up vote
5
down vote

The two pins you mention drive the gates of triacs. Obviously the ground that the cathodes of the triacs are connected to is the same ground that the micro is connected to. One way or another, a low voltage supply is created somewhere to run the micro from, and the negative output of that supply is tied to the system ground.

share|improve this answer

answered 4 hours ago

Olin Lathrop

278k28331781

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks Olin, but the pin 36 "sense" about 220 V from the 1K resistor, regardless it is in high state (220-5v in this case) or low. Don't this voltage destroy the pin circuitry? Thanks.
  – daigs
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @daigs: Your comment makes no sense. Pin 36 is going directly to the gate of a triac, with the cathode of the triac grounded.
  – Olin Lathrop
  4 hours ago
  

  
  
  
  

add a comment | 

up vote
5
down vote

The two pins you mention drive the gates of triacs. Obviously the ground that the cathodes of the triacs are connected to is the same ground that the micro is connected to. One way or another, a low voltage supply is created somewhere to run the micro from, and the negative output of that supply is tied to the system ground.

share|improve this answer

answered 4 hours ago

Olin Lathrop

278k28331781

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks Olin, but the pin 36 "sense" about 220 V from the 1K resistor, regardless it is in high state (220-5v in this case) or low. Don't this voltage destroy the pin circuitry? Thanks.
  – daigs
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @daigs: Your comment makes no sense. Pin 36 is going directly to the gate of a triac, with the cathode of the triac grounded.
  – Olin Lathrop
  4 hours ago
  

  
  
  
  

add a comment | 

up vote
5
down vote

up vote
5
down vote

The two pins you mention drive the gates of triacs. Obviously the ground that the cathodes of the triacs are connected to is the same ground that the micro is connected to. One way or another, a low voltage supply is created somewhere to run the micro from, and the negative output of that supply is tied to the system ground.

share|improve this answer

answered 4 hours ago

Olin Lathrop

278k28331781

The two pins you mention drive the gates of triacs. Obviously the ground that the cathodes of the triacs are connected to is the same ground that the micro is connected to. One way or another, a low voltage supply is created somewhere to run the micro from, and the negative output of that supply is tied to the system ground.

share|improve this answer

answered 4 hours ago

Olin Lathrop

278k28331781

share|improve this answer

share|improve this answer

answered 4 hours ago

Olin Lathrop

278k28331781

answered 4 hours ago

Olin Lathrop

278k28331781

answered 4 hours ago

Olin Lathrop

278k28331781

278k28331781

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks Olin, but the pin 36 "sense" about 220 V from the 1K resistor, regardless it is in high state (220-5v in this case) or low. Don't this voltage destroy the pin circuitry? Thanks.
  – daigs
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @daigs: Your comment makes no sense. Pin 36 is going directly to the gate of a triac, with the cathode of the triac grounded.
  – Olin Lathrop
  4 hours ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks Olin, but the pin 36 "sense" about 220 V from the 1K resistor, regardless it is in high state (220-5v in this case) or low. Don't this voltage destroy the pin circuitry? Thanks.
  – daigs
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @daigs: Your comment makes no sense. Pin 36 is going directly to the gate of a triac, with the cathode of the triac grounded.
  – Olin Lathrop
  4 hours ago
  

  
  
  
  

Thanks Olin, but the pin 36 "sense" about 220 V from the 1K resistor, regardless it is in high state (220-5v in this case) or low. Don't this voltage destroy the pin circuitry? Thanks.
– daigs
4 hours ago

Thanks Olin, but the pin 36 "sense" about 220 V from the 1K resistor, regardless it is in high state (220-5v in this case) or low. Don't this voltage destroy the pin circuitry? Thanks.
– daigs
4 hours ago

2

2

@daigs: Your comment makes no sense. Pin 36 is going directly to the gate of a triac, with the cathode of the triac grounded.
– Olin Lathrop
4 hours ago

@daigs: Your comment makes no sense. Pin 36 is going directly to the gate of a triac, with the cathode of the triac grounded.
– Olin Lathrop
4 hours ago

add a comment | 

up vote
1
down vote

The schematic is only partial but it looks to me like they are using the mains neutral as "system ground". To add to the confusion it looks like they are using the "earth ground" symbol to represent system ground.

In designing an electronic system with logic controlling mains there are essentially two options. One option is to refer the electronics to the mains supply (either live or neutral) and put safety isolation between the logic and the user. The other option is to have the logic either floating or reffered to mains earth and put safety isolation between the logic and the mains.

In large volume the former approach is often more economical as it avoids the need for a bunch of isolation components. Yes it means your buttons and displays need to have safety isolation but that can often be done at very little cost through careful design of the front panel.

share|improve this answer

answered 21 mins ago

Peter Green

10.9k11837

add a comment | 

up vote
1
down vote

The schematic is only partial but it looks to me like they are using the mains neutral as "system ground". To add to the confusion it looks like they are using the "earth ground" symbol to represent system ground.

In designing an electronic system with logic controlling mains there are essentially two options. One option is to refer the electronics to the mains supply (either live or neutral) and put safety isolation between the logic and the user. The other option is to have the logic either floating or reffered to mains earth and put safety isolation between the logic and the mains.

In large volume the former approach is often more economical as it avoids the need for a bunch of isolation components. Yes it means your buttons and displays need to have safety isolation but that can often be done at very little cost through careful design of the front panel.

share|improve this answer

answered 21 mins ago

Peter Green

10.9k11837

add a comment | 

up vote
1
down vote

up vote
1
down vote

The schematic is only partial but it looks to me like they are using the mains neutral as "system ground". To add to the confusion it looks like they are using the "earth ground" symbol to represent system ground.

In designing an electronic system with logic controlling mains there are essentially two options. One option is to refer the electronics to the mains supply (either live or neutral) and put safety isolation between the logic and the user. The other option is to have the logic either floating or reffered to mains earth and put safety isolation between the logic and the mains.

In large volume the former approach is often more economical as it avoids the need for a bunch of isolation components. Yes it means your buttons and displays need to have safety isolation but that can often be done at very little cost through careful design of the front panel.

share|improve this answer

answered 21 mins ago

Peter Green

10.9k11837

The schematic is only partial but it looks to me like they are using the mains neutral as "system ground". To add to the confusion it looks like they are using the "earth ground" symbol to represent system ground.

In designing an electronic system with logic controlling mains there are essentially two options. One option is to refer the electronics to the mains supply (either live or neutral) and put safety isolation between the logic and the user. The other option is to have the logic either floating or reffered to mains earth and put safety isolation between the logic and the mains.

In large volume the former approach is often more economical as it avoids the need for a bunch of isolation components. Yes it means your buttons and displays need to have safety isolation but that can often be done at very little cost through careful design of the front panel.

share|improve this answer

answered 21 mins ago

Peter Green

10.9k11837

share|improve this answer

share|improve this answer

answered 21 mins ago

Peter Green

10.9k11837

answered 21 mins ago

Peter Green

10.9k11837

answered 21 mins ago

Peter Green

10.9k11837

10.9k11837

add a comment | 

add a comment | 

daigs is a new contributor. Be nice, and check out our Code of Conduct.

 

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