Can i use a Reed switch to detect if my motor is spinning?

[Lucien Nunes]

We're not engineering a solution, we're responding with some food for thought for the OP rather than simply answering a flat 'No' to his original question. Benz had to discover how to make a car go, before quantifying the risks involved if it wouldn't then stop!

 

[Megawatt]

Nope, that's engineering the solution before quantifying the risks.

Nope, that's engineering the solution before quantifying the risks.

if the fans are a part of the machine then do they have starters for each fan, if so then why don’t we look at inside the panel and see if you can monitor the fans much more accurate. I believe that you can use the contacts on the starter to turn on a light or something to let you know when it’s down. Your best bet is to get inside the panel where the fbetter than putting reed switches if nothing at all I believe that it can be done with relays or something with dry contacts you can use
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if the fans are a part of the machine then do they have starters for each fan, if so then why don’t we look at inside the panel and see if you can monitor the fans much more accurate. I believe that you can use the contacts on the starter to turn on a light or something to let you know when it’s down. Your best bet is to get inside the panel where the fbetter than putting reed switches if nothing at all I believe that it can be done with relays or something with dry contacts you can use

Does this machine have a PLC ?

 

[Spoon]

if the fans are a part of the machine then do they have starters for each fan, if so then why don’t we look at inside the panel and see if you can monitor the fans much more accurate. I believe that you can use the contacts on the starter to turn on a light or something to let you know when it’s down. Your best bet is to get inside the panel where the fbetter than putting reed switches if nothing at all I believe that it can be done with relays or something with dry contacts you can use

The problem the OP has with monitoring the supply to the fan is if one of the fans malfunctions then you will still have a signal saying the fan is operating as it will still have a supply to it.

 

[Holewski]

Thank you for everyones input. The company has been making fire place for 25 years. we test to all standards required to sell into north America. We normally do not require fans for operation of the fireplace. This is the first fireplace that uses glass as its saftey screen. Code says that the users has to be able to touch the screen for 5 seconds and not get burnt, the screen has to measure under 150F. the firebox is a totally sealed box. this is where the combustion takes place. there is a 4inch gap infront of the firebox then there is another piece of glass. the front piece of glass is what needs to be cooled. this is totally seperate to the firebox. see attached image of a similar unit. from the standpoint of the design of the fireplace. we've got that handled. it functions great and have made multiple prototypes.
as much as the thermal switch is a good idea we need to individually know which fan has failed so that a service tech will know which one of the 7 fans they need to replace.I completely agree that we should have had an electrical engineer design this circuit from the beginning, but thats not my call. im trying to find a solution at this stage of the product design process.
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The problem the OP has with monitoring the supply to the fan is if one of the fans malfunctions then you will still have a signal saying the fan is operating as it will still have a supply to it.

if the fans are a part of the machine then do they have starters for each fan, if so then why don’t we look at inside the panel and see if you can monitor the fans much more accurate. I believe that you can use the contacts on the starter to turn on a light or something to let you know when it’s down. Your best bet is to get inside the panel where the fbetter than putting reed switches if nothing at all I believe that it can be done with relays or something with dry contacts you can use
[automerge]1573830916[/automerge]

Does this machine have a PLC ?

i wish. that wasnt a direction we wanted to go over a year ago when we started this project. this will probably what we decide to do for any future similar models. this would make our lives much easier.

 

[Megawatt]

Thank you for everyones input. The company has been making fire place for 25 years. we test to all standards required to sell into north America. We normally do not require fans for operation of the fireplace. This is the first fireplace that uses glass as its saftey screen. Code says that the users has to be able to touch the screen for 5 seconds and not get burnt, the screen has to measure under 150F. the firebox is a totally sealed box. this is where the combustion takes place. there is a 4inch gap infront of the firebox then there is another piece of glass. the front piece of glass is what needs to be cooled. this is totally seperate to the firebox. see attached image of a similar unit. from the standpoint of the design of the fireplace. we've got that handled. it functions great and have made multiple prototypes.
as much as the thermal switch is a good idea we need to individually know which fan has failed so that a service tech will know which one of the 7 fans they need to replace.I completely agree that we should have had an electrical engineer design this circuit from the beginning, but thats not my call. im trying to find a solution at this stage of the product design process.
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i wish. that wasnt a direction we wanted to go over a year ago when we started this project. this will probably what we decide to do for any future similar models. this would make our lives much easier.

Holewski we all was trying to help and we wish you all the luck in the world

 

[PEG]

I will have to guess,then,that these are solid fuel or wood burners?

If so,this limits the extent of action,on having a fan fail,to input air restriction,audible or visual warning,on account of the complexities,of fitting a Halon system

 

[Holewski]

Holewski we all was trying to help and we wish you all the luck in the world

HAHAHA thanks. i think im going to need it!

 

[Spoon]

Maybe then, you best bet is to find a fan with a built in hall sensor.
These fans have 3 wires. 2 for power and one generates pulses while the fan is rotating.
You could monitor these pulses to see if the fan has stopped or is not running at speed.

 

[Megawatt]

I will have to guess,then,that these are solid fuel or wood burners?

If so,this limits the extent of action,on having a fan fail,to input air restriction,audible or visual warning,on account of the complexities,of fitting a Halon system

PEG if I had to guess it would be gas

 

[Holewski]

Maybe then, you best bet is to find a fan with a built in hall sensor.
These fans have 3 wires. 2 for power and one generates pulses while the fan is rotating.
You could monitor these pulses to see if the fan has stopped or is not running at speed.

good idea, ill talk to our fan manufacturer. they have to be a class 4 fan so they can withstand the heat
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I will have to guess,then,that these are solid fuel or wood burners?

If so,this limits the extent of action,on having a fan fail,to input air restriction,audible or visual warning,on account of the complexities,of fitting a Halon system

natural gas & propane

 

[PEG]

good idea, ill talk to our fan manufacturer. they have to be a class 4 fan so they can withstand the heat
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natural gas & propane

Ahhh,groovy,you have at least the shut-down or modulation option?

Just in case,you thought i was a bit mr.safety....we have a shoot-hut,with a woodstove,made,ironically,from an old propane cylinder,and last week,the wind got up a bit,and even though we shut the air-damper tight,the bottom third was glowing bright red ?

 

[Holewski]

Ahhh,groovy,you have at least the shut-down or modulation option?

Just in case,you thought i was a bit mr.safety....we have a shoot-hut,with a woodstove,made,ironically,from an old propane cylinder,and last week,the wind got up a bit,and even though we shut the air-damper tight,the bottom third was glowing bright red ?

must have been nice and toasty!!! when we make wood stove we purpose fully over fire the crap out of them. external fans on them. ALLLL the wood. same with the gas stoves we purposefully find just before the air/gas saturation point and explode them multiple times.......... its the best bit about my job! the gas stoves have electronic valves with remotes and built in safety systems....

 

[static zap]

Reeds are very delicate temprametal mechanical devices ,
that require the correct actuating field for reliable operation.
Hall effect devices have no moving parts .
Mixing electronics and heat is a specialist design situation.
(Will my grill stay lit with no electricity for its cooling fan..)

 

[SheffSimon]

We're not engineering a solution, we're responding with some food for thought for the OP rather than simply answering a flat 'No' to his original question. Benz had to discover how to make a car go, before quantifying the risks involved if it wouldn't then stop!

That's great. Unfortunately it has precisely zero relevance to machinery or product design in a modern, litigious world.

Engineers are a nightmare in risk assessment meetings. Always desperate to engineer the solution before you even know what you are trying to protect against. I should know, I am one.

 

[Holewski]

Thanks for the responses. the general consensus is that I need a hall effect sensor. is there a way of using this on a totally analog circuit? there arent any PLCs (next time for sure)