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E-Stop

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Bsquared

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So the last part of my Electric set up I need is the E-Stop. I ordered the big red mushroom, and have an in-line fuse holder for the 1amp fuse, but I am a little stumped on the two 1Ω resistors. The resistors I am picturing are the ones that get soldered in to a board. are these the ones people use? How are these incorporated with a wire? are they just soldered in-line to the wire? or is there a better way.

Thanks in advance for the help.
 

samc

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Are you talking about the P-J device? If so I just carefully, soldered a wire on the metal leads.
 

audger

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anything that gives you a little resistance will work. for only 1ohm, you can probably even get away without it- though i wont tell you to do that without seeing the whole wiring diagram. i believe all its for is to trickle a little current to the ground wire to trip the GFCI. a standard 1/8th watt resistor with some 28 or 26ga wire will work for that.

do you have a specific wiring diagram to confirm?
 

kellzey

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Yes, you need something like this... these are 1 watt resistors



I think the ones in post #4 or 1/8, 1/4, and 1/2 watt

I picked up from my local electronics surplus place...
 
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Bsquared

Bsquared

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Sweet,Thanks. I did not see the 1K 1W this morning. I have a good electronic component shop I go to down the street. I'm sure they will have them.
 

kellzey

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If you get stuck, i can get some more and send some to you.
 

lschiavo

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Using two 1k resistors results in 7 Watts dissipated and 60mA of fault current. I assume the wattage of the resistors doesn't matter much as the Gfi should trip before the resistors have much chance to heat.

I think the fault current could be reduced by raising the resistance and maybe splitting the load into three resistors. Then the wattage rating of the resistors would not be exceeded. Is this worth doing? Wouldn't 15 or 20mA be sufficient to trip the gfi? I think this is a brilliant way to provide an e stop but I never really understood the excessive current or undersized resistors.
 

P-J

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Please keep in mind that once the E-Stop is pressed the GFCI will cut all of the power to the control panel within a millisecond. There is no need to have higher wattage resistors or resistors that limit the current draw to a lower level. We are talking about 0.06A for less time that it would take for you to blink your eye. Will the resistors heat up? NOT a chance.!
 

lschiavo

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P-J said:
Please keep in mind that once the E-Stop is pressed the GFCI will cut all of the power to the control panel within a millisecond. There is no need to have higher wattage resistors or resistors that limit the current draw to a lower level. We are talking about 0.06A for less time that it would take for you to blink your eye. Will the resistors heat up? NOT a chance.!
I agree. The wattage rating of the resistors is really not a factor considering the speed of the GFCI. Can you then explain the function of the 1A fuse when the resistors will fry at about 20mA? Aren't the resistors already acting as a fuse? And do you really want a fuse in such a critical circuit? Why not drop the fuse and design the circuit to be capable of sustained fault current?
 

P-J

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I agree. The wattage rating of the resistors is really not a factor considering the speed of the GFCI. Can you then explain the function of the 1A fuse when the resistors will fry at about 20mA? Aren't the resistors already acting as a fuse? And do you really want a fuse in such a critical circuit? Why not drop the fuse and design the circuit to be capable of sustained fault current?
Please keep in mind that fuses and circuit breakers are placed to protect the wiring. I place that fuse in the circuit for that exact purpose - to protect the wiring. It allows you to run a relatively small wiring set to the E-Stop switch and a low current switch as well. If you are not comfortable with that, do it your way.

As far as "design the circuit to be capable ..." - that already exists within the GFCI breaker. One only needs to walk to the power panel and press the test button when an emergency presents itself. Hey, it could be a long walk, but, what the heck.
 

lschiavo

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P-J said:
Please keep in mind that fuses and circuit breakers are placed to protect the wiring. I place that fuse in the circuit for that exact purpose - to protect the wiring. It allows you to run a relatively small wiring set to the E-Stop switch and a low surrent switch as well. If you are not comfortable with that, do it your way.

Are we worried about protecting the wire when our brewery is melting down around us? I do not believe that a fuse belongs in a critical circuit. You seem knowledgeable. Have you ever wired a fire pump? Protecting the wire is the last concern.

As far as "design the circuit to be capable ..." - that already exists within the GFCI breaker. One only needs to walk to the power panel and press the test button when an emergency presents itself. Hey, it could be a long walk, but, what the heck.
So a GFCI will never fail? It will never require more than a millisecond to trip? What if it takes just a fraction of a second longer to trip than the resistors take to burn up? Why build in a fail?

Let's say we put 4 1k 1W resistors in series. 30mA fault current should be plenty. You can hold the button all day and not fry the resistors.

Here's a scenario you may not have thought of...say your a safe brewer and you test your GFI before each brew session. This time it doesn't work. Now replace the breaker and the resistors you just fried.

I dunno, makes sense to me.

Edit...sorry I typed in the middle of your quote...stupid phones...
 

lschiavo

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P-J said:
Do what ever you want to do. Just go for it.!
You don't like the way I present a drawing?
Don't use it.

I'm done.!!!!
I am offering constructive criticism. I don't want a fight. I saw what I believe to be a flaw in your design and offered a fix. I also complemented you at the start of our discussion. Does you being "done" mean I'm right?
 
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Bsquared

Bsquared

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I'm sure there are a million ways to skin this cat, but I'm going to stick with PJ's diagram. I was just confused on mainly on how to integrate the resisters into the wiring. But also I guess on the size of the resisters too. :p

On a side note I'd like to thank PJ again for all the help directly and indirectly on my electric build.

Thanks PJ!
 

jsguitar

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I twisted and soldered the wires going to and from the resistors and twisted and soldered the resistors to each other. I then used heat shrink on the whole thing. Worked fine.
 

lschiavo

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jsguitar said:
I twisted and soldered the wires going to and from the resistors and twisted and soldered the resistors to each other. I then used heat shrink on the whole thing. Worked fine.
This is exactly what I did but with 4 1k resistors and no fuse.

I'm in the middle of building a panel now and I really think this estop method is smart and I borrowed it from PJs drawing. I'm not trying to bash PJ but I think the fuse is a waste of time and money and the resistors fail if not for the gfi tripping.

This circuit is only meant to carry current in an emergency. I want mine to work when I need it to. I don't want it to have weak links and inherent fails. If you do, build the circuit as drawn. I'm just trying to offer a fix that is cheaper and much more failproof.
 
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