Re: Remote pump control ideas.
Ok, time for more details, since it's getting interesting Here's a picture of the box holding all the high power parts, including the contactor. In the original setup, their power supply was in here too, so I kinda rolled with it and put it in the corner there myself. Looking at it now, I realize all my wires going back and forth in there are a bit too close for comfort to those big three phase wires sticking out the top of the contactor, and to the contactor itself for that matter, so that's one aspect which may be a no-no, despite most of them you see being outputs to the LED indicators on the door and these are GNDs which are "behind" optocouplers.
The only "direct" connection to my Nucleo144 is the GND wire and the 12v wire - the rest seem to be isolated, the way I see it, of course. There IS one other wire which is connected directly to the perfboard, which is a 5v wire coming from the PSU (12+5v output supply) which I send to the transistor sides of each of the optocouplers to drive the bases of the 2n2222a transistors which in turn provide the LEDs (and small control relay) with their GND, allowing them to switch on. I didn't want to use the Nucleo's built-in 5v regulator for fear I may overload it - since I have a 5v-capable supply, I figured I should use that.
My "brains" sit in a box right above this one, with the Nucleo at the very top, that brown perfboard in the middle and a GSM dialer module at the bottom. I realize now, after testing it some more today, that this GSM module may be causing interference of its own - more on this later, as it can easily be removed and it's not mission-critical ATM. I just found it there and decided to keep it...
The contactor is this one, in case someone's curious, plus it also allows me to look up the actual current draw of the coil, which the datasheet gives as 190VA at pull-in which then drops to 16VA holding (if I'm not mistaken by the numbers on pages 3 to 4). I was thinking these figures may be relevant when trying to design some sort of snubber for it.
About this: varistor vs. snubber. I read about varistors and know what they are in general, having worked with power supplies in consumer electronics before which all have them, but reading more closely about their performance over time and also the possible fires they can start concerns me. This is out in the middle of nowhere, where power is anything BUT stable....so there's that. I'm not sure how an RC snubber would perform by comparison, what its strengths and weaknesses are and whether that formula I found holds true for AC as well...
Let's talk about this: in the picture, you see two fat leads coming in at the bottom of the box. The bundle on the left, which goes into the MCB, is the three-phase input and the one on the right is the output to the pump from the contactor (after one of the phases passes through that motor protection). From what I can assume, since I'm no electrician, the fat blue wire is our neutral. However, I don't see a PE wire as well. The fat green/yellow "PE" conductor visible, which SHOULD ground the box is just going out to the pump, but I'm not sure if this is floating or is tied to the neutral conductor in the distribution box somewhere, so that may be of concern. The PE could be floating for all I know, since unless the fat green lead is tied to earth where the pump is at the other end of the loom on the right side, I'd say there IS no PE as it stands, so the box is "floating", since the white neutral terminal block at the far right (next to the "Eldon" fan thermostat) does not contact the metal frame, while the green ones purposely do, since they ARE meant to contact the metal frame and I measured them and it makes perfect sense to be that way. The blue wire does nothing but carry the neutral into my box and that's it...and I'm not comfortable enough to actually tie blue to the green PE wire (and chassis), even though I'm pretty sure this is a TN-C system and they are ALREADY tied together at the distribution box...this takes an electrician to do, which I'm not.
This would mean the PE of my Meanwell supply up there is floating and not dissipating anything. Construction-wise, I'm expecting the supply itself to have a blue Y cap between the PE screw terminal and the the 12v GND terminal (our negative 12v, or "return" as I've seen it written on some supplies when talking about the SECONDARY side)...
Oh and don't worry about that junction box at the far left - that's just something I threw in there to allow me connect multiple wires to GND or 12v more easily, since I knew I'd wouldn't be able to stuff all of that directly onto the screw terminals of the power supply, so I added those pre-assembled busbars to give me more screws to work with
Ok, time for more details, since it's getting interesting Here's a picture of the box holding all the high power parts, including the contactor. In the original setup, their power supply was in here too, so I kinda rolled with it and put it in the corner there myself. Looking at it now, I realize all my wires going back and forth in there are a bit too close for comfort to those big three phase wires sticking out the top of the contactor, and to the contactor itself for that matter, so that's one aspect which may be a no-no, despite most of them you see being outputs to the LED indicators on the door and these are GNDs which are "behind" optocouplers.
The only "direct" connection to my Nucleo144 is the GND wire and the 12v wire - the rest seem to be isolated, the way I see it, of course. There IS one other wire which is connected directly to the perfboard, which is a 5v wire coming from the PSU (12+5v output supply) which I send to the transistor sides of each of the optocouplers to drive the bases of the 2n2222a transistors which in turn provide the LEDs (and small control relay) with their GND, allowing them to switch on. I didn't want to use the Nucleo's built-in 5v regulator for fear I may overload it - since I have a 5v-capable supply, I figured I should use that.
My "brains" sit in a box right above this one, with the Nucleo at the very top, that brown perfboard in the middle and a GSM dialer module at the bottom. I realize now, after testing it some more today, that this GSM module may be causing interference of its own - more on this later, as it can easily be removed and it's not mission-critical ATM. I just found it there and decided to keep it...
The contactor is this one, in case someone's curious, plus it also allows me to look up the actual current draw of the coil, which the datasheet gives as 190VA at pull-in which then drops to 16VA holding (if I'm not mistaken by the numbers on pages 3 to 4). I was thinking these figures may be relevant when trying to design some sort of snubber for it.
About this: varistor vs. snubber. I read about varistors and know what they are in general, having worked with power supplies in consumer electronics before which all have them, but reading more closely about their performance over time and also the possible fires they can start concerns me. This is out in the middle of nowhere, where power is anything BUT stable....so there's that. I'm not sure how an RC snubber would perform by comparison, what its strengths and weaknesses are and whether that formula I found holds true for AC as well...
Originally posted by redwire
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This would mean the PE of my Meanwell supply up there is floating and not dissipating anything. Construction-wise, I'm expecting the supply itself to have a blue Y cap between the PE screw terminal and the the 12v GND terminal (our negative 12v, or "return" as I've seen it written on some supplies when talking about the SECONDARY side)...
Oh and don't worry about that junction box at the far left - that's just something I threw in there to allow me connect multiple wires to GND or 12v more easily, since I knew I'd wouldn't be able to stuff all of that directly onto the screw terminals of the power supply, so I added those pre-assembled busbars to give me more screws to work with
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