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BTW: I have a bilge pump that I use to pump out a window well. The controller is very sensitive to over voltages and a reverse polarity will kill it. So, if this pump has any electronics in it's guts and your using an unregulated supply, it could be an issue.
It might help to use a regulated supply and/or place a TVS or MOV across the motor, but something just tells me it died. A fuse per pump probably makes the most sense at this point. Changing the FET to a fully protected low side switch would increase the reliability of the circuit. Alternatively, you could use a fully protected high side switch as well with a little rewiring. The issues with the high and low side switches is that most packages are surface mount only.
You could consider making a PCB, or you could ask Boncuk if he would lay one out for you. He would need a bill of materials and you would probably add some screw terminal pluggable headers to the mix.
This is one of the cheapest prototyping services: http://iteadstudio.com/store/index.php?main_page=index&cPath=19_20 A friend recent used them and was pleased, but not as good as BatchBCB. There was a review on eevBlog where the board didn't turn out quite right. He needed a small quantity of some very small simple PCB's and was very happy for what he got for the price.
Hello again every one. MAN this thread just keeps going and going. If I would have known it was going to go on for this long, I would have brought snacks.
I'm still thinking that the pumps use brushless/solid state motors and that an internal FET for the speed controller likely gave up the ghost. That or it's some kind of fancy space alien technology that I can't even explain or spell. My two cents. Now.... Back to work.
I guess a short could develop over time. The enamel coating on the wire of a winding is extremely thin, and if the wire had been, say, nicked or kinked during assembly there could have been a weak point of slightly higher electrical resistance resistance than the rest, resulting in a hot spot. That could have damaged the insulating ability of the enamel.
No sign of anything like that. Pumps were in a bucket of clean water.
Thanks all-it would be great to arrive at a definitive reason for this failure.
Maybe I could get the manufacturer to answer a question or two. If only I knew what to ask. Any chance I could get some help there?
1: Some pumps with circuitry inside them can't withstand even the slightest unclean voltages. (Like yours maybe)
2: It might help to use a TVS (Transient-voltage-suppression [diode]) or a MOV (metal-oxide varistor) to protect the pumps.
(Your supply SHOULD be regulated if you bought the unit I suggested off of Ebay. But It can't hurt to use a MOV or TVS anyway)
3: Swapping the FET for a fully protected low side switch (Also known as an "Intelligent power switch") Would make things less breakable. IPS's are basically like supper FET's made of Carbonite X Kevlar + magic. But they *CAN* be broken (if your really really good at it like me that is).
4: Most Intelligent power switches are surface mount devices, which NORMALLY would need a printed circuit board. (And they are more expensive.)
5: The rest is some cheep PCB manufacturing plugs..... I mean links.
If you want to go and use the IPS's, You can still use proto board. But I'm not guna lie, it's harder soldering to be sure. It will be more like metal working/soldering. But I'm sure you'll manage. You may need a bigger wattage iron to solder them. Also you need to plan your layout more carefully. But basically, you just want to take into account that the tab is the drain, and is huge. That's about it. I normally just solder a wire onto the tab... F-it... add a new leg... works for me.
I think it will put a cut right through a blown up water pump. You can try it, not my hacksaw blade. HE HE.
Just kidding. In all honestly it may tell us something, but I can bet the epoxy is all through the whole pump enclosure. And there is going to be high silicon iron for the stator coils you'll have to cut through. The PCB with the blown MOSFET is most likely just behind the epoxy, then the coils are behind that, If you keep going you start to hit desk or vice or whatever you have the pump sitting on. I'd try a heat gun and screw driver or chisel first. Some epoxy softens up mighty easy that way. Some doesn't.
A bit late in the day, but can you confirm the pumps are specified for continuous running? Are they spec'd as having brushless motors or needing any peculiar supply arrangements?
4pyros, I bought PS seperate from pumps.
Yes, I am sure they are to be run nonstop. This type of pump in AC has been around for decades, and they run forever.
Never ran them dry. Would never do such a thing. Maybe other really stupid things, but not that.
Alec, I feel confidant that there are no bushes in these pumps.
Definitely found electronic components inside the pump. In the second pic, I hope you can see the three legged component mounted underneath. FET maybe?
()blivion, heat worked real well to soften the epoxy. It peeled right off after I took a torch to it. Thanks for that good idea.
Yeah, that is definitely a brushless motor alright. No two ways about it. The FET likely got hot and self destructed. Being submersed in water SHOULD help with the cooling so make sure you always keep running them that way and not in the air.
(Would work better if they hadn't covered the damned FET's with heat insulating plastic :mumbles various curses at manufacturer
One of the two black things that are soldered down flat to the PCB is likely what is dead, they are just n-channel FETs. When removed and tested (tab to the right hand pin) *IF BLOWN* it will most likely read ~0 ohms/shorted with a multimeter both ways. You will need to test both of the devices.
The smaller black three pin thing underneath (in the second picture) is a magnetic sensor, not an FET. Most likely a hall effect sensor. Incidentally, the sensor is prolly fine, but you can test it if you want. The exact test depends on the Hall effect sensor type you have. Refer to this video and use a search engine on the numbers on the device you have.
The pump circuit *MAY* also employ an emf feed back component. Most cheaper brushless motors use back emf of some kind to do rotor positioning. I would need to see the exact coil layout to know for sure. But this is not important or likely for your pump in all reality. I just feel like mentioning it. Back emf sensing is used more often when the rotor has a larger mass and low torque load, so the rotor can "flywheel" a bit. And these type of systems don't usually have an independent sensor of any kind. So I'm guna stick with no back emf effects until it is proven otherwise.
It's possible to repair the electronics, but is it possible for one to repair the physical pump? LOL, it don't look like it from the pictures to me. Worst case scenario, salvage the sensor and make something neat.
4pyros, I bought PS seperate from pumps.
Yes, I am sure they are to be run nonstop. This type of pump in AC has been around for decades, and they run forever.
Never ran them dry. Would never do such a thing. Maybe other really stupid things, but not that.
Alec, I feel confidant that there are no bushes in these pumps.
Definitely found electronic components inside the pump. In the second pic, I hope you can see the three legged component mounted underneath. FET maybe?
()blivion, heat worked real well to soften the epoxy. It peeled right off after I took a torch to it. Thanks for that good idea.
The motor setup looks pretty simple. Probably a unipolar hall effect sensor such as https://www.digikey.com/product-detail/en/TLE4935G/TLE4935GINCT-ND/520119 coupled with two FETS and a gate current limiting resistor. It could be a sensor with a bipolar linear output too. The cool part is where it's mounted. I think it's sensing the coils magnetic field and not an external magnet. So, you would probably find one or both of the FETs shorted. Two MOV's or TVS for each coil would be the right thing to do but that makes the pump more expensive.
A MOV and reverse biased diode close to the motor and a fuse sized to protect the motor would be your best insurance for the motor itself. A self protecting switch rather than a simple FET would be the best change for the circuit reliability.
Though I agree with your assessment of the circuit, I respectfully disagree with your assessment of the sensor's role in the circuit. I think the sensors EXACT position was more than likely caused by Salty's "less that careful" disassembling of the pump (not that I'm complaining salty, you did fine). I think the part in question was exactly 90° perpendicular to the PCB originally, which would make the business end directly face the axis of the rotor. With that configuration, I am fairly sure it is sensing the rotor magnet directly since this is not optimum positioning of the sensor for picking up the coils themselves.
If I'm correct in my understanding, (and to use layman friendly terms for the benefit of the less experienced), the rotor and the "pump blade piece" are one whole unit that slides into a cavity in the center of the assembled pump. It should go right through the hole in the laminated metal "core" that the hall sensor is just hovering over in picture two. In a nut shell, it works and assembles much like a small AC induction motor, (like you would see in a house fan) but with a permanent magnet, hall sensor speed controller, and DC power instead.
This is more or less the standard configuration for a brushless motor using a hall effect sensor.
I dont think its a speed sensor.
It should be used to switch between the two coils.
Unless there is a chip hiding in there someware it cant do speed control with just a sensor. IE PWM
One of the two black things that are soldered down flat to the PCB is likely what is dead, they are just n-channel FETs. When removed and tested (tab to the right hand pin) *IF BLOWN* it will most likely read ~0 ohms/shorted with a multimeter both ways. You will need to test both of the devices.
They are both soldered super tight to what seems like a heatsink, so I cut the legs and tested them with my DMM on the 2000K setting. One of them registered 1235, but with the probes reversed registered 1 (as though the probes were touching nothing). That does not make sense to me, so I did it a number of times with the same result. The other registered 1, reversing the probes also registered 1.
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It's possible to repair the electronics, but is it possible for one to repair the physical pump? LOL, it don't look like it from the pictures to me. Worst case scenario, salvage the sensor and make something neat. [/QUOTE]
Yeah, that pump is a goner. I'm hoping to use it to figure out why it fried.
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