No beeper in this photo. Could be a piezoelectric disk hidden some where they are small and thin. what’s on the other side of the PCB? Also look stuck to the plastic, piezos are often stuck to the casing to use it as a sounding board.
Edit: not sure what the yellow thing, cap maybe, can you get a better picture of the text on it ?
Is the capacitor an x2 cap for voltage surges? Looks like it. The rest is just normal stuff. Not my field, been out of school for years and am an idiot. That being said I’m curious: what’s the inductor by the Emi suppression capacitor for in this circuit? Is it just to form a tank circuit to heat the kettle more efficiently?
idk, not familiar with those things. the kettle can has 5 modes of temperatures: 60–100 °C. Its really nice, just insanely loud. More pictures if case it gives more info, sorry for the bad quality, hope its readable
Top is a relay, bottom is a capacitor. Thanks! The sound you’re hearing is probably from a piezo buzzer like some one else mentioned. I wish I was home so I could send you a picture of one. They can be really loud!
i would follow the wires until you find either a black plastic cylinder around 5-10mm in diameter with a hole on top, or a brass-colored disc around an inch in diameter. that would most likely be a piezo speaker.
A lot of kettles use sound to indicate state. If you’re nervous you should alert your local authorities rather than wait. Better safe than sorry.
Edit: Sorry folks. I thought op meant beeper as in the radio device. It’s late where I am and I’m tired, hah. Was just trying to encourage a bit of safety.
I’d agree with the tip of that ground plane is close to the high voltage part. And there’s still space left on the right.
The ULN2003A claims to have the flyback diodes and they’re connected. So you don’t need another set.
I’m not an electronic expert myself. But I don’t get why the fuses are the way they are. Most of the times I see boards having one fuse and when it’s blown, the whole board is separated from electricity. You’re kind of splitting it up 3 ways.
And the 5A of the fuses doesn’t match with the 10A rating of the relais or the 400W you wrote for the connectors. But I get that you have maybe 6 motors moving simultaneously.
(And why do you have the N trace to the connectors split in the middle and a whole other trace going all the way around? Is that to balance things when there’s much current going over that single trace? Or to match the 2 fuse design?)
The main reason for splitting up the relays into two sets is that with 10A traces the connector pins would violate minimum separation distances. I would have to get even larger connectors. The ones in the design have 5 mm pitch.
I’m assuming the original board also did this for the same reason although their board is set up for 8 motors split into sets of 4.
I’ve also had some trouble sourcing a 10A fuse suited for inductive loads but I’m sure I could find one with some more time.
The whole board is on its own house circuit fused with a 16A breaker.
Thanks for explaining. Yeah, I’m sure it’s pretty much alright with your circuit breaker. I suppose your main concern for having the fuses is so that those relais can’t start a fire once the current is between 10A and 16A for too long. I was just thinking about failure modes. And having something fail, the fuse blow and then half the board still has 230V feels a bit strange. But I guess it’s alright. I’m not an expert anyways.
I saw those PCB mounted 5V power supplies coming up in ESP32-projects before. I always thought they were some cheap chinese stuff and you shouldn’t trust them. But if they have a proper fuse inside and do proper 5V… Maybe I need to change my mind and start digging deeper.
Idk about mixing 10A relais and 5A traces and connectors. Everytime I buy some shelly stuff, I just have a look at the print on the relais before I wire something up. That’d be wrong in case someone had made the traces smaller. But I guess you can just write 5A MAX on the pcb and everyone can see that, even if one day somebody else does some maintenance. In this case you obviously need a 5A fuse.
I haven’t got enough time on my hands right now to review the whole desingn, but one thing that jumps to mind is that you’ll want to use an antiparallel diode on each relay coil to suppress the negative voltage spikes when switching it off.
Be sure to keep adequate distance between high and low voltage traces. The ground plane seems awfully close to the N trace.
Other than that, I’d happily welcome more PCB and/or personal project discussions!
increase the resistors by a factor of 100 or so and add a very small cap across the lower one. The cap inside the ADC is absolutely tiny, pF at best. So a 100nF cap would easily do the trick and supply the voltage as required.
I believe this lead configuration was designed to help with vibration resistance at very low cost, negating the need for a glue down. It could also be a bit more compatible with conformal coating? I suspect they’re special order on account of the leads and maybe the dimensions (could be demanding at the time), and the space constraints didn’t really allow them to claim a full 680μF.
I’ve never tried super hard, but I’ve never manged to source these from anywhere. I think this technique has mostly been replaced by multi-lead (three to five) configurations. I don’t think I’ve seen these from anything built in the last 20 years or so. I suspect you’ll have to retrofit to get things running again.
There’s some risk but I’ve managed to make a standard snap-in capacitor work by using a pair of pliers to rotate one of the leads on it’s rivet and bending both leads for the proper angle. This doesn’t help with vibration so I’d recommend fixing it with selastic as well.
Alternately you can modify the board to fit standard capacitor leads if everything lines up ok. Don’t forget that the PTH in the mounting holes might be connecting planes on opposite sides of the board. Make some sturdy vias if necessary.
If you’re really feeling froggy you can take a page from the vintage electronic restoration handbook and (kind of) restuff the cap. It’s usually done to be pretty, but in this case you could do it without care for looks and only in order to retain the terminals. This may be unwieldy given the size. I imagine it’d essentially be cutting the base off, wiring it to the new cap, and gooping everything together neatly with silicone.
I concur on the retrofit. It’s a two layer board, and the negative and positive rails are on opposite sides. I should be able to reuse the slot for the negative rail and make a slot for the positive (bottom side) rail. That way I can still get snapin terminals, as I’m concerned about the cross section of terminals if I had to resort to some round ø1.0mm pins.
I considered the approach you suggest with turning the terminals on the rivet, but all the riveted terminals I’ve seen have been potted partly, so I’d be concerned that turning them would put stress on the rivet and internal connection. That hasn’t been an issue for you? Anyway the caps I’ve found are just short of 20€ a piece, and I’m cheap, so I don’t feel like playing around.
Restuff the caps? Has anybody ever called you a cowboy? 🤠 I guess you could do that from an aesthetic POV, and maybe with enough selastic it would work. But somewhere in the back of my mind I know that it will fail at the worst time, and I’ll have to retrofit some other caps anyway… Only this time it’ll be raining and 2°C when I have to take the inverter apart.
Thanks for the idea of retrofitting. I was so stuck sourcing a drop in replacement that I hadn’t really considered that approach. The real estate is there to take a drill press with a 1mm drill and make a slot for normal snapin connectors. It’ll even maintain the same center, somewhat at least. Time to play with some selastic!
I’d be concerned that turning them would put stress on the rivet and internal connection. That hasn’t been an issue for you?
Hasn’t come up yet in a handful of tries over the years. The clamping force in the ones I was working with was insufficient to turn the rivet when the lead was rotated so I don’t suspect damage. The potted/sealed caps wouldn’t tolerate this at all, nor would any given particularly well riveted model. I totally understand not wanting to get weird with expensive parts. The one’s I was working with were only a few USD. https://discuss.tchncs.de/pictrs/image/0037be12-4142-480e-b8ea-db83ea241f1f.jpeg
I figured I’d dig through the junk pile and see if I could demonstrate. On the left is an Elna CE-W series 470μF 200WV, Ø30mmx50mm I had lying around, probably from the late 80s/early 90s. These are likely from an old switching supply, back when they made them specifically for US 120V mains. Just included it for fun as I wasn’t sure I still had one around.
The one on the right is an unbranded 1200μF 200WV Ø30mmDx35mm with a 2011 datecode. I used the pliers in the background to give one of the leads a 90deg turn. It’s dodgy with such thin leads as these, but it can be done. Solder tie lugs are much better as they have a flat square lead shape that’s less likely to tear off. So definitely possible, but definitely dodgy.
Restuff the caps? Has anybody ever called you a cowboy?
I don’t always have the best ideas, but I do tend to have a lot of them. :)
I try to cast a wide net cause it’s not always obvious what priorities folks have in their repairs. I doubt anyone would care about the aesthetics, for sure, but you would get to do all your arts and crafts work without involving the board itself, which could make some folks nervous.
Time to play with some selastic!
If you have time for the shipping you can get some Kafuter K-704N from aliexpress et. al. pretty cheap. It’s exactly the white selastic used for electronic holddown. Also the datasheet for whichever capacitor you order should have details for the recommended board footprint and drill size so you can be sure things will line up.
Thanks for all your input, it’s been fantastic. And the ideas thing? Right there with you pal.
For future reference, I found a source for the cap. Turns out that setting your parametric filter to exactly 660uF was the trick. Found chemo-con EKHJ451VSN661MA59M on mouser with a moq of “only” 200@12€… But digikey sells them individually at the same price.
I hope you know the consequences of having batteries in parallel? I mean, if they have different voltages you’ll get some current going between the batteries until they equalize. And the consequence of having one in reverse is probably also much worse than having them in series.
I don’t know. You’re connecting the two batteries. The one that has more voltage will charge the battery with less voltage. And because it’s just a strip of copper between the two, without significant resistance, it’ll happen fast. The thing limiting current flow is probably the internal resistance of the battery itself. And for example alkaline batteries, you’re not supposed to charge them.
I haven’t tried what exactly happens. AA batteries aren’t as powerful as for example Li-Ion batteries. So you’ll probably be alright. Maybe in the worst case one battery gets hot and smells funny. But I don’t think this will cause a proper fire. If it’s only a bit, it’ll get a bit warm and you waste some energy, that’s probably it.
If you connect one in reverse I’m not so sure anymore. I once had a rechargeable battery that was connected in reverse get really really hot and bulge. Once you do things like this with Li-Ion rechargeable batteries, I think you’re in the realm of starting a fire.
Any strong magnet can magnetize other things, depending on the material. Iron can be relatively easily be magnetized, while neodymium magnets require a huge (but obtainable) field.
That looks like a big electromagnet, from a motor, it will probably work, but you have to feed it DC, not AC. (Or else the object will be demagnetized when removed)
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