This TOY sample takes AC only ?  Batteries connect via a small CAPACITOR ! - Page 1
Forum section: electronics / general

author: RJSV
author_rank: Super Contributor
timestamp: August 09, 2025, 04:24:48 am
content: Hey there:Has anyone else seen a low power device taking it's power only by way of a small capacitor soldered directly to the '+' terminal ?Sorry this phone refuses to do posts, with a message that reads:'1000 mb'.The little capacitor looks like a high frequency type but I suppose, on a transient basis, that the set-up can work. The musical toy has a fake record turntable, and plays pre-recorded music. Made by Fisher-Price.Never seen a battery supply used like that !

author: RJSV
author_rank: Super Contributor
timestamp: August 09, 2025, 04:25:53 am
content: (oops, forgot to say phones camera cannot post a photo)- - Rick B.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 05:32:30 am
content: Rick, I think you know enough about electronics to know that that cannot possibly work, right?A capacitor will block DC.Does the power gothroughthe cap, or is the cap connected between + and -?

author: RJSV
author_rank: Super Contributor
timestamp: August 09, 2025, 05:46:30 am
content: Yeah, why do I DREAD communicating with you (your snarky attitude). Physically, my system drops, a point, when I see your always rapid, attitude coming back with, the gaslighting, 'Are you SURE, RICK'.Heck, you are such a dependable, little, asshole, it doesn't get to me too much....just enough to disrupt the current feeling, seeing that you've done the thing you do:Disrupt, gas light the author...("Are you sure, Rick").At any rate, yes, it is a small hf cap. going in series to the usual logic board, from the plus terminal on the battery holder. That holder has 4 cells, AAA, and my summary guess is that the processor takes 'little gulps' of DC power, that come via that little cap. Makes some sense, that some circuits COULD function, doing transient pulls on the plus supply, but would need some kind of start-up, I'd think.Sorry, no picture possible, like I've stated, this smartphone.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 05:54:23 am
content: Quote from: RJSV on August 09, 2025, 05:46:30 amWell then fuck you too.You and your goddamn motherfucking smortphone.I've had it with your meshuggah word salad anyhow ...

author: RJSV
author_rank: Super Contributor
timestamp: August 09, 2025, 06:15:23 am
content: (you, A.K.) don't really seem interested, in contributing to solving the issue(s) raised, and persist, really fast, in those quick, jerky responses. Other readers, maybe embarrassed by this, otherwise I'd attempt to ignore these immature taunts.Back to biz: That rectangular cap-like thingy might be some kind of fuse, but it is dull yellow or orange, and does have some tiny, illegible printing on it. I should at least check with ohmmeter, and I'll report that.A mystery.

author: RJSV
author_rank: Super Contributor
timestamp: August 09, 2025, 06:24:59 am
content: Ahh, ohmmeter reads 0.1 ohms, (I should have checked for shorted, earlier). That component is maybe a shunt for factory testing ? It has some purpose ?The leads from the part have the usual bends, for being inserted into a through-hole (appearing like a small cap.). Must have some use ?(Sorry about the, uh, distractions)

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 06:58:30 am
content: Quote from: RJSV on August 09, 2025, 06:24:59 amSo all the bullshit here's on you, pal.You very stupidly ventured that there was acapacitorin series with your DC supply.Something which youknowisn't possible.My only advice to you is:think before you post.Something which obviously ain't happening.

author: AVGresponding
author_rank: Super Contributor
timestamp: August 09, 2025, 08:52:19 am
content: Maybe it's a polyfuse

author: SteveThackery
author_rank: Super Contributor
timestamp: August 09, 2025, 09:56:58 am
content: Quote from: RJSV on August 09, 2025, 05:46:30 amRick, you owe AK an apology. He was right - you DO know it can't have been a capacitor, and you DO know your "gulps" theory is nonsense. Yet as soon as AK pointed it out, you went straight for the jugular.Be a man, and apologise. People will respect you for it.

author: coppercone2
author_rank: Super Contributor
timestamp: August 09, 2025, 04:21:47 pm
content: Wow this is the most unreadable thread I have seen after the 1st post.The way it works is the capacitor has a frequency dependent resistance (only considering this to make it easy)https://www.allaboutcircuits.com/tools/capacitor-impedance-calculator/You put in the frequency you expect and the capacitance and it gives you a impedance. This impedance is relevant at your frequency. All it means is that the AC in the circuit will see that impedance (resistance you calculated) and the DC signal will see "open circuit".You still need a return path through ground, because in this case of a capacitor it is still a circuit. Re-do your analysis by substituting resistance and treating DC voltage to be zero.If the grounds are disconnected, then you might still see some random impedance connection, because of the 'general capacitance' between the two circuits. Probably in the pF.No matter how you make it, there is always going to be another capacitor (and inductors) connecting your two circuits grounds because of parasitic effects, which may allow your circuit to 'work' with only a single connection capacitor.To understand how power flows, look at this. There are capacitor isolated systems, ranging from digital isolators to stuff like thishttps://www.analog.com/en/resources/design-notes/isolated-power-using-capacitors.htmlhttps://www.monolithicpower.com/en/learning/resources/capacitive-isolation-articleUsing light is the most isolated, because you might think of it as more like a far field circuit. The wavelength of infrared light is in the single micrometers, so with the optical isolator its more like using a radio control (the signal is 'photons')r. For capacitor and inductors, its 'near field'. The key with capacitor isolators is that the signal is REALLY WEAK (sensitive circuits) and uses 'demodulation' meaning it has very high noise immunity, which gives it very high immunity to random noise (for signal isolators). Since the circuit works on high impedances (capacitor isolator), very little 'noise' can get through because you can think of the 'impedance' between the two parts to be very high (mega or giga ohms or possibly more), so it does not transfer power, but a signal can go through because it is modulated (so it is like a 'key' that triggers a very sensitive mechanism that ignores everything else)For instance imagine a amplifier and a speaker. Lets say when you use a resistor to connect the speaker to the amplifier and its 1 ohm, and you are interested in 20KHz. You can take out the resistor and plug in a 8uF capacitor. This will also have a 1 ohm resistance @ 20KHz, and the system should work the same. Of course there is the complex component, which I won't get into. But if you disconnect the ground wire, it won't work because the circuit is broken. There will be a little bit of capacitance between the speaker and the amp, but if you run the math on it, you will see the resistance is extremely large, so the circuit is 99.999999 blocked. However, if you replaced the 8 uF capacitor with a 16uF capacitor and put another 16uF capacitor to connect the two circuits grounds, the speaker (from a resistive analysis) should work and see a 1 ohm series resistance (with 0.5 ohm on one lead and 0.5 ohm on the other lead).https://i.sstatic.net/VBZ7Q.png

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: August 09, 2025, 04:38:28 pm
content: Quote from: RJSV on August 09, 2025, 04:25:53 amRick;Could you download your phone's photos to a computer, and then post them here?You know what they say, a picture is worth 1000 words, (as long as the photo is a clear and properly focused one, of course).It would help tremendously.

author: Zero999
author_rank: Super Contributor
timestamp: August 09, 2025, 04:47:37 pm
content: Of course it's a resettable fuse, not a capacitor.https://en.wikipedia.org/wiki/Resettable_fuse

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 05:53:53 pm
content: Quote from: coppercone2 on August 09, 2025, 04:21:47 pmYou're as bad as producing word-salad bullshit as the OP here.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 05:56:06 pm
content: Quote from: SteveThackery on August 09, 2025, 09:56:58 amNo apology necessary here.I'll be happy if he just takes a few more moments to reflect before making a post.Something we all could benefit from here.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 05:58:00 pm
content: Quote from: UnijunctionTransistor on August 09, 2025, 04:38:28 pmI don't think he has a computer. He's apparently on a limited budget.Maybe someone could help him figure out how to post pics with his 'phone, which you'd think should be possible.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 06:01:04 pm
content: Quote from: Zero999 on August 09, 2025, 04:47:37 pmUm, maybe not.We don't know what it looks like yet.My guess®™ would be a diode.Why? Think about it:It's a child's toy.Who's going to be putting the batteries in this device?Besides, why would you need a fuse for such a low-power device anyhow?

author: Zero999
author_rank: Super Contributor
timestamp: August 09, 2025, 06:26:36 pm
content: Quote from: Analog Kid on August 09, 2025, 06:01:04 pmIn the first post you said "The little capacitor looks like a high frequency type" now you say you don't know what it looks like.Small batteries can get hot and leak nasty, corrosive chemicals, so a fuse is a good idea. What would happen if the turntable jammed?

author: mathsquid
author_rank: Frequent Contributor
timestamp: August 09, 2025, 06:31:58 pm
content: Would this circuit be a capacitive dropper?https://www.digikey.com/en/maker/projects/capacitive-dropper/965d2328b35e43079e4eb99cf717137f

author: Gyro
author_rank: Super Contributor
timestamp: August 09, 2025, 06:34:17 pm
content: He said it measured 0.1R. My bet is Polyfuse.We have no information on size or number of batteries, but a few Alkalines will put out a couple of amps, so some sort of short protection is probably desirable. If it does have reverse battery protection (which is often provided by just narrowing the plastic molding around the +ve contact) it could be an inverse parallel diode after the Polyfuse. That would avoid unnecessary voltage drop in normal operation.

author: Gyro
author_rank: Super Contributor
timestamp: August 09, 2025, 06:44:18 pm
content: Quote from: mathsquid on August 09, 2025, 06:31:58 pmHi. No, capacitive droppers only work with AC input (the mistake that the OP made).

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 07:10:55 pm
content: Quote from: Zero999 on August 09, 2025, 06:26:36 pmYou mixed me up with the OP; he said that. I have no idea what that thing looks like, as he hasn't been able to post any pictures with his phone.QuoteMaybe, but remember he described it as a "fake turntable", so probably not even operative. But who knows?

author: Bud
author_rank: Super Contributor
timestamp: August 09, 2025, 07:26:03 pm
content: Have any of you seen fuses in battery powered toys, let alone reverse protection by a diode, where manufacturers are trying to shave off every extra cent.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 07:32:21 pm
content: Quote from: Bud on August 09, 2025, 07:26:03 pmWell, this toy hassomethingin line with the battery supply. We just don't know what it is yet.

author: Gyro
author_rank: Super Contributor
timestamp: August 09, 2025, 07:38:03 pm
content: ... and probably never will. This is the second 'toy' thread with no photos...https://www.eevblog.com/forum/beginners/yet-another-convenience-store-toy-tear-down/

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 07:40:05 pm
content: Quote from: Gyro on August 09, 2025, 07:38:03 pmGuy just needs some help with figuring out how to use his damn phone.For that he has my sympathy. I hate those fucking things.

author: Bud
author_rank: Super Contributor
timestamp: August 09, 2025, 07:42:57 pm
content: QuoteYeah, doubt anyone can help with this one.

author: Bud
author_rank: Super Contributor
timestamp: August 09, 2025, 07:44:01 pm
content: Quote from: Gyro on August 09, 2025, 07:38:03 pmAh, from same OP,

author: Gyro
author_rank: Super Contributor
timestamp: August 09, 2025, 07:51:34 pm
content: Quote from: Analog Kid on August 09, 2025, 07:40:05 pmI've noted your attempts to be as nice and helpful to him as possible. I admire your patience considering the abuse you get in return.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 09, 2025, 07:56:57 pm
content: Quote from: Gyro on August 09, 2025, 07:51:34 pmIt'd be nice if someone could help him sort out his phone problems.I have a hard time believing that any phone sold in 2025--even a stupid flip-phone (and his is a smortphone)--wouldn't be capable of posting pictures to a web site.

author: Gyro
author_rank: Super Contributor
timestamp: August 09, 2025, 08:01:58 pm
content: Agreed. It's not going to be me unfortunately. Patience aside, I never post from my phone, I transfer my images to my laptop (using Signal, note to self), then resize and post from there. That's probably not optimal but at least it works.[Edit: Personally, I find it difficult to see how anyone manages to post to forums from a phone, not enough screen space, painful scrolling etc. but that's probably just ageing me!]- OT.

author: tom66
author_rank: Super Contributor
timestamp: August 09, 2025, 09:15:43 pm
content: Rick,Serious suggestion - if you cannot get the forum attachments to work, use a service like Google Photos or imgur, these are usually free for a small number of uploads. You can copy links to these images and leave them in your post.If others desire, they can upload them as attachments, which should last longer (as long as Dave keeps them, essentially).

author: Gyro
author_rank: Super Contributor
timestamp: August 09, 2025, 09:31:33 pm
content: Quote from: tom66 on August 09, 2025, 09:15:43 pmThat is the recommended (by Dave too) method. We lost far too many valuable images (eg. Imagur free hosting) in the past.

author: SteveThackery
author_rank: Super Contributor
timestamp: August 09, 2025, 09:39:01 pm
content: Quote from: Analog Kid on August 09, 2025, 07:56:57 pmYou'd be right. Of course his phone will do it.

author: Zero999
author_rank: Super Contributor
timestamp: August 10, 2025, 02:24:15 pm
content: Quote from: SteveThackery on August 09, 2025, 09:39:01 pmGoing by the original post, the files are too large for the forum.Quote from: RJSV on August 09, 2025, 04:24:48 amI doubt they're 1GB. The limit is 8MB. Probably a typo.Perhaps there's an app or setting you can change to make the files smaller. I would just upload them to my desktop and edit them with GIMP, but if I just had a phone, I would struggle.

author: themadhippy
author_rank: Super Contributor
timestamp: August 10, 2025, 03:25:12 pm
content: Quotestart believing,theirs sevral, nokia 105 being just one example,you wouldn't be able to take the piccy in the first place as it dont have a camera

author: Analog Kid
author_rank: Super Contributor
timestamp: August 10, 2025, 09:38:35 pm
content: I'm fairly confident that RJSV's phone has a camera and is capable of posting pictures to the web.It's no doubt either a configuration issue or he just can't figure out how to do it. (No reflection on him there.)

author: John Coloccia
author_rank: Super Contributor
timestamp: August 10, 2025, 10:37:56 pm
content: I've had issues uploading from my phone on forums. I don't know why.Give him a break. I'd like to see pictures too so we can help each other and figure out what's going on.So I'll offer to reach out to me, I'll give an email you can send to, and I'll post them.

author: SteveThackery
author_rank: Super Contributor
timestamp: August 11, 2025, 12:26:18 am
content: Quote from: Analog Kid on August 09, 2025, 05:56:06 pmI was thinking it's as much for his benefit as yours. It's important to admit to yourself when you've behaved like an asshole, and to find the fortitude to suck it up.Consider it good for his character.

author: MK14
author_rank: Super Contributor
timestamp: August 11, 2025, 02:16:19 pm
content: Adding to what others have said, about being suspicious that it is a polyfuse device. Rather than a, perhaps 10 picofarad capacitor. Which would have passed, almost zero current to the device.I would suspect, it is because the device is for toddlers/kids to use, who might either hold on to the turntable, freezing its motion, or pile toys/stuff on top of the unit, also jamming the turntable, for extended periods of time.That could risk, powerful batteries, damaging the weak plastic (speculation) gearbox wheels and/or over-heating the small stalled motor and/or over-heating the batteries.So, I think it makes a lot more sense, for it to be a polyfuse, rather than a tiny value capacitor.

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: August 11, 2025, 04:45:16 pm
content: Quote from: RJSV on August 09, 2025, 04:24:48 amRick;Let me help you out with posting photos on EEVBLOG.The error message you copied means that the photo file is larger than the allowable forum maximum. I have run into this myself.The file requires to be smaller. The workaround is to take an image from 2 feet away and then crop it.The resulting image will be well within limits.See example below.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 11, 2025, 06:30:47 pm
content: That might be good advice, but do we know exactly where that message comes from and what it means?Pretty terse, that: "1000 mb". Is that the size of the image? or the remaining phone memory? or something else?Is that message from the phone? or from this site?We need a few more details from the OP here.But thanks for helping anyway.An image would have to be pretty damn humongous to be that big. I doubt that's the size of the pic he's trying to post.Think about it; that's a gigabyte.

author: RJSV
author_rank: Super Contributor
timestamp: August 16, 2025, 08:00:59 am
content: Just viewed the photo from Zero999 and that rectangular component, on far right of picture, is the component that I spotted, in series with the '+'.But I'm not sure what the term 'resetable' means ?

author: tooki
author_rank: Super Contributor
timestamp: August 16, 2025, 08:08:20 am
content: Resettable = able to be reset.Resettable fuse = fuse that resets itself once it’s had time to cool. Aka Polyfuse (already named as such in the thread).

author: RJSV
author_rank: Super Contributor
timestamp: August 16, 2025, 08:20:39 am
content: Ah, ok, it resets when cools down. I can understand that, but as someone else has stated, a toy like that usually expect to have cut corners on component costs, but I suppose the motorized 'model' turntable could be held stationary, (and thus possibly cause an energized motor overheat).Just seems like a questionable cost vs function thing. If it's a safety issue, you would think that many other toys would have fuse protection, as well.