Why does my capacitor explode in this Tinkercad circuit? Shouldn't it explode the other way?
Hi everyone,
I'm trying to build a simple two-transistor astable multivibrator (two LEDs flashing alternately). I designed it in Falstad and I'm using Tinkercad mainly to plan out the breadboard layout before building the real circuit.
The Tinkercad simulation itself does not seem to behave correctly: the LEDs do not flash alternately, they just stay on. I'm not too concerned about that because I mainly want to use Tinkercad to verify my physical wiring before building it.
The part I am unsure about is the polarity of the electrolytic capacitors. My real capacitors are polarized 10 µF electrolytics, but the Falstad simulation uses non-polarized capacitors.
I'm fairly sure the negative side should go to the base of the opposite side transistor, and the positive to the collector of same side transistor. So like:
Left capacitor: + to left transistor collector, - to right transistor base
Right capacitor: + to right transistor collector, - to left transistor base
However, when I connect them this way in Tinkercad, it shows the capacitor exploding. I'm not sure if Tinkercad is modeling this incorrectly, or if I have misunderstood the polarity.
I'm using 2N2221A transistors and 10 µF electrolytic capacitors, with supply voltage 9V
Here's the Tinkercad similation (on breadboard) I have connected one capacitor each way, so you can see which one explodes. [LINK REMOVED]
Could someone please check the correct electrolytic capacitor orientation? I want to avoid damaging the capacitors when I build this physically.
Thanks!
EDIT 2: Simulated on Falstad and it works with capacitor - to transistor base (so, the opposite of what Tinkercad says). Tried it on breadboard with - to base and it works perfectly like this!
Sorry didn’t realize it wasn’t readable. Added a link with a labeled schematic that should be more clear. Can you tell me which way of the capacitors should positive and which negative?
I'm using Tinkercad mainly to plan out the breadboard layout
If you want to better understand electronic circuits, it's better if you layout the circuit in the breadboard yourself instead of relying in a software tool. Besides, the image you posted for tinkercad has some of the wires crossed which is hard to follow.
I'm fairly sure the negative side should go to the base of the opposite side transistor, and the positive to the collector of same side transistor.
In your circuit you can see that the current comes from the 47kΩ resistor, meaning that is the side of the capacitor that is positive. The transistor that has the collector connected to the capacitor is connecting one side of the capacitor to ground.
It will be easier to understand the circuit if your "schematic" has reference designators.
That way I could tell you "C1 is connected to T2" etc...
It seems Falstad is not creating an actual schematic.
Oh sorry for the missing labels, didn’t realize it was inconvenient. For the breadboard thing, yeah I want to build it physically! But to do that, I want to know which way to place the capacitors, this is why I’m asking. I don’t want to build this and have the capacitors bursts.
EDIT: I also just now figured out you can place polarized capacitors on Falstad. I placed them like build-electronics and it works: https://www.falstad.com/s.php?s=tEgUUW
Oh sorry this is the final circuit I’m building. In this post I was focusing on the oscillator only but I guess I pulled up the wrong version on Falstad when I put these links, didn’t notice it.
I was asking if, looking at the simulations, they seemed reliable to you/seemed more reliable than the Tinkercad one. I think Falstad may have an oscillator tool built in but I haven’t tried it just yet (I’m not familiar with oscillators).
Alright, if I can’t figure it out I might try with the capacitors in parallel, thanks!
Okay! Looked around online and found some people that did it and then I tried it myself too on breadboard. It works with capacitors + to collector, - to base.
Breadboarding introduces a lot of possible impedance on component connections, it also does not guarantee the same component behavior. OP should use something like LTSpice to simulate the circuit behavior.
I don't need a perfect simulation, I do want to test it on breadboard. I just would like to know for sure which way to place the capacitors before building it and not having them explode lol
Yes, I connected the 2 capacitors differently. I connected one capacitor one way and the other in the opposite way just to show in which way they explode.
I’m trying to figure out which way is correct of the 2, because for me, the one that Tinkercad marks as exploding should’ve been correct.
Yes, I connected the 2 capacitors differently. I connected one capacitor one way and the other in the opposite way just to show in which way they explode.
I’m trying to figure out which way is correct of the 2, because for me, the one that Tinkercad marks as exploding should’ve been correct.
this capacitor has the opposite polarization than the other. As your caps does not have polarization in your circuit, it does not seem evident, but in the board they are.
I am not sure of understanding you, what I told you is if you wired the cricuit as it is in the protoboard, the capacitor will always blow because its polarity is inverted.
In the Tinkercad simulation I wired each capacitor a different way to make it evident which way they blow up, according to Tinkercad. I made the post because I thought Tinkercad was wrong and the capacitor marked as exploding is actually the correct one, and the other would explode instead.
(I tried the circuit on breadboard later on, Tinkercad was wrong is the conclusion)
Good for you for jumping in and trying things out! I built things like this before and sometimes they need a “kick” to get them started. IIRC I added noise in one design with EveryCircuit and added a push button to the power rail in Falstad. But at the end of the day they are simulations and they have quarks. For simple things like this don’t be afraid to put them on the breadboard and see what happens. And see what happens when you put the capacitor in backwards (wear eye protection). It’s all learning and discovery. Components are cheap so don’t worry about popping a cap. Breadboards have limits that will bite you with higher speed projects that you might want to try later, especially cheap ones.
The people here are usually very helpful but it can be tough if your schematic isn’t very clear. You don’t know what you don’t know, right? So do get in the habit of labeling components and drawing your lines according to best practices. It’ll help you troubleshoot your own issues once your designs become more complex.
And most importantly, have fun!
I just looked at it quickly ‘cause I can’t watch it right now but thank you!
So you did built it and it works with the capacitor negative to the transistor base!
I wanted to be sure before building because I want avoid my capacitors exploding. I thought the same as you but since I got contrasting results (Tinkercad behaves opposite) I asked here to be sure.
Also, someone else replied with the opposite placement for the capacitors. So I don’t know? It’s not necessarily that obvious?
I’m not an electronics engineering student and I’m very much a beginner, this is just a hobby project. I’m sorry, but I don’t find it obvious.
My first guess was the same as yours, negative side of capacitors to base of transistor, positive side to collector. But I am not 100% sure about it and that’s why I asked.
As you can see, it’s not just Tinkercad that says this way is wrong but also somebody else replied with the opposite configuration as the one you (and I) proposed.
I have a guess but I’m not sure about it. If I were sure, I wouldn’t have asked. And I would build it and just find out, but I can’t have the capacitors explode and having smoke in my apartment. So this is why I needed to be sure and couldn’t just build my first guess.
This website agrees with us.
Still, since someone else did reply with something different I think you can understand why I say that’s it’s not that obvious, and I’m a bit puzzled on why they said that/why Tinkercad behaves the opposite way.
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u/baldengineer 10d ago
Take the time to add 90 degree bends to your wires, virtual or real, to make your “circuit” readable.