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Quick Electronics Question (555 Theory)
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File: 555 wut.jpg (15 KB, 307x354) Image search: [iqdb] [SauceNao] [Google]
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Hey electronics /diy/ers. I was just looking at some simple circuits, and theres just one thing I don't really understand about the operation of a basic astable or monostable 555 circuit.

This guy gives a good run-down here: http://pcbheaven.com/wikipages/555_Theory/

Scroll down to "Up and down in 4 steps!".

What I don't understand is this. When the capacitor is fully charged, and it is looking for the least resistive path to ground (see pic), why does it seem to discharge "backwards", rather than just discharge to the ground path directly below it?

Maybe there is something about capacitor theory that I'm missing?
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Caps have polarity based on which way they're charged.
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>>932864
And this one is charged through Vcc as shown in pic. I guess this is where the fault in my understanding lies, thanks.
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>>932832
well basically it is disharging through the ground since the emitter of the transistor is also connected to ground (cap->gnd->transistor emitter->transistor collector->resistor->cap).
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>>932895
>>932864
If you take a capacitor apart, you'll see it's made of two electrodes separated by an insulator.

DC cannot cross the insulating dielectric of a capacitor, so whatever charge is in an electrode can only discharge from that same electrode. It can't pass to the other one and discharge through it.

At least not in an ideal capacitor. Real-world capacitors "leak" because the dielectric is not a perfect insulator.
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>>932897
>caps block DC
Ah, of course! This really clears things up actually. Thank you!
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>>932895
Yeah to discharge it, you must connect the pin that was charged positively (so Vcc) to ground, to make a circuit.
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>>932897
If caps cant be used in a dc circuit then why are they errywhere?
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>>933329
For decoupling/noise reduction
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>>933329
They pass AC. If you want 5V DC, but have 5V DC + 1MHZ 0.3V AC, just shunt a cap to get something much closer to 5V DC.
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>>933329
No-one said they can't be used in a DC circuit: all that was said was that they block DC.

Heatshrink and fiberglass block DC too, and lots of circuits use them.
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File: IMG_3054.jpg (3 MB, 2592x1936) Image search: [iqdb] [SauceNao] [Google]
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Hello fellow diy electricians

i thought my understanding of electrical circuit illustrations was above average.
But when i tried to connect this wireless switch/receiver to my living-room lamp it does not work. That is to say; i can either switch the light on or i can switch it to flickering.

>inb4 leaving the light on all the time

So my question is;

Doesnt the dot where the horizontal N&L line meet the vertical L1&N line mean a joint/connection?

Neither English nor electrical terms are my strong sides.
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>>934195
cant seem to turn the image, but its supposed to turn 90* right
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>>934195
1) Make sure you're actually switching the live, not the neutral
2) Try it with a Tungsten bulb and see what happens

LED bulbs flickering when they're supposed to be off is a pretty common complaint.
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>>934218
ah, it might be the bulbs,
i doubt the electrician changed thee color of L&N when he did the wires, but ill try.

the dots on the drawing is a connection then.

tnx for the tip

i use 3xled 200ml 3w in my ikea lamp now. so i will have to change that then. (this is european 220-240v)