Mod edit:
Please note that what is described here is dangerous even if you do know what you are doing.
I have just been sitting about (while bored), and just done the basic DC power supply from the 240ac mains. I bought a little 30 quid oscilloscope, that has a screen that is about a 3rd of my cellphone screen. Just wanted to test it out, with basic stuff (breadboard). The circuit is literally just:
210k Ohms of resistors, with a little ELV being taken off a 10k resistor (around 12vac). I could have used a variable, but I was not that bothered
4 X 1n4007 diodes for the bridge
a 50v 100uF smoothing capacitor
no Zeners at all, just the above
The DC-out looks almost PERFECT (on my farty little Oscilloscope)! It is beautiful. Corroborated with my DMM as well. I was at least expecting something more like:
No doubt anyone who has done any electronics education has seen that diagram. I admit I have not put a load to it, and I most certainly would not use it with anything like a photo-switch. I was really expecting something not as good as what I got out.
Yes, even putting a DMM on it with the Oscilloscope attached, it does change somewhat in the reading (on osc). The DMM obviously should have little effect, due to its configuration. I see a little bit of change in signal. Bear in mind I have used the cheapo configuration of using resistors as a potential divider instead of a transformer.
No, it is not. But that depends on the experience of the person in question. That was not what I was asking. It is not dangerous to someone who knows what quantities are expected, at all (no I am no expert on electronic design, but I find it amuzing to go back to the experimental phase, regardless of whether I am not some super genius in electronics (which I am not)). This literally comes down to OHMs law etc... and a rather large amount of experience regarding a 4 year apprenticeship, years of experience, and all the qualifications that went along with that (yes, I am getting tiresome in my attestations of experience, etc).
These are simple concepts of electrical engineering. Danger comes when someone does not know the quantities expected, or simply has no prior knowledge. It is easy to misunderstand the experience of a person, regardless of whether they "appear" inexperienced. I may seem to be asking a rather silly question, but it does not come without decades of experience.
I will admit I am out of the loop, but no I will not kill myself
210k ohms, 240vac = 1.1ma running through the entire circuit (and YES, I know that the voltage to kill you is in reference to the resistance of you body at any given point, regarding HOW you are connected to the circuit, e.g. water/ mole grips attached to the in/out of the supply (no I am not attaching mole grips to the live and neutral cables connected to the mains, whilst having wet hands!))
The 10k ohms part (directly from the mains) has a voltage of around 10-11vac. The subsequent circuit has whatever it has, from any point.
I had a little to-and-fro with someone else as well (I believe Jim-P). Feel free to provide a response, but no, I am not inexperienced. Just a little rusty.
First understand that I am addressing 2 audiences: you and whoever else might be reading this.
Unfortunately you have not reassured me, I'm just as concerned as I was before. My concern is based on your description of your circuit, which I might be interpreting incorrectly. If you wish to continue this please post a schematic of your circuit, hand drawn and photographed is fine.
What exactly was it that you were asking? If it was just the question in the subject of your post, then no. I don't wonder why a full wave rectifier with a smoothing cap works so perfectly; largely because it doesn't.
The power supply you built looks great, under theoretical conditions and no load. Once you start using actual power with it, the performance will go down considerably. This is why people use pi filters and other components in a 'simple' power supply. You also left out any circuit protection. Also, please be careful connecting mains voltage to a breadboard! Hopefully you are only connecting the 12V to the actual breadboard itself.
You know what power supply looks super smooth and great when you are only using 1 mA? A battery.
Fine, but I am not suggesting people do what I do. Far from it. Nobody knows everything. I used to be some swanky guy who went around in companies with a big oscilloscope tuning/ calibrating electronic circuits. I was not designing them, and maybe some people (even some engineers, on the same pay grade!) may have thought of me as some super-smart electronics guy
No, I am not, but I knew my stuff. As engineers we tend to just know the job, but it does come without experience/ necessities. Electrical engineering was not something I had a problem with when it came to safety. I even had jobs that involved safety testing (PA testing). You just do the job, based on your abilities and experience/ qualifications. It is best not to guess what people can or cannot do safely. But, OK, sorry I got tetchy. I know you meant well, sorry.
Of course I used the breadboard! It was 1-2ma max. Breadboards have a capability of around 1-2 amps. Do the maths. Precisely what heating effect are you concerned with by putting a low voltage like 240vac into a device with 210K OHMs of resistance?
Look, I know I would not suggest to people to do what I do, but yes, the breadboard can handle 1-2ma quite easily... I am not a health and safety inspector for the Arduino forum. If someone does not know the maths, then they may burn something out.
What you are concerned with is the current rating of the device. When you have 240vac RMS into a resistance of 210K OHMs, it is a current of around 1-2ma. In fact, the total current rating should be around (almost exactly):
No they would not, because nobody knows everything Jim. We all have gaps in our experience and training/ experience. We experiment for a reason. We want to fill the gaps we do not have filled (some people do anyway). I do not produce power supplies Jim, I never have, and I do not intend to. But it is wonderful (at least interesting to me) just experimenting.
I honestly can't tell if you're just trolling right now, but if you are, good job!
In the slim chance that you are actually serious, then you should know that it is not the 1 mA current on the breadboard that we are worried about, it's the voltage. It took me less than 10 seconds to find this on Google.
I really hope you are just trying to troll people here.
So that would indeed include you. By stating that you were suprised by the results you saw, you are basically admitting to your inexperience with electricity and electronics. That is why everyone here is so concerned with your safety.
What is it you are concerned with then Emily? The breadboard has a current rating of around 1-2 amps. It can handle something that is a fraction of that, like 2ma. if someone is unsure then simply DON'T!
OK, look, I am out of the loop, and this stuff is not complicated to me, but I have found it interesting coming back to it! I love messing with electronics, because I find it amusing. It is cool.
I would never denigrate someone who has less experience, and I love all the variabilities of people's experience. I am someone who has handled this stuff as a job, and career. What the impression is that get is, that I don't think some people have done enough electrical experience, to appreciate that.
Maybe I am a bad influence! Maybe I am scary ! It just that I have dealt with all of this stuff before, and it is second nature. Maybe I am insane lol! Nobody knows everything though! We just do our jobs lol.
It is the current rating that you need. Yes, you do not want high voltage on them, i.e. 1000v. If you have high voltage, 1000v, no do not use that on a breadboard. If it is low voltage, in other words below 1000v, then it is not a problem.
High voltage has a tendency to arc, This is the reason why we define ELV (50v), low voltage (below 1000), and high (1000v and above). I doubt it would be any different in USA.
Because of this I think a BIG DISCLAIMER should be placed by mods at the beginning of this post warning that what OP is suggesting is dangerous and stupid.
You're fine. No one will take your assertion that you are some kind of engineer seriously.
With the addition of the disclaimer in your post, I think we can conclude that in the words of Douglas Adams, you are "Mostly harmless."
Confirmed that user is a troll. This is the same sort of person that posts on the internet how mixing ammonia with bleach makes a great cleaning solution, with no regard for the fact that he may very well be injuring or killing someone in real life.
I just ignored this user account forever, and I hope everyone else on this thread does too.
! It just that I have dealt with all of this stuff before, and it is second nature. Maybe I am insane lol! Nobody knows everything though! We just do our jobs lol.