Seeking Elec Engineer or some with circuit knowledge

[Sully]

Is anyone in here an EE? Or just have extensive circuit experiences or a lot of theory under thier belt? I know it isn't security related, but I have some questions that takes forever on other forums to find answers for.

Sul.

[Bill_Bright]

I am not a EE, but I am a formally trained electronics technician with a couple electronics degrees and over 40 years experience maintaining electronic communications equipment.

And perhaps more importantly, I Bing Google is my friend.

That, of course, does not guarantee I know the answers, but I might be able to point you in the right direction. So, what are the questions?

[Sully]

Thank you. I won't bother the security forum with completely non-security diatribe. Incoming PM.

Sul.

[Bill_Bright]

Sorry, but I don't "work" problems via PM. The whole concept of "forums" is to have an "open" discussion, where every one has an opportunity to participate, share and learn.

But I will say this - you are indeed asking questions dealing with electronic design/engineering issues - and not really computer issues. I understand your questions, but I am out of practice (read - getting too old and slow) discussing discrete circuit and component-level specifics anymore - especially since discrete component level repair of circuit boards (including motherboards) is rarely cost effective these days. Plus that level of discussion is not really suited for here.

When I had similar questions in the past (ancient past), I was fortunate enough to be able to get my hands on a device that used such circuitry, and stick meter and 'scope probes into it to see what was happening - often with my trainer looking over my shoulder, quizzing me on things I was seeing and answering my questions.

Perhaps that is why I find troubleshooting computers that come across my bench today much easier than troubleshooting computers problems here in the forums.

For me now, I would need to see and study the circuit diagram to offer an opinion for your bridge rectification questions. For your cap question, yes, you can use the 50V - if its potentially larger physical size does not interfere physically or reactively in the circuit layout. It is the capacitance rating of the cap that matters most here - assuming the correct type of cap is used.

I suggest you visit some of EE sites again - tell them you are NOT an EE and ask them to slow down. I might suggest, All About Circuits. A lot of those guys do component level design and repair everyday and still practiced at it.

Also, while I understand the need to "cut to the chase" and skip all the basics, a solid foundation in electronics established with formal training in theory is something you should consider if you are going to be getting deeper into designing yourself. It will fill in many of those gaps you get when self-taught.

[Sully]

Thanks for the reply.

I have the same sentiment about forums actually. Sometimes I post stuff only a very few might be interested in so that other people using a search engine can find info on something I could not.

Your comment that the topic is not suited here confirms my own thought.

Thank you for the advice. I have been to that website many times in the past. They have an excellent informational site. I will look into that more.

Sul.

[Bill_Bright]

Good luck and oh (from PM),

I have a very healthy respect for mains voltage

Yeah, getting thrown across the room by an improperly grounded freezer in my early teens did that for me.

Good luck.

[NGRhodes]

More of a respect for amps person myself

[Bill_Bright]

More of a respect for amps person myself

That's really what it's all about, huh?

[mirimir]

Originally Posted by Nick Rhodes

More of a respect for amps person myself

Even a few mA at 5KV DC will keep one on the wires. I know that from experience But there was (AFAIK) no permanent damage, because the current was so low.

[treehouse786]

Originally Posted by Nick Rhodes

More of a respect for amps person myself

hi Nick, seeing as you are from the UK like me, can you tell me how much damage a standard UK 240V electric shock from a wall socket can do to a person? if they touched it direct without going through an appliance?

i ask this as i have been shocked twice and all i felt was excruciating pain for a few seconds then i was fine after a minute, is this normal? or did i get lucky?

[NGRhodes]

I've had similar shock to you from very slight contact before.
Heard of lots of people get shocks.
Heard of people getting blinded, have heart problems, muscle spasms, but I don't know the probabilities... worst case is death and it has happened.

[JRViejo]

Originally Posted by Nick Rhodes

Heard of lots of people get shocks.

Learned a valuable life lesson 40 years ago. I was called in to fix a plastic banding machine (220V, 3 Phase, 10 Amps) in an assembly line factory, and was in a hurry. Said machine was plugged in to an electrical floor outlet, about a foot off the ground. I crouched down (like a baseball catcher) to unplug the machine, and before I knew it, I found myself laying on the floor, 15 feet away from the machine, with my hands tightly closed (like a boxer), and sweating profusely from my chest.

Days later, I found that a single strand of wire was protruding from the machine's plug, and because I held the back of the outlet with one hand, I had completed the circuit to ground.

To make a long story short, the doctor told me that my saving grace was that the electric shock had extended my legs, thus separating myself from the plug, otherwise I would not be here today. Moral of the story: when working with electricity, always disconnect any equipment via the circuit breaker first!

[treehouse786]

Originally Posted by Nick Rhodes

I've had similar shock to you from very slight contact before.
Heard of lots of people get shocks.
Heard of people getting blinded, have heart problems, muscle spasms, but I don't know the probabilities... worst case is death and it has happened.

wow so i guess i got lucky then as i made full contact with the live wires, first due to changing the switch and second due to sticking an uninsulated knife in an open socket (i was young) and to still be unhurt, but my family seem to think i am weird but i think was the case before the shocks

@JRViejo thats an amazing story and result!

[mirimir]

Through miscommunication with a coworker, I once cut a live 240V mains line with wire cutters. I wasn't shocked, because the tool was insulated and I wasn't grounded. But ~1g steel was vaporized, and I had a steel-plated (and flash burned) forearm for a while.