diy solar

diy solar

how much volt is needed to be noticable when short to ground via human body

Scph9002 said:
talking offgrid dc. My ground is actual earth ground and bonded to negative. Positive battery reaches 56volt and positive solar reaches 140v. If i want to play around with my 5 strings on panels i could parallel them to keep up close to 700volt at 10 amp load.

I try ask again, in normal use case, how much voltage is needed to push though my body and a shit ton of building material between my feet and ground/negative/earth
Click to expand...
What are the building materials? What is the humidity level? How sweaty are you? What are you wearing?


Ok… let us try this question…

What are you trying to do? 700V will certainly kill you.

140V can kill you, but if safety practices are followed can be handled…
 
dianea said:
Even 40V from solar panels can create a large plasma arc with enough heat to destroy a hand. It's all about maximum power transfer.
Click to expand...

Nope. It's about current as dictated by voltage and resistance.

Current will kill you. The amount of current that conducts through you is dependent on the voltage and the resistance of your skin and tissues. A low power/high voltage source could kill you were a very high power, low voltage source wouldn't even be noticed. Automotive 12V lead acid batteries can easily deliver 500-1000A at 7.5V (7500W), but you can touch them with dry skin without any fear of even a slight shock.

Take 10 5W panels and string them in series to get 220VDC/50W. Could actually kill you.

7500W can't kill you except in extraordinary and odd circumstances where you're trying to get killed, yet 50W could kill you without much special effort.

Worth a read:

www.scienceabc.com

How Much Current Can The Human Body Withstand?

Of course, more voltage draws more power, but it is not the caliber that kills us but the bullet it shoots. Regardless of the voltage, the real cause of death is the current forced through the body.
www.scienceabc.com www.scienceabc.com
 
AC can be more dangerous than DC, because a few cycles of it mixes up the ion polarities in your heart muscle cells.

academic.oup.com

Electrical cardiac injuries: current concepts and management

Abstract. Electrical injuries are a commonly encountered hazard in both the home and workplace. However, clinicians are often uncomfortable when faced with the
academic.oup.com academic.oup.com

The body (with skin) is a non-linear resistor.

With an ohm meter, I measured 300k ohms hand to hand. impedance analyzer at 60 Hz, 150k ohms.
Neither of those explains injury at 200V, only about 1 mA.

According to literature, the skin's resistance breaks down at high voltage, leaving 500 ohm to 1000 ohms.
That gives 1/4 to 1/2 amp through the body. Not many milliseconds needed to upset the heart.
 
sunshine_eggo said:
Nope. It's about current as dictated by voltage and resistance.

Current will kill you. The amount of current that conducts through you is dependent on the voltage and the resistance of your skin and tissues. A low power/high voltage source could kill you were a very high power, low voltage source wouldn't even be noticed. Automotive 12V lead acid batteries can easily deliver 500-1000A at 7.5V (7500W), but you can touch them with dry skin without any fear of even a slight shock.

Take 10 5W panels and string them in series to get 220VDC/50W. Could actually kill you.

7500W can't kill you except in extraordinary and odd circumstances where you're trying to get killed, yet 50W could kill you without much special effort.

Worth a read:

www.scienceabc.com

How Much Current Can The Human Body Withstand?

Of course, more voltage draws more power, but it is not the caliber that kills us but the bullet it shoots. Regardless of the voltage, the real cause of death is the current forced through the body.
www.scienceabc.com www.scienceabc.com
Click to expand...
My attempt was to show a low DC voltage may facilitate a high current arc. Many watts of power in a plasma fireball of small size that will BBQ the hand. This experiment is easy to do with a dozen panels in parallel on a sunny day: short the wires and hardly a spark. Now open the two conductors and watch the fire. This also demonstrates why DC breakers and disconnects have massive arc chutes to extinguish the flame, whereas AC breakers and disconnects take advantage of the zero crossing.
 
I was previously released for full return to work, just no high places. Now no restrictions.

I've been concerned about erratic and high blood pressure from around-the-wrist monitor, but each time at the ready-care clinic it has been fine. EKG is back to normal. I've decided my gizmo was unreliable, will stop in to drug stores to use theirs.

It had been erratic in the hospital the couple days I was there, so I didn't question the readings from this cuff.

617cxgWk7VS.jpg
 
Hedges said:
Now no restrictions
Click to expand...
That was a serious situation. I didn’t realize you’d been hospitalized over it. Grateful it worked out for you.
There’s things you don’t “come back” from and it sounds like you were way into that no-fly zone and yet escaped.
 
12VoltInstalls said:
That was a serious situation. I didn’t realize you’d been hospitalized over it. Grateful it worked out for you.
There’s things you don’t “come back” from and it sounds like you were way into that no-fly zone and yet escaped.
Click to expand...

Thanks.

No one else was in the room. Even if they were, some/most of my colleagues haven't been trained in CPR. Bet they would fumble through voice-prompts of AED if that was even on their mind, and it requires CPR between shocks. In the time it took EH&S to respond to the phone call I would have been dead. What saved me was brief period of time completing the circuit, and didn't go entirely into fibrillation.

Company's new policy now requires 500V electrical gloves when working on SELV Safe Extra Low Voltage!
Electrical gloves require leather outer gloves (or else send back for retest after one day's use.) Good thing we aren't (always) handling microelectronics, mostly just boxes with cables and test leads.

The hospital stay was initially to monitor while EKG was bad, alarm would have told them to come resuscitate me.
Then waiting a couple days until they could run an echo-cardiogram (tech can do 6 per day) to determine settings of "Life Vest" wearable defibrillator. I finally said, "I'm Outa Here!" on Sunday evening and walked away. I read the doctor's interpretation of the sonoscan later which said left ventricle ejection fraction was in the normal range. Reading up on Life Vest, if < 35% that's when it is recommended.

diysolarforum.com

⚡Shock⚡ through the heart,

And you're to blame, You give solar a bad name! Meant to be safer than a cheater cord, power cord with shrouded banana plugs + Similar wire and banana connected to equipment under test. Now it's easy to stack banana plugs and plug in HV scope probe. It's just as easy to mix up Line and...
diysolarforum.com diysolarforum.com
 
I'm on the paranoid side which makes it easy to decide on how many volts is bad...

ALL OF THEM !

If I'm working on power stuff from dc to ac I do not EVER consider the wires "safe". I handle them like they are all live and all dangerous. Either insulated tools and or gloves at all times.

But thats just me.
 
Hedges said:
hospital stay was initially to monitor while EKG was bad, alarm would have told them to come resuscitate me
Click to expand...
You’re scaring me.
I took a datsun ignition jolt in 1991 and “lost” a half an hour or so. All I remember was stumbling to go into the garage to sit down, feeling rubber-legged, and near as I could tell I guess I did sit down and “came to” sitting down leaning against the wall 45 minutes later
 
It is mostly an AC problem. Several cycles of line voltage leaves ion polarities scrambled resulting in heart muscle cells not working in sync (so they say, not my field). Doesn't take much to do that, and GFIC would cut power before that occurs.

Previous shocks (all 120V) were one hand and probably poorly grounded through shoes. This one was 200V or so, hand to hand. Very brief, having just touched the tip of finger on left hand, but long enough. After a few minutes I lay down for a while, in other lab after telling colleagues about the incident.

higher voltage DC and AC more likely to cause immediate severe burns.

Both AC and DC can make your muscles tighten, keep you attached until it has accomplished its work. So I'll tap a wire with my hand or pliers before gripping it, even though I've tested for zero volts.

Just ignition system did that to you?
I've put my arm on a small engine spark plug or magneto with engine running and it sure got my attention. But didn't knock me down for the count.
 
Hedges said:
Just ignition system did that to you?
Click to expand...
Ya, coil. 1983 Datsun 4cyl pickups have two coils and eight spark plugs. I don’t remember what I was doing/checking (didn’t then either- I remember not remembering) but one coil wire was unplugged from the coil when I went back to it.
I’ve been magneto lawnmower and chainsaw jolted before but other than disliking it to a great degree it never took me out.
 
It is pretty amazing what it takes to kill you that is heart related. I had a yearly physical with EKG. It said my heart rate was 157 and abnormal. An EKG can be hard to read, but this problem could be seen from across the room. The doctor never looked at it. I went three months seeing multiple doctors before I found one who finally diagnosed it, at that time I deteriorated to the point of liver failure. You really need to be your own advocate and I can't stress how useful KARDIA is, that EKG on your phone device. And the doctors can be really dismissive of it. Recently went to my GP for my annual and told him I no longer have a heart rate. He listened to my heart and told me it was fine and people are calling him all the time with these health monitors. A week later I see my cardiologist. I had sent him EKG graphs earlier and he said I was fine. Pacemaker told him I was in 70% AFIB. Why He wouldn't download my monitor two months earlier I don't know. I go into the hospital to get zapped and they do an EKG before. Nurse says I look fine and they may cancel procedure. I got it and I am fine for now. I was in AFIB last June and they waited till January for an operation. You can go a long time with serious heart issues before it kills you. Get a KARDIA. It will show a lot of false issues, but get used to your normal pattern and serious issues will become obvious.
 
sunshine_eggo said:
Nope. It's about current as dictated by voltage and resistance.

Current will kill you. The amount of current that conducts through you is dependent on the voltage and the resistance of your skin and tissues. A low power/high voltage source could kill you were a very high power, low voltage source wouldn't even be noticed. Automotive 12V lead acid batteries can easily deliver 500-1000A at 7.5V (7500W), but you can touch them with dry skin without any fear of even a slight shock.

Take 10 5W panels and string them in series to get 220VDC/50W. Could actually kill you.

7500W can't kill you except in extraordinary and odd circumstances where you're trying to get killed, yet 50W could kill you without much special effort.

Worth a read:

www.scienceabc.com

How Much Current Can The Human Body Withstand?

Of course, more voltage draws more power, but it is not the caliber that kills us but the bullet it shoots. Regardless of the voltage, the real cause of death is the current forced through the body.
www.scienceabc.com www.scienceabc.com
Click to expand...
 
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