Safety Risks In Electronics & How To Avoid them

[pickle9000]

Lots of good info but what to do after a fire for example.

- Can you unplug your bench (the whole bench) without reaching over it.
- Do you leave your bench unattended while testing?
- Get a fire extinguisher, or at least a metal bucket with some sand.

and so on.

[VK5RC]

My comment would be NOT to rush.
Invariably when I stuff up I am rushing to finish and make a stupid mistake. Best advice I was given was after you 'finish' take a walk for 2 minutes then come back and go through the circuit or modules prior to powering up, amazing the number of potential 'smokings' I've avoided.
I would add a bit of tidiness also helps, wires everywhere etc doesn't lend to a safe outcome for biology and silicon.

[Wim_L]

Not seeing loud bangs mentioned here.

Electrolytic capacitors can explode with some violence when reverse polarized. Don't be peering closely at them when they go off.

High voltage capacitors such as the ones used for xenon discharge tubes can make a loud bang if discharged accidentally through a short or a spark gap. Such once happened to me accidentally and I nearly jumped out of my seat. It is a bad idea to be close to anything hard or sharp when being startled like that.

Related to that, the xenon arc lamps themselves can also explode violently when mishandled.

[TheEPROM9]

Congratulations on making it 40 years + without ever working with idiots.

If you're saying modern CRTs don't implode, there are about a dozen Youtube videos that would prove you wrong. 

TV type CRTs have an implosion band/strap to help prevent it from happening.  However, if you've ever worked on a maritime RADAR PPI display from before the raster scan era, you would know that the old round P7 phosphor tubes were very fragile. Same with certain high resolution P5 phosphor CRTs used in film recorders prior to the advent of Powerpoint and LCD projectors. Oscilloscope CRTs vary.  It always seemed the more expensive the tube, the more fragile it is.


Now when it comes to safety, this attitude of "it can't happen" is exactly what gets people injured or killed.  The chance of someone reading this and then working on an old scope or antique TV are quite high, so you are doing them a disservice by saying there is no hazard.   I will agree that the odds are pretty slim; but they multiply rapidly in the presence of idiots and untrained personnel.

The point is, when you're working with this stuff, think ahead, be extra mindful of yourself and your surroundings, and don't take anything for granted. Think about the process before you loosen the first screw, for example, where are you going to set this thing down once you get it out of the case, so it doesn't slide off the table and hit the floor?  You don't have to be frightened of a CRT, but it is best to have a healthy respect for them and treat them with extreme care.

In my experience there are only maybe two things more hazardous in the electronics field than a CRT: one is transmitter high voltage - particularly multi-kilowatt power amp B+ where if you're working with the interlocks disabled you need to keep one hand in your pocket, and the other is  tower climbing. I have lost two friends from collapse due to structural failures on small towers on two separate occasions. Neither were professional climbers and in both cases it was not their own but a friend's tower that killed them.

I was going to mention the PPI CRTs,but considered it unlikely for beginners to come across them---perhaps incorrectly,but I have not seen anything similar available to the general public in my country since the late '50s,early '60s.

Enthusiasts used some of the early small & large electrostatically deflected tubes for home made TVs.prior to the availability of proper TV CRTs,& I  remember seeing one very big old Brit radar tube fitted with a TV deflection yoke---don't know if it worked though.
Of course,a lot of these enthusiasts were ex military,& knew how to handle them.

I've handled most of the other tubes you refer to,but,as I said before,they are less hazardous because of their smaller size.

We used to chuck TV CRTs that weren't up to re-gunning into a big dumpster.
That very rarely broke the tube neck,so we would smash it with a long "star picket" or piece of pipe.
A gentle sigh,& that was it--no huge spread of glass.
We found some 12" tubes out of 1950s monitors,which did smash on impact ,but not a big bang--no glass flying.

You say," You don't have to be frightened of a CRT, but it is best to have a healthy respect for them and treat them with extreme care."

Reading your original posting in isolation would scare people off having anything to do with CRTs,or even small receiving tubes.

In order of hazards,I would put them well behind:-

Transmitter HT supplies,

Transmitter aerial interlock supplies----sometimes these are several hundred volts & are still present on the supposedly dead Transmitter--Ouch!-- That hurt!

3 ph Mains in all its forms

Single phase Mains

Switch mode supplies

Ladders

Ladders & Mains--nasty shock,nastier fall!

Lightning----I know,it is unlikely,but setting up an OB link on a hill & seeing a lightning strike about a hundred yards away persuaded me to delay the setting up for a while

All the towers I've climbed have been big ones that had been there for years & weren't going anywhere,but I remember a friend in the two-way radio side of things telling horror stories about small towers.

As a poor Ham,I've never been able to afford a proper tower.

It will need careful wording, on one hand you what to make people aware, but on the other you don't want the you run for the hills or whatever the local geography of your local area. Mike's Electric Stuff could do some good examples and demonstrations. Safty does not have to be the boring dross at the office, Don't cut your self on some paper or there's about 1000 page form to fill in.

[KJDS]

Big old linear power supplies. aren't doing my back any favours at the moment. I've moved about a dozen in the last week at an average of 31kg. Wrapping those up for shipping is hard work.

[CM800]

If  you are working with larger transformers, wear steel toecaps, im rather careful moving my larger isolation transformer, my variac or my other bigger transformers around, some of them weigh 30Kg+ and many of these transformers have fairly sharp edges, enough to take your toes off likely if dropped at an angle, and enough to break a fair few bones if dropped flat.

[Doug_in_Minnesota]

I am pretty careful, safety wise........far from an idiot, with a decent amount of experience working with electronics, and with building and repairing stuff.

And yet,,,,,

Within the past 4 months, I have:

1. Melted the windings of (and let LOT's of the magic smoke out of) a very large 110 volt transformer built into a large car battery charger. This charger was a commercial product (Sears) that I was messing with. Designed to operate on various output ranges up to 150 amps Boost capability.  Hint for new players.....don't try to replace a 12 volt Lead Acid Cell with a 10 ohm 5 watt resistor....   

2. broken (and "imploded") TWO crt's. One by dropping it on the concrete garage floor, and one by tripping on something else, and falling into the TV knocking it off the top of a pile of other stuff. This was a very large TV CRT, so the mess was really something.

3. Burned my finger (on THREE SEPARATE occassions) on resistors in circuits I was building, where I forgot to factor in the Power portion of the Ohms law equation. I seem to have a tendency (hopefully not to be repeated soon, since I have now "learned"), to do fine with the V, I, and R, but forgetting to figure the W.  Having spent three separate evenings holding ice cubes to the tip of my finger, I think I won't make that mistake again soon.

4. Been hit with a hell of a "wake-up" from charged power supply caps on my open chassis Macintosh computer. This was DAYS after it was unplugged. So much for bleeder resistors across power supply caps. I've done the math, and I "think" that the charge was in the 300+ VAC range. It certainly felt like it. I knew right away that it was WAY over 110 volts. I was quite surprised to learn that the large power supply heat sinks are electrically "hot" (I didn't touch the cap's, I touched the heat sink)

5. Burned myself picking up a scrap populated circuit board from which I was harvesting parts, including some fairly large parts with heat sinks, which required a fair amount of heat to loosen----my mistake was in not realizing how much heat these boards can hold (and the heat spreads all over the place via the traces), and not realizing how long they can stay hot.

So there, even somebody who is careful and intelligent can still get hurt. About the only thing I haven't done yet is touch my soldering iron (keeping my fingers crossed on that one).

Best Regards

[Dave Turner]

Doug_in_Minnesota

How's your insurance?

[Doug_in_Minnesota]

Insurance?

Surely you jest......

I HAVE avoided burning down my house, so far.

AND, I haven't hurt myself since all of those earlier incidents, so maybe I'm getting more careful (or more lucky).

-Doug

[Dave Turner]

Of course I was jesting.

I was recalling a time in the late 60's when a friend and I were trying to figure out what was wrong with a colour TV.
Whilst probing around with a screwdriver I inadvertently shorted the HV capacitor. Woke up a little later on the other side of the shack with a melted screwdriver still in my hand. The ^%$££ bleed resistor had failed. I've never forgotten that lesson.

[gildasd]

One of the potential safety issues new (and old) people face is cutting component legs with side cutters and getting hit in the eye/face.

Because the width is quite small, the speed quite fast and ends quite sharp they can easily embed themselves in soft things.

Blunt cutters don't really have this problem. They can't cut through the entire component width at the same instant, meaning they can't transfer your cutting grip force into velocity.
However get some nice Lindstrom cutters (or other good brand) and you get a satisfying click as the wire cuts followed by pings from the other side of the room as the bit of metal bounces off the walls.

This is true of most manual work. I have long ago invested in a pair of Oakley's with the Plutonite lenses.
http://en-be.oakley.com/innovation/optical-superiority/impact-protection
Expensive? Yes, but because they are "good looking" I tend to wear them much more than the ordinary protection glasses.

And yes I've gouged a couple of lenses while working, 70$ each time, less expensive than a new eye.

[gilbenl]

Don't like to rehash old topics, but I logged in specifically to suggest this type of video. Can't seem to find a comprehensive safety video oriented to the hobbyist out there. Loads of info on how to not blow up your equipment and keep a hand in the pocket, but very little on how to avoid zapping your short and curlies into straight and smokies...if you know what I mean.

It may also be interesting to discuss the consequences of touching the wrong thing. 100mA directly across the ticker will send one into vfib. >200mA will clamp. However, touching this with dry fingers versus with your tongue will have dramatically different results. One should avoid leveraging these realities to tempt fate, but rather better play by the rules. And it's always good to know the rules.

[retrolefty]

It may also be interesting to discuss the consequences of touching the wrong thing. 100mA directly across the ticker will send one into vfib. >200mA will clamp. However, touching this with dry fingers versus with your tongue will have dramatically different results. One should avoid leveraging these realities to tempt fate, but rather better play by the rules. And it's always good to know the rules.

 Good advice. I often forget that rule about not licking electronics components while they are powered. 

[gilbenl]

It may also be interesting to discuss the consequences of touching the wrong thing. 100mA directly across the ticker will send one into vfib. >200mA will clamp. However, touching this with dry fingers versus with your tongue will have dramatically different results. One should avoid leveraging these realities to tempt fate, but rather better play by the rules. And it's always good to know the rules.

 Good advice. I often forget that rule about not licking electronics components while they are powered. 

The reward of hyperbole is the sarcasm it elicits. So you're saying I shouldn't do this anymore?


If you're stupid enough to taste test your circuit, its probably natural selection in action and I wouldn't want to interfere. However, people do dumb things not always because they themselves are intrinsically stupid, but because they lack the understanding to know what they're doing is dumb. Great example was something I (almost) did in chem lab as a freshman undergrad. Asked to make 500mL hydroflouric acid stock solution, I poured up a sizable amount of anhydrous HF and was just about to start adding the water when the professor came by and put a stop to it. I'm very thankful he did.

Stories and jokes aside, textbooks rarely describe the nuances of personal safety, at least not the ones I'm learning from. I also don't have a professor watching over my shoulder. This is why I've promoted this suggestion for a video. My arduino isn't going to hurt me, but the 125W electronic load I'd like to repair just might.

(Disclaimer: I may very well be intrinsically stupid. Jury's still out. Also, not my kid-google image)