Battery safety

Hi guys, I was wondering if it's dangerous to touch two wires hooked up to a 9v battery to each other. They heat up really quick, could they make the battery explode or do something else bad if left like that for any long period of time? I tried to search for the answer, but couldn't find it.

Posted by Lithium Rain 10 years ago  |  last reply 10 years ago


Bycycle safety

Weird Bicycle safety film that I found. Were you ever exposed to this at school?It's entitled "One Got Fat" on account of he had all their packed lunches on his bike, and the rest of them got killed / hospitalised before it came to eating them... But? Erm, everyone else is mangled / dead and the "smart" kid is going to compound upon their stupidity by forcing their butties down his gullet making himself obese?L

Posted by lemonie 9 years ago  |  last reply 9 years ago


Instructables safety

Hi! I love the site and all of the features. I do however have one concern, that is regarding the safety of the users/builders. I believe it's just a matter of time before someone gets killed or seriously hurt by attempting some of the instructions. I've seen way too many instructions without any type of warning text or concern about user safety, these instructables often involving high voltage, significant overheating risks and high powered lasers. A couple of these have also been featured instructables. My suggestion is something like big red bar just above every page of the instructable, saying like "DO NOT ATTEMPT THIS PROJECT WITHOUT ADEQUATE KNOWLEDGE/EXPERIENCE". To make this bar show up I suggest one final pop up question before each project is published saying something like "Could building/using project possibly cause any risk of injury?" and if true the banner would appear. Admins should also be able to turn on this bar manually. I believe the current focus is to prevent project that intends to cause harm, but many other projects will likely cause harm if the builder doesn't have enough knowledge. Especially if the original maker himself also lacks knowledge about the risks with their design. I would ask you to consider not allowing instructables that involves tampering with high voltage connections if you don't like the idea of a warning banner. I don't want to see some kid loosing their eyes after attempting to build a DIY laser engraver or worse, killed during a rainstorm holding their ungrounded DIY high voltage spotlight.

Posted by johanmoberg 3 years ago  |  last reply 3 years ago


safety matches...

Ok, i am thinking of creating an instructable on how to ignite saftey matches with-out the box, but i dont know if people would be interested or already know how to do this, please say "yay" or "nay" for this instructable to go ahead, thanks.

Posted by andy60 11 years ago  |  last reply 11 years ago


Fire Safety!

I became interested in hobby electronics after seeing this instructable: Light BarWith projects like this, the more components I buy, the cheaper each component is (ex: buying LEDs in bulk) so I will likely end up with more parts than I would want for myself. If I make a lot of these things (or similar projects) and give some to friends, how can I make sure that they are completely safe?

Posted by NOOBLMAO 10 years ago  |  last reply 10 years ago


Safety symbols for instructables

Hey guys! Just an idea; In the symbols section when writing an instructable, if we had a symbol for; Goggles, Ear Defenders and Dust Masks it could be useful to add to each step as simple safety advice. Anyway....     Just an idea :)

Posted by Toms Workshop 5 years ago  |  last reply 5 years ago


Safety or lack thereof

Hi, Does Instructibles have a duty of care with regard to the safety on the ibles that are presented on the site? In the past, people would put "please don't try this at home, please be instructed on soldering/HV/lasers/...." now I am seeing some 'ibles that are carelessly dangerous. Some examples are: - connecting a microwave magnetron to a high gain waveguide antenna output - circuits and places to purchase lasers that are not eye-safe, even likely to blind and burn (1W diode lasers) - HV circuits that have no protection / current limiting, creepage and clearance considerations etc. Maybe I am a grumpy old man, but it does worry me! I would hate to see kids blinded just because they read an ible without understanding the dangers, build something up and become blinded.  Would you like it if that was your kid and they saw it on ibles? For the budding inventors out there, to get the product to market they will have to consider safety in the designs.  Why not start now as part of the product concept? Not trying to be a scaremonger, just trying to understand where people are coming from and provide some suggestions on how to improve things: - provide check boxes or an icon that people can tick (eg skull and crossbones for chemicals, laser safety icon etc.) - provide standard warnings - refuse to publish or ask for rework of 'ibles that are recklessly dangerous - sponsorship for a 'safety first' ible competition? - ..... Is this something that 'ibles would be interested in? Regards Steve

Posted by kutvpiheg1955 8 years ago  |  last reply 7 years ago


Basic Electronic Safety

Hello all! I'm beginning down the route of hobbyist electronics. As to basic safety precautions I'm really quite unsure. I know inside many electronics parts and devices (For example, a TV one would strip for parts,) there are many nasty chemicals. I don't want to get lead poisoning or any other sickness. If you could point out some safety precautions, I would be incredibly grateful (Ex. Always wear gloves, wear a mask when soldering, when stripping a TV...., etc.). Thanks for your time and help!

Posted by I Am That Guy 6 years ago  |  last reply 6 years ago


Heating HDPE and Safety

Hi, I have a light and am bothered by the glare below the shade. I have cut a piece of HDPE from a plastic milk bottle and have slipped the section below the bottom of the bulb (60 Watt  - 75 Watt bulbs) ca. 1 inch below, and the bottom of the  lamp shade.. There are gaps between the plastic and shade to allow heat dispersal. I have noticed that the HDPE gets quite warm, but looks and feels alright. I am concerned about any possible toxic emissions, ethylene gas (no smell) etc. Can anyone advise regarding safety? Thanks

Posted by anon_private 4 years ago  |  last reply 4 years ago


electrical safety question Answered

1) how many 100 watt equivalent bulbs can i safely run into a normal heavier guage orange household extension cord? 2) can it be unsafe to leave the extension cord plugged in and powering the safest number of light bulbs on for days and weeks at a time?

Asked by hobbssamuelj 9 years ago  |  last reply 9 years ago


Safety, Electricity and Death

I came across this AC safety info and found it useful enough to share. Link: www.cdc.gov/niosh/docs/98-131/overview.html FTA: 1 mA Barely perceptible 16 mA Max current an average person can grasp and let go 20 mA Paralysis of respitory muscles 100 mA Ventricular fibrillation threshold 2 Amps Cardiac standstill and internal organ damage 15/20 Common fuse or breaker opens circuit I later found this DC info... Link: www.allaboutcircuits.com/vol_1/chpt_3/4.html FTA: "AC ... is 3 to 5 more dangerous than DC of the same voltage and amperage." Slight sensation felt at hands DC Men: 1.0mA, Women: 0.6mA 60 Hz AC Men: 0.4mA, Women: 0.3mA  ... Painful, but voluntary muscle control maintained DC Men: 62mA, Women: 41mA 60 Hz AC Men: 9mA, Women: 6mA ... "In industry, 30 volts is generally considered to be a conservative threshold value for dangerous voltage. The cautious person should regard any voltage above 30 as theratening, not relying on normal body resistance for protection against shock."

Posted by milsorgen 9 years ago  |  last reply 9 years ago


Making safety easier

I have seen many users ask questions like "how do you report a user"  and " is there a button for flagging a user after I flag the instructable?" Well I myself already know but that doesn't help the other few million users(wow) that don't know. After this forum post I plan on emailing service@instructables.com but maybe there is another way. I was thinking that maybe an admin could send a private message to every new and old user saying that the way to report a user is to go to the about page  https://www.instructables.com/about/  click on an instructables team member then to send them a private message telling them what the user did, where and why it should be removed( user and/or instructable). It would be even better if the instructables team got together and made groups open to the public again. I did some research and groups used to be easy to get to https://www.instructables.com/edit/new?type=group but if you copy and paste this and try to go to it it won't work. I did some more research and it seems that all the current groups are run by businesses or companies. I just want to make things easier for the average user so that we can make this a more enjoyable site. Also I would like to make a group for younger users so that we can post instructables to each other. It would be cool to have our own circle.  -gearup500

Posted by gearup500 4 years ago  |  last reply 4 years ago


Shattered CRT Safety

I'm thinking of cutting the phosphorecent screen off of a CRT and seeing what effects I can produce by shining some high intensity UV light on it. Removing the screan is going to be tricky since the entire CRT is a vacuum on the inside. I know I'm going to have to be really careful and let the pressure in slowly or it could implode and send shards everywhere, but I'm also worried about what dangerous substances might be in the CRT that I could expose myself to. Does anyone know if there is a danger of lead/mercury/etc on the inside of the CRT, and what safety precaussions I can take?

Posted by kramerr 9 years ago


Safety Tips, anyone?

Ok, obviously, "don't drop hot steel on your feets" is the first safety thing we need to think about, but what abut others? Any chemical hazards or others people'd like to share?

Posted by Vendigroth 11 years ago  |  last reply 8 years ago


Heath and Safety Flag

I think it would be a good idea to add a new flag category: Health and Safety, to cover instructables whose use could cause bodily harm or have unintended consequences. Many ideas pass through here, some are not as well thought out as others, and some are just dangerous and unsafe.

Posted by ringai 5 years ago  |  last reply 5 years ago


safety razor blade? Answered

ok i just got me a safety razor and it came with some blades and was looking to see whats a good blade to go with i heard merkeur is a good one and i heard about a feather blade but i just started shaving with a safety i love it but i want on a basic idea which one is better i have rough hair and i heard about missing LDC with the cream to make the hair softer and its supposedly makes shaving alot easier any thoughts would be great thank you

Asked by nightninja87 8 years ago  |  last reply 8 years ago


Tesla Coil Safety?

My high school recently had an engineering fair, and my friend had built a tesla coil. Its has multiple spark gaps, an RF filter (I think thats what its called), a 120 to 20000v transformer, and toroid top-load, if any of that matters. We/I would entertain ourselves by standing away from the coil and holding a fluorescent tube (by the glass with bare hands, not by the contacts) near the top-load and watching it light up. Even though I was well away from the coil, my forearm muscles would twitch, especially it the coil spark hit the contact on the other side of the tube. Then if anybody touched me, both of us would feel a shock and the same slight twitching (the same kind of twitching you feel from those electric muscle stimulators with the pads you put on sore muscles). We even set up a chain of about 5 people holding hands, and all of us would feel a shock, even though only the first person in the line (aka me)  was holding the fluorescent tube near the coil, with my hand on glass, no where within range of the streamers coming from the top-load. Now for my question: is this dangerous? (I know its non-lethal, im talking about my nerves) And what exactly was happening? because it was not an incredibly large coil, and i know that the field of a coil is much larger than the actual streamers. I also read somewhere that insulators dont work the same at incredibly high voltages. I think what I was feeling was the skin effect, and the charge came from the excited electrons in the tube. If my ideas are correct, then wouldn't me holding the tube be just the same as if i had just put my hand near the top-load and let the streamers hit me?

Asked by masterbuilder 5 years ago  |  last reply 5 years ago


safety valve bbq propane

I understand the pressure relief valve. I understand the float valve which prevents overfilling. But is there any mechanism to prevent liquid propane from leaking if the tank tips?

Posted by Toga_Dan 3 years ago  |  last reply 3 years ago


Capacitor-bank safety issues

Okay, so I'm going to be the wet-blanket old guy.... Has anyone considered adding a topic to this group (or an I'ble) on electrical safety with supercaps? Even the low-voltage ones put out tremendous current, enough to put you into convulsions or stop your heart (50 joules) if applied correctly. These devices are amazingly cool to work with -- better than batteries when you need high current, outstanding AC line filters, and terrific party toys when you need some bang for your buck. They can also turn around and bite you on the arse without warning...

Posted by kelseymh 10 years ago  |  last reply 9 years ago


Occupational Health & Safety 'Ibles

After running a short thread about NOT sanding glass without serious respiratory protection, the idea of having Occupational Health and Safety Instructables was brought up. (Thanks, psycholily!)There are a lot of great howtos around here, and many of them touch on potentially harmful techniques. Not that this is a bad thing, and most authors will remark on safety issues, but I feel that many do not discuss how to keep safe.If we could have a few professionals post simple ibles about how to keep safe while performing various tasks that appear regularly on the site, that would be GREAT.Things such as:Respiratory protection - what do you need for sanding, painting, glasswork, welding, etc.Eye protection - wood work, soldering, welding, etc.Physical covering - is a long-sleeved shirt and jeans sufficient? Do you need gloves?Proper Cleanup and Disposal of various materials - what's safe, what's legal?

Posted by Coffeebot 10 years ago  |  last reply 10 years ago


Help with sketch, and a safety question? Answered

The model I'm building calls for 13 LED's and fiber optics running from about 6 more LED's. I have managed to get them all running on one arduino and breadboard, will this be safe? The arduino will run on a mains adapter and has a pot for flashing speed, a pot for brightness, and an on/off switch. After lots of trial an error and a lot of luck I have the other LED's acting just as I want. But I am having trouble getting 11 and 12 to stop flashing, any ideas? int sensorValue = 0; //make a variable where you can store incoming //analog values void setup(){ pinMode(12, OUTPUT); //tell arduino what you'll be using these pins pinMode(11, OUTPUT); // for (output). pinMode(10, OUTPUT); pinMode(9, OUTPUT); pinMode(8, OUTPUT); pinMode(7, OUTPUT); pinMode(6, OUTPUT); pinMode(5, OUTPUT); pinMode(4, OUTPUT); Serial.begin(9600); //initialize serial } void loop(){ //we put the code we want executed in a loop Serial.print("sensor = " ); //sends what's in quotes via serial Serial.println(sensorValue); //sends our variable (sensorValue) //via serial digitalWrite(12,HIGH); // lights the led digitalWrite(11,HIGH); digitalWrite(8,HIGH); digitalWrite(4, HIGH); sensorValue = analogRead(0); delay(sensorValue + 25); digitalWrite(4, LOW); delay(15); digitalWrite(6, HIGH); sensorValue = analogRead(0); delay(sensorValue + 25); digitalWrite(6, LOW); delay(15); digitalWrite(5, HIGH); sensorValue = analogRead(0); delay(sensorValue + 25); digitalWrite(5, LOW); delay(15); digitalWrite(7, HIGH); sensorValue = analogRead(0); delay(sensorValue + 25); digitalWrite(7, LOW); delay(15); digitalWrite(5, HIGH); sensorValue = analogRead(0); delay(sensorValue + 25); digitalWrite(5, LOW); delay(15); digitalWrite(10,HIGH); sensorValue = analogRead(0); delay(sensorValue + 25); digitalWrite(10,LOW); delay(15); digitalWrite(9,HIGH); sensorValue = analogRead(0); delay(sensorValue + 25); digitalWrite(9,LOW); delay(15); }

Asked by lifeofB 3 years ago  |  last reply 3 years ago


Is there a knex pistol with a safety on this site? Answered

Asked by Master_Zane 9 years ago  |  last reply 9 years ago


microwave transformer safety question?

if I plug a microwave transformer in and unplug it, does the transformer itself hold a charge?

Asked by ChrisS521 2 years ago  |  last reply 2 years ago


Build It: Wanky The Safety Cat

Http://jalopnik.com/...This is on the front page of diggHow to make a stuffed animal turn and brake signal for your carShould I make this an instructable

Posted by frank26080115 12 years ago


How does instructables address some projects that I see have some serious safety and liability issues?

Some projects that are on the instructables website have some serious safety and hazard concerns. In particular electrical and electronic projects that interface with 120 volts or higher. Though many of these projects are incredibly creative and brilliant, some oft these projects could put people at risk along with their associated liability.The "instructables" organization itself might be liable as well if it has not done more than some superficial notice to it's membership. I suggest that projects that could be hazardous be inspected by any controlling authority (such as building and safety) prior to their being displayed on the instructables website.

Asked by SeanFeeley111 1 year ago  |  last reply 1 year ago


SOPA?

Does instructables support SOPA? 

Posted by ExitPass 7 years ago  |  last reply 7 years ago


How safe is the "Copper Fire Log Heater: Burns clean with alcohol!" project?

The Instructable itself seems fairly risk free; however, I noticed one comment stating that it could potentially become a big problem (the internal gases build up and you get a pipe bomb...). I have no problem operating the equipment necessary to create it, but I would like to know of any hazards of the product - besides general fire safety.Here is a the link: https://www.instructables.com/id/Copper_Fire_Log_Heater_Burns_clean_with_alcohol/Thank you for any amount of the time that you spend answering this question!

Asked by TheBeginning 9 years ago  |  last reply 9 years ago


Delta sidekick saw with broken safety guard? Answered

We have a Delta sidekick 10inch motorized miter box. With a broken safety guard. This hadn't been used very much when it broke and we were unable to buy a spare. We have started using it again, carefully , but I would feel a lot happier if it had a guard. Does anyone know if another make of guard will fit this  saw. Many thanks

Asked by Kiwi girl 6 years ago  |  last reply 4 years ago


Poll Question: Do you think health and safety has gone crazy?

I know that on Instructables we do some fairly dangerous stuff with all the potato guns and weaponry. This 30 years ago was perfectly acceptable, but in the modern society health and safety makes you wear goggles and be safe. The fact is you can do practically nothing in an open environment without being told to be safer. I brought up this topic when i heard that one school had banned all pencil cases as well... It might contain sharp objects-like pencils! So what do you think, is all the politics making health and safety a bit over the top or is it just there to protect us?

Posted by Mr Tenacious 11 years ago  |  last reply 10 years ago


places to get gear online

So Im looking to find some decent prices on safety gear online from an at least somewhat reputable dealer. I have been eying leatherup.com has anyone bought from them before? alternatively what online retailers have you used and whats your opinion of them?

Posted by cokebottle tuque 10 years ago  |  last reply 7 years ago


Is sugru safe?

Hello, Doe's anyone know if it is actually safe to use sugru on our project? I mean, is it safe to let a kid use something that got sugru on it, or to put sugru near our ear/mouth/eye?

Posted by ac1D 8 years ago  |  last reply 8 years ago


Bones from stores?

I bought some flavored bones for my dog at a store and found that they are pig bones.  She had blood in her stool (lots). I gave her peroxide and she threw up about 30 shards.  they were sharp enough to remove a sliver from your finger.  Never give you dog pork bones, EVER.  I don't know everywhere they are sold but I got mine at TSC  My dog is fine by the way.

Asked by VICPETERS 3 years ago  |  last reply 3 years ago


Question about my microwave

I just discovered that the inside of my microwave has two rust spots in it. It's also seems to have air leaking from it when it runs, or at least I can feel heat. My question is, since I know little about microwaves other than usuing them, is this microwave still safe to use? (My guess it isn't, but thought I'd ask) It's an older one given to me by my cousin. Thanks.

Posted by LisaAC 11 years ago  |  last reply 11 years ago


safely handling glass and rigide plastic

Today i learned how not to store a mirror i intended to use, then forgot about. the price of this knowledge: 4 stitches and a tetanus shot. the mirror cracked, and a large chunk fell on my ankle. im hoping, after reading this story, those of you with Plexiglas or mirrors lying around (not hung up) will make sure they are properly stored. btw: the mirror broke exactly along the blue line i marked on the mirror for where i wanted to cut it.

Posted by tech-king 11 years ago  |  last reply 10 years ago


What do you look for to know if you are in the 'bad' part of town?

I like to wander around, but, growing up in the country/farmland, I don't know how to read the city.  Does anyone have any practical ways to tell if I should be choosing different areas? BTW, naming neighborhoods is useless, because I don't know where I'll be using the info.  I'm looking for things that I could see while walking without a map.

Asked by jtobako 8 years ago  |  last reply 4 years ago


Is there a site I can get free (or very cheap) MSDSs? Answered

I have a small collection of chemicals in my work area, and not all of them are in containters that came in. As such, I was wanting to be proactive and get a small binder with all the MSD sheets in one spots (much like anywhere else). Only issue is, I can not seem to find a site that offers free MSD sheets. They either have an odd rule of "you can only look at five" or its a rather pricey paid subscription. Thanks in advance! 

Asked by DoctorWoo 3 years ago  |  last reply 3 years ago


How can I make a simple ultrasonic dog repeller?

I have been chased by some neighborhood dogs while biking in the last few months, and I need some defense. I don't like the mace or whatever sprays, and I certainly don't want to hit them with anything. I know there are some ultrasonic gizmos but they are awfully expensive. I have found some ultrasonic (25KHZ and above) transmitters at Mouser, and I was wondering if anyone could help with how to make my own portable dog stopper. Please Save My Ankles!

Asked by darryllicht 10 years ago  |  last reply 5 years ago


Could one re-purpose a respirator to prevent noxious fumes from escaping?

Hi there! I have had this idea in my head for some time, especially now that I am looking into metal etching. But I am an apartment dweller, with a cat. Now, I know that this is pretty broad. So I will give a specific example: if I build this https://www.instructables.com/id/Electrolytic-Etcher/. Can I build also a tank using say, these acid-gas cartridges http://www.mcmaster.com/#5834t66/=walor0 in-line with the exhaust of a vent system to clean out the chlorine? Would this work? Would it be safe? Would it allow the relatively slow out-gas of hydrogen to disperse, or would it concentrate it? Any thoughts at all? Thanks! Ernest.

Asked by eruger 4 years ago  |  last reply 4 years ago


Safety Shutoff Bumper on Electric Wheelchair

Friend has Parkinsons.  I'm setting him up with electric wheelchair. Best if he doesnt run it through walls, or run over anyone. need electric shutoff on bumper front and back. How, exactly? and. Go.

Posted by Toga_Dan 2 years ago  |  last reply 2 years ago


Is there a pin or safety pin shaped like this? Answered

I need  small pins shaped like this - a safety pin like thing maybe 3/8 to 1/2 inch diameter.  Do they exist?

Asked by mole1 7 years ago  |  last reply 7 years ago


Bypass safeties in electronic Neon Transformer

I have a neon sign transformer that i would like to use for high voltage projects. The problem is it has an electronic safety circuit that (I believe) checks to see if there is a neon tube is attached.  Does anyone know how to bypass the safety system? the transformer box is full of insulating tar so accessing the electronics is near impossible. when turned on it sends out several short HV pulses and then the warning light illuminates, it seems to be searching for some type of load. 930CPX120 ALLANSON 9000V 30MA NEON TRANSFORMER,

Asked by BlitzkriegBrain 4 years ago  |  last reply 2 years ago


Safety Warnings -- how to do it right!

I saw this on the MAKE blog today.  It is, I think, the single greatest effort at a properly respectful (to the intelligence of the user) safety warning that I've seen.  Kudos both to the tech writer who came up with it, and the lawyers who had enough common sense to release it into the wild. My only complaint is that on SparkFun's Web page, the instruction manual is a completely inaccessible JPEG image.  Perhaps part of being "safe" is not allowing anyone with low vision or who reads a language other than English, to know about the product?  (Yes, I've contacted them directly about it.)

Posted by kelseymh 8 years ago  |  last reply 8 years ago


Rear and front bikelights and road safety

A good bike rider learns from good and bad experiences during the initial rides. I pedal a bike on busy roads of my city. I realized that bikelights, especially the rear ones, are crucial for safety purpose. I got a backpack with solar panels and it has got a LED light as a rear bikelight, but it’s too dim, and the tail light sounds nothing like a good indicator for motorists. Either I would need suggestion on a bikelight safety kit or something else. I could do with my self-powered backpack. Is there is any DIY idea to replace it with a more bright option?

Posted by bikelightsuk 4 years ago  |  last reply 4 years ago


how to bypass the safety on a battery charger?

Ive been working on a cd welder for battery tab.. very simple car audio capacitor with a battery charger. today i rebuilt the whole thing with new leads wiring and new battery charger that will shut off when it hits a full charge. now it wont charge at all because it apparently wont charge anything thats not a car battery with proper voltage already existing. since the capacitor dumps the charge and leaves nothing, the charger just thinks there is nothing there. can anyone give me a crash course in float chargers and how they work so i can single out what i need and bypass everything else

Asked by snowfox222 3 years ago  |  last reply 3 years ago


Garage door safety sensor wiring?

I believe it is an infrared sensor with two wires on each. I have wired them to a 120V plug and the LEDs on them turn on and my motor spins slightly (probably just because it is a 120V motor and it's not getting enough electricity) but I try to line up the sensors and they do nothing different even when crossed. What I want to happen is for the motor to remain off until the beam is crossed. Once crossed I want it to spin and to keep spinning until I disconnect it. I would really like to put an alarm on it so when crossed an alarm goes off. Does anyone know the additional things I need and how to wire them? Thanks

Asked by chiefs543 6 years ago  |  last reply 6 years ago


Mains Ground Safety for Power Supply? Answered

I'm trying to build my first switched mode power supply. I'll be using it to drive two 24v 50W heating elements. I don't want to use a transformer. The design I have so far seems to work well in simulations, but I need some advice regarding mains ground. The control electronics will be operated on power from a small transformer. This provides isolation from mains. I've done this a million times.  However, the mains power connects directly to the loop that produces the 24V signal. This is the loop after the FET, containing a diode, inductor, and capacitor. The wire coming from this loop and going to the comparator is where I'm having trouble. This is a voltage sensing wire and carries very little current, and is used by the comparator to produce negative feedback. This feedback loop is what allows me to get 24V from 120V. The comparator is powered by the 12V isolated supply. In order for it to sense the voltage properly, the comparator's ground must be at the same voltage as the power supply's ground. But the power supply's ground is tied directly to mains ground. Is that safe? Am I allowed to do that? In mains wiring in the US, the left notch is neutral, the bottom hole is ground, and the right notch is hot. Neutral is basically ground, except ground is connected to the actual ground and neutral is this mysterious thing I probably don't completely understand. Is it safe to use it as ground? What if the person using this circuit flips the plug over and suddenly the circuit's "ground" is fluctuating wildly between +/- 120V? The circuit may function just fine, but someone using a switch or knob connecting to ground could get a nasty shock. How do I make sure the ground of my circuit is always connected to actual ground? Do I need to preserve the isolation of the control circuitry? I know how to use Gate Drive Transformers for the FETs, but the sense wire for the comparator still needs to have both halves of the circuit with their grounds at the same voltage. Any advice is greatly appreciated.

Asked by laserjocky 5 years ago  |  last reply 4 years ago


Lack of regard to personal safety or the safety of those who read a post.

I'm just wondering as to why there as so many ibles posted that are an accident just waiting to happen? Does anyone check out as to how safe the end product will be?  Do Instructables.com have some kind of get out clause to stop themselves getting sued to buggery when some less than bright child does one of these and becomes a Darwin award winner? I'm all on for the self cleansing of the gene pool by guys who blatantly disregard thier own and others health and safety. I dont believe that we should be making the the job easier by showing them how to do idiotically dangerous things. I am an engineer by trade, I have always been aware of safety issues, but still managed to collect a fine collection of injuries and scars over the years. If there are featured and winner banners why not one for marking the dangerous or unsafe ones?

Posted by Dr Qui 8 years ago  |  last reply 5 years ago


Ionizing vs. non-ionizing radiation, units, and safety (updated)

Note: This was originally intended as a reply in the Americium-241 Science forum topicWhen people talk about "radiation," they are referring to many different things, and are probably thinking of some things that don't even apply. "Radiation," the invisible energy given off by radioactive materials, can be either "subatomic" particles or electromagnetic. The most common particles emitted are "beta rays," high-energy electrons, and "alpha particles," helium nuclei. Some sources can emit neutrons, protons, or "positive beta rays" (anti-electrons, or positrons), but those are much less common.The units we use to measure radioactivity are becquerels (Bq, decays per second) or curies (Ci, 3.7 x 1010 decays per second). Since the effects of radiation depend on their energy, another unit of interest is absorbed dose, the energy deposited per unit mass of target, measured in grays (Gy).Safety experts classify radiation into "ionizing," meaning there is enough energy to knock electrons out of atoms or molecules, and "non-ionizing." Infrared and ultraviolet light are non-ionizing, as are neutrons. Alpha particles (helium nuclei), beta particles (electrons) and gammas (as well as lower energy X-rays) are all ionizing radiation. The three have substantially different effects on biological systems, even at the same absorbed dose. Consequently, for radiation safety purposes, scaling factors are applied to produce numerical measures (sieverts, Sv) of "effective" or "equivalent" dose, that can be compared across different kinds of sources.Here's a small table with information for some commonly encountered sources. Isotope Source Activity Dose rate Am-241 smoke detector 35 kBq (1 µCi) 11 µSv/yr @ 1m Te-99m MRI contrast 740 MBq (20 mCi) 1.6 Sv/hr @ 1cm C-14 atmosphere, body 0.23 Bq 10 µSv/yr K-40 bananas, body 4.4 kBq 200 µSv/yrWhat you should see clearly from this is that the natural radioactivity in your body is comparable or larger than that in a common smoke detector. At SLAC, the limit for exposure to sources at the lab by most staff (including me) is 20 µSv/yr (5 mrem).As I noted above, neutrons are sometimes lumped in with ionizing radiation in non-technical "radiation safety" classes (we call them "the photon is your friend" training :-). That is not really accurate -- neutrons don't interact with electrons(*), and so cannot ionize directly. They can interact with hydrogen nuclei (protons), knocking them out of complex organic molecules, and leave behind ionized fragments and free radicals. The can also be absorbed by otherwise stable nuclei, making them radioactive; those new nuclei may in turn give off ionizing radiation.Neutrons lose energy much more slowly in passing through material, and so can penetrate much farther than ionizing particles or gammas. The nuclear interaction [http://en.wikipedia.org/wiki/Cross_section_(physics) cross-section] is much more important here than dE/dx (ionization) energy loss. Materials rich in carbon and hydrogen (for example, paraffin) are far more effective at neutron shielding than dense metals like lead.(* for the expert readers) Yes, there is n-e scattering through W and Z exchange, but the cross-section and energy scales are completely irrelevant to this discussion.

Posted by kelseymh 10 years ago  |  last reply 10 years ago


How should I protect my eyes when working with a laser?

I want to built a laser cutter and have bought a 7W laser for it. How should I protect my eyes? What is important in building it to make it safe / have no risk left to hurt my eyes...

Asked by macmoritz 10 years ago  |  last reply 10 years ago


Is regular 22 gauge steel wire okay to make earring findings out of? Answered

I am currently using blackspur 22 gauge steel wire to make earring findings but I am worried it could be harmful. Please help? Is this okay to use? No one has yet wore these

Asked by The Science Guy 6 years ago  |  last reply 6 years ago