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  • I made this error when writing down some notes for an electronics experiment; and thankfully as the error was on paper no harm occured; but its equally important for harm reduction with substances.

    Earlier in the day I had been working with some LEDs. You need to put a resistor in the circuit for most power supplies; or too much electric current flows and the LED burns out.

    LEDs do not use a great deal of current – 20 mA or 20 / 1000 (0.02 A). A glow lamp with the same light uses 200 mA (0.20 A).

    It is easy to get confused by decimal points so LED current is usually written in miliamperes (1/1000A) in the same way a entire gram of most drugs would make you ill or put you in hospital so they are dispensed in miligrams (1/1000 g)

    To work out the value of the resistor (or how much current flows in a circuit) you use Ohms law where V (voltage in VOLTS) = I (current in AMPS) x R (resistance in OHMS).

    As you also have to take into account the voltage drop across the LED(s) and the main power supply voltage and may use more than one LED a more complex set of equations is used ( and most folk use the online calculators). The maths is still based on the same principles.

    Later that evening; I was trying to work out calculations for some other equipment using 1.5 A of current and Ohms law. But I had got confused by the online calculators; and used 1500 in my calculations (still thinking in MA). So I had a circuit drawing 1 500 AMPS(!).

    I thought “strange, the protective resistor would be that small it would be one tiny piece of copper wire!” then realised what I had done..

    what would happen if I tried to draw 1500A from the mains?

    As well as the incomer circuit breakers All 3 breakers in this would most likely trip ; 150 or more houses would go off supply and I expect I would be hearing a Police helicopter in the distance and seeing its searchlight and the streets would be swarming with old bill and UK Power Networks vans. It is very difficult to make mistakes like that without being traced and arrested and you can be charged with criminal negilgence and sued for the distress and financial losses to others in the street.

    Making mistakes of powers of 10 with units for measuring substances can have similarly unpleasant consequences.

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    Excellent post GL and powers of 10 certainly are interesting powers, especially when used as the increments on scales. Take the Richter scale, a level 1 is nothing, a level 2 isn’t much more but it’s still a facvtor of 10 from a leverl 1. With levels 3 to 4, you’re gonna start having a bad day.

    Stock exchanges and the like at very bad places to misplace a zero or make an unfortunate error with a , or a decimal point. That shit can cost millions, of tax payer money you thieving banking bastards.

    Another time when using correct units is essential, drugs. Many digital scales weigh in 0.001mg, 0.01mg and 0.1g plus they weigh in in ounces and some even in karats. With some compounds andseemingly trivial mistakes in measuring can have serious consequences. Luckily it’s never happened to me but it did happen to a friend. He thought he was using a microgram/0.001 scale to weigh something but hadn’t noticed it was only 0.01 and instead of weighing out 5ug, he weighed 50mg. He was lucky the chem had a pretty reassuring safety profile or things could have been a lot moreserious.

    @Tryptameanie 574341 wrote:

    Stock exchanges and the like at very bad places to misplace a zero or make an unfortunate error with a , or a decimal point. That shit can cost millions, of tax payer money you thieving banking bastards.

    unfortunately (and coincidentally) this is one of the main arguments used worldwide to justify prohibition and drugs testing of staff in safety (and now even business) critical rôles by the political right wing (many of them are blaming cocaine use by bankers for the 1980s financial upheavals even though there were many other reasons).

    Computer systems can (and should be) programmed to check for vlues that are way out or abnormal; for instance a telephone system control unit that can sense a telephone line that has no voltage present on it whatsover (should be -48V) should flag an alarm the line could be disconnected and definitely not try to use it to make calls from. similarly data values which are way out should cause alarms to be generated.

    What happens with financial markets and the high pressure high competition environments wihch breed the systems used there is more like the practice of selling cheap LED christmas tree lights that use marginal quality LEDs in a series string and feed them with full 230V mains downstream of cheap diode rectifiers; with more forward current than recommended. So they give up the ghost the same as the old glow lamp ones and have to be replaced every few years; thus “feeding the market” even though it negates the good of LED lighting (which uses less electric).

    I’ve encountered too many otherwise well educated enginers who try and justify bullshit like this as “the free market in action” (totally ignoring the harm it causes especially to the countries what make the chemicals in LEDs (far worse than drugs) to the point I am glad guns are not legal in my country or I’d hunt down these blighters with an old style British revolver (these make you take care not to use too many bullets and to gather up cartridge cases to avoid excessive litter (and leaving evidence).

    Have you been on the humourjuice GL LOL? That was quite an amusing post my friend 🙂

    @Tryptameanie 574353 wrote:

    Have you been on the humourjuice GL LOL? That was quite an amusing post my friend 🙂

    Unfortunately not; other than cheap sherry (which I cannot drink at work and then ride my bike as the streets are full with bobbies and PCSOs checking everything with wheels) it has to go in the CD register down here -last time I had to check the fax machines were working I’ve got away with saying to a nurse “by Christ; all that lot would knock a Big Issue seller stone dead within 10 seconds; and the old lady gets the same every week”

    I that case bud I’m gonna have to infrorm a geriatric nurse as I’, concerned about you bud’
    LMAO

    I was just speaking to one 5 minutes ago :laugh_at: (most likely I’d only get sent to the same place I work at anyway :laugh_at: )

    Are you sure it was 5 minutes ago and a nurse and not an elephant?

    deifnitely; elephants have to be declared for health checks (and would have to get up a hill; the traffic jam caused would be immediately obvious). Most visitors do not bring in anything larger than dogs; though we’ve had a duck brought in in a cat basket before…

    They must have thought the cat was quackers.

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Forums The Vibe Chat Why units are important when measuring anything…