To Sunray

[ericmark]

As said before, to transform is change some thing, be it current into voltage, or high voltage to low voltage, so a one to one isolation transformer is not technically a transformer, but a switch mode power supply is. Yes I know we tend to consider the wire wound device as a transformer but we have to accept the English definition will also include this

they transform and so does a switched mode power supply.

 

[SUNRAY]

As said before, to transform is change some thing, ...so a one to one isolation transformer is not technically a transformer, ...

You are wrong and I have to take you to task on this one Eric. An isolation transformer will normally isolate something from an earthed supply.
So technically it will transform from an an earthed supply to isolated.

 

[crystal ball]

I watched it ten times, still never blew

 

[bernardgreen]

I watched it ten times, still never blew

It needs a strong puff from Winston!

 

[SUNRAY]

Originally posted in the wrong thread, thanks to Mod for allowing me to move it.

The first LEDs I saw was way back in 1973 from RS and they were available in red, green, or yellow.

Oh I see... the first YOU SAW! but that is not the same as 'The first line of that link is rubbish. Green LEDs we’re available from the outset along with red and yellow.' is it?

So we'll take that as WRONG AGAIN.

Some of us have longer (possibly better?) memories and red was most deffinitely the first to be invented/discovered early 60's and to be commercially available but only for expensive commercial equipment (like lab kit) mid to late 60's, then came orange/amber which progressed to yellow and green a year or two after red but not commercially viable until several years after red, possibly 70's. Blue was possibly 10 years later, very expensive and much brighter. My guess, and I stress it is a guess, is that the blue version led to the rapid improvement in the earlier colours. I have deliberately not put dates as my memory is not good enough to be certain.
This is from memory and as always I'm happy to accept that I may not be in possession of all the facts and reality may be different to this.

I remember the cost of red being a fraction of amber , yellow & green and into the 80's having to pay several tens of pounds for for a single blue 5mm LED Vs 10p for the other colours.

AND if I were to start looking for your mistakes I'd start with this: 'The first LEDs I saw was way back in 1973 from RS and they were'

Please don't bother looking for my linguistic errors as I know I make mistakes... unlike you.

 

[ericmark]

I also seem to remember red LED was the standard for many years, you could get other colours but at many times the price, the voltage across a red LED was around 1.2 to 1.4 volt, so putting a red LED common to negative with a 7412 chip raised the voltage to 13.2 to 13.4 volt, it was a cheap way to charge a lead acid absorbed glass mat battery, so using a red LED to show charging was very common.

 

[SUNRAY]

I also seem to remember red LED was the standard for many years, you could get other colours but at many times the price, the voltage across a red LED was around 1.2 to 1.4 volt, so putting a red LED common to negative with a 7412 chip raised the voltage to 13.2 to 13.4 volt, it was a cheap way to charge a lead acid absorbed glass mat battery, so using a red LED to show charging was very common.

I'm doing a bit of sorting out at the moment and come across part of a flyer list of components which I think was TK Electronics and I'm guessing from mid 70's: 3mm LED's red 12p, amber & yellow 17p, yellow green 24p, green 86p, no mention of blue yet.

Yep adding forward biased diodes to the common leg has always been my go to method of altering (increasing) a voltage regulators output. For charging gel batteries I use a green LED which usually comes out at about 1.6 volt making around 13.6V.

For a 13.8V supply it's 3 carefully chosen 1n4001's typically 0.55 to 0.7V each.

But you imply the LED is only lit when charging, the following is what I've always done:

I've never looked at the operation of packaged voltage regulators so I've always added the resistor to forward bias the diode. Now I need to experiment with the ubiquitous little devils to see what happens with the 0V leg current when current is being drawn from the o/p.

My more common method of sensing charging has been to detect the voltage across a resistor in the charging circuit or a reed relay which if far less accurate.

 

[ericmark]

It was not my idea, it was the method used with CB power supplies, seem to remember a CB was limited to a very low output anyway, my radios needed more power and also I was worried about over voltage, so either a crowbar or a battery to ensure no over voltage, in those days a 2 meter radio was rather expensive before the pofung and the like came out with £35 duel band radios.

But most things used red LED's, although there were other colours they were more expensive so the bugin lamp holders got replaced with LED's and a resistor.

 

[333rocky333]

you imply the LED is only lit when charging

I have noticed the led don't light if the batteries unplugged also, which is a bonus if you forget to plug it in

 

[SUNRAY]

I have noticed the led don't light if the batteries unplugged also, which is a bonus if you forget to plug it in

As mentioned before it had never crossed my mind, my concern was stability so I always ensured the diode was fully forward biased.

Everyday a school day as they say.

 

[SUNRAY]

I converted some of this style of car accessory warning light to LED:
https://www.arc-components.com/0-60...-with-12v-2w-ba7s-bulb-chrome-bezel-3582.html
Initially I simply soldered LED and R to the fitting and slipped in behind the lens but the effect was not all that. Then I drilled a 3mm hole in the lens so the LED finished slightly proud of Flush. Suddenly it seemed they were the coolest thing to add to dashboards in boy racers cars and started getting the holes turned in a lathe in bulk. Fashion can be such a silly thing.

 

[ericmark]

One has to be careful with warning light wattage when used to show alternator charging, Lucas used the current through the bulb to start off the charging, so if bulb failed alternator would not charge, and Paris Rhone made some single phase alternators and the bulb always glowed, so French cars had a dark glass in the charge warning light so you would not see the glow.

Relays and LED is also a problem with back EMF blowing the LED.

I remember early Mini with speedo in centre, making a surround in plastic coated steel from JS&S Shotton later British Steel, with two 8W fluorescent tubes to light the dash/glove box, and as lonnie donegan putting on the style said, gloves borrowed form my dad.

 

[bernardgreen]

I had a 12 volt 7 watt florescent lamp as the rear fog lamp on my Spitfire,

It is from memory that I recall the wattage being reduced from 8 to 7 watts to be compliant with the then vehicle lighting regulations.