Hi all,
Just an academic question.
What used to be used in Car Battery charger to convert the AC - DC before silicon diodes/bridge rectifiers came along?
And did they do full rectification or just half wave?
Not sure about battery chargers in particular but older rectifiers were either a vacuum tube or a selenium rectifier.
MBQ
points i'm afraid) has technology moved on since the 70's? or are todays chargers still a transformer, rectifier and a fuse in a box?
Supplementary:
What used to be used in car battery chargers to convery 240v to 12v when the mains was DC?
(my train set used a small rotary converter)
Explain please
Thinking about it, I think I still have the "Transformer" that my parents bought for the family train set in my loft C 1966 or so, and I remember it having bugger all in it apart from a transformer and some kind of overcurrent trip. I wonder what is in there?
I did have a look at the wikipaedia article mentioed earlier and also followed the link to Bridge Rectifiers and the later link to vibrators (electrical). Fascinating stuff!
I think my friend's late uncle's battery charger probably had a centre tapped transformer and a couple of metal diodes (centre tapped so as to get full wave rectification with just of two diodes) thus saving the cost of two diodes. I suppose this made sense in the olden days when diodes were relatively expensive compared with an extra tapping on the transformer.
================================== As far as I know the vacuum tube type ('valve') was used in radios etc. The plate type 'selenium plate' were used in more rugged environments such as battery chargers. Picture here:
Cic.
Any of the following: vibrator rectifier synchronous motor with commutator rectifier tungar mercury discharge diode selenium rectifier stack
AFAIK the old electrolytic rectifiers werent used in commercial car chargers, but quite possibly in home made ones.
Vacuum valves were no use for this task.
Any of the following: series impedance, no transformation or isolation vibrator & transformer with synchronous rectifier motor generator
NT
Nice picture of a mercury rectifier here (bottom picture)
and
Kind of reminds me of casper the friendly ghost...
to think thats nothing more than 6 diodes!
NT
I had one C1960. The transformer was a seperate unit to the "Train controller" which had a miniature "Tram Controller" type handle combining reversing and rheostatic speed control, smooth operation of which was very poor and sticky. It also had a single red button which functioned as a primitive (I think magnetic because it buzzed) circuit breaker. I think all this adds up to a centre tapped rheostat and bi-phase half wave rectification with germanium diodes.
The transformer also had a 1.25" fuse which blew very readily in case of a derailment or just a short circuit both of which were quite frequent in the days of Hornby 3 rail track. It was quite expensive to keep on replacing fuses out of a 12 year old's pocket money. :-(
It's possible, but each diode would need 2x the current carrying capacity for the same current output.
I'm sure some cheap low powered ones just had a single diode and half wave rectification if the way they buzzed and the way the needle on the ammeter used to vibrate was anything to go by.
DG
What I said. In the late 1950s our mains was DC at 240 volts. Transformers don't work on DC. So what was used?
I had a Tri-Ang train set. It used 12 volts DC. I had a little motor/generator combined (240v motor, 12v generator) in a perforated metal case, about 12 inches by 6 by 6 (perhaps a little smaller). Excitement when my dad came home with a small red box and said "We'll be using this instead from next week". That was a transformer/rectifier box to use when they changed our mains to AC.
on 13/09/2007, snipped-for-privacy@connectfree.co.uk supposed :
Selenium rectifiers - easy to spot by the large metal cooling fins. Any over heating in the selenium and they would be easily damaged. Once you have smelt one failing, you could instantly recognise it the next time. I think most were full wave, either using the two diode method or four.
snipped-for-privacy@connectfree.co.uk explained on 13/09/2007 :
They have moved on. The older ones had to be watched to prevent them over-charging and damaging batteries. The more modern ones at least stop charging when a full charge has been put into the battery. Even better modern ones use a three stage intelligent charging process.
DC in the 1950's surely they stopped using DC back in the 1930's
On Thu, 13 Sep 2007 18:23:43 UTC, "Sam Farrell" top posted:
Harry Bloomfield was thinking very hard :
smelt = smelled :-(
There is an example of one on Ebay...
This turns out not to be the case.
It took me ages to find a reference but...
Andy
1956 round here, Twickenham SW London
I remember the changeover (in Brighton) and I was born in 1950.
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