Gee, and all these years (50+) when I've needed to charge an automobile,
I've grabbed the closest available TRAIN 'Power Supply', checked the
polarity, and done the deed!!! (slow, but sure)
Chuck D.
Aww Klaus, just apply an expensive piece of equipment that will burn out
if more than 12 volts is applied to it - it will detect the higher
voltage quicker than you can say "B****R!"
13.8 volts isn't the voltage of an automotive battery charger, it is the
maximum voltage an automotive battery will hold.
An (decent) automotive battery charger is normally several volts higher.
(circa 16 volts DC)
Your train power supply is unregulated, other than the rectifier and
rheostat.
Even at "12 volts" the output is in pulse form reaching close to 17
volts peak.
That difference (17 - 13.8v) allows charging current to flow even when
full battery charge is reached.
A regulated 12 volt supply would only half charge your car battery.
On Fri, 21 Dec 2007 21:38:47 +0100, I said, "Pick a card, any card"
and "Klaus D. Mikkelsen" instead
replied:
Multimeters don't apply much of a load by design. My claim was based
on a statement that the voltage on a 12 volt supply read more than
12 volts. Made by another poster, not me. I know for a fact, and
based on your experiences stated below, that this is common with
some poorly designed or special purpose power supplies. They rely on
the load to have full regulation. It saves the manufacturer money.
Not at all. Anything above 10MOhm is not considered a load.
I've only got 40 years. Tubes were on the way out and transistors
were very expensive back then. Integrated circuits were only dreams
but they did exist when I started out. Built my first S-100 machine
from scratch using a brand shiny new, Z80 (Soooooo expensive!).
I only do design work for myself now. I teach a bit at the local
tertiary schools here in Perth whenever I'm asked. I am a former
third party rep for MicroChip but gave it up when I moved to
Australia from San Diego. I truly love embedded control and use any
excuse at all to drop a PIC into a project.
Well done.
--
Ray
On Sat, 22 Dec 2007 10:08:19 +1300, I said, "Pick a card, any card"
and Greg Procter instead replied:
Go and measure you car battery. It's only 12 volts. If your charger
didn't output 13.8 volts or more, it would discharge the battery.
That's the nature of lead-acid batteries. No kidding, Greg. I'm
really trying to educate you here. Just accept it for now and verify
it when you get a chance. Ask a lead-acid battery manufacturer. Go
to Jaycar or your local battery shop. Anywhere at all except inside
your own head.
--
Ray
On Sat, 22 Dec 2007 10:18:03 +1300, I said, "Pick a card, any card"
and Greg Procter instead replied:
Correct. Or, if it's only a 12 volt supply, it will actually drain
his battery.
--
Ray
On 12/20/2007 11:23 PM Ray Haddad spake thus:
Data point: I measured my car's battery voltage (in good shape & fully
charged). 12.5 volts (both my multimeters agree).
Sounds about right!!!
A "NORMAL" 'Train Power Supply', will charge an attached 'capacitor' to
close to 20 volts, because of the peaks in voltage available for a very
small amount of time.
Chuck D.
Ray Haddad skriver:
We totally agreee......
Shitty powersupplies depend on load, but regulated doesnt.
Darn - Z80 was in my youth (I'm "only" 35:-)
Did you ever get the ZX spectrums ?
formatting link
it was british build and based on the Z80A. They keyboard was
rubber and was later used as "anti slip mats in showers" :-)
Neat :-)
Thanks. Another of my proud job was a late night, we were pretty drunk,
when my friend pulled out an DVD player with defective switchmode
powersupply. It took about 10 minutes and then it was running again -
typical error, toasted power diode and dead capacitors.....
The next morning i had headache......
Klaus
On 12/21/2007 2:55 PM Klaus D. Mikkelsen spake thus:
I still think the Z80 is one of the most underutilized and
underappreciated machines ever built in the late 20th century. All that
power and speed in such an unassuming package. Like those totally kewl
alternate register sets and the instructions that swap them with the
regular set, for high-speed interrupt processing ...
On Fri, 21 Dec 2007 23:55:37 +0100, I said, "Pick a card, any card"
and "Klaus D. Mikkelsen" instead
replied:
Most here seem to be hunting the cheapest of the cheap and probably
buy the wall wart type. More than half of those are only partially
regulated relying on the equipment on the load side to finish the
regulation. Awful practice, that, but it does make for cheap power
supplies when you need them.
I nearly used an 8080A but the Z80 came available and I switched.
All wire-wrapped. What a headache that was. Tedious but fun.
I had a Sinclair ZX80, the membrane keyboard type. Designed a 64k
memory expansion for it and published the design in the old Popular
Electronics magazine sometime in the '80s. I forgot which name I
published under for that one. I use pen names mostly to avoid flame
wars here on USENET over something I publish.
I picked up a dead, second-hand, rack mounted P4 Quad Core PC used
for 6 months as a server before it failed. It was failing big time
according to the seller and I verified that. But, his company had
replaced it with a bigger and better server with 4 terabytes of hard
drive. This one had 4 320GByte ATA/IDE drives, 2 500GByte SCSI
drives, 2 SCSI controllers and a 4 port RAID controller. On
inspection, I found a lightning damaged burned trace at the DMA
controller chip and fixed the unit. It's a screamer with more hard
drive space than I can use in a lifetime. It cost me a whopping
$10.00 yesterday. I wiped all the drives clean as promised.
Now, what shall I do with it? I think I'll sleep on it. It has sharp
pointy corners but with a thick enough blanket I can at least have a
nap on it.
Oh, rats. I meant to send this by e-mail but it's too much bother to
retype it or cut and paste it. So, it goes on the newsgroup with a
copy by e-mail. Sorry it's so horribly off topic, guys.
Well, I can make it on topic easy enough. I believe I'll use that
new PC to automate my trains. There. On topic now.
--
Ray
[snip prior chit chat]
LOL
PS: I "built" me a new PC with an MSI board (1000MHz FSB) and a 2.4GHz
Intel Dual Core, 2GB 800MHz DDR, two 250GB SATA, 256MB PCI-X video card,
and a floppy drive. Still feel uneasy without a floppy drive. Had to put
it in a tall tower, else the CPU fan wouldn't fit under the PSU. Just
plugged all the bits and pieces together, turned it on, installed a
brand new copy of XP Pro/SP2, copied a pile of zips and install packages
from a CD, and starting playing with it. Erm, I meant _working_ with it. ;-)
Fastest machine Ive ever used.
On 12/21/2007 3:37 PM Ray Haddad spake thus:
I've taken apart lots of wall warts (to cannibalize the parts within)
and don't remember ever seeing any with a regulator. Just a transformer,
a bridge rectifier (or two diodes) and filter capacitor(s).
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