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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Car Batteries
I'm showing my age!!
Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary |
#2
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Car Batteries
On Fri, 01 Feb 2008 05:37:33 GMT, "Ivan Vegvary"
wrote: I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary Use two 6 Volt batteries? Gerry :-)} London, Canada |
#3
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Car Batteries
"Ivan Vegvary" wrote: (clip) Can present day batteries be tapped somehow? Any ideas? ^^^^^^^^^^^^^^^^^^ Those bus bars must still be there, only covered with tar, or other black insulating material. I suggest you figure out where the correct bus bar ought to be, and try digging down to see whether you can make contact. You might just try probing with a meter lead. If you find the spot, run a self-tapping screw in and connect to it. |
#4
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Car Batteries
Wow! Can you say 'void the warranty'?
Anyhow, I don't know how much current it takes to run the instrument panel, and I don't know your level of electronic expertise, but you might want to consider a simple voltage regulator. Single chip regulators in 1 amp varieties are available in most voltages. And ones that can handle greater currents are not that difficult to build. "Ivan Vegvary" wrote in message news:xeyoj.2424$fg.157@trndny03... I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary |
#5
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Car Batteries
On Feb 1, 7:09*am, "Leo Lichtman" wrote:
"Ivan Vegvary" wrote: *(clip) *Can present day batteries be tapped somehow? Any ideas? ^^^^^^^^^^^^^^^^^^ Those bus bars must still be there, only covered with tar, or other black insulating material. *I suggest you figure out where the correct bus bar ought to be, and try digging down to see whether you can make contact. *You might just try probing with a meter lead. *If you find the spot, run a self-tapping screw in and connect to it. I've done just this many years ago to power a 6V radio. The lead bars were there, just buried. However, if you go this route be very careful and don't blame me if it goes wrong. The voltage regulator option is far better. John |
#6
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Car Batteries
On Feb 1, 1:10 am, Gerald Miller wrote:
On Fri, 01 Feb 2008 05:37:33 GMT, "Ivan Vegvary" wrote: I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary Use two 6 Volt batteries? Gerry :-)} London, Canada I like that answer best, Simple reliable elegant Second to that a few IC's and a few circuits on the web would easily make a 6v regulator that owuld happily feed the instrumentation with a few amps of power if the instrumentation needs that much. I think a single Power op amp can do it easily and quickly in fact |
#7
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Car Batteries
In article
, John wrote: On Feb 1, 7:09*am, "Leo Lichtman" wrote: "Ivan Vegvary" wrote: *(clip) *Can present day batteries be tapped somehow? Any ideas? ^^^^^^^^^^^^^^^^^^ Those bus bars must still be there, only covered with tar, or other black insulating material. *I suggest you figure out where the correct bus bar ought to be, and try digging down to see whether you can make contact. *You might just try probing with a meter lead. *If you find the spot, run a self-tapping screw in and connect to it. I've done just this many years ago to power a 6V radio. The lead bars were there, just buried. However, if you go this route be very careful and don't blame me if it goes wrong. The voltage regulator option is far better. I've done it too, the lead bars are usually submerged under acid. Can be done, it's messy Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/ |
#8
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Car Batteries
Brent fired this volley in
: Second to that a few IC's and a few circuits on the web would easily make a 6v regulator that owuld happily feed the instrumentation with a few amps of power if the instrumentation needs that much. I think a single Power op amp can do it easily and quickly in fact Oh, come on! A 78H05 and one 1.3v zener diode would do it (or two ordinary silicon diodes in series, and forward biased). For this simple an application, any-ol NPN power darlington and a 6.8v zener would work, too. LLoyd |
#9
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Car Batteries
On Fri, 01 Feb 2008 06:34:59 -0600, the renowned nick hull
wrote: In article , John wrote: On Feb 1, 7:09*am, "Leo Lichtman" wrote: "Ivan Vegvary" wrote: *(clip) *Can present day batteries be tapped somehow? Any ideas? ^^^^^^^^^^^^^^^^^^ Those bus bars must still be there, only covered with tar, or other black insulating material. *I suggest you figure out where the correct bus bar ought to be, and try digging down to see whether you can make contact. *You might just try probing with a meter lead. *If you find the spot, run a self-tapping screw in and connect to it. I've done just this many years ago to power a 6V radio. The lead bars were there, just buried. However, if you go this route be very careful and don't blame me if it goes wrong. The voltage regulator option is far better. I've done it too, the lead bars are usually submerged under acid. Can be done, it's messy Isn't that going to unbalance the cells? Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
#10
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Car Batteries
Ivan Vegvary wrote:
I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary Use a large 6V Zener in series with the load. Depending on the current use a good heatsink. Very easy. ...lew... |
#11
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Car Batteries
Lew Hartswick fired this volley in
: Ivan Vegvary wrote: I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary Use a large 6V Zener in series with the load. Depending on the current use a good heatsink. Very easy. ...lew... Even simpler, but it might need to be a VLZD to dissipate up to 25 watts! Some of those old hot-wire gauges are pretty current-hungry. LLoyd |
#12
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Car Batteries
On Fri, 01 Feb 2008 05:37:33 GMT, "Ivan Vegvary"
wrote: I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary this should answer your questions http://www.painlessperformance.com/f...c.php?f=2&t=26 if not search other hot rod or street rod web sites. Thank You, Randy Remove 333 from email address to reply. |
#13
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Car Batteries
There is a thriving industry making period batteries for correct restorations.
Here is one site: http://www.antiqueautobattery.com/ -- Dennis |
#14
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Car Batteries
In article xeyoj.2424$fg.157@trndny03,
"Ivan Vegvary" wrote: Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. 7806 - most will do an amp at 6 volts, some will do an amp and a half - just 12V, ground, 6V, a couple of capacitors. You'll want a heat sink. If you need to feed things that want more than that all together, the simplest method that will work safely is to break them out into multiple 6V feeds that will each work on 1.5 amp or less, as "paralleling" the outputs can be messy. There are other ways to get more amps out (combining a regulator with a transistor), but they are somewhat more complicated, and KISS rules. 54 cents for a 1.5 amp version he http://www.mouser.com/Search/Product...zoIq32Jw%3d%3d (Just a customer. Stick to mail on the shipping method...) You could do it with a switching DC-DC converter, but that's more complicated. KISS. Drilling a hole in the battery - not so KISS. -- Cats, coffee, chocolate...vices to live by |
#15
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Car Batteries
"Ecnerwal" wrote in message ... In article xeyoj.2424$fg.157@trndny03, "Ivan Vegvary" wrote: Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. Here's a solution, not cheap but allows 12V starting while not changing the car in any way. http://www.restorationbattery.com/6_12battery.html -- Stupendous Man, Defender of Freedom, Advocate of Liberty |
#16
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Car Batteries
Ivan Vegvary wrote:
I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary Yup so inefficient that Ford used a dropping resistor on it's gauges right up until 1995! Nothing made today has open connections. Best bet is to install individual dropping resistors OR replace the original meter movements with 12 volt items. I did that on a couple vehicles. Not very hard since most are just crimped together. -- Steve W. Near Cooperstown, New York Life is not like a box of chocolates it's more like a jar of jalapenos- what you do today could burn your ass tomorrow! |
#17
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Car Batteries
"Spehro Pefhany" Isn't that going to unbalance the cells? ^^^^^^^^^^^^^^^^^ I assume the current draw is going to be small, so the battery probably won't even notice. If you are really worried about it, you could switch to the other half of the battery every month or so. If you are REALLY obscessive about it, you could install a flip-flop type relay to do the switching for you every time you start the car. That would probably cost more than some of the more sophisticated electronic methods that have been described, but it is more easily understood by an old fart like me. |
#18
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Car Batteries
"Steve W." wrote in message ... Ivan Vegvary wrote: I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary Yup so inefficient that Ford used a dropping resistor on it's gauges right up until 1995! Nothing made today has open connections. Best bet is to install individual dropping resistors OR replace the original meter movements with 12 volt items. I did that on a couple vehicles. Not very hard since most are just crimped together. -- Steve W. Near Cooperstown, New York Life is not like a box of chocolates it's more like a jar of jalapenos- what you do today could burn your ass tomorrow! Hi Steve I too wanted to comment about the use of "inefficient". It didnt seem that the gauges used alot of power. It sure is easy to install resistor/resistors to make the gauges work in all the systems I have seen.. I thought all car manufacturers used resistors to set their guage voltages. If the car has a 6 volt solenoid type starter it sure is better to replace the solenoid with a 12 volt one. That will save alot of wear on the drive (and flywheel ring). Jerry |
#19
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Car Batteries
Leo Lichtman wrote:
"Spehro Pefhany" Isn't that going to unbalance the cells? ^^^^^^^^^^^^^^^^^ I assume the current draw is going to be small, so the battery probably won't even notice. If you are really worried about it, you could switch to the other half of the battery every month or so. How are you going to do that with everything on a common ground? |
#20
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Car Batteries
On Fri, 01 Feb 2008 07:09:23 GMT, "Leo Lichtman"
wrote: "Ivan Vegvary" wrote: (clip) Can present day batteries be tapped somehow? Any ideas? ^^^^^^^^^^^^^^^^^^ Those bus bars must still be there, only covered with tar, or other black insulating material. I suggest you figure out where the correct bus bar ought to be, and try digging down to see whether you can make contact. You might just try probing with a meter lead. If you find the spot, run a self-tapping screw in and connect to it. The intercell connectors in most batteries no longer run "over the top" and the cases are hard plastic. You will NOT be successful digging in the top of the battery. Better to just get a solid state voltage regulator and use it for the gauges. I've done it many times on 12 volt vehicles where the old thermal regulators caused radio noise. -- Posted via a free Usenet account from http://www.teranews.com |
#21
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Car Batteries
On Fri, 01 Feb 2008 06:11:58 -0700, Lew Hartswick
wrote: Ivan Vegvary wrote: I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary Use a large 6V Zener in series with the load. Depending on the current use a good heatsink. Very easy. ...lew... A zener does not make a good series regulator Lew. -- Posted via a free Usenet account from http://www.teranews.com |
#22
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Car Batteries
clare at snyder.on.ca wrote:
A zener does not make a good series regulator Lew. And why not? It's a perfectly good constant voltage drop over its operating range. I've use them that way over the 20+ yrs I've been in the business. ...lew... |
#23
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Car Batteries
consider a 7805 regulator
this will give you nice stable 5VDC at up to 3 amps -- Posted via a free Usenet account from http://www.teranews.com |
#24
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Car Batteries
Thanks everybody. Great answers!!! I will follow up on the ones that I understand (e.g., buy this or that product). Thanks again, Ivan Vegvary |
#25
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Car Batteries
cavalamb himself wrote:
William Noble wrote: consider a 7805 regulator this will give you nice stable 5VDC at up to 3 amps The 78xx series are only up to one amp depending on packaging. http://www.fairchildsemi.com/pf/LM/LM7805.html Try LM350 adjustable regulator - Guaranteed 3 amps. http://www.national.com/mpf/LM/LM350.html (with sechematic) Richard The 78xx are 3A in TO-3 packaging. |
#26
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Car Batteries
On Fri, 01 Feb 2008 19:16:30 -0600, "Pete C."
wrote: cavalamb himself wrote: William Noble wrote: consider a 7805 regulator this will give you nice stable 5VDC at up to 3 amps The 78xx series are only up to one amp depending on packaging. http://www.fairchildsemi.com/pf/LM/LM7805.html Try LM350 adjustable regulator - Guaranteed 3 amps. http://www.national.com/mpf/LM/LM350.html (with sechematic) Richard The 78xx are 3A in TO-3 packaging. Not so. Current limit doesn't change with package. |
#27
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Car Batteries
Why not a voltage regulator or better yet - a 12V DC to 6V DC switcher.
There are lots of power supplies like this about the size of a hand or less. Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com/ Ivan Vegvary wrote: I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. On old batteries you simply drove a sheet metal screw into the lead buss on top of the battery and tapped as many cells as you needed to get a lower voltage. Can present day batteries be tapped somehow? Any ideas? Thanks, Ivan Vegvary |
#28
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Car Batteries
William Noble wrote:
consider a 7805 regulator this will give you nice stable 5VDC at up to 3 amps The 78xx series are only up to one amp depending on packaging. http://www.fairchildsemi.com/pf/LM/LM7805.html Try LM350 adjustable regulator - Guaranteed 3 amps. http://www.national.com/mpf/LM/LM350.html (with sechematic) Richard |
#29
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Car Batteries
On 2008-02-01, Gerald Miller wrote:
On Fri, 01 Feb 2008 05:37:33 GMT, "Ivan Vegvary" wrote: I'm showing my age!! Does anybody make a car battery that has external connectors (buss) between cells. If I remember correctly all batteries use to have this back in the '50's ±. Here's my problem. I converted my 1948 Pontiac to 12 volts. All bulbs have been changed along with the ignition coil and the alternator. (6 volt starters LOVE 12 volts. Spin real fast!!) However the standard solution to run the gauges is to install a giant drop resistor. Seems to be an inefficient way to handle this. [ ... ] Use two 6 Volt batteries? That's what MG did with the MGA. Two small 6V batteries, on either side of the driveshaft, accessed through a removable panel behind the driver's and pasenger's seats. There was a short jumper cable which curved over the driveshaft to connect them in series. Of course, the car still ran positive ground, which was a bit of a nuisance. :-) Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#30
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Car Batteries
On Fri, 01 Feb 2008 15:32:02 -0700, Lew Hartswick
wrote: clare at snyder.on.ca wrote: A zener does not make a good series regulator Lew. And why not? It's a perfectly good constant voltage drop over its operating range. I've use them that way over the 20+ yrs I've been in the business. ...lew... Because a Zener only STARTS to conduct above a certain voltage. Zener regulators are GENERALLY shunt regulators. The load is in series with a low value, high power resistor, and the zener goes across the load in such a manner as to short excess voltage to ground, causing the voltage drop across the resistance to absorb/regulate to the zener resistance. Diodes in SERIES are generally used for minor voltage adjustment (not regulation) with the forward drop of various diodes generally running in the 0.64 volt range for silicon diodes, Schottky diodes drop significantly less, Germanium diodes significantly more. See: http://www.kpsec.freeuk.com/components/diode.htm if you don't want to take my word for it. By the way, what business are you in? 25+ in the automotive, and almost as long now in computer electronics. -- Posted via a free Usenet account from http://www.teranews.com |
#31
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Car Batteries
On Fri, 1 Feb 2008 16:20:55 -0800, "William Noble"
wrote: consider a 7805 regulator this will give you nice stable 5VDC at up to 3 amps With a REAL GOOD heat sink. The common 7805 is considered a ONE AMP device. Some 7805P devices are rated at 1.5 amps.. This is with nominal heat sinking. Bare they are a 500ma device. 3 amps is definitely running the "ragged edge" A Linear Technologies LT323 is a 3 amp unit. An LT1003 is a 5 amp unit. It is obsolete. -- Posted via a free Usenet account from http://www.teranews.com |
#32
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Car Batteries
Don Foreman wrote:
On Fri, 01 Feb 2008 19:16:30 -0600, "Pete C." wrote: cavalamb himself wrote: William Noble wrote: consider a 7805 regulator this will give you nice stable 5VDC at up to 3 amps The 78xx series are only up to one amp depending on packaging. http://www.fairchildsemi.com/pf/LM/LM7805.html Try LM350 adjustable regulator - Guaranteed 3 amps. http://www.national.com/mpf/LM/LM350.html (with sechematic) Richard The 78xx are 3A in TO-3 packaging. Not so. Current limit doesn't change with package. Actually, it does. The MAX on a 78xx is 1 amp. Smaller packages are rated lower - down to the 78Lxx parts in TO-90 and SO8 packages(100 ma). http://www.national.com/mpf/LM/LM78L05.html The LM350 would be my choice. Richard |
#33
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Car Batteries
either one is fine - just make sure it is mounted to some aluminum to
provide a heatskink. The 78XX is cheap - around ten cents the last time I bought a bunch, the LM350 costs a little more - and a fixed regulator is a lot easier for someone to use who doesn't do a lot of electronics - it has an input terminal, and an output terminal, and a ground terminal, nothing to mess up. They do come in various voltages, but 5V is very common/cheap/easy to get, and will be fine for a 6V car to run gauges. You may wish to measure current drawn by the gauges though - I think 1 amp should be enough. And, the regulators are so cheap you could put one on fuel gauge and another on the temp gauge if it is electric and not mechanical. "cavalamb himself" wrote in message ... William Noble wrote: consider a 7805 regulator this will give you nice stable 5VDC at up to 3 amps The 78xx series are only up to one amp depending on packaging. http://www.fairchildsemi.com/pf/LM/LM7805.html Try LM350 adjustable regulator - Guaranteed 3 amps. http://www.national.com/mpf/LM/LM350.html (with sechematic) Richard -- Posted via a free Usenet account from http://www.teranews.com |
#34
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Car Batteries
On Fri, 01 Feb 2008 22:20:42 -0800, cavalamb himself
wrote: Don Foreman wrote: On Fri, 01 Feb 2008 19:16:30 -0600, "Pete C." wrote: cavalamb himself wrote: William Noble wrote: consider a 7805 regulator this will give you nice stable 5VDC at up to 3 amps The 78xx series are only up to one amp depending on packaging. http://www.fairchildsemi.com/pf/LM/LM7805.html Try LM350 adjustable regulator - Guaranteed 3 amps. http://www.national.com/mpf/LM/LM350.html (with sechematic) Richard The 78xx are 3A in TO-3 packaging. Not so. Current limit doesn't change with package. Actually, it does. The MAX on a 78xx is 1 amp. Smaller packages are rated lower - down to the 78Lxx parts in TO-90 and SO8 packages(100 ma). http://www.national.com/mpf/LM/LM78L05.html The LM350 would be my choice. Richard For most uses, 78xx is indeed generally regarded as a 1-amp part. Fairchild even calls it that, but notes that this depends some on conditions. It is not a max rating by any means. http://www.fairchildsemi.com/ds/LM%2FLM7805.pdf STM calls it a 1.5 amp part, but the specs are the same. Fairchild was the original designer and mfr of the 78xx. It may have been Jim Widlar's last design at Fairchild before moving to LM-land (National). Excluding 78Mxx and 78Lxx, the same die is used regardless of package. The current level at which it goes into limiting is not tightly specified and can be as much as 2.2 amps -- regardless of package. It can also be considerably less in some parts of same partnumber but different lots or different mfr. The 78xx also has internal temperature limiting, so part temperature can also cause it to shut down. That is a function of package, but also of (Vsupply - Vout), heatsinking and ambient temperature. There are certainly cases where the thermal limit would govern: e.g. full-MIL temp range (up to 125C), minimum dropout voltage and junction-to-case thermal resistance could establish a max current due to thermal limiting that is lower than the current limit would be under other condx with the same part. I don't know enough about Ivan's app to have a preferred approach. |
#35
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Car Batteries
On Sat, 02 Feb 2008 01:09:12 -0500, clare at snyder.on.ca wrote:
On Fri, 01 Feb 2008 15:32:02 -0700, Lew Hartswick wrote: clare at snyder.on.ca wrote: A zener does not make a good series regulator Lew. And why not? It's a perfectly good constant voltage drop over its operating range. I've use them that way over the 20+ yrs I've been in the business. ...lew... Because a Zener only STARTS to conduct above a certain voltage. Zener regulators are GENERALLY shunt regulators. The load is in series with a low value, high power resistor, and the zener goes across the load in such a manner as to short excess voltage to ground, causing the voltage drop across the resistance to absorb/regulate to the zener resistance. Diodes in SERIES are generally used for minor voltage adjustment (not regulation) with the forward drop of various diodes generally running in the 0.64 volt range for silicon diodes, Schottky diodes drop significantly less, Germanium diodes significantly more. See: http://www.kpsec.freeuk.com/components/diode.htm if you don't want to take my word for it. By the way, what business are you in? 25+ in the automotive, and almost as long now in computer electronics. I'll bet you're very good with autos and computers -- but don't quit your day job to design power elex! A Zener would indeed provide a fairly constant drop and they are sometimes used that way. This wouldn't be a regulator, just a drop that is fairly constant over a reasonable range of load currents. The output would not be regulated, but it would be reduced by a fairly constant amount. |
#36
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Car Batteries
On Fri, 01 Feb 2008 20:37:00 -0600, "Martin H. Eastburn"
wrote: Why not a voltage regulator or better yet - a 12V DC to 6V DC switcher. There are lots of power supplies like this about the size of a hand or less. Martin Might be a radio noise issue with an AM radio. Some of the "simple switcher" chips are very easy to use, though. I've built little switchers by epoxying parts on the back of a wallwart -- no circuit board at all, just haywire things and then glop 'em good. |
#37
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Car Batteries
clare, at, snyder.on.ca wrote:
On Fri, 1 Feb 2008 16:20:55 -0800, "William Noble" wrote: consider a 7805 regulator this will give you nice stable 5VDC at up to 3 amps With a REAL GOOD heat sink. The common 7805 is considered a ONE AMP device. Some 7805P devices are rated at 1.5 amps.. This is with nominal heat sinking. Bare they are a 500ma device. 3 amps is definitely running the "ragged edge" A Linear Technologies LT323 is a 3 amp unit. An LT1003 is a 5 amp unit. It is obsolete. An obsolete regulator would be appropriate for an obsolete car, no? |
#38
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Car Batteries
Don Foreman wrote:
On Fri, 01 Feb 2008 20:37:00 -0600, "Martin H. Eastburn" wrote: Why not a voltage regulator or better yet - a 12V DC to 6V DC switcher. There are lots of power supplies like this about the size of a hand or less. Martin Might be a radio noise issue with an AM radio. Some of the "simple switcher" chips are very easy to use, though. I've built little switchers by epoxying parts on the back of a wallwart -- no circuit board at all, just haywire things and then glop 'em good. AM radio??? Certainly a switching supply would be more efficient than a linear. |
#39
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Car Batteries
clare at snyder.on.ca wrote:
By the way, what business are you in? 25+ in the automotive, and almost as long now in computer electronics. Well for about 25 years I worked for a private electronics research and development Co that did about 95% work for the millitary. We were one of the two bigest in the Infrared surveliance business. After a big cut back in that business I designed and built special equipment and interfaced some regular equipment to computers for a "well known" university whose football coach is also very well known :-) for another 10 yrs and moved to NM to do similar work for UNM for 8 more. Is that sufficient background to give you some idea of my experience. ...lew... |
#40
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Car Batteries
Don Foreman wrote
I'll bet you're very good with autos and computers -- but don't quit your day job to design power elex! A Zener would indeed provide a fairly constant drop and they are sometimes used that way. This wouldn't be a regulator, just a drop that is fairly constant over a reasonable range of load currents. The output would not be regulated, but it would be reduced by a fairly constant amount. Thanks Don. :-) ...lew... |
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