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#1
Posted to rec.audio.car
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Question about resistors
I know this isn't *typically* an audio question - but it has to do with
a display that I'm wiring for my amplifier (to check the temperature). The display I'm using runs on a range of 5 to 12 volts (with a suggested typical voltage of 9), and I'll be running it off of the car battery. I know that a direct (switched, of coarse) line from the battery would eventually blow this since a car battery can get up to 14+ volts... I know that a resistor or two would/could solve my problem. What I don't know, and am hoping that someone here does, is what rating this/these resistors would need to be. Anyone? ~Mister.Lull |
#2
Posted to rec.audio.car
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Question about resistors
A resistor won't decrease the voltage, but the amperage. -- Francious70 |
#3
Posted to rec.audio.car
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Question about resistors
Mister.Lull wrote:
I know this isn't *typically* an audio question - but it has to do with a display that I'm wiring for my amplifier (to check the temperature). The display I'm using runs on a range of 5 to 12 volts (with a suggested typical voltage of 9), and I'll be running it off of the car battery. I know that a direct (switched, of coarse) line from the battery would eventually blow this since a car battery can get up to 14+ volts... I know that a resistor or two would/could solve my problem. What I don't know, and am hoping that someone here does, is what rating this/these resistors would need to be. Anyone? A single resistor inline will only limit the current. You'd need to use two resistors in a voltage-divider setup, but then you'd need to know the current draw of the display to properly select the resistor values. A better solution, if you're that concerned about it, would be a basic one-chip voltage regulator, such as a 7809 (http://www.national.com/pf/LM/LM78L09.html) --- avast! Antivirus: Outbound message clean. Virus Database (VPS): 0621-3, 05/24/2006 Tested on: 5/25/2006 12:12:07 PM avast! - copyright (c) 1988-2006 ALWIL Software. http://www.avast.com |
#4
Posted to rec.audio.car
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Question about resistors
The current draw is only 6 - 10 mA... that help?
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#5
Posted to rec.audio.car
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Question about resistors
In article .com, "Mister.Lull" wrote:
The current draw is only 6 - 10 mA... that help? Some displays need an isolated supply, but since this is only temperature I'm sure it will be OK. A vehicle can get up to 16 volts. Any equipment must be designed to handle peaks of that plus spikes. If this is going to stay on all the time you certainly don't want to draw any more current. Even a few milliampers is enough to drain weak batteries, but that 9 volt regulator sounds like the the best option. You could also use a 9 volt zener diode across the meter and only use a single dropping resistor of 250 ohms. That would draw 20 ma. at 14 volts nominal charge rate. However, if you just use two resistors of 350 ohms each, tap off the center to get at least 5 volts minimum. The dissapation would be over a quarter watt between them. The simple way. Use two unequal resistors. This is a compromise. Use 600-700 ohms on the top side, and 350 on the bottom ot thereabouts. greg |
#6
Posted to rec.audio.car
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Question about resistors
....Yes, the LM78L09 would be the best option.
Does anyone know where I can get just 1 of them at a physical location (near Seattle) ? I'm starting this whole thing tomorrow night... Ideas? |
#7
Posted to rec.audio.car
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Question about resistors
Negative for Radio Shack
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#8
Posted to rec.audio.car
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Question about resistors
Radio Shack DOES have resistors, if anyone wants to clarify the options
for that for me... Remember, I'm only half stupid - I know how to wire the voltage regulator but I'm completely lost on resistors. So I need to know how to wire resistors as well as which ones I'd need to use... ~Mister.Lull |
#9
Posted to rec.audio.car
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Question about resistors
Mister.Lull wrote:
Negative for Radio Shack The 7809 is a somewhat less common unit - they SHOULD have SOME sort of voltage regulators that fall within your spec, either a 7805 (+5V) or 7812 (+12V), or some equivalent (those are common part numbers, mostly used by National Semiconductor, if memory serves; there are lots of others under different manufacturer part numbers). Go to radioshack.com, search for "voltage regulator" - they list both the 7805 (catalog# 276-1770) and the 7812 (cat# 276-1771), as well as the adjustable-output LM317 (cat# 276-1778). --- avast! Antivirus: Outbound message clean. Virus Database (VPS): 0621-3, 05/24/2006 Tested on: 5/26/2006 1:00:18 AM avast! - copyright (c) 1988-2006 ALWIL Software. http://www.avast.com |
#10
Posted to rec.audio.car
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Question about resistors
DUDES!!!
I stopped by Fry's Electronics last night (for those of you who might not know - they're more or less Outpost.com) and found an equivelant part!!! The NTE1902 9Volt output voltage regulator!!! Problem solved, next stop - stereo bliss. ~Mister.Lull |
#11
Posted to rec.audio.car
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Question about resistors
FRY'S ROCKS!!!
That's where I buy EVERYTHING. Their prices cannot be beat ANYWHERE in the Seattle area. I go to the one in Renton, I don't know if they even have another location or what. But it's a TOTALLY FUN STORE!!! It has truly EVERYTHING you can possibly imagine related to ANY electronic product. MOSFET "Mister.Lull" wrote in message ups.com... DUDES!!! I stopped by Fry's Electronics last night (for those of you who might not know - they're more or less Outpost.com) and found an equivelant part!!! The NTE1902 9Volt output voltage regulator!!! Problem solved, next stop - stereo bliss. ~Mister.Lull |
#12
Posted to rec.audio.car
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Question about resistors
That's the one!!!! I had no idea they'd carry THAT kind of part,
though... I think I found my new favorite gadget store... ~Mister.Lull |
#13
Posted to rec.audio.car
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Question about resistors
equivalent? from NTE? probably not... if their regulators are as bad as
their replacement bipolars, look out. That's like saying the Yugo is equivalent to a Civic. JD Mister.Lull wrote: DUDES!!! I stopped by Fry's Electronics last night (for those of you who might not know - they're more or less Outpost.com) and found an equivelant part!!! The NTE1902 9Volt output voltage regulator!!! Problem solved, next stop - stereo bliss. ~Mister.Lull |
#14
Posted to rec.audio.car
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Question about resistors
What's the worst that can happen?
~Mister.Lull John Durbin wrote: equivalent? from NTE? probably not... if their regulators are as bad as their replacement bipolars, look out. That's like saying the Yugo is equivalent to a Civic. JD Mister.Lull wrote: DUDES!!! I stopped by Fry's Electronics last night (for those of you who might not know - they're more or less Outpost.com) and found an equivelant part!!! The NTE1902 9Volt output voltage regulator!!! Problem solved, next stop - stereo bliss. ~Mister.Lull |
#15
Posted to rec.audio.car
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Question about resistors
Dr. Egon Spengler: There's something very important I forgot to tell you.
Dr. Peter Venkman: What? Dr. Egon Spengler: Don't cross the streams. Dr. Peter Venkman: Why? Dr. Egon Spengler: It would be bad. Dr. Peter Venkman: I'm fuzzy on the whole good/bad thing. What do you mean, "bad?" Dr. Egon Spengler: Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light. Dr Ray Stantz: Total protonic reversal. Dr. Peter Venkman: Right. That's bad. Okay. All right. Important safety tip. Thanks, Egon. Mister.Lull wrote: What's the worst that can happen? ~Mister.Lull |
#16
Posted to rec.audio.car
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Question about resistors
VERY NICE!!! :-) Thanks for that (I love that movie)...
~Mister.Lull Brandonb wrote: Dr. Egon Spengler: There's something very important I forgot to tell you. Dr. Peter Venkman: What? Dr. Egon Spengler: Don't cross the streams. Dr. Peter Venkman: Why? Dr. Egon Spengler: It would be bad. Dr. Peter Venkman: I'm fuzzy on the whole good/bad thing. What do you mean, "bad?" Dr. Egon Spengler: Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light. Dr Ray Stantz: Total protonic reversal. Dr. Peter Venkman: Right. That's bad. Okay. All right. Important safety tip. Thanks, Egon. Mister.Lull wrote: What's the worst that can happen? ~Mister.Lull |
#17
Posted to rec.audio.car
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Question about resistors
Dead short, lots of stinky smoke. I' go with a TI or motorola 7809.
Chad "Mister.Lull" wrote in message oups.com... What's the worst that can happen? ~Mister.Lull John Durbin wrote: equivalent? from NTE? probably not... if their regulators are as bad as their replacement bipolars, look out. That's like saying the Yugo is equivalent to a Civic. JD Mister.Lull wrote: DUDES!!! I stopped by Fry's Electronics last night (for those of you who might not know - they're more or less Outpost.com) and found an equivelant part!!! The NTE1902 9Volt output voltage regulator!!! Problem solved, next stop - stereo bliss. ~Mister.Lull |
#18
Posted to rec.audio.car
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Question about resistors
I think I'm going to walk on the wild side and keep it in there...
It's freakin' superglued, and soldered into place. If it blows, the input is fused - I'm not too scared. ~Mister.LivinOnTheWildSide.Lull Chad Wahls wrote: Dead short, lots of stinky smoke. I' go with a TI or motorola 7809. Chad "Mister.Lull" wrote in message oups.com... What's the worst that can happen? ~Mister.Lull John Durbin wrote: equivalent? from NTE? probably not... if their regulators are as bad as their replacement bipolars, look out. That's like saying the Yugo is equivalent to a Civic. JD Mister.Lull wrote: DUDES!!! I stopped by Fry's Electronics last night (for those of you who might not know - they're more or less Outpost.com) and found an equivelant part!!! The NTE1902 9Volt output voltage regulator!!! Problem solved, next stop - stereo bliss. ~Mister.Lull |
#19
Posted to rec.audio.car
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Question about resistors
Mister.Lull wrote: The current draw is only 6 - 10 mA... that help? could you not just run it off a 9v battery then? |
#20
Posted to rec.audio.car
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Question about resistors
I could, but that would have to be replaced.
This will never have to be... ~Mister.Lull metal_flowboard wrote: Mister.Lull wrote: The current draw is only 6 - 10 mA... that help? could you not just run it off a 9v battery then? |
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