what wattage resistor
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=80110
Printed Date: April 29, 2024 at 2:48 PM
Topic: what wattage resistor
Posted By: mrcllusb
Subject: what wattage resistor
Date Posted: July 09, 2006 at 5:24 PM
I need to add resistors for my lock unlock hook up with my clifford arrow alarm.Do i use 1/2 watt or 1 watt resistors?
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"ole blake"
Replies:
Posted By: bmwpwner
Date Posted: July 09, 2006 at 5:54 PM
i use 1/2 watt resistors and have for years. to be honest i'm not sure what the difference is though. i really should do some searching on that. but for sure 1/2 watt will work. good luck and hope this helps.
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"I cannot teach anybody anything, I can only make them think."
-Socrates-
Posted By: meltingplastic
Date Posted: July 10, 2006 at 7:43 PM
if you dont know what difference between different wattage resistors is.. im quite scared..
yes half wat will work fine.. most remote start systems put out mAs so u dont have to worry about them overheating and blowing them
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Driving a Bagged, Caddied 02 s10
Posted By: bmwpwner
Date Posted: July 10, 2006 at 10:18 PM
so what is the difference? i have never claimed to know everything and i'm always willing to learn.
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"I cannot teach anybody anything, I can only make them think."
-Socrates-
Posted By: meltingplastic
Date Posted: July 11, 2006 at 12:13 PM
the wattage means how much power through the resistor it can handle before it blows.. like if u have a 1 watt resistor.. take the current output and multiply it by the voltage through it.. so typically in car its 12v(or 14.4 u wanna be more exact) and most outputs in alarms are like 500mA so uve got (12)*(0.5A) = 6 watts. now even though your going over the wattage its not long enough for it to blow the resistor due to it not being on that long. i dont remember how long there is until itll blow but basically it heats up and burns..
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Driving a Bagged, Caddied 02 s10
Posted By: meltingplastic
Date Posted: July 11, 2006 at 8:49 PM
well the main reason i need to know about the power rating of resistors is cause im going to school for electronics engineering and am in an Analog Electronics class and we build power s upplies and amplifiers and if our load resistors recieve a power greatre then their spec'd wattage we have to split the load into multiple resistances as to not blow them
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Driving a Bagged, Caddied 02 s10
Posted By: texxasaudio
Date Posted: July 11, 2006 at 9:31 PM
when you split the load in varios resistors also you are bringing the wattege capacity up
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TEXXASAUDIO
Posted By: meltingplastic
Date Posted: July 11, 2006 at 11:29 PM
bingo! simple KCL!
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Driving a Bagged, Caddied 02 s10
Posted By: dualsport
Date Posted: July 12, 2006 at 9:15 AM
About the calculation of the power dissipation from the example, if the resistor is used as a dropping resistor, the voltage across it isn't going to be 12V, so you wouldn't end up with that large a wattage rating.
Being in series, the voltage is decreased by the load (e.g. door lock actuator).
Usually wouldn't have the resistor connected from the source directly to ground in most cases, since that would just be a load, and not too useful, except for power supply testing.
In general, though, using a larger resistor is always safer. Tradeoff is that it just costs more and takes up more space.
Posted By: meltingplastic
Date Posted: July 12, 2006 at 12:34 PM
yea.. they are voltage dropping resistors i just didnt wanna make the calculations too much lol
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Driving a Bagged, Caddied 02 s10
Posted By: bmwpwner
Date Posted: July 12, 2006 at 6:59 PM
hum, that is really good to know. i guess when you have just been doing something for so long and have never had a need to use anything else you start to just take that information for granted and assume that is the end all be all solution. thanks for all the input on this topic and again i like to learn something new everyday.
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"I cannot teach anybody anything, I can only make them think."
-Socrates-
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