Have been looking at the polling questions and thought it would be good to introduce others to Ohm's Law and how to calculate wattage, voltage, resistance and current flows.
Here's a primer of the "P.I.E.R." chart to help folks out:
http://www.installer.com/tech/ohmslaw.html
In a nutshell, if we know 2 elements on the chart, we can calculate all 4 parts with a few simple equations.
If people like the tool and print out a copy, maybe we can toss out some numbers and let others use the chart to find the right answer.
Example:
An amp is rated at 500 watts into a 2 ohm load. How much current will this amp draw at full power?
1. We know the supply Voltage is ~14.4 volts
2. We know the amp is rated for 500 Watts @ 2 ohms (That's "P")
What is the current draw at 500 watts? So, 14.4 is the supply Voltage and Power output is 500 watts right?
Okay, P/E = I or 500/14.4 = 34.7 amperes is the current draw.
Tech Tip: This is true if an amplifier were 100% efficient. There's no such animal out there. Class A/B amps are about 60-65% efficient. Class D amps are typically 80-85% efficient. The losses are due to heat and circuit designs used.
Knowing that, we have to factor in efficiency to get the right number. Want to go deeper?
Class A/B amps draw more power to obtain the desired wattage output. (500/0.65 = 769 watts of Power consumed)
Class D amps draw less power to obtain the desired wattage output. (500/0.8 = 625 watts of Power consumed)
Got all that? If yes, now run the new wattage numbers and see what the actual current consumption is.
Class A/B scenario: 769/14.4 = 53.4 amperes of current drawn.
Class D scenario: 625/14.4 = 43.4 amperes of current drawn.
See the difference in current draw? That 10A savings might be just enough to keep the stock vehicle electrical system from tanking or the ALT having a heart attack and eventually burn out.
Anyway, if we look at this comparison, there are many poll questions that can be derived from either scenario.
Examples:
What is the common voltage output of a typical ALT?
a. 18.2 volts
b. 14.4 volts (Correct answer)
c. 10.3 volts
What if the typical efficiency rating of a Class A/B amplifier?
a. 80%
b. 34%
c. 60-65% (Correct answer)
How much current will a Class D amp draw when its putting out 500 watts to the subs?
a. 43.4 amperes (Correct answer)
b. 55.2 amperes
c. 22.6 amperes
What wire gage power/ground lines should be used to hook up a 500 watt amplifier?
a. #12 gage
b. #8 gage (Correct answer in either case)
c. #4 gage (A little over-kill, but also the best option)
d. options b and c are both correct
Enough for now huh? See how many questions can be sifted from the earlier scenarios? There's a lot more ?'s we can add too.
Enjoy your headache, GRIN
Swez
Replies (10)
admin on 10/26/2008 08:04:44
I was already on this path myself. And in the result screens show the correct answer and the ratios of rights and wrongs.. Great, I love it..
Victor on 10/26/2008 09:22:26
Indeed....
admin on 10/26/2008 09:26:38
I work on this during the week. We can even use the Test Maker and i'll pick from them as well.
The test based polls will only allow you to see the results to ones you've already answered hehe
swez on 10/26/2008 09:42:09
Swell... I was hoping Admin would chime in on this one and post some comments.
Granted, this seems a bit technical for the average newbie. But in time, knowing how to use the Ohm's Law "PIER" chart will be very helpful when choosing a system or designing from scratch. (Make sure the "RIDE" can handle the new gear)
IMHO, all Golds should be familiar & competent with Ohm's Law details as they are fixed and immutable factors in a well designed system.
Walt, I like the tragectory of the polling feature you've created and am just trying to lend support and direction for this feature as it evolves. If you have need of a side-kick to expand on polling questions, I'd be glad to help and Victor and ttocs will probably add ideas as time permits.
We can support this feature now and eventually expand this into CK test materials as well. The value of any test is measured by prior information and good study and retention habits. If one is tested, they need the background information to prep for a test. (Study Guide) The rest is digging for the details and learning how things work as a system and even back to component levels.
Basically, we drop a few seeds, water them as needed and then see what the results are. If the yields are high, we're on the right track. If the yields are low, the teachers and students need more communication to fill in the gaps.
What say y'all?
Swez
How's that sound to you?
Swez
admin on 10/26/2008 11:49:33
How about I add a link under each Test Like Poll that says, "Click here to study this first", and it takes them to an FAQ,article, Forum Topic or external link with the material needed to answer the question? Of course, if we can supply all the content in the form of guides right here on CK, it would be better than sending them offsite.
It's shaping up I think. What say you?
swez on 10/26/2008 12:12:52
Like that idea with a twist... let other Golds weigh in and see what the collective minds have to offer as we morph into new and uncharted waters.
If there is one thing I have learned in life and on this forum, w/o real team support, good ideas can falter and fall apart w/o concenses and common goals.
Example: We embarked on a big mission to create tests and help others find their center. The idea has merit, but lacked direction, concenses and it fell by the wayside. To avoid this mistake again, a little more input and support from other Golds would be advised.
Yes, 2-3 guys can accomplish a lot when they are in sync and motivated by a common and clear goal. Until we get a few more Golds on board and adding some spice/more hands on deck to the mix, we may end up going nowhere.
In a nutshell, we are both idealogs and have complimentary skill sets. (One feeds off the other and visa-versa) I love that part of this forum. But at the same time, we have several talented Golds with tons of talent and experience to add to the mix. Shall we give them some time to check in before making the next series of steps? (I think it best)
Swez
admin on 10/26/2008 12:16:23
Agreed COFFEE
swez on 10/26/2008 12:55:33
Roger that... let's see what comes in and then go from there!
That's all for tonight and "Good night Nurse"
Swez is gone and outta here for now.
Victor on 10/26/2008 17:55:03
We sure need to edit many articles and add much more reading material if we were to post 'test' type polls ....
I did update the wiring diagram article with an ohms law clarification.
also posted a new gain settings article.
There is a long pending sound & vibration damping article that is half done... long means more than a year now...haha... took some help from swez then... hopefully "WE" shall try to finish that soon GRINGRINGRIN...
I agree with swez, the test thing was a long time lingering plan in my head too, but since that period had very less traffic on CK and only a few golds visiting, and only a couple of active members, it was not really an idea put into practice...
this is a real good upgrade for CK, if Walt could make this customizable for golds, just like we have the (edit) option besides the articles, it could make it much easier to post poll, and test questions at every golds time and convenience...
About writing backup FAQ's and reading material,
I am up for it...
Will give 1 hr a day for 1 week, starting from 1st of next month... SMILE
how can i help ???
Victor,,,
swez on 10/29/2008 14:09:28
Ditto! I have revised some of the older material and need to review/edit as well. Finding/making the time to update those will be a challenge until things slow down at work. Sigh... we all have better things to offer now. But as usual, time-pressure and insight don't always fit huh?
Swez
Here's a primer of the "P.I.E.R." chart to help folks out:
http://www.installer.com/tech/ohmslaw.html
In a nutshell, if we know 2 elements on the chart, we can calculate all 4 parts with a few simple equations.
If people like the tool and print out a copy, maybe we can toss out some numbers and let others use the chart to find the right answer.
Example:
An amp is rated at 500 watts into a 2 ohm load. How much current will this amp draw at full power?
1. We know the supply Voltage is ~14.4 volts
2. We know the amp is rated for 500 Watts @ 2 ohms (That's "P")
What is the current draw at 500 watts? So, 14.4 is the supply Voltage and Power output is 500 watts right?
Okay, P/E = I or 500/14.4 = 34.7 amperes is the current draw.
Tech Tip: This is true if an amplifier were 100% efficient. There's no such animal out there. Class A/B amps are about 60-65% efficient. Class D amps are typically 80-85% efficient. The losses are due to heat and circuit designs used.
Knowing that, we have to factor in efficiency to get the right number. Want to go deeper?
Class A/B amps draw more power to obtain the desired wattage output. (500/0.65 = 769 watts of Power consumed)
Class D amps draw less power to obtain the desired wattage output. (500/0.8 = 625 watts of Power consumed)
Got all that? If yes, now run the new wattage numbers and see what the actual current consumption is.
Class A/B scenario: 769/14.4 = 53.4 amperes of current drawn.
Class D scenario: 625/14.4 = 43.4 amperes of current drawn.
See the difference in current draw? That 10A savings might be just enough to keep the stock vehicle electrical system from tanking or the ALT having a heart attack and eventually burn out.
Anyway, if we look at this comparison, there are many poll questions that can be derived from either scenario.
Examples:
What is the common voltage output of a typical ALT?
a. 18.2 volts
b. 14.4 volts (Correct answer)
c. 10.3 volts
What if the typical efficiency rating of a Class A/B amplifier?
a. 80%
b. 34%
c. 60-65% (Correct answer)
How much current will a Class D amp draw when its putting out 500 watts to the subs?
a. 43.4 amperes (Correct answer)
b. 55.2 amperes
c. 22.6 amperes
What wire gage power/ground lines should be used to hook up a 500 watt amplifier?
a. #12 gage
b. #8 gage (Correct answer in either case)
c. #4 gage (A little over-kill, but also the best option)
d. options b and c are both correct
Enough for now huh? See how many questions can be sifted from the earlier scenarios? There's a lot more ?'s we can add too.
Enjoy your headache, GRIN
Swez
Replies (10)
admin on 10/26/2008 08:04:44
I was already on this path myself. And in the result screens show the correct answer and the ratios of rights and wrongs.. Great, I love it..
Victor on 10/26/2008 09:22:26
Indeed....
admin on 10/26/2008 09:26:38
I work on this during the week. We can even use the Test Maker and i'll pick from them as well.
The test based polls will only allow you to see the results to ones you've already answered hehe
swez on 10/26/2008 09:42:09
Swell... I was hoping Admin would chime in on this one and post some comments.
Granted, this seems a bit technical for the average newbie. But in time, knowing how to use the Ohm's Law "PIER" chart will be very helpful when choosing a system or designing from scratch. (Make sure the "RIDE" can handle the new gear)
IMHO, all Golds should be familiar & competent with Ohm's Law details as they are fixed and immutable factors in a well designed system.
Walt, I like the tragectory of the polling feature you've created and am just trying to lend support and direction for this feature as it evolves. If you have need of a side-kick to expand on polling questions, I'd be glad to help and Victor and ttocs will probably add ideas as time permits.
We can support this feature now and eventually expand this into CK test materials as well. The value of any test is measured by prior information and good study and retention habits. If one is tested, they need the background information to prep for a test. (Study Guide) The rest is digging for the details and learning how things work as a system and even back to component levels.
Basically, we drop a few seeds, water them as needed and then see what the results are. If the yields are high, we're on the right track. If the yields are low, the teachers and students need more communication to fill in the gaps.
What say y'all?
Swez
How's that sound to you?
Swez
admin on 10/26/2008 11:49:33
How about I add a link under each Test Like Poll that says, "Click here to study this first", and it takes them to an FAQ,article, Forum Topic or external link with the material needed to answer the question? Of course, if we can supply all the content in the form of guides right here on CK, it would be better than sending them offsite.
It's shaping up I think. What say you?
swez on 10/26/2008 12:12:52
Like that idea with a twist... let other Golds weigh in and see what the collective minds have to offer as we morph into new and uncharted waters.
If there is one thing I have learned in life and on this forum, w/o real team support, good ideas can falter and fall apart w/o concenses and common goals.
Example: We embarked on a big mission to create tests and help others find their center. The idea has merit, but lacked direction, concenses and it fell by the wayside. To avoid this mistake again, a little more input and support from other Golds would be advised.
Yes, 2-3 guys can accomplish a lot when they are in sync and motivated by a common and clear goal. Until we get a few more Golds on board and adding some spice/more hands on deck to the mix, we may end up going nowhere.
In a nutshell, we are both idealogs and have complimentary skill sets. (One feeds off the other and visa-versa) I love that part of this forum. But at the same time, we have several talented Golds with tons of talent and experience to add to the mix. Shall we give them some time to check in before making the next series of steps? (I think it best)
Swez
admin on 10/26/2008 12:16:23
Agreed COFFEE
swez on 10/26/2008 12:55:33
Roger that... let's see what comes in and then go from there!
That's all for tonight and "Good night Nurse"
Swez is gone and outta here for now.
Victor on 10/26/2008 17:55:03
We sure need to edit many articles and add much more reading material if we were to post 'test' type polls ....
I did update the wiring diagram article with an ohms law clarification.
also posted a new gain settings article.
There is a long pending sound & vibration damping article that is half done... long means more than a year now...haha... took some help from swez then... hopefully "WE" shall try to finish that soon GRINGRINGRIN...
I agree with swez, the test thing was a long time lingering plan in my head too, but since that period had very less traffic on CK and only a few golds visiting, and only a couple of active members, it was not really an idea put into practice...
this is a real good upgrade for CK, if Walt could make this customizable for golds, just like we have the (edit) option besides the articles, it could make it much easier to post poll, and test questions at every golds time and convenience...
About writing backup FAQ's and reading material,
I am up for it...
Will give 1 hr a day for 1 week, starting from 1st of next month... SMILE
how can i help ???
Victor,,,
swez on 10/29/2008 14:09:28
Ditto! I have revised some of the older material and need to review/edit as well. Finding/making the time to update those will be a challenge until things slow down at work. Sigh... we all have better things to offer now. But as usual, time-pressure and insight don't always fit huh?
Swez
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