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metron9
08-31-2006, 11:12 AM
I have found a site that has a schmitt trigger calculator and it shows the formula (Attached file)

Problem is, I never learned how to read the math symbols they are using so I am having a hard time converting this information to an excell spreadsheet format.

Can anyone help me understand it. I really do hat the fact that I usually gloss over the math examples in electronics books because I don't understand what is written on the page. I never got a chance to go to college.

I have tried

V2 = (((R1 * R2 * R3) / R2) * VREF) + (((R1 * R2 * R3) / R3) * VCC)

V2 = (((100 * 200 * 300) / 200) * 5) + (((100 * 200 * 300) / 300) * 5)

With R1=100, R2=200, R3=300, VCC=5 then V2 should = 2.272727 and I get 250,000

So I don't get what R1||R2||R3 is

From the math symbol table here: http://whatis.techtarget.com/definition/0,,sid9_gci803019,00.html

It looks like || means "The Product of" and from my 8th grade math education I think that means multiply

Why do they have to be so greek to me? http://forums.parallax.com/images/smilies/rolleyes.gif

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Think outside the BOX!

Post Edited (metron9) : 8/31/2006 4:17:45 AM GMT

PAR
08-31-2006, 12:14 PM
metron9 said...
I have found a site that has a schmitt trigger calculator and it shows the formula (Attached file)

...o I am having a hard time converting this information to an excell spreadsheet format.

Can anyone help me understand it.
...
So I don't get what R1||R2||R3 is

From the math symbol table here: http://whatis.techtarget.com/definition/0,,sid9_gci803019,00.html

It looks like || means "The Product of" and from my 8th grade math education I think that means multiply

Actually, in this case, " || " is not a "math symbol" but a wiring convention symbol. It represents resistors wired in parallel, and "R123 = R1 || R2 || R3" means to calculate the equivalent resistance of parallel-wired·resistors 1, 2 and 3 (to get R123). Then, use that answer in the formulas given in your wiring diagram.

To calculate the equivalent parallel-wired resistance,

1 / Req = (1 / R1 ) + ( 1 / R2 ) + ( 1 / R3 )··

So, for example, given parallel-wired resistors, R1=10, R2=20, R3= 50 ohms, you want to find·the equivalent resistance, Req, ·provided by a single resistor, as:

1 / Req· = 1/10 + 1/20 + 1/50
········ = 0.10 + 0.05 + 0.02
········ = 0.17 ohms

So, R123 = Req·= 1 / 0.17· = 5.88 ohms

The ballpark check on the·answer for parallel equivalent resistance,·Req, should be less than the smallest resistor (among the parallel-wired ones), and 5.88 is smaller than 10, so the answer is in the ballpark direction.

(BTW, " || " is the math "absolute value" symbol; in the table you cited, the symbol you mistook for "||" and which does represent "the product" is the symbol Pi in that table. The table symbol Pi was a bit illegible.)

·PAR

metron9
09-01-2006, 12:19 AM
Thank you PAR, I really should teach myself these symbols because I do simply skip over the math that has symbols I do not understand.

There must be some handbooks of symbols, electronic and math so i will look at the bookstore.

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Think outside the BOX!