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  #1  
Old 12-05-2007, 10:03 PM
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FredM FredM is offline
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Default Electronics Formula Excel Cheat Sheet Project

I needed to calculate the voltage on a capacitor after a given time, and also needed to calculate the time required to charge a capacitor to a given voltage.. maths being rusty (and losing my SC which had all the formulas programmed in ) I resorted to Excel.

The attached .xls (in .zip) may be of use to others.. it contains 2 simple routines..

1.) Given applied voltage, R, C, and time (t), it outputs the instantaneous voltage across the capacitor at t.

2.) Given applied voltage, R, C, and the voltage required across the capacitor, it outputs the time at which this voltage appears across the capacitor.

You will need the LN() function installed in Excel or (other spreadsheet)
Attached Files
File Type: zip Capacitor Voltage time.zip (11.7 KB, 1682 views)

Last edited by FredM; 12-05-2007 at 10:07 PM.
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  #2  
Old 12-06-2007, 03:26 AM
agentofdarkness agentofdarkness is offline
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If you have an RC circuit, you can solve the following differential equation:

EMF = Vr + Vc (Kirchoff's Voltage Rule)
Vr = IR = (dq/dt)*R
Vc = Q/C
EMF = (dq/dt)*R + (Q/C)

After solving the 1st order differential equation, you get
q = C(EMF)(1-e^(-t/(RC)))
i = dq/dt = (EMF/R)e^(-t/(RC))
This is for a DC circuit where the capacitor and resistor are in series.
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Old 12-06-2007, 09:29 AM
Dave Dave is offline
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Quote:
Originally Posted by FredM View Post
I needed to calculate the voltage on a capacitor after a given time, and also needed to calculate the time required to charge a capacitor to a given voltage.. maths being rusty (and losing my SC which had all the formulas programmed in ) I resorted to Excel.

The attached .xls (in .zip) may be of use to others.. it contains 2 simple routines..

1.) Given applied voltage, R, C, and time (t), it outputs the instantaneous voltage across the capacitor at t.

2.) Given applied voltage, R, C, and the voltage required across the capacitor, it outputs the time at which this voltage appears across the capacitor.

You will need the LN() function installed in Excel or (other spreadsheet)
This is a pretty good idea. I usually resort to the old pen and paper.

It might be an idea to run a small project that implements and graphs all of the major electronics formula and functions for people new to the subject. Perhaps this could be the spring board from which to build from.

I'd be interested in helping out.

Dave
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Old 12-09-2007, 04:40 AM
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Quote:
Originally Posted by Dave View Post
This is a pretty good idea. I usually resort to the old pen and paper.

It might be an idea to run a small project that implements and graphs all of the major electronics formula and functions for people new to the subject. Perhaps this could be the spring board from which to build from.

I'd be interested in helping out.

Dave
Hi Dave -

Non-linear stuff is where I have problems, which is why I resorted to Excel.. However, there is no reason why a single spreadsheet could not be produced which contains the major formulas - from ohms law up..

If a worksheet was done for each 'group', this could be quite an interactive project - and need not be limited to formulas.. Simple circuits (standard op-amp configurations, 555 timers etc) could be 'simulated' quite simply.

I attach an example, based on the computations of the last..
This is a spreadsheet to calculate frequency and M/S ratio of 555 timer acting as oscillator..

I cannot spend any more time on the above 'project' at the moment, but would be happy to participate in the new year.. I dont think much co-ordination is required though.. If peeps leave worksheets unprotected, and are free to use / modify what has been created, or create new sheets.. they could be pasted here and collated later.
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File Type: zip 555 Oscillators.zip (32.7 KB, 593 views)
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Old 12-09-2007, 04:06 PM
Distort10n Distort10n is offline
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Hello Dave,

This is a really good idea. Many engineers that I work with use Excel for everything. I have several Excel files myself showing how to calculate the input common mode range of single supply in-amp.

Maxim also has an application note called "Exact Circuit Analysis" which uses Excel to calculate the impedance of an RC circuit. It then uses it to calculate the phase shift in the open loop curve of an op-amp.

I think this would be a great project for things like Ohm's law, Power, Reactance, transistor curves, etc.
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Old 12-09-2007, 04:15 PM
Dave Dave is offline
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Hi FredM and knightofsolamnus,

I'm glad we think this may be a good idea; to honest I'm surprised we haven't embarked on something like this before. I am willing to act as a coordinator, unless someone has the desire to take charge.

FredM's spreadsheet is a good starting point. knightofsolamnus, if you want to upload your spreadsheets, I can merge them with FredM's and a couple of working spreadsheets I have and we can get the ball rolling. I can then post up a first version covering the basics.

If FredM is happy for me to do so, I will change the thread name to something that better reflects the objectives of the project and I will stick it to the top of the Electronics Resources forum.

If anyone else wishes to get involved please post and get involved.

Dave
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Old 12-09-2007, 09:04 PM
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FredM FredM is offline
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Quote:
Originally Posted by Dave View Post
If FredM is happy for me to do so, I will change the thread name to something that better reflects the objectives of the project and I will stick it to the top of the Electronics Resources forum.
Dave
I am more than happy with this..
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  #8  
Old 12-10-2007, 07:14 AM
Dave Dave is offline
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Quote:
Originally Posted by FredM View Post
I am more than happy with this..
Done. I'll get grafting on some basics. If anyone has any formula that would be good for putting into this, please let me know.

I hope we can have a good working version in the new year.

Dave
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  #9  
Old 12-29-2007, 01:10 AM
Distort10n Distort10n is offline
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Here is an Ohm's Law calculator. I was going to use VB scripts in Excel (bought a book to learn how to do it) but just relied on simple Excel formulas for now.
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File Type: zip Ohms Law.zip (10.6 KB, 665 views)
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  #10  
Old 12-30-2007, 10:05 AM
Dave Dave is offline
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Quote:
Originally Posted by knightofsolamnus View Post
Here is an Ohm's Law calculator. I was going to use VB scripts in Excel (bought a book to learn how to do it) but just relied on simple Excel formulas for now.
Hi knightofsolamnus,

Good starting point and it looks quite snazzy with the colours and chart in the middle.

I did consider the options of using VB macros, and even the idea of doing it in C++, however this is intended to be a simple calculator type application for general use. Why spend time implementing features that are readily available in Excel (I'm sure we will hit a stumbling block at some point when a bit of VB code will be needed).

I encourage anyone else who has Excel worksheets for calculating values in just about any electronics applications to submit it - it would be great to have a collective effort covering a wide range of formulas.

Dave
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