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#1
07-09-2008, 09:16 AM
 studiot E-book Developer Join Date: Nov 2007 Location: Somerset UK Posts: 3,951

It has occurred to me that a thread where posters could pass on useful tips, tricks, rules-of-thumb, and conventions that may be of use for when you need a 'how to answer' not an in depth understanding. Please don't use this thread for asking questions.

I will kick off with a very simple but useful formula for making a non standard resistor by adding a parallel resistor to a standard one.

$R_{1} = \frac{R_{2}R_{d}}{R_{2} - R_{d}}$

$R_{1}$ is the required shunt resistor

$R_{d}$ is the desired non preferred value

$R_{2}$ is the (next) higher preferred value

Last edited by Dave; 07-09-2008 at 11:02 PM.
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#2
07-09-2008, 09:50 PM
 SgtWookie Expert Member Join Date: Jul 2007 Location: In the vast midwest of the USA; CST Posts: 22,030

In retaliation for StudioT's post...

Attached files:
1) Series_ParallelResistanceCalculator.zip - contains an Excel spreadsheet that has StudioT's formula in it, and also does series of lookups on standard E6 thru E192 series resistance tables to ensure use of only the standard values in the results. Just put in the resistance you want where indicated, and resistor combinations for all E-series are displayed.
2) E24PLL.ZIP - contains E24PLL.TXT, a rather large (224kb) text file that you can scroll through to find pairs of resistors to use in parallel to obtain a particular resistance.

Here's a handy web page that does both series and parallel calculations for you, for E12 and E24 series resistors:
http://www.qsl.net/in3otd/parallr.html
Note that you must select E12 or E24 each time you enter a new value, or you will receive an error message.

[eta]
3) CapSMTMarkings is an excerpt from a KEMET Packaging and Marking document, for identification of SMT capacitor values.
If there are two letters and a number, the manufacturer is the first letter. If just a letter and a number, only the value and multiplier is specified.

Attached Images
 CapSMTMarkings.PNG (78.7 KB, 1244 views)
Attached Files
 Series_ParallelResistanceCalculator.zip (8.7 KB, 860 views) E24PLL.zip (64.6 KB, 637 views)
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General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.

Last edited by bertus; 02-08-2014 at 03:38 PM. Reason: showing image full size
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#3
07-10-2008, 05:07 AM
 thingmaker3 Super Moderator Join Date: May 2005 Location: Rural, Oregon GMT -8 Posts: 5,072 Blog Entries: 6

Rule of thumb for calculating power supply filter capacitors:

C = 0.7(I)/ΔE(f)

Where I = load current, ΔE = acceptable ripple voltage, and f = pulses per second from the rectifier.

For full wave rectified 60Hz, this works out to:
C = 0.00583 * I / ΔE
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#4
07-10-2008, 07:46 AM
 miconos New Member Join Date: Jun 2008 Posts: 2
RFIC inductance calculation

Rule of thumb for RFIC inductance calculation:
1mm ~ 1nH
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#5
08-16-2008, 12:09 AM
 yubyub Junior Member Join Date: Aug 2008 Posts: 19

Tip: check things more than once when soldering a big project. (i just soldered 50 transistors backwards)
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#6
11-04-2008, 07:36 PM
 KL7AJ E-book Developer Join Date: Nov 2008 Location: North Pole, Alaska Posts: 1,540

If any of you can get a copy of the November 2008 QST, I have an article in Technical Correspondence called "Making the Glass Half Full." I discuss in detail the reciprocal impedance parameters: conductance, susceptance, and admittance. These GREATLY simplify otherwise daunting parallel impedance problems.

73,

Eric
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#7
12-18-2008, 01:15 PM
 eblc1388 Senior Member Join Date: Nov 2008 Location: UK Posts: 1,542

If your 9V battery connection is too short for the power supply, why not try the following and kill your project.

You won't need to power it up anymore.
Attached Images
 9VBat.jpg (42.0 KB, 1807 views)
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L.Chung

Last edited by bertus; 07-13-2014 at 07:41 AM. Reason: showing image full size
#8
01-14-2009, 12:47 AM
 electratech Junior Member Join Date: Jan 2009 Location: Massillon, OH. Posts: 21
VIP chart

VIP chart for quick guide

Attached Images
 E-VIP chart.gif (7.5 KB, 1912 views)

Last edited by bertus; 02-08-2014 at 03:35 PM. Reason: showing image full size
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#9
01-30-2009, 03:09 PM
 Skeebopstop Senior Member Join Date: Jan 2009 Location: Melbourne Posts: 358

Remember the skin effect. When trying to rid yourself of EMI, don't try to run it out of your system on a regular wire, rather ensure the wire has a large surface area (i.e. shielding).
#10
01-30-2009, 06:32 PM
 leftyretro Senior Member Join Date: Nov 2008 Location: Hercules, Ca. (SF Bay Area) Posts: 394

When designing power supplies be sure to size the input protection fuse so that the equipment being power blows up first so as to protect the power supply fuse from blowing open first.

Lefty
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