Electronics Tips and Tricks Thread

Discussion in 'General Electronics Chat' started by studiot, Jul 9, 2008.

Thread Status:
Not open for further replies.
  1. studiot

    studiot Thread Starter E-book Developer

    Joined:
    Nov 9, 2007
    Messages:
    4,027
    Location:
    Somerset UK
    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 a moderator: Jul 9, 2008
    nepdeep and Niharika narayan like this.
  2. SgtWookie

    SgtWookie Expert

    Joined:
    Jul 17, 2007
    Messages:
    22,044
    Location:
    In the vast midwest of the USA; CST
    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.

    [​IMG]

    Attached Files:

    Last edited by a moderator: Feb 8, 2014
  3. thingmaker3

    thingmaker3 Moderator Staff Member

    Joined:
    May 16, 2005
    Messages:
    5,072
    Location:
    Rural, Oregon GMT -8
    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
    PackratKing likes this.
  4. miconos

    miconos New Member

    Joined:
    Jun 23, 2008
    Messages:
    2
    Rule of thumb for RFIC inductance calculation:
    1mm ~ 1nH
    PGB1 and nepdeep like this.
  5. yubyub

    yubyub Member

    Joined:
    Aug 13, 2008
    Messages:
    19
    Tip: check things more than once when soldering a big project. (i just soldered 50 transistors backwards)
  6. KL7AJ

    KL7AJ E-book Developer

    Joined:
    Nov 4, 2008
    Messages:
    1,547
    Location:
    North Pole, Alaska
    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
    pabonbd71 likes this.
  7. eblc1388

    eblc1388 Senior Member

    Joined:
    Nov 28, 2008
    Messages:
    1,542
    Location:
    UK
    If your 9V battery connection is too short for the power supply, why not try the following and kill your project.

    [​IMG]

    You won't need to power it up anymore.

    Attached Files:

    Last edited by a moderator: Jul 13, 2014
  8. electratech

    electratech Member

    Joined:
    Jan 5, 2009
    Messages:
    21
    Location:
    Massillon, OH.
    VIP chart for quick guide

    [​IMG]

    Attached Files:

    Last edited by a moderator: Feb 8, 2014
  9. Skeebopstop

    Skeebopstop Active Member

    Joined:
    Jan 9, 2009
    Messages:
    358
    Location:
    Melbourne
    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. leftyretro

    leftyretro Active Member

    Joined:
    Nov 25, 2008
    Messages:
    394
    Location:
    Hercules, Ca. (SF Bay Area)
    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
    gisdude likes this.
  11. Skeebopstop

    Skeebopstop Active Member

    Joined:
    Jan 9, 2009
    Messages:
    358
    Location:
    Melbourne
    Er... aren't fuses meant to protect circuitry? I think you meant so that the 'fuse' blows up first to protect the circuitry and not the other way around.

    On the topic of fuses, make sure your fuse is placed as the first part of the system, before any surge protection. I recently had someone put 415VAC across a design intended to only allow 300VAC, so the VARistors popped, but the fuse downstream from the VARistor didn't, so then 600+VDC creeped into the circuit unimpeded. In reality, when the VARistor started to suck large amounts of current, the fuse should have been upstream so that it got a chance to blow from the VARistor current.
  12. studiot

    studiot Thread Starter E-book Developer

    Joined:
    Nov 9, 2007
    Messages:
    4,027
    Location:
    Somerset UK
    No, the primary function of fuses and other disconnection devices in mains equipment is to avoid electric shock to users from faulty equipment.

    The secondary function is to avoid electrically caused fires to property.

    Protection of the equipment itself is only a tertiary consideration, and a bonus if that can also be acheived.
  13. sumithra

    sumithra New Member

    Joined:
    Feb 1, 2009
    Messages:
    1
    capacitor reactance is inversely propotional to frequency and inductive reactance is directly propotional to frequency.As frequency increases capacitive reactance decreases and inductive reactance increases.
    nepdeep likes this.
  14. pkennedy

    pkennedy Active Member

    Joined:
    Feb 27, 2009
    Messages:
    44
    Location:
    Alabama,USA
    this one helped me when I first started learning about transistors just passing it on
    when looking at a schematic of a transistor the arrow always points to the n device
    this is true in fets also
  15. Dave

    Dave Senior Member Staff Member

    Joined:
    Nov 17, 2003
    Messages:
    6,961
    The way to remember it is for an NPN transistor the arrow is Not Pointing iN.

    Dave
    Sodar likes this.
  16. livewire09

    livewire09 New Member

    Joined:
    Mar 22, 2009
    Messages:
    5
    I can vouch for all the above said,thanks for the useful information and keep uploading more stuff for novices like us!
  17. Gus 67

    Gus 67 New Member

    Joined:
    Jan 21, 2009
    Messages:
    3
    Funny,I also had the same trick put for PNP....PoiNing in (I know it's missing a P at the end,but it works for me)
  18. thingmaker3

    thingmaker3 Moderator Staff Member

    Joined:
    May 16, 2005
    Messages:
    5,072
    Location:
    Rural, Oregon GMT -8
    I think "pin-up" for PNP - like a tack holding a poster to the board. At least I used to. I seem to finally have the association down after all these years.
  19. studiot

    studiot Thread Starter E-book Developer

    Joined:
    Nov 9, 2007
    Messages:
    4,027
    Location:
    Somerset UK
    Please this thread is meant to be a list of Tips, not a discussion thread.

    Here is another one.

    π does not appear in plane formulae.
    1/2π appears in cylindrical formulae
    1/4π appears in spherical formulae.

    For example

    The field E above an infinite plane charge density Q,

    E = Q / ε

    Field near a long line, linear density Q

    E = Q / 2πεr

    Field surrounding a point charge

    E = Q / 4πεr^{2}
  20. Skeebopstop

    Skeebopstop Active Member

    Joined:
    Jan 9, 2009
    Messages:
    358
    Location:
    Melbourne
    Thermal time constants of resistors de-rate them under duty cycle. A 5W resistor at continuous might be thought to allow 50W at 10% duty cycle (i.e. 50W pulses). This is incorrect! Generally the de-rating at 10% would allow more like 10W pulses and not 50! The internals of them heat up much faster than they can dissipate it into ambient!

    I recently got 'burned' on this. (Pun intended.)
Similar Threads: Electronics Tips
Forum Title Date
General Electronics Chat Electronics Tips / Posting on Instructables Jan 9, 2014
General Electronics Chat Electronics tips and tricks- Part II Nov 13, 2012
General Electronics Chat Testing of common electronics components Wednesday at 1:48 PM
General Electronics Chat Electronics Components Shopping List Aug 8, 2014
General Electronics Chat best book for power Electronics Jul 27, 2014

Thread Status:
Not open for further replies.

Share This Page