Electronics Tips and Tricks Thread

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

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  1. RAH1379

    Well-Known Member

    Dec 13, 2005
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    always turn power off before removing or inserting circuit boards.always connect the negative or ground lead of test equipment before contacting high voltage with the "hot" lead, and always apply power to cmos circuits before applying input signals.in stereo amplifier troubleshooting you can compare voltages from each channel to quickly find a problem area.
     
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  2. Wendy

    Moderator

    Mar 24, 2008
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    Cutting wire for protoboards is a hassle, at least if you want it neat. They used to make tools for that, but I haven't seen them for quite a while.

    Here is my solution.

    [​IMG]

    I used a round toothpick cut down and marked in 0.1" increments.
     
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  3. sintau.tayua

    Member

    May 11, 2009
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    @ Bill Marsden: Perhaps something like this ( http://evilmadscience.com/partsmenu/68-bender ) would be the commercial version of your tool?

    Anyways, the link goes to a 'resistor lead forming tool', which is certainly useful if you do a lot of surface mount (or breadboad) stuff.

    My next tip is to do with surface mount soldering. Instead of trying to manually solder all the tiny leads by hand, use a hotplate:
    -Get a stove, oven thermometer, and your pcb.
    -Apply solder paste.
    -I find it helps to put a piece of metal (aluminium, copper, iron) 1/8-1/4 inches thick over the heater element, to spread the heat out better. This is not necessary, but very useful.
    -Place components on board, and board on hotplate. Place the oven thermometer so that the 'sensor' tab is in firm contact with the heater element (or piece of metal, if you use it)
    -Crank up the heat. When desired reflow temperature is reached, turn off heat and wait for it to cool.
     
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  4. Wendy

    Moderator

    Mar 24, 2008
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    Thanks for the pointer, that was the tool I was thinking about. For cutting insulation to size though, I think my solution has the edge.

    I have done what you are talking about with the hotplate, except for one thing. You don't need the hotplate to melt the solder, just get the temperature differential where it is closer than room temperature. The solder will melt faster and flow better with a soldering iron afterwards. It makes hard to solder jobs much easier to work with, and damages the PCB less.
     
  5. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
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    $7 !*#?

    They used to give these things away free with electronics magazines.
     
  6. radiohead

    Distinguished Member

    May 28, 2009
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    Everyone knows that fuses protect against over-current. A good way to protect against over-voltage is to add a simple regulator at the power-in stage of your project. A good way to protect against reverse polarity is to use a bridge rectifier with the input going into the AC pins. You may notice a drop of about 2 volts due to two forward biased diodes.
     
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  7. radiohead

    Distinguished Member

    May 28, 2009
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    SAFETY ALERT !!! FLOATING GROUND. This occurs when you have a device, let's say a 12VDC device in a metal chassis in a vehicle with a multiple battery (24 VDC) system. When connected to the ungrounded battery, you will have a 24 VDC potential between the device chassis and the vehicle ground. This can destroy the device, destroy the vehicle's charging system, cause a battery to violently vent, or give you an electric shock. Make sure you connect 12V devices to the GROUNDED battery.
     
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  8. gotumal

    Active Member

    Mar 24, 2008
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    While using scopes; especially for HV testing, keep in mind that ground probe is connected to mains earth. I burnt two probes!
     
  9. bertus

    Administrator

    Apr 5, 2008
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    Last edited: Oct 5, 2012
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  10. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
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    Good pictures, thank you Bertus, you do seem to find some interesting sites.
     
  11. DC_Kid

    AAC Fanatic!

    Feb 25, 2008
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    depending on the type of circuit needing encapsulation (high vs low voltage, although this can work for hv if careful), using quality glass bead (the type for "sand" blasting) can be used as a encapsulating/insulating material, and/or a filler before using expensive high voltage encapsulating epoxy. it flows well into complex spaces/voids, etc. i use fine glass bead unpacked as a filler before using a quality epoxy to encapsulate (saves epoxy). my stuff is all "low" voltage. at 60vdc with electrodes at 0.1mm apart i was able to achieve 0.0uA (0.1uA is the best resolution my Fluke can read). i have not done any testing with higher voltages yet.

    notes:
    1. unpacked or packed glass bead has a dielectric that will vary depending on how much moisture is in the air and how packed it is.
    2. quality vs non-quality glass bead means 100% glass bead or glass bead that has small amount of "dirt" mixed in with it. dirt can also affect the dielectric rating.
    3. be sure you know the composition of the glass. just because it says "glass bead" doesnt tell you much about the glass itself, which can affect the dielectric rating.

    4. using this method for high voltage means you must validate the dielectric ability before proceeding.

    glass bead is just a low cost alternative to other encapsulation methods. lots of info on the net about this.
     
    Last edited: Jul 19, 2009
  12. BobaMosfet

    AAC Fanatic!

    Jul 1, 2009
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    Work the math. Trust the math. Use the math correctly. Know that you're using it correctly.
     
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  13. AJFishdude

    New Member

    Aug 11, 2009
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    Something that I always find helpful when remembering which side of the diode is anode and cathode, is that in the schematic symbol the arrow of the diode points from A to C. Meaning, for current to flow through a diode with normal forward bias, you want greater voltage on the anode (A) than on the cathode (C), hence the A points to the C. You could also think of it alphabetically, A before C. Or just A>C

    Don't forget that on LEDs, the longer lead is ALWAYS the anode. At least, I have never seen an LED where the longer lead is not the anode.

    If you have any chemistry background, don't get confused with the anion/cation terms. The anode of a diode is the more positive side, whereas the cathode is the more negative side. But an anion is a negatively charged ion and a cation is a positively charged one. That kind of messed me up when I was first learning all this stuff.
     
  14. dnsalazar

    New Member

    Aug 27, 2009
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    For all beginners in Electrical Engineering visit my blog here: <snip>
     
    Last edited by a moderator: Jul 14, 2010
  15. mscreations

    New Member

    Dec 14, 2009
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    Here's something a friend once told me to remember the polarity of an anode and cathode:

    "Andy wants to get with Cathy, but Cathy is a very negative person."

    Helps me remember at least...
     
  16. andreapg

    Active Member

    Feb 2, 2010
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  17. Georacer

    Moderator

    Nov 25, 2009
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    When designing a voltage divider to obtain a certain voltage, a good rule of thumb is the following:
    Select the divider's resistors so that the current that goes from Vcc to Ground is 10 times the current that the circuit that uses the dropped voltage consumes.
    This will prevent the alteration of the desired voltage due to excessive load.
    Refrased: I(resistor)=10*I(load)
    I had real issues before I heard that.
     
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  18. SgtWookie

    Expert

    Jul 17, 2007
    22,201
    1,807
    Battery capacity, battery temperature, and battery maintenance habits all impact the life of your lead-acid batteries.

    The attached spreadsheet (Excel 2003 version) will help you to determine how to maintain your batteries over a wide range of temperatures.

    If you do not have Microsoft Excel, you can download the free Excel Spreadsheet Viewer from Microsoft's website. Alternatively, you can download the free OpenOffice suite from openoffice.org.

    Note that you should find the datasheet for your battery, and enter the values for the fields with a yellow background.

    An image of the spreadsheet is attached for a preview.

    [​IMG]

    If you don't have Microsoft Excel, you can download the Excel Viewer, here: http://www.microsoft.com/downloads/...f9-ce06-4e1c-8dcf-f33f669dbc3a&displaylang=en
     
    Last edited by a moderator: Feb 8, 2014
  19. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    Over the years I've found it handy to keep a variety of wall adapters around for those quick and dirty prototypes that need to be tested "in place" instead of just on the bench.

    The next time you pass a thrift shop with some extra time take a moment to browse through it, I often find "orphaned" wall adapters they'll sell for pocket change since they don't fit anything in the store. Last time I did this I picked up a 9V and four 12V adapters, all rated at over an amp each, for less than $2 total.

    I also mentioned in another thread that some local HVAC parts suppliers have 120V:24 VAC 2A transformers for around $5 each, and today I bought one that has 120/208/240/480 input windings to 24V 3A out for $7.50. I don't know what I'm going to do with it but I figured at that price I may as well buy one.
     
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  20. Nik

    Well-Known Member

    May 20, 2006
    55
    3
    I've got to store 25-of 6n139 optocouplers (8-pin DIP) *in order* and anti-static after I tip them out of their transit tube. I don't have a big enough piece of anti-static foam, and my usual trick of layered cooking foil lets chips jump out and dance if I so much as blink the wrong way...

    I nearly soldered a bag full of DIP sockets to a square of strip-board, planning to add a shorting wire across the grain, but then I had an idea.

    Have you seen those 32-strips of tiny plugs & sockets for 'daughter board' connections ? I got three rows of plugs, wove and soldered a shorting wire down them, then plugged them into a long, narrow proto-board. Each protects 8 chips, leaving only #25 needing a wire jumper. The proto-board would protect up to 32 8-pin DIPs if I'd used a fourth plug strip.
    :)

    Two gotchas:
    Bell-wire is almost too springy. After the first length jumped off its pins when I touched it with my soldering iron, I hooked start and end down and around the lower pins, tack-soldered the end pins then cropped excess.

    The plug strip has different diameter pins on 'board' and 'plug' sides. There's only a whisker difference, but one side just slides into the proto-board while the other won't.

    FWIW, the matching plug-sockets accept terminated proto-board jumpers. This would have saved me soldering 'stacking screw connectors' to a break-out board that didn't require such heavy-duty kit. Also, plug-sockets are 0.1" pitch, but screw connectors are 0.2", requiring crowded strip-breaks and soldered jumpers...
     
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