555 Timer Freeform vs. breadboard

Discussion in 'General Electronics Chat' started by daroc26, Oct 23, 2009.

  1. daroc26

    Thread Starter Active Member

    Apr 4, 2009
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    Hi All,

    I've been breadboarding basic 555 timer circuits, experimenting with different component values. I found a set that gave a decent hz rate for the LED.

    R1= 1kohms, R2= 10kohms, R3= 120ohms, C1=100uf, 9V.

    I don't have perfboard and I wanted to practice my soldering skills for BEAM projects that I want to try out down the line. I decided to freeform the circuit, soldering components to the 555 timer.

    Please take a look at the photo. I know the soldering is sloppy and it is really ugly. I used a metal paperclip as rails for ground and + voltage.

    For some reason, the LED lights up, but it does not blink. I've swapped capacitors several times, testing them on the breadboard afterward, and the components seem to be working. I've also taken a second look at solder joints, desoldered, and reheated with a fresh coat of solder. Could the IC be fried from all of the soldering and heat?

    Any suggestions would be great!

    Thanks!
     
    Last edited: Oct 23, 2009
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    They call this the "dead bug" assembly technique for a reason. :D
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    You're right, it IS ugly! :D

    It's really difficult to tell by the photo, but is the LED shorted against one of the cap leads?

    Usually when you're making a "dead bug" type prototype, you glue or solder the components to a plain or copper clad board. The board serves as a physical support; if it's copper clad the copper also serves as a ground plane.

    Trying to wire stuff in midair is bound to give you lots of problems.

    You might consider picking up some prototype boards, like this one:
    http://www.radioshack.com/product/index.jsp?productId=2102845

    Makes it a lot easier than the "dead bug" method.

    Paper clips are not very good for power rails. They are generally nickel-plated steel; hard to solder.

    It takes some practice to get good at soldering. If you apply heat (too much, too long) you'll roast your components.

    Your parts must be clean before soldering. Isopropyl alcohol (90% or better) is a good components cleaner. Be careful with it though, as it is flammable, and burns with a nearly invisible blue flame.

    If you've handled your components, they will have finger oils on them which will make them really hard to solder. Clean with the isopropyl alcohol and a small brush, let dry. Apply heat to the joint for a couple of seconds, and then touch the solder to the joint, not the iron. If your parts are thoroughly cleaned, you shouldn't need flux - however a bit of rosin flux will make the solder flow a bit easier. Clean flux off using isopropyl alcohol.

    The easiest solder to use is Sn63/Pb37 (63% tin, 37% lead). It has a fairly low melting point, and is eutectic - it has no "plastic" state. With other types of solder, if you move the parts while the solder is cooling, you will wind up with a "cold solder joint"; it will look gray and dull. A good solder joint will look bright silver, and will "flow" over the component leads. Use small amounts of solder.
     
  4. daroc26

    Thread Starter Active Member

    Apr 4, 2009
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    Thanks for the tips SgtWookie!

    Speaking of tips, I wanted to show you guys what I am working with. This is probably the ugliest looking soldering iron too. I got it from electronics gold-mine, 60watt for a bargain $4.95. The tip is completely corroded and oxidized.

    Maybe a better iron would be a good investment. But if I'm making dysfunctional circuits like the one I made tonight, I can't justify the expense.

    I'll keep trying, I've already recognized techniques I could use to improve the aesthetics of the thing.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    60W is far too much. You should be using a 15w to 30w iron.
    The tip being corroded/oxidized makes it pretty worthless. It will take too long to heat up your parts.

    Spend a few bucks on another iron before you ruin a pile of parts.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Dead bug can also use Altoids Mint cans, card board, plywood, anything to keep the parts organized. Google the term, there are some good examples out there, and it can look really good.
     
  7. bertus

    Administrator

    Apr 5, 2008
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  8. daroc26

    Thread Starter Active Member

    Apr 4, 2009
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    Hi All,

    I thought I would give this freeform-deadbug-style another shot and I got it to work!

    In the first attempt, I think I was missing a critical connection between pin 2 and 6.

    This one came out much cleaner and more aesthetically pleasing.

    Thanks for the help!
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    Uhhh, OK! :rolleyes: ;)
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    Glad you got it working - it's still really ugly though! :eek: ;)

    On your component selection:
    R1= 1kohms, R2= 10kohms, R3= 120ohms, C1=100uf, 9V.

    Generally, you are far better off to use a low value for C1 and higher values for R1, R2.

    One reason for this is, that capacitors get really large as they increase in uF rating, and resistors (more or less) stay the same size.

    Of greater concern is that large capacitors take a lot more current to charge up than smaller capacitors do.

    Try repeating your experiment, but instead of a 100uF capacitor, use a 1uF cap.

    Then use a 100k resistor for R1, and a 1 MEG resistor for R2.

    The flash rate will be the same, but you will be using a lot less current in the charging/discharging of the timing cap - and your battery will last longer.
     
  11. daroc26

    Thread Starter Active Member

    Apr 4, 2009
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    Great advice, thank you!

    I was actually thinking of asking the board how long this circuit would last using these component values? How would I figure out how long it would take before the battery ran out? There must be a formula out there for this. I'm thinking Ohms Law?

    And I know this thing is hideous. Eventually I'd like to get to this level.
    Haha, maybe in a few years :D
     
    Last edited: Nov 22, 2009
  12. SgtWookie

    Expert

    Jul 17, 2007
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    Well, 9v "transistor" batteries are generally rated for about 150mAh; which is derived by subjecting them to a fixed-current load over 20 hours. They are considered exhausted when the output voltage falls below a certain point; can't remember what that is offhand.

    The lower your current draw is, the longer the battery will last.

    You didn't mention the value of the current limiting resistor you're using on the LED.

    It's always good to know where you are, and where you want to go. :)
     
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