Bought my kit, need help.

Discussion in 'The Projects Forum' started by Joeyvenkman, Dec 2, 2011.

  1. Joeyvenkman

    Thread Starter New Member

    Nov 19, 2011
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    I recently purchased a 10 LED chaser kit from allelectronics.com. I placed and soldered all of the components where they go on the board. When I supply power to the circut, the first LED lights up, than the second LED lights up. Then it just stays on the 2nd LED. If I tap right by the 555 Timer on the board, it moves on to the next LED in the sequence. I suspected it might have been a soldering problem, but I dont see anything wrong on that. Ill problably have to upload pictures too, and I would need help on that. Thanks for reading, I appreciate it.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Hello Joey,
    It's likely a solder whisker or ball on the back side of the board.

    It will help if you post a link to the exact kit that you bought.

    Taking good photos of circuit boards is actually kind of difficult. You need very even, bright lighting that is not "harsh". Flash attachments give very harsh lighting. Incandescent indoor lighting is usually not bright enough to give decent details.

    The best light is outside on an overcast day; as the light is very even.

    To post your photos, click the "Go Advanced" button at the bottom of the thread, then "Manage Attachments" at the bottom of the next screen. It's more or less self-explanatory from there.

    Please be certain that the photos are focused. Fuzzy photos are useless. Harshly lit photos are usually of little value. Take photos of both sides of the board.
     
  3. Joeyvenkman

    Thread Starter New Member

    Nov 19, 2011
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  4. SgtWookie

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    Jul 17, 2007
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  5. Joeyvenkman

    Thread Starter New Member

    Nov 19, 2011
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    What do you mean by "end points"? Are you referring to the lines on the TP-1?
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    The trim pot will only rotate so far in either direction.

    Gently find out what those limits are, and then position it halfway between those ends.
     
  7. Joeyvenkman

    Thread Starter New Member

    Nov 19, 2011
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    I have set it halfway, but nothing changed.
     
  8. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Do you have a DMM?
     
  9. Joeyvenkman

    Thread Starter New Member

    Nov 19, 2011
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    What exactly is a DMM?
     
  10. thatoneguy

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    Feb 19, 2009
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    Digital Multi-Meter. Voltmeter or just "meter".

    Lets you measure voltage, resistance, current, sometimes capacitance and frequency as well depending on what you get. Having one is a requirement if you are going to do electronics as a hobby. I suggest Fluke used from eBay, but they get spendy, others here are happy with the $3 ones, which actually are all that somebody needs. Or a $10-$20 one from Radio Shack. You will be using it nearly continually when working with circuits, especially for measuring resistors until you have the color codes memorized.


    This is from the current "Car Amp" thread to get an idea of what they look like, though Red isn't a common color, yellow or grey are seen around more often, but with the same general layout:

    http://forum.allaboutcircuits.com/attachment.php?attachmentid=37230&d=1322880350 <-- Click for large image
     
  11. Joeyvenkman

    Thread Starter New Member

    Nov 19, 2011
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    I think im gonna pick one up tommarow. Thanks for all the help!
     
  12. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    That, and a photo of your board, top and bottom, and we will get it working for you.

    Go over your joints with solder wick if there are any that are "blobs" where you can't see the pin anymore, make sure the joints are all shiny, and that no solder bridges between traces are present.

    Sometimes it will look fine, but there can be a bridge when too much solder is used. Running an X-Acto knife lightly between pads also lets you "feel" if there is a bridge present or not.

    Look for the opposite problem as well, too little solder, places where the solder is just sticking to the board and not the pin (from uneven heating), etc.
     
  13. wayneh

    Expert

    Sep 9, 2010
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    And I hope I'm not the only one, but having good bright light and a magnifying glass can make all the difference in the world when you need to inspect something small. I've been amazed many times how something that looks so ordinary to unaided eyes will be something altogether different when viewed properly.
     
  14. Joeyvenkman

    Thread Starter New Member

    Nov 19, 2011
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    It is likely a soldering mistake or I fried a chip. This is my first time soldering on a PC board, so it was a little difficult.
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    Soldering is not intuitive. It takes practice to make a good solder joint.

    My first soldering sessions resulted in something that looked like miniature gray piles of slag. :rolleyes:

    Your parts and board must be absolutely clean before you start soldering. I use a 3M(tm) Scotchbrite(tm) pad to remove any corrosion or residue from the PCB and the leads of components, then insert components in the board, and rinse them with 90% or better isopropyl alcohol applied with an "acid brush" (these have black nylon bristles and a rolled metal handle, available from auto parts stores).

    If your parts to be soldered are absolutely clean, and your iron is clean, tinned, and the proper temperature, you can even solder without using flux; as flux simply helps to lift dirt/contaminants to the surface while the solder is liquid.

    I use just a bit of liquid rosin flux. I also use Sn63/Pb37 (that's 63% tin/37% lead) solder, and try to avoid handling it while soldering.

    Finger oils will hinder making good solder joints, as will almost any other contaminants.

    The iron needs to be the proper temperature. Too low, and your solder won't "flow" easily. Too high and you risk burning up components & damaging the board.

    Read through this page a few times:
    http://www.elexp.com/t_solder.htm

    Practice soldering using some cheap perfboard or stripboard and surplus components; that way you won't risk ruining an expensive kit.

    Your solder joints should be clean, bright and shiny. Too little solder results in a weak joint. Too much solder risks overheating the board and/or component being soldered.
     
  16. Wendy

    Moderator

    Mar 24, 2008
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    It wasn't so much soldering that got me on the first kit I built, it was grabbing the wrong end of the iron. I paid much more attention to what I was doing after that.

    It was building a small VOM, Volt Ohm Meter, the kind with a meter, not digital.
     
  17. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Did that too, as a youngster! The iron had a slim handle which slipped all too easily between the fingers. It dropped, I grabbed - ouch!
    I was more careful from then on: I got an iron stand (highly recommended), and later an iron with a better handle.

    To return to topic, parts may be overheated during assembly, but this should not be a big problem once you get the hang of soldering. At least, not for silicon through-hole devices: SMDs, germanium, and other exotica may be another story. With ordinary through-hole parts though, if it is taking long enough for this to be a serious hazard (typically more than a few seconds each joint), then there are likely to be other issues such as lifted tracks on the PCB.
    It is really worthwhile learning how to avoid that.

    LEDs, especially with short leads, may be less tolerant, and personally I don't like to mount them flush to a board. It is worth having the board pre-tinned, and trying to work as quickly as is consistent with a sound joint. Some suggest the use of heat shunts (haemostats etc.) on the leads
    of sensitive things like LEDs, but this may be physically difficult, and can lead to difficulty with getting the joint heated reasonably quickly.

    Heat is not the only thing that can damage things though. Electricity is another possible problem, whether due to static charges on yourself, on the work-piece, on the iron, or perhaps AC mains leakage from the iron. Simple irons that plug into the mains should have a direct ground connection for your safety, which will be adequate provided nothing else has a charge. More elaborate irons with isolated power supplies may ground the iron via a resistor, better in theory for avoiding damage to things, but only safe for the user if the power unit is very well made. Whatever iron you have, always use it with a properly grounded outlet.

    It may be advisable to use a wrist strap
    with a series safety resistor of at least 1MΩ, and maybe a grounded anti-static work mat.

    The above is an attempt to describe good practice, and it may be that not taking some such precautions has lead to your problem. It's worth saying though that when newly built projects fail to work, you should check for the following:


    1. Incorrect assembly: wiring errors, and incorrect or wrongly placed parts. This easily happens with colour-coded resistors. This includes wrong-way-around mounting of parts like ICs, transistors, diodes including LEDs, and electrolytic capacitors.
    2. Short-circuits, particularly solder bridges and escaped strands from the ends of flexible wires.
    3. Open-circuits, such as wires not fitted or soldering so bad that there is no contact at all.
    4. "Dry" or "cold" soldered joints with a grey matt appearance, likely to give bad contact.
    5. Faulty components. Maybe not so common, but frequent enough with some cheap semiconductors. Incorrectly marked resistors are also not unknown. To avoid this last problem, and any risk of making mistakes whether due to eyesight or other difficulty in reading colour codes, you could measure resistors before fitting them.
    6. Finally, if using a battery, ensure that it is still good. You would be surprised how often problems are due to flat batteries.
     
  18. Wendy

    Moderator

    Mar 24, 2008
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    Once you get a spot of liquid solder it is easy. The one major mistake is to hold that iron too long on a joint, but the entire pad and wire should be engaged with the solder. I've been doing it so long it is completely second nature to me.

    Nomally you will not need flux. Only time I have had to use solder flux is with old oxidized wires, then it is a life saver.
     
  19. SgtWookie

    Expert

    Jul 17, 2007
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    If you have old oxidized wires and 3M(tm) ScotchBrite(tm) pads won't take it off (or it's just impractical to use ScotchBrite(tm) pads), if you are careful you can dip the wires into concentrated muriatic acid for about 30 seconds, and then rinse them thoroughly with fresh water. You have to be careful with the muriatic acid though, as it eats through many things that you would not have thought it would (like nylon)
     
  20. Joeyvenkman

    Thread Starter New Member

    Nov 19, 2011
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    0
    A question- Ive been playing with the kit for a while now, and I have discovered that when I tap the board right by the 555 timer, it moves to the next LED in the sequence. When you fry a chip, what happens to the circut with the chip?
     
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