My trip to Radio shack

Discussion in 'General Electronics Chat' started by MusicTech, Apr 21, 2008.

  1. MusicTech

    Thread Starter Active Member

    Apr 4, 2008
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    So, I went to Radio Shack and picked up a whole bunch of goodies. Now, I gots alotsa mucho problemos.

    K so I get the the most basic that they have in timers, (at least I didn't see anything more basic) the 555CN (2761723). So there are no labels or anything, as I am a complete noob, I am probably not seeing something. The unit is like a brushed plastic look, with a little circle of plastic that is unbrushed, as in still shiny, does this represent lead number 1.

    Also I got some caps with numbers on them. These numbers are in uf, right? Also, how would you figure the volts they would hold? Sorry for the dumb questions
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    The timer you purchased is an NE555.

    [​IMG]

    See the lettering and the unbrushed circle in the image? When the lettering is so that you can read it (if the photo were rotated 90° to the left) then pin #1 would be at the lower left corner, #4 lower right, #5 upper right, #8 upper left.

    What kind of caps did you get? The disk capacitor assortment? If so, those numbers are in pF (PicoFarads).
    1000nF = 1uF; 0.001uF = 1nF
    1000pF = 1nF; 0.001nF = 1pF
    1,000,000pF = 1uF; 0.000001uF = 1pF

    I forget what their disk capacitor voltage rating is, but if you're powering the circuit with batteries you won't have to worry about it.

    Post what some of the markings on the caps are.
     
  3. MusicTech

    Thread Starter Active Member

    Apr 4, 2008
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    THanks a lot, I thought that's what it was, but I just wanted to make sure.

    I got the 100 pack assortment. They say 221,561 1KV, 10 and 7
    So, if I completely understand caps they will not charge to above their source, correct? I see no polarity markings, so it is fair to say they are not polarized
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    You got the 100 pack assortment of disk capacitors?

    221 = 220pF (first 2 digits taken literally, last digit is # of zeroes)
    561 = 560pF, 1KV = 1000 volts
    10 = 10pF (there isn't a 3rd digit, so you take the two literally)
    7 = 7pF

    For audio purposes, you would have been better off with an assortment of electrolytic capacitors. However, you can still generate higher frequency signals (say, 4kHz-10kHz) with your 560pF and 220pF caps with some fairly large resistors.

    Caps won't charge to above their source? I'm not quite sure what you're talking about there. If you mean voltage, no - they will only charge up to the voltage that they are supplied with.

    Ceramic disk capacitors are not polarized.
    Generally, most electrolytic and some tantalum capacitors are polarized.
    There are also non-polarized electrolytic caps; internally they are actually two polarized electrolytics that are connected back-to-back (not exactly, but that is the easiest way to explain it.)
    I can't think of other polarized types off the top of my head.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    OK, I'm sure you're dying to hook something up and make some noise. ;)

    See the attached image.
    Use the closest resistor values that you have for R1 and R2.

    For R1, anywhere between 420K and 560K will work.

    For R2, use somewhere between 300K and 420K.

    For C2, you could use one of your 560pF caps - might make the frequency a bit unstable, but that's OK.

    Now for the output; that's between pin 3 and ground (or your power supply return)

    But, you can't simply hook up a speaker or headphones. You will need to limit the current with a resistor, otherwise you will damage the 555 timer or your headphones/speaker.

    A 555 timer can sink or source up to 200mA, or 0.2A, but let's limit the current to half that much for the moment.

    Let's say you're powering it from a 9v battery.
    Rlimit = Voltage / Current
    Rlimit = 9v / 0.1A
    Rlimit = 90 Ohms
    91 Ohms is the closest standard value. You could use a 100 Ohm resistor in series with your speaker/headphones if you wanted.
     
  6. MusicTech

    Thread Starter Active Member

    Apr 4, 2008
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    ok, I will have to get more resistors, mine are all way to much or not enough. Thanks though, that doesn't look hard at all.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Good DVMs have come way down in prices too. Modern units have frequency counters, capacitance meters, and more built in, which is nice. Radio shack is an excellent source for quick parts, but they are lacking in many ways. Test equipment tends to cost a lot (400%) more than it needs to.

    Online stores, like BG Micro, offer meters like these and more. Last I checked the DVM I was talking about was $15.
     
  8. MusicTech

    Thread Starter Active Member

    Apr 4, 2008
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    Yeah, even mouser, which isn't even one of the super cheap sites cells the 555 I got for give or take 41 cents, but again, I am not at the point where I would buy like 10 or 100 or something to make the shipping worthwhile. I mean I don't even know what to do with 1. hahaha
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    ROFLMAOOOOO!!!

    Holy cow, is that funny! Well, I've wound up with quite a number of them. I don't even want to tell you HOW many. My other half keeps putting stuff in boxes and stashing them in closets, attics, under the bed...
    OK, the other day I finally tracked down MOST of them ... 21 so far (wait, one of them is a super-low power TLC555...) ... but that's just the 555's.

    Wait until I find the 556's!

    I'll be two-timing in no time at all!

    Wait, that didn't sound good... nevermind.
     
  10. MusicTech

    Thread Starter Active Member

    Apr 4, 2008
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    Well, it was a good pun. Two times yet on parallel, none at all.

    One thing I am not seeing with your schematic: Where do the positive and negative battery terminals go?

    Ok thanks.
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    Vcc is + voltage. Have fun, I love that little chippie.
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    Like Bill said, the + voltage gets connected to the top of the schematic.
    The - voltage gets connected to "ground".
    On the schematic, see the three triangles made up of horizontal lines that are at the bottom? That is a ground symbol. They are all electrically connected together.
     
  13. MusicTech

    Thread Starter Active Member

    Apr 4, 2008
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    ok, thanks, I see everything now
     
  14. jericko

    Member

    Apr 21, 2008
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    the pin directly left of the circle (pin closest to the circle) represents pin 1, counting left side down 1,2,3,4 right side up 5,6,7,8
    also a DMM is great for determining cap values, thats what i use most of the time, building circuits take awhile so cheat as much as you can is my motto.

    ps. the DMM (digital multi meter) must be designed for such methods.
     
  15. MusicTech

    Thread Starter Active Member

    Apr 4, 2008
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    Sorry I have been away from the forum for so long, I had three research papers to do Anyway, no that that is finally over I have one question:

    How to you determine the output voltage of the 555?

    Also, after looking at many similar schematics and doing much research, I cannot get that circuit wookie gave me to work. I attached a copy of it I drew by hand, if someone could give me a tip, that would be greatly appreciated, thanks:).
     
  16. Audioguru

    New Member

    Dec 20, 2007
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    The 555 won't do anything unless its pin 1 is connected to 0V from the battery.

    Your 470k resistor connects to the wrong pin on the 555.
     
  17. thingmaker3

    Retired Moderator

    May 16, 2005
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    What AudioGuru no doubt meant to say was "move the 470K resistor to pin 7."
     
  18. Audioguru

    New Member

    Dec 20, 2007
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    I gave a hint for him to find the mistake by himself.
    The resistor was completely shorted so it should have been obvious.
     
  19. MusicTech

    Thread Starter Active Member

    Apr 4, 2008
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    ok, I will give that a tr sorry i have been away for so long again, I have been working hard to finish some end of year term papers
     
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