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Need Help with Radio Shack Kit Project

Discussion in 'General Electronics Discussion' started by Bricago, Nov 8, 2016.

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  1. Bricago

    Bricago

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    Nov 8, 2016
    Hello,

    First timer here! I dusted off my old 160 in One Project Kit to try to learn something about circuits, and discovered that the manual wasn't exactly written for beginners. I found what appears to be the simplest project in the book to start with. The instructions suggest a couple of modifications to the circuit, but they don't tell you how to do it(!)

    I've attached a photo of the page and notated the four (probably very simple) modifications. If you're inclined to provide some guidance, I would be very grateful.

    Thank you.
     

    Attached Files:

  2. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Your notes are hard to read, so this will go better if you ask specific questions here.

    To answer one question: No, polarity does not matter *in this circuit*. This circuit has no semiconductors (transistors and diodes), so current is free to flow in both directions.

    Note that "series" is not a verb. You don't "series batteries", you connect two batteries in series. Batteries have + and - terminals, so it is important that they be connected to each other correctly.

    ak
     
  3. Bricago

    Bricago

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    Nov 8, 2016
    Thank you for the reply. I apologize for the illegible notes. Please ignore those. If you have advice on which connections to make (additions to the "Wiring Sequence" shown below the breadbox image) to achieve the four mods described, that would be very helpful. (Connecting the batts in series, inserting the resistors, and short circuiting the resistor).
     
  4. hevans1944

    hevans1944 Hop - AC8NS

    4,617
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    Jun 21, 2012
    There is one Radio Shack "learning kit" that I recommend, but this one isn't it. However, the purpose of this "lesson" is to teach you some of the properties associated with all relays: namely pull-in voltage and current, and drop-out voltage and current. There is a 9V battery and two series-connected 1.5 V cells forming a 3 V battery, all located in the lower right corner of the breadboard. The 9 V battery has its positive terminal connected to terminal 120 and the negative terminal connected to terminal 121. The two 1.5 V series-connected cells have their positive terminal connected to terminal 122 and their negative terminal connected to terminal 123. Depending on how you connect these two voltage sources in series, you can obtain 6 V (series opposing) or 12 V (series aiding).

    The relay coil is apparently rated for a minimum of 3 V DC, but the explanation for that is poorly written. Quoting from the page image, "The Relay used here has a resistance of about 500 ohms and requires a minimum of 6 mA (milliamps) to initially pull the armature (the moving part) in. This means that the voltage required (minimum) is 0.5 x 6 = 3 volts." This explanation sucks, although the result is correct. The operating equation is V = I x R, where V is measured in volts, I is measured in amperes, and R is measured in ohms. So, plugging in I = 0.006 A and R = 500 Ω and multiplying, we do indeed get 3 V. But a novice wouldn't have a clue where "0.5 x 6 = 3 volts" came from.

    As for the "mods" or "experiments"... (1) wiring the voltage sources in series opposing to get 6 V is supposed to show you that this particular relay will definitely pull in (actuate) provided you use fresh cells. (2) Inserting a 100 Ω resistor usually allows the relay to operate from the 6 V source. WTF does this teach you? Nothing, IMHO. Now try the 9 V battery alone? You know it works with 6 V, so what does operating it from 9 V teach you? Try operating from the 9 V supply with first a 470 Ω resistor and then with a 1 kΩ resistor in series with the relay. What did you learn from that? The relay probably operates with the 470 Ω resistor, but fails to operate with the 1 kΩ resistor? So what? (3) Insert a 1 kΩ resistor in series with the Relay and then (4) momentarily short circuit across the 1 kΩ with a piece of wire. You may already have the 1 kΩ resistor inserted in series with the Relay from experiment (2), so what (4) is asking you to do is deliberately place a wire across this resistor, effectively removing it from the circuit and replacing its resistance with the very low resistance of the wire. This temporary connection works, but to advise a novice learner to deliberately create a short-circuit seems to me to be bad instruction. What experiment (4) is trying to teach you is the relay will actuate with 9V and zero resistance and will stay actuated when the zero resistance is suddenly replaced with 1 kΩ resistance by removing the shorting wire.

    If none of this is clear to you, I suggest you start with a very basic instructional text that teaches fundamentals of electricity and electric circuits. Performing "monkey see, monkey do" tasks where you connect wires to various components will teach you absolutely nothing of value. And purchase an inexpensive digital multi-meter from one of the big-box home improvement stores. You cannot learn about electricity (or electronics) without making electrical and electronic measurements. You may be able to build a house with only a hammer, nails, and wood but a tape measure would certainly help keep things sorted. The multi-meter is the electrical and electronic equivalent of the carpenter's tape measure. Buy one and learn how to use it. Most of all, have fun!
     
    KJ6EAD likes this.
  5. Bricago

    Bricago

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    Nov 8, 2016
    Hevans, you nailed it. This kit is full of WTF and 'so what?' gems. Now I don't feel so bad about not learning anything when I played with this as a kid. One of my favorite blunders is a warning to set the control knob correctly before beginning the project in order to prevent damage to the components. Of course the warning is printed at the END of the instructions!

    I appreciate your detailed reply to my questions. Just curious, which learning kit would you recommend and why? I like the idea of learning what role components such as relays, transistors, and IC's play in a circuit. But this "monkey see, monkey do" approach raises more questions than it answers.

    Thanks again for your time.
     
  6. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    KJ6EAD and hevans1944 like this.
  7. Bricago

    Bricago

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    Nov 8, 2016
    Thank you, 73's.
     
  8. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    I highly recommend the Radio Shack Learning Lab. Here is a link to the why. In a nutshell: excellent kit design, excellent instructions.

    I grew up reading Forrest Mims III articles, mainly in Popular Electronics. This man was (unknown to him, of course) my early mentor in electronics. There are two printed manuals included with the RS Learning Lab, one for analog circuits, and the second one for digital. Mims explains everything you need to know to get a firm foundation in electronics.

    A few years ago I purchased a RS Learning Lab as a Christmas present for one of my grandchildren in Virginia Beach, VA. I liked it so much that, upon returning to Dayton, OH, I purchased another one. My initial thoughts were to use the one in Dayton to guide my grandson in Virginia Beach through Mims' instruction manuals. That hasn't happened yet (he may have been too young to appreciate the gift), but I have hopes that he will "grow into" it. It is never too early (or too late) to learn.

    Thanks to @73's de Edd for posting a link to the 160-in-One Electronic Projects Kit. There are quite a large number of interesting circuits described, and they can all be "wired up" for instant gratification. Whether the person doing the wiring will actually learn anything is problematical, but it's a start. Back in the day, when this kit was first offered, there was no convenient way to breadboard circuits. Mounting components behind a "control panel" with springs connected to their leads made it easy to connect and re-use said components. The recommended RS Learning Lab still uses this method for a few panel-mounted components, but the major portion of the circuit construction uses the ubiquitous multi-pin solder-less breadboard technique. This has the important, even essential, advantage of allowing for easy construction of "what if" scenarios by simply removing one component and replacing it with another.

    I like the battery specification and wiring of multiple D-size cells in series, with taps brought out to the solder-less breadboards' power rails. You can make your choice of voltage(s), depending on how many cells you select. And D-size ensures that you will have many hours of power available compared to wimpy AA or AAA cells. However, since I was in the RS store, I also picked up some RS re-chargeable D-cells and a battery charger for them. Normally I use a wall-wart and a voltage regulator IC for solder-less breadboard power, but it is nice to have everything self-contained in one portable box.
     
  9. Bricago

    Bricago

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    Nov 8, 2016
    Thank you hevans. I like the look of that kit. The voltage flexibility is particularly interesting. I'm considering this kit too. It has the same solder-less breadboard, and the companion book appears to be well written.
     
  10. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    I think I bought similar parts kits a few years ago, mainly so I would have a box to keep them sorted... more or less. You can never have too many parts on hand; problem I have is finding them when I want to use them.
     
    duke37 likes this.
  11. 73's de Edd

    73's de Edd

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    1,312
    Aug 21, 2015
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