I need someone to point me in the right direction.

Discussion in 'General Electronics Chat' started by Hextejas, Sep 29, 2017.

  1. Hextejas

    Thread Starter Member

    Sep 29, 2017
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    Hello everyone and nice to meet you. I am a retired computer programmer analyst and my main interest is learning how to build circuits that can be controlled by an Arduino.
    I am fairly knowledgeable about the program coding side but breadboarding, circuit boards, measuring, etc is the work of the devil. (just kidding as it fascinates me )
    I have started with the Forrest Mims book, Getting Started in Electronics, and it has a lot of good stuff in it and I am trying to work through the exercises, taking measurements as appropriate.
    So, my 1st exercise is to breadboard a circuit using:
    1) Zener diode
    2) 12v DC source
    3) 60 ohm, 1/2 watt resistor.

    The exercise doesn't really specify the components except for the resistor.
    Well what I have laying around are these:

    1 Zener Diode 1n4007 ( I think ) the numbers are bloody small.
    2) DC 14.5 v
    3 ) 300 ohm, 1/2w

    The exercise shows 12v coming in and 9 v coming out and I figured that I might get something similar.
    Foolish mortal. Hah !

    So, is there a formula that I could use to predict what I should get.
    It seems that knowing the input voltage, the resistor value, and some number from the diode data sheet, I ought to be able to predict the output.
    Using a digital VOM, I get all kinds of weird readings. A lot having to do with terrible breadboarding skills..
    I expect that I will eventually master the breadboarding and I would like to be able to predict the outcome ?

    Is there any hope for me ?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    12,087
    2,625
    A 1N4007 is not a zener diode. Most diodes have a reverse breakdown voltage, but an actual zener diode has a very sharp knee in the breakdown characteristic. In the breakdown section of the characteristic curve you need the resistor to limit the current through the diode. Consult the 1N4007 datasheet for additional details.
     
  3. Reloadron

    Distinguished Member

    Jan 15, 2015
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    Going to have a problem there, the 1N4007 is a standard silicon diode member of the 1N4000 family. This is where data sheets become your new best friend and learning to read them.

    Guess I clicked a little late. :)

    As to the Arduino? They have some great online tutorials as well as pictorial drawings with bread boards.

    Ron
     
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  4. Papabravo

    Expert

    Feb 24, 2006
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    From the datasheet it appears you will need more than 1000V in the reverse direction to get more than 5 μA of reverse current.
     
  5. MrChips

    Moderator

    Oct 2, 2009
    18,530
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    I need someone to point me in the right direction.

    Go ESE young man!
     
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  6. Hextejas

    Thread Starter Member

    Sep 29, 2017
    187
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    Thank you all and Papa, what on the data sheet told you about the 1000 v ?
     
  7. Papabravo

    Expert

    Feb 24, 2006
    12,087
    2,625
    112.5° would be the correct heading for ESE.
     
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  8. Raymond Genovese

    Well-Known Member

    Mar 5, 2016
    1,643
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    Yes, there is hope for you.

    As you have probably already figured out, you mistook a general-purpose silicon rectifier diode (1n4007) for a zener diode.

    So, right here on the site, there is a ton of reference information....e.g., go here...scroll down to question 9 - you could breadboard that as soon as you get a zener...and all along the way, you can look at the textbook here and use search terms and so on an so forth.

    One last thing - get one of these [​IMG]

    Welcome to the site.
     
    Last edited: Sep 29, 2017
  9. OBW0549

    Distinguished Member

    Mar 2, 2015
    2,863
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    If you want a 9 volt Zener diode, try a 1N4739A. The 1N4728 - 1N4764A series is very popular for general-purpose use. The 1N4007 you're trying to use isn't a Zener, it's a rectifier diode.
     
  10. philba

    Active Member

    Aug 17, 2017
    959
    302
    Welcome! You picked a wonderful area to study.

    This might help you out. While I appreciate the way that AAC approaches teaching, that is a little more traditional.
    Here is a pdf on zeners and gives you the part numbers for specific voltages. From the chart, you'd want a 1N4739A (9.1V, don't sweat the .1). Note that these are fairly low current devices but for experimenting they're perfect.

    One thing you should commit to memory is Ohm's Law. V = IR. You will use it all the time. It's your friend.

    And by the way, your 14.5 VDC, is probably from an unloaded wall wart. The more current you draw from it, the lower the voltage. Ohms law in there somewhere.
     
  11. #12

    Expert

    Nov 30, 2010
    18,076
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    The questions I have often noticed on here is: How to get a microprocessor to control anything in the outside world. Processors don't throw much power so most of what you need is voltage or current boosters. Here are a few circuits:
     
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  12. Hextejas

    Thread Starter Member

    Sep 29, 2017
    187
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    Boy oh boy, there is a lot of good stuff here.
    The 1n4007 just happened to be on a scrap board that I had and it looked the same,

    The 14.5 DC that I have is from a desktop power supply for my ham radio. ( another new hobby )
    So much to learn !
     
  13. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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  14. tranzz4md

    Member

    Apr 10, 2015
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    Ohm's law: E=IR
    Translation: volts=amps x ohms

    Further simplified:
    (electrical) pressure= current x resistance
     
  15. Hextejas

    Thread Starter Member

    Sep 29, 2017
    187
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    Thank you kiss and the circuit in the link you posted is exactly the one that I am trying to build.
    In the past I have been able to build circuits by getting the proper components in place but I thought that this time I would try and learn what all this stuff actually does.
    The zener write up is very good.
    Now I need to learn how to read a data sheet
     
  16. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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    My father just "futzed" with stuff. TV's were valve/tube based and he could make a couple of bucks testing tubes and fixing TV's and me being a little kid learnt too. He repaired stuff, if he could for fellow co-workers. We had three electronics parts stores in the area. My first real piece of test equipment was a EICO TVM for Transistorized Voltmeter. He graduated to early tube and then transistor car radios, but had trouble understanding transistors, so I had to help.

    My forte' has been amplifier and instrumentation repair, but I can design stuff too now, so I can fix the short comings so the stuff won't break again. I can also tell the manufacturer that you made a mistake, e.g. Put a 10 A rectifier where a 40+ Amp one should go. That required a new transformer and rectifier that they replaced for free. We had a good relationship. Or tell Keithley Instruments that your brand new meter, destroys our samples. They were able to verify and created an external part immediately until a solid fix could be engineered and they fixed it.

    And high power/High Voltage anything. e.g. 13 kV @ 1.5 A regulated DC power supply and a 0.1 A 100 kV power supply for X-ray diffraction.

    I worked at the low end of the scale too. 4e-12 Amps at +-100 V and precision measurements around +-100 mA or less and between +-1.5V.

    Currently, I'm working on an OEM car amp that notoriously has problems. No one knows what the problem is. My few measurements:
    Remote signal drops from 12V to 0.22 when connected to the AMP. 34K resistance; inf / 0.9V diode test of the broken one in the car and the measurements were of the broken OEM amp that was replaced. Same problem. Works depending on temperature. The lower the better,

    Inspection revealed a cracked turn-on transistor. Next step should probably be remove and jump.

    Will I likely just replace it - NO! There is no positive spike protection, only negative voltages. That has to be remedied. You don;t use 16 VDC working voltage for a capacitor for a car. That has to be fixed, but there's clearance problems. I can upgrade to 25 V and surge protect real close to that. I may try to change the transistor to a FET.

    For sound improvement, I will try to upgrade the coupling caps and fix the thermal issues.

    The AMP isn't a bad idea. Differential inputs and differential out and the rear amp tells the head unit to output pre or speaker level outputs. The AMP is 4-channel and has a fixed equalizer for the car interior. But $300 to $400 for a new one. Yikes! And used ones break. I have to fix the root cause.
     
    Last edited: Sep 30, 2017
  17. Hextejas

    Thread Starter Member

    Sep 29, 2017
    187
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    Interesting problem Kiss and it sounds like it might be a bit of a challenge for you.

    Quote: You don;t use 16 VDC working voltage for a capacitor for a car. Endquote:
    I would love to be able to get my knowledge to the point where I could make that statement with
    the confidence that it would be believed.

    It reminds me of some of the coding I have seen by junior programmers that had me scratching my head.

    Anyhow, from reading the excellent article on diodes, the instructor wants me to measure the components and predict the various voltages and currents throughout the circuit,
    I am willing and eager to do this but I would like to learn what numbers from the diode data sheet I will need to use. Maybe there is a " Data Sheets for Dummies " book somewhere and i will go look gor it.

    In my example, 12v in, a 60ohm resistor, and a mysterious diode yielded 9v out.
    So, somewhere on the data sheet will be a .75

    Off I go.
    And I really appreciate your help.

    George
    KG5TKY
     
  18. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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    A first order approximation for a Silicon diode is that it will drop about 0.6 to 0.7 V across it. When things start to get complicated, diodes or PN junctions can be used as a temperature sensors. The datasheet fine tunes this, but usually it's not necessary. The material the diode is made of changes the assumed voltage drop.window

    And the assumption falls apart for diodes used in high voltage. The drop could be 10 V.
     
  19. Hextejas

    Thread Starter Member

    Sep 29, 2017
    187
    11
    Oh boy this is fun I say as I fan away the smoke !

    A few questions.
    1) I did not have a 5vdc supply but I do have a lot of 9vdc batteries laying around, so I thought that I could make a 4.5 supply by putting 2, 1watt resistors is series and grab 4.5v off of one of them. That seemed to work ok as my meter showed me 4.5v.
    So I wired up the rest of the diode circuit and then came the smoke. The 9v got kinda hot ! No sweat as i have tons of them.
    2) Given my exemplary circuit I expected that I had fried the diode. I tried to test it with my multimeter which has a diode setting but I get nothing. I can read resistance as 5.8m one way and 0 reversed.
    I had used the same meter before I started and in the diode setting it read .7v and 0 v.
    The diode is a 1n5231b.
    Did I fry my meter ? It seems to still work, all except for the diode setting.
    I think it was in the circuit when I powered it up. Oops.
     
  20. Hextejas

    Thread Starter Member

    Sep 29, 2017
    187
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    This is what I was building to.
    IMG_0204.JPG
     
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