Voltage Addition

Discussion in 'General Electronics Chat' started by khanz, Apr 7, 2008.

  1. khanz

    Thread Starter Member

    Mar 24, 2008
    21
    0
    Hi all,
    I am just a beginner. I want to design a circuit that add's two voltages. How can I do this. I tried 741 IC with input of 1k ohm Resistance but it's not working.
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
  3. khanz

    Thread Starter Member

    Mar 24, 2008
    21
    0
    Thanks but it's not working. I have already tried this. I am using a +12V and -12V DC on the 7 and 4 input of LM741 Respectively. And for the input at the non-inverting input I am using a 1K ohm and 2 K Ohm reistance. And for the supply for those inputs I am using adapter of different milliamperes. One is 500mA and the other is 400mA. But still it's not working. What should I do. If I don't want to use LM 741. What else I have an option.
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Can you please post a schematic so that we can see the circuit hookup you have attempted to describe?

    hgmjr
     
  5. khanz

    Thread Starter Member

    Mar 24, 2008
    21
    0
    Instead of using LM741 Now I am using this circuit. Please look at this. Will it work properly.
     
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  6. khanz

    Thread Starter Member

    Mar 24, 2008
    21
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    For the Voltage addition I am using only two resistors now shown in the above reply. Will it work. As through multimeter I have seen the voltage addition. It works properly. Can you tell me what will be drawback of this circuit. If it's OK can I use it in my control panel.
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    I don't quite see the necessity of the resistors. Stacking two batteries for a higher voltage should work just fine. If it's something like a reference voltage, then it should work.
     
  8. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    The milliampere rating of your adapters is an indication of the maximum current they are able to provide - not necessarily the current they will provide in a given application. The actual current drawn from them will depend on your load resistance. I = E/R where I is the current in Amperes, E is the EMF in volts, and R is the load resistance in Ohms.

    Based on your drawing, total EMF is 12V, and total resistance is 3.0K so total current will be 12/3000 = 4 milliAmps. "Stacking" the power supplies will work in this instance.

    One cautionary note: I'm assuming the adapter outputs are isolated from earth ground. If this is not the case, then one of the adapters will be shorted out.
     
  9. khanz

    Thread Starter Member

    Mar 24, 2008
    21
    0
    The Full circuit Diagram is like this, Now is it correct or not, will it work properly and what about the current. I have already made the circuit but the 6V transformer is heating, why it's happening.
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The way to produce a larger variable voltage is to tie the secondaries together at one point to make a common reference. The end points will be, in effect, the end points of a transformer with a higher voltage rating. Then you can rectify and use that voltage as your variable source. The secondaries have to be phased properly, which is difficult unless the leads are marked.

    That method will always cause problems with current. The amount you can supply will be quite limited and will vary as the load changes. That is why it's more atisfactory to use a voltage regulator like the LM317.
     
  11. khanz

    Thread Starter Member

    Mar 24, 2008
    21
    0
    The Circuit with +ve and -ve signs is like this, now what you suggest, and how to use LM317, would you suggest the use of potentiometer is not a good one, Please help me, I did my best, but stuck here, how to move forward on this project.
     
  12. sayem

    New Member

    Apr 26, 2008
    1
    0
    Mate!

    Can any one give me a better idea about 3 phase supply line 440V, 50Hz. There is no neutral line on it. How can I use this power for my 22OV lighting Circuit?

    Thanks SAM
     
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