simple auto battery charger by 555

Discussion in 'The Projects Forum' started by ahmed115, Mar 7, 2014.

  1. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    hi
    this is my project for auto battery charger by ic 555

    [​IMG]
    the componant
    12 v relay
    ic 555
    q1 - bc338
    D1 , D4 red and green led
    1N4732-4v7 zener, 1N4734-5v1 zener
    10nf capacitor represent the battery
    10k the load of battery
    5r charge resistance
    this is a video
    https://www.youtube.com/watch?v=QOu3fTdJKys
     
  2. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    i would like to discuss any suggeswtions to make the project without mistake
    if any friend found any thing wrong in the circuit please comment
     
  3. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    the same circuit by connecting the relay on disscharge pin

    [​IMG]
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    The only quick thing I see is there should be a capacitor (0.1µF or so) on pin 5 to ground.

    Also, is the 555 OK with 15V? I don't recall but I would be tempted to start with just 9V or so until I was sure everything was working nicely. Something that may survive 5-9V for a few seconds will go poof at 15V.

    You may get more feedback if you describe the function of the circuits and ask more specific questions.
     
  5. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,034
    1,639
    The standard 555 timer IC is usually rated for 16 volts but most are robust enough to run at 20 or so without problems.

    I have seen that happen in a number of circuit is where the primary 12 DC regulator IC lost its grounding connection.
     
  6. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    thank you for your comment
    the 0.1 μf not important her
    555 is ok with 15 v
    the circuit charge the battery for 14.3 v and reset to allow to battery to connect to the load ( i put 10k ohm only for the samulation)
    when the voltage of battery down to 9.5 v the 555 make set across pin 2 anad again charge across the charge resistance 5 Ω(u lemit it as your battery capacitance)
     
  7. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    Is the relay OK without current limiting, and will the coil current stay below 200mA (the 555 pin 7 rating)?
     
  8. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    u must put resistance in series to take the voltage difference between the source and coil voltage
    =15-12=3 v
    R = 3/0.15 =20Ω
     
  9. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    i do not know the max current of discharge pin 7
    u can use the output 3 insteade as the first circuit with transistor if aproblem happen from connection to pin 7
     
  10. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    this site :
    http://www.sentex.ca/~mec1995/gadgets/ne555.htm



    Absolute Maximum Ratings:

    Lead temperature (soldering, up to 60 sec) 300 °C. Supply voltage for SE555 +18 volt. For NE555 & SE555C +16 volt.
    Discharge current (pin 7) is 200mA.
    Power dissipation 600 milliWatts. For the MC1455 is that 680mW.
    Operating temperature range for NE555 0 to 70 °C, for SE555 & SE555C -55 to -125 °C.
    Storage temperature range from -65 to -150 °C.
     
  11. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    important notice
    u can use this circuit for auto charge for different batteries voltages not only 12 v battery by changing the power source ( voltage regulator ic like lm317 ) and changing zener diod and u can also use diod for accurate voltage value with the zener
    and u can also use diod only if the voltage differnece between charge voltage and seperating voltage is afew
     
  12. AfdhalAtiffTan

    Active Member

    Nov 20, 2010
    117
    11
    In your circuit case,
    With 15V supply, and no modification on 5th CV-pin:

    The trigger-pin will drive the output HIGH when the voltage falls below 1/3Vcc on pin 8, in this case, 5V.

    The threshold-pin causes the output to be driven LOW when its voltage rises above 2/3Vcc, in this case, 10V.

    With proposed zener-diodes, making the relay turn-on when the battery drops below 10.1V, and turns-off when reaches 14.7V.

    I can't see any problem here.

    Improvement maybe on the stability of the reference voltage.
     
  13. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    this is my design and i am aske about any thing not normal may be u and other fried found it and so
    i see that the circuit is good
    with respect to pin 5 it not importanat to connect capacitor in this circuit
    thank u
     
  14. AfdhalAtiffTan

    Active Member

    Nov 20, 2010
    117
    11
    When I said reference voltage, it doesn't mean only the 5th CV-pin.

    Other than the Vcc stability, the zener voltage is highly affected by temperature, which is not good for any reliable test result.

    What you've done is a crude battery plate conditioner, cycling charge repeatedly.

    As previously mention, there's no flaw that I could think of, it's another creative use of 555 chip. :)

    If I really need to guess, I would suggest adding a pull-down resistor each at both 2nd and 6th pins to avoid any stray charge holding the voltage.

    Those zeners might need some current to flow to induce voltage drop.
     
  15. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    zener is affected only by volatge and have amaximum current
    if the voltage of the battery is high than zener volatge it will be pass current that limitted by input resistance of the pin
    thank u
     
  16. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    Some observations:
    1. I see that the load is not connected during charging. Is that what you want? To avoid this you could use another set of contacts to switch the load from battery to 15V during charge. Of course, 15V would have to be okay for the load to handle. If the load is very small like 10KΩ then you could leave it connected to the battery all the time.
    2. The test load is very small, but if it was 10Ω then some load current drops across R4 (5Ω), which is significant. Is that what you want? To avoid this, move R4 to be between the relay contact and +15V.

    Have Fun,
    Ifixit
     
  17. AfdhalAtiffTan

    Active Member

    Nov 20, 2010
    117
    11
    It seems like you know everything.
    Have constructed the circuit in real life yet?

    I simulated your circuit with LTspice, and it shows that some reverse-current is needed in order to get the desired voltage drop.

    But, it could be another spice simulator limitation though...

    You asks us for any correction to be made, and you seems to deny every single suggestion with your fact, which is fine, but, what did you really expect?

    You previously said to look for anything 'not normal'.
    Now, define: what is normal to you?

    I watched your video, and everything is ok to me.
    You even made a discrete logic for 555.

    My simulation also says it will runs fine.

    What kind of answer did you expect from us?
    Improvement? Flaw? Tweak?

    As I mentioned before, it's one of the creative use of 555, which is feasible, and I believe the internet could appreciate you to share the circuit, but again, what did you expect from us?

    I'm blurred...
     
  18. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0

    [​IMG]



    it is good idea to make the load connected to the supply during charging and also good idea to make the charge resistance out of battery durring loading
    thanks for your good suggestions
     
  19. Metalmann

    Active Member

    Dec 8, 2012
    700
    223

    Looks like a cool charger circuit, but in the video....way too many "Uhs"...
    very distracting.:confused:
     
  20. ahmed115

    Thread Starter Member

    Dec 21, 2013
    32
    0
    if u can added more improvement i will thanks for u
     
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