Switching BC 547 with CMOS signal output

Discussion in 'General Electronics Chat' started by formax, Nov 26, 2010.

  1. formax

    Thread Starter New Member

    Nov 26, 2010
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    can someone please help me with the values of the following Schematic?
    I want to switch three relays using the three outputs (pin 4,5,6) of 4060B
    R1?
    R2?
    or please advice me if the components should be re arranged or should be added or removed.


    [​IMG]
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    What is the final application of this?

    This could be simpler with a 555 timer.
     
  3. formax

    Thread Starter New Member

    Nov 26, 2010
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    Im going to use this for light three pairs of Christmas bulbs strings at three different rates. Yeah its little bit odd. but this way i can use any type of bulbs or diodes through the relays.

    i selected this circuit because as i know, (Im a beginner) 4060 has a different pulse rate for each output. i think it will look nice when three flashing pairs of strings sparkling on my Xmas tree than four channel running system?. No?
    its hard to me understand those formulas. i appreciate if you have any suggestions. if this circuit is wrong,
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    A 3 volt relay requires a lot of coil current. Most of that current will go toward unnecessary heating of R2. You should try to match your relay to your supply voltage, or vice versa. If you do this, R2 is unnecessary.
    Even 6*1.5V AA batteries will not last long with 3V relays. Also, BC547 may not work, depending on the coil current requirement of your 3V relays.
    The 4060 will have a square wave (50% duty cycle) on each pin. Pin 5 will have the highest frequency. Pin 4 will switch at exactly half the rate of pin 5. Pin 6 will switch at exactly half the rate of pin 4. For example, if the LEDs driven by pin 5 flash 4 times per second, then the pin 4 LEDs will flash twice per second, and the pin 6 LEDs will switch once per second. You can change the flash rates by changing the setting of the 47k pot (variable resistance), but the 4:2:1 ratios will remain the same. You can change the range covered by the pot by changing the 0.1uF capacitor.
    Is that what you want?
     
  5. formax

    Thread Starter New Member

    Nov 26, 2010
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    Well, if i change the power source to 3v the circuit wont work. it need at least 9v. the output pulse rates are fine. I got just like you said.

    I suppose to use a 9v 150 mA power supply. So which transistor should i use to make the relay work? im totally out of calculations.
    So can you Please tell me these?

    The transistor that i should use,
    R1
    R2
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    What is the resistance of the coil in the 3v relay, or the rated coil current at 3A?

    We can't tell you what to use, unless you tell us what that is first.

    I'd use a "wall wart" type supply instead of a battery. You're going to be spending a LOT of money on batteries.
     
  7. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Why don't you choose a 9V relay? It will require a lot less current, and you can use your BC547.
     
  8. formax

    Thread Starter New Member

    Nov 26, 2010
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    Dear sir,

    unfortunately i already have the relays.
    its JQC-3F(ATT73)
    5A28VDC 10A28VDC
    7A240VAC 10A125VAC
    SHR-3VDC-2008
    thats how printed on its case. i cant find out the rated coil current.
    my power supply is an AC/DC power adapter. 9v 150mA

    is this information enough to tell me what transistor and the two resistors i should use?
    thanks
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    According to the relay datasheet, coil power is 360mW. This means the coil current will be 120mA. To drive most BJTs into saturation, you need Ib=Ic/10, so the base current would need to be 12mA. CD4060 cannot provide that much current from an output.
    I would recommend changing the transistor to an N-channel MOSFET. Do you have any? If not, can you get some?
    Also, all three relays will sometimes be on simultaneously. This means your 9V power supply needs to provide up to 360mA.
     
  10. formax

    Thread Starter New Member

    Nov 26, 2010
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    sir
    1. which mosfet should i have? if it is a commonly used one, i must be able to get em from a local store. would you please recommend?

    2. yes i can find a over 360mA 9v power supply too. i think 450 or 500mA may fix the problem.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    Well, he could use one BC547 as a voltage follower to source base current for another BC547; if our OP already has a bunch of the BC547s and some resistors, they could use them. See the attached schematic & simulation.

    R3 is shown as a 1W resistor, but actually should be rated for 2W.

    IRLD014 or IRLD024 MOSFETs would work great for this application, but since we don't know where you are, I don't know if you can obtain them. In the States, you can order them from places like Digikey, Avnet Express, Mouser, etc.
     
    Last edited: Nov 29, 2010
  12. formax

    Thread Starter New Member

    Nov 26, 2010
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    sir , if i couldn't find any of above mosfet, i think its better using two BC 547s. (im a sri lankan) Its bit difficult to find some components here. but BC547 is cheap and available.,
    i will post here if i found the mosfet.
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    You should put your location information in your profile.
    Click on the "User CP" link at the top.
    On the next page, scroll down to "Location", and type "Sri Lanka" in the box provided.
    Then scroll to the bottom, and click the "Save changes" button.

    I have no idea what might be available in Sri Lanka, but you obviously can get the BC 547 transistors, which is why I posted the schematic for them. Resistors are usually very cheap. It means more soldering connections, but it should work just fine - if you use the values shown. 1/4W resistors will work fine for all except the 51 Ohm resistor, which should be rated for 2 Watts. Alternatively, you could use a 6v incandescent light bulb rated for 900mW.
     
  14. formax

    Thread Starter New Member

    Nov 26, 2010
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    sir,
    many thanks for the schematic. Now i can start the project from where i stopped.
    thanks again.
     
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