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Project - Conveyor system using 555's

Discussion in 'General Electronics Discussion' started by Mecha_Tronic, Apr 19, 2014.

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  1. Mecha_Tronic

    Mecha_Tronic

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    Apr 19, 2014
    Hello everyone, I'm new to the forum and i know very little about electronics.I'm trying to solve my doubts about my project and would appreciate it if you guys could help.The thing is: I'm doing a project for my course involving a conveyor system, and these are controlled by a two CI555's in the monostable mode,and they will turn on for about 10 seconds by using a push-button switch.The problem is that the motors that control the conveyors will consume together about 600mA of current, and from what I saw the maximum output of the CI555 is 200ma.Is there a way I could amplify the output current of the 555 to meet the consumption needs of the conveyors or some other integrated circuit that is similar to the 555 in monostable mode and has a higher output current? Thanks guys.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    A simple transistor can boost the output current sufficiently for your motor's requirements. An example is here (ignore the 555's circuit, it's the transistor circuit that's important for you) or Google "555 motor control" (without the quotation marks). You will be shown lots of pages that use similar technology to boost the 555s current using MOSFETs (like the page I linked) or bipolar transistors.
     
  3. Mecha_Tronic

    Mecha_Tronic

    4
    1
    Apr 19, 2014
    I did some research about bipolar and MOSFET transistors and i saw someone talking about relays so i looked into that too.I found that relays can be used to trigger higher current and voltage circuits since the coil is separated from the switch,and it uses much less eletrical energy for the coil to close the switch,than the circuit or component connected to it requires to function (wich is exactly my case).Can i use a relay connected to the 555 and a adjacent circuit containing both motors so the 555 will activate the relay,and then the relay will activate the adjacent circuit for the pre-defined time in the 555's circuit?Is this fine or is it more pratical to use a transistor?I didn't really understand how a transistor amplifies current so i'm still looking into that.
     
    Last edited: Apr 20, 2014
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Yes, you can use relays. Drive the relay coil from the 555's output, and connect a diode across it as in these circuits:
    http://encrypted-tbn2.gstatic.com/i...26jf4gJMY6yuEuBfPszbC0vW0gosLLFSJBeRD79Wc442A (relay activates when 555 output is high)
    http://encrypted-tbn1.gstatic.com/i...NXzki0BW7QNmCYOYletrzV2KnWqDlreXbrtZpqLIsTtdO (relay activates when 555 output is low).
    The relay coil must not draw more than 200 mA (under 100 mA is better) and should have a rated voltage equal to, or a bit less than, the power supply rail voltage.
     
  5. Mecha_Tronic

    Mecha_Tronic

    4
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    Apr 19, 2014
    Thanks for the reply.I cant access the links for some reason.
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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  7. zulkarnain

    zulkarnain

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    Apr 19, 2014
    i made this circuit for u which can sport up to 1 amp current
     

    Attached Files:

  8. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Thanks for trying to help, but...
    1. The OP is using his 555s as monostables, not astable oscillators; your circuit shows an astable oscillator;
    2. Your circuit cannot provide 1A because the 2N2222 is only rated for 800 mA collector current (600 mA from some manufacturers). Even if it was rated for 1A you would not operate it at 1A, especially into a motor load, because motors draw extra current when they start up.
    3. Your circuit also cannot provide 1A because the 2N2222's base current is less than 600 µA. At the minimum specified current gain of 40 (for the STMicroelectronics 2N2222), this amount of base current corresponds to about 23 mA collector current. If you try to draw 1A through its collector-emitter path, the transistor will not pass that much current. The voltage across the load will be very low, and the transistor will overheat.

    You could increase the maximum output current by reducing RI and deleting RI1 (it isn't needed), and/or replacing the transistor with a Darlington, or with a MOSFET (that can be driven directly from pin 3, eliminating the need for RI, or preferably through a low-value series resistor).

    Other changes you should make are: (a) remove R1 between the RESET pin and VCC as it isn't needed; (b) add a reverse-connected diode across the motor to protect the switching device agianst possible back EMF from the motor, and (c) add at least one decoupling capacitor on the 555 from pin 8 to pin 1 to help the 555 operate more reliably.
     
    Last edited: Apr 21, 2014
    Arouse1973 and zulkarnain like this.
  9. zulkarnain

    zulkarnain

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    Apr 19, 2014



    bro your anser is the perfect anser i have have ever lisent to and it perfect anser to this . . . . .i think i will get a lot to learn from u . . i had actualy made this ciruit for produccing sound . . . and just modifided for this .and i dident notesed that needed monostable mode . . . . and also metal caned pakeg of 2n222a provides a amp current
     
  10. zulkarnain

    zulkarnain

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    Apr 19, 2014
    now this circuir will sport upto 5 amps of current
     

    Attached Files:

  11. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    That's better. There are still a few errors.

    1. RT1 shouldn't be there, obviously. It will limit the motor current to about 1 mA!

    2. If the load is inductive, when the transistor turns off, the peak current through D1 could be as high as the operating load current. If that is 5A, you should use a bigger diode than a 1N4007. For example, a 1N540x will handle up to 3A. These diodes can withstand much higher pulse currents than the continuous rating, so a smaller diode may be suitable if the load inductance is small.

    3. If you want to drive the transistor's base directly from the 555, with a pullup resistor, you need to use pin 7, not pin 3. If you want to use pin 3, you need to connect the resistor between pin 3 and the base of the transistor, and no pullup resistor is needed.

    4. That circuit is not strictly a triggered monostable. It's closer to a "delayed release" circuit. While the pushbutton is held down, the load is kept energised. When the pushbutton is released, the circuit keeps the load energised for a short extra time, determined by RT and CT.

    5. You should have at least one decoupling capacitor between pins 8 and 1 of the 555.

    6. Voltage drop across the transistor will be significant because it's a Darlington. The TIP122 (Fairchild's version) states Vce(sat) is up to 2V at 3A with 12 mA base current, and up to 4V at 5A! So firstly, at 3A and 5A the load is only guaranteed to see 10V and 8V of the 12V supply voltage, and secondly, the transistor will dissipate significant power - up to 6W at 3A, and up to 20W at 5A, so it will need significant heatsinking. These problems can be eliminated by using an N-channel MOSFET with a low ON resistance.
     
    zulkarnain likes this.
  12. zulkarnain

    zulkarnain

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    Apr 19, 2014
    i think is appropriate to use RT1 their because ti provide bisaaing voltage. . because in the flip flop inside at 0 it is connected to ground and at 1 i is connected ti vcc and it can early delver 50 mA current to drive the transistor


    1n4007 has a normal current rating of 1 amp so it is sufficient to sport the 600 ma load curret


    i agery it is collser to delay releasr circuit

    he can also use bd139 insted of tip 122. . . (bd139 sports 1.5 amps current ) and is not darlington
     
  13. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    RT1 isn't used for biasing. It's in series with the motor.
    You said the circuit can switch up to 5A. Not 600 mA.
    Not without providing a lot more base current. The minimum current gain for a BD139 is only 40. That's why I suggest using an N-channel MOSFET.
     
    zulkarnain likes this.
  14. zulkarnain

    zulkarnain

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    Apr 19, 2014
    but by simply ussing MOSFET he will get 180 digree phase shift
     
  15. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    An N-channel MOSFET connected in place of the transistor, with gate=base, drain=collector and source=emitter, will behave similarly to an NPN transistor. When the gate is driven positive, the MOSFET will conduct current through its drain-source path and the load will be energised.

    The main difference is the input characteristics of the MOSFET. Google MOSFET characteristics and behaviour to learn more about them.
     
    zulkarnain likes this.
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