Amplifying current after a 4017IC

Discussion in 'The Projects Forum' started by Stills00, Feb 27, 2010.

  1. Stills00

    Thread Starter Member

    Feb 16, 2010
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    I am building a Road construction Light bar and need some help! I have built three different circuits to get my lights what i want them to do. Two of the circuits are 555 and 4017 circuits (for the left to right flashing) and one is a double 555 and relay to get my Wig Wag effect. Everything works fine and looks great but i am having problems lighting the lights on the top of the truck. I need more current coming from the 555 and 4017 circuits. I need to amplify the power and cant figure out the correct transistor and necessary resistors to power both my in truck display and the lights on the top of the truck? I dont know how to draw up a schematic but i can post pictures of what i have and can explain what everything does.

    There are two different project boxes one is the control box with 10 Led's on the cover along with three different sweitches. One is a three way switch that controls the left and right and the red switch contols the wig wag the smaller one on the right is the power on or off. The Wig Wag powers the lights on the top of the truck fine but it is the other two Left and Right curcuits that need more power to power the lights on the top.

    My problem is that i have to power the LED's on the control pannel and the ones on top. I added four 2N3904 Transistors trying to get the power up but when i do it makes the light on the display constantly on... So what resistor values do i need to make the light turn on and off but still amplify the current to the 12 LED lights on top of the truck? (There are 2 lights with 6 LED's on each output of the 4017) I have two lights connected to each output, it looks better. So instead of having the 4017 count through all 10 individually it only counts through 5 and flashes two lights at once. The whole thing is powered by 12v and im having problems. Please help me out i have tried to understand the calculations for my transistors but cant seem to get it right.
     
  2. soda

    Active Member

    Dec 7, 2008
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    At the output of your 4017 you use In4148 diodes forward bias to protect the 4017. This then go to NPN darlington transistors like MPSA14(800mA Ic) or KSP14 . Use 1k resistors at the base of the darlingtons. If it's necessary, you can add small relays to the output of the darlingtons. You connect the relays between the collector and the supply rail. Remember to add the 2 protecting diodes across the coil terminals of the relays.
     
    Last edited: Feb 27, 2010
  3. soda

    Active Member

    Dec 7, 2008
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    I attached a diagram for you. This was actually use to drive a display but use this so you can see how to connect the darlingtons.
    I hope i was able to help you
     
    Last edited: Feb 27, 2010
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Schematics are the "language" that most of us speak. They answer thousands of questions. If you did not make the original schematic(s) for your project, then please indicate where you found the schematics, or at least scan and post them. This will help us to help you much more quickly.

    Nice description, but a schematic could've said all of that along with eliminating any possible ambiguity with really very few words written.

    OK,
    The 4017 normally has all but one output low (near ground/Vss) and one output high (near Vdd/Vcc/+12v). Unfortunately, the 4017 IC can source (output) very little current. If you tried to drive 2N3904 transistors directly from the outputs of the 4017, you would place a very heavy load on it. Transistors need current limiting resistors on their bases.

    We really need to know more about your light bar. What I'm thinking at the moment is that you could use the 4017 to turn on commonly available N-channel MOSFETs like the IRF510, which would sink current from your lightbar. The leads that are now being used to source current to the lightbar would need to be connected to +12v, and the ground side of the lights in the lightbar would be switched by the MOSFET.

    This is actually how it's typically done. If you want to power the LEDs how you have them wired at the moment, it will be lots of extra work.
     
  5. Stills00

    Thread Starter Member

    Feb 16, 2010
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    Thanks Guys Thats A lot of help Where can i make a Schematic? i can make one and include the websites i found my ideas from later this week.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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  7. soda

    Active Member

    Dec 7, 2008
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    sgtwookie

    To safe time i do all my work the way i show it here. I do all my diagram myself. I usually tried not to use other peoples diagrams because all for my own reasons. If you don't like my way of doing things, then call on my name next time when you speak about using schematic.
    If you wasn't talking to me, then please just ignore this reply
     
  8. Stills00

    Thread Starter Member

    Feb 16, 2010
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    I asked him to give me information on Schematics nothoing involving you... your Schematic you provided Soda is very Usefull....So thank you
     
  9. Stills00

    Thread Starter Member

    Feb 16, 2010
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    Ok so i am working on a Schematic so you can get what i am doing and will post it soon. So what your saying is that i cannot use what i have set up? it will put to much strain on my IC and wont work?
     
  10. Stills00

    Thread Starter Member

    Feb 16, 2010
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    Ok here it is!! hope it helps. Im trying to increase the current to the lights on top of the truck, (top of immage). Any ideas would be great !
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    Soda,
    The schematic software suggestion was for our OP. What works for you, works for you. However, you might find the software I suggested convenient for you, after you have gone through the "learning curve".

    Stills00,
    Since your LED's are already wired up so that current has to be sourced to them rather than sunk from them, you need a source-type driver for the 4017's.

    This is one way to do that:

    [​IMG]

    Only one output is shown to keep things simple. You will need one NPN Darlington and one PNP transistor with the associated resistors per output channel used.

    It may be easier to change your lights so that you can sink current from them, rather than source current to them. In that case, a ULN2804A could be used (one per 4017, if you are using 8 outputs or less) to sink current at the 4017 end.

    If you need more than 0.5A per channel, the 2N2907A transistors could be replaced with P-channel power MOSFETs.
     
  12. Stills00

    Thread Starter Member

    Feb 16, 2010
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    When you say sink current from them what does that mean? I understand sinking current to them but how do you sink current from them?
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    When you are sourcing current to a load, you are supplying a more positive voltage, and the load (your LEDs) has a ground on the other side of it (the cathodes)

    When you are sinking current from a load, the load (your LEDs) has the positive supply on the anodes, and you are sinking current (applying a ground) from the other side (cathodes).

    In either case, you'd still need current limiting resistors on each LED.
     
  14. Stills00

    Thread Starter Member

    Feb 16, 2010
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    I get what your saying, but how could I turn my circuits into Negative output instead of positive output?
     
  15. Stills00

    Thread Starter Member

    Feb 16, 2010
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    By the way thank you! you really know your stuff!
     
  16. Audioguru

    New Member

    Dec 20, 2007
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    Hi Stills,
    The LEDs on your schematic are shown upside-down. Their anodes are connected to ground instead of their cathodes.
     
  17. Stills00

    Thread Starter Member

    Feb 16, 2010
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    Thanks i will fix that hahaha it was my first Scematic so i will fix that thanks! Any thing else wrong?
     
  18. Stills00

    Thread Starter Member

    Feb 16, 2010
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    Ok here is the new Schematic So if i add MPSA14 and 2N2907A to each of the outputs then i will increase the current to each Channel? and the LED's and Lamps will both Light up and Shut off when the 4017 tells it to?
     
  19. SgtWookie

    Expert

    Jul 17, 2007
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    Try using the Erc function. It's under Tools/Erc; it's also on the tool panel to the left.

    When connecting a single wire to a component pin, you do not need to use a junction (the green dot). However, if you are connecting a wire to another wire, or multiple wires to a component pin, you need to use a junction, or Erc will complain about it.

    You must connect wires to the ends of pins. Erc will complain about the wires for D1 overlapping the relay coil wires on K1, for example.
    IC4 (555 timer) - R5, the 33k resistor, has a junction on the left side, which is proper. You don't have a junction on the right side, and ERC will complain about it.

    C4 has a wire running through it.

    Use more +V and GND symbols rather than running wires for them everywhere.
     
  20. SgtWookie

    Expert

    Jul 17, 2007
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    Yes, if you add them in as I've shown.

    Manufacturers used to make what were called "source Darlington arrays", however nobody stocks them anymore. Everyone has gone to ground-side switching (sinking current) rather than sourcing current, as it's much easier to control.
     
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