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Momentary closure (20ms), wait 1 second, and momentary close (20ms)

Discussion in 'General Electronics Discussion' started by BBourdage, Feb 10, 2013.

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  1. BBourdage

    BBourdage

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    Feb 10, 2013
    I need a RGB chasing light string to run a certain pattern, I have not been able to get any of the controllers to run the exact pattern unless I press and release the on button, wait 1 second, and then press and release the on button again. I am able to solder across the on button matrix pretty easily.

    Can anyone think of a simple solution for this ?. I need to have 4 individual strings controlled like this.

    Any help would be appreciated.

    Barry
     
  2. pwdixon

    pwdixon

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    Oct 14, 2012
    Write code to do it, what's the controller/setup?
     
  3. BBourdage

    BBourdage

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    Feb 10, 2013
    I am using the dc 99 controller, what programmer do you use that will do that many outputs ?
     
  4. pwdixon

    pwdixon

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    Oct 14, 2012
    As you are using a predesigned controller you'll be trapped by whatever sequence control that controller allows. Sorry I have no experience of these controllers, I would have been able to comment if you were designing your own controller.
     
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    I would use a reed relay, driven by a transistor that is driven by a monostable (e.g. a 555) in such a way that it activates the relay briefly on both positive and negative changes on the monostable output.

    You press a button to trigger the monostable; the transistor activates the relay briefly. After a second, the monostable times out and activates the transistor and the relay briefly again.

    Any words here you're not familiar with, look them up on Wikipedia.

    I'll draw up a circuit design if you want to go ahead with the idea.
     
  6. BBourdage

    BBourdage

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    Feb 10, 2013
    This sounds like exactly what I am looking for.

    A design would be great, thank you very much !

    Barry
     
    Last edited: Feb 10, 2013
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    What power supply voltage(s) are available? 12V would be good
     
  8. BBourdage

    BBourdage

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    Feb 10, 2013
    12VDC
     
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    [​IMG]

    Here's a nice simple circuit that should do what you want.
    The 555 is connected as a monostable. When you trigger it by closing the switch connected to pin 2, its output (pin 3) goes high (to +12V) and about a second later, returns low.

    The time is proportional to the product of RT and CT. Actually it would be better to use different values from the ones on that diagram:

    RT use a 1 megohm trimpot (aka preset potentiometer). You can adjust this with a screwdriver to get the exact delay you need.
    CT use a 2.2 uF capacitor with a tolerance of 5% or better. Something like
    http://www.digikey.com/product-detail/en/C1206C225J8RACTU/399-9333-1-ND/3522851 (multi-layer ceramic surface-mount part)
    http://www.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=CWR29JB225JCBC (tantalum surface-mount part)
    http://www.digikey.com/product-detail/en/R82CC4220AA70J/399-6027-ND/2704681 (probably your best option)

    Each time the 555's output changes state, C3 charges or discharges, generating a spike of voltage across the relay coil as shown on the waveform diagram. This spike is about 20 ms wide from the start until the point where it drops below about 2~3V, which is roughly the point where the relay will drop out.

    If the relay stays on too long, decrease C3, and vice versa.

    The relay I've specified is a very sensitive type, with a coil resistance of 2 kilohms and a coil current of only 6 mA. http://www.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=306-1292-nd. You could use a different reed relay with a higher coil current but you will need to increase C3 in proportion to the increase in current, to get the same pulse duration.

    The reed relay must NOT have an internal diode in it. (Some reed relays have diodes built in.) This is because the coil is energised with both polarities in this design. If you use a relay with a diode across the coil, it will only activate in one direction.

    Also, add a decoupling capacitor (another 4.7 uF electrolytic will do) across the power rails near the 555.
     

    Attached Files:

    Last edited: Feb 11, 2013
  10. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    [​IMG]

    This diagram is a bit clearer.

    I've changed CT to a 1 uF capacitor, either a surface-mounted multi-layer ceramic, or a through-hole part (probably better), and replaced RT with a 680k fixed resistor in series with a 500k trimpot. Set the trimpot to get exactly the required delay between the two pulses on the relay.

    I've also shown the decoupling capacitor across the power rails. The value is not critical so I've specified 0.1 uF, the same as the decoupling capacitor on pin 5 of the 555.

    And I've renamed C3 to CC, and replaced the switch with some text (this just simplifies my simulation of the circuit).

    Everything else is the same as in the previous post.
     

    Attached Files:

  11. BBourdage

    BBourdage

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    Feb 10, 2013
    Amazing !!!.

    I am going to get parts today and try one.

    I am a bit confused on where the output for the contact closure is ?.

    is that one side of the coil, and ground ? or where the two lines go off on the left hand side ?.

    Thank you for all of your help.

    Barry
     
  12. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    The inductor marked L1 represents the coil of the reed relay. The contacts of the reed relay aren't shown; they need to be connected across the start/stop pushbutton in the controller. Sorry for not being clear about this.
     
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