Electric window blinds

Discussion in 'The Projects Forum' started by boatsman, Jun 18, 2014.

  1. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    Thanks to members assistance I have successfully built a 555 timer circuit with variable timing. The output from my circuit will be connected in parallel with a wall switch on/off/on which controls the raising and lowering of an electrically operated window blind. My problem is that when the circuit is automatically operated by a time clock the blind will wind up to a predetermined height. Then after 15 minutes (minimum time delay from the time clock) the electricity is switched off to the circuit. The next time the switch is activated the blind will rise until it is stopped by the motor limiter. Is there any way I can fix it so that the second time the relay activates it connects to the down side of the switch? Any advice greatly appreciated.
     
  2. elec_mech

    Senior Member

    Nov 12, 2008
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    Could you post a schematic of what you have thus far and a simple schematic of the blind switch (up/down/on/off)?

    I'm sure this is possible, we just need to be able to "see" everything first.
     
  3. inwo

    Well-Known Member

    Nov 7, 2013
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    A ratchet relay will change states with each 15 minute time-on cycle.
     
  4. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    Thank you inwo. I probably haven't explained my problem very clearly. I intend to use the circuit to raise the blind in the morning by means of a time clock and using the same time clock to lower the blind in the evening. My reference to the 15 minutes of the time clock was only to explain that I can't get a single pulse only a minimum time on of 15 minutes. The circuit I am using was posted on this site over a year ago, in reply to my query of 8/10/13
     
  5. inwo

    Well-Known Member

    Nov 7, 2013
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    I'll look for it.

    I think I understand correctly.

    By using the ratchet relay, each activation of the timer will reverse direction. 1 minute-1 hour on = no difference. Some accommodation may have to be made if coil heating is an issue.

    If I understand correctly, run time (distance) is set by your 555 circuit.

    Post complete circuit, to get better suggestions or solid state (flip-flop) version.
     
    Last edited: Jun 19, 2014
  6. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    I downloaded the circuit I am using from the projects forum sometime in October last year but I don't know how to put it on this forum. The switch for the blind is simply a single pole two-way switch with the centre position being off.
     
  7. inwo

    Well-Known Member

    Nov 7, 2013
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    Not knowing anything about your blinds or control voltage. Here is a relay logic solution using only two components.

    1-120vac from clock toggles direction and runs for timer set period.
    2-interval timer turns off power to motor.
    3-wait for next clock signal.
     
  8. elec_mech

    Senior Member

    Nov 12, 2008
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    I think I understand what the OP is doing and attempting to do. In essence, he's using a 555 with a relay to close a contact between the COM and UP position of his switch. I've drawn this in the top drawing. OP, let us know if this is correct.

    Building on inwo's idea of using a racheting or latching relay, I've drawn a possible solution, similar to inwo's I think. The 555 closes the first relay which allows power from the COM of the switch to go through to the COM of the second relay. The coil of the second relay is also connected to the 555, so each time the 555 goes high, the ratcheting relay changes states. This assumes the ratchet relay uses a small DC voltage to control the coil.

    I *think* this will work. Hopefully inwo will spot any flaws.
     
  9. inwo

    Well-Known Member

    Nov 7, 2013
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    Looks good to me!

    If we new the power levels, could probably put a FF in there.
     
  10. elec_mech

    Senior Member

    Nov 12, 2008
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    I was thinking the same thing. One could use a CD4013 configured as a T flip flop or even another 555 in bistable mode.

    I've assumed the power across the switch controlling the blinds (up/down) is AC based on the mention of a wall switch, hence the design above. If, however, it happens to be low voltage DC, oh boy, this could be made with a simple circuit quite cheaply.
     
  11. inwo

    Well-Known Member

    Nov 7, 2013
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    +1

    A little feedback will help!:D
     
  12. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    Thank you both for the advice. I don't know if it is of importance but my mains supply is 220 VAC 50 Hz. Is there any other way of making the circuit work without any extra relay? Is it possible to utilize the extra contacts on the relay? I want to be able to assemble the circuit including the time clock in a standard wall box inside the wall.
     
  13. inwo

    Well-Known Member

    Nov 7, 2013
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    A (selecting-DT) relay does not have an "off" position.
    The mind readers must not be online.:)
    What powers your 555 circuit?
    What relay? Voltage?
     
    Last edited: Jun 20, 2014
  14. elec_mech

    Senior Member

    Nov 12, 2008
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    This doesn't tell us much. Is this to say the blinds are powered directly from 220VAC or that 220VAC powers some type of power supply which outputs something less than 220VAC or even DC?

    OP, inwo and I are trying to work with you, we really are. But you must understand we can only provide solutions and answers if you provide information. As inwo mentioned, we can't read minds. :confused: The more information you provide, the better we can help.

    Thus far inwo and I have made some gross assumptions and you've provided next to zero information. We're working in a vacuum. I'm not trying to be harsh, but to really get helpful information from AAC, you need to answer some questions and provide specifics about what you already have, preferably a schematic.

    The simple answer, based on the little information we have and the aforementioned assumptions we've made, is no. You need one relay to switch between up and down and another to apply/remove power. This is based with the underlying assumption the blinds are powered directly with 220VAC. A little research shows some blinds are powered with 12VDC or 24VDC which would open up a lot of smaller options to do what you want.

    Draw something on a napkin, take a picture, and post it. If nothing else, take good, clear pictures of your built circuit and whatever powers the blinds and the wall switch. Also,

    What is the make and model of the blinds?

    What voltage is going through the wall switch? Is it VAC or VDC?

    What is the current going to the blinds when the switch is pressed (up or down)? If you don't know, hopefully knowing the power supply to the blinds will determine this.

    What is the part number of the relay you are currently using?

    Is this time clock the 555 circuit or whatever you're using to trigger the 555? Post a picture of it too.
     
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  15. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    The blind motor runs off 220 VAC 50 Hz.
     
  16. inwo

    Well-Known Member

    Nov 7, 2013
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    Then the relays may be the best.

    By the time you build a dc supply, logic circuits, and triac(ssr) switches, the two relay method will take up less real estate.
     
    Last edited: Jun 22, 2014
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  17. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    Thank you inwo. I see from your attached thumbnail that you are are using two micro switches back to back. This seems so simple the only snag being how to operate it with the 555 circuit. From what I understand from your previous diagram using two relays in series the first connects the current from the common of the On-Off-On switch to the common of the second relay. I can understand that when the first relay is energised it completes the circuit to either the up side of the mains switch; but what I can't follow is how it reverses the direction when the circuit is energised the second time by the time clock so as to lower the blind.
     
  18. inwo

    Well-Known Member

    Nov 7, 2013
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    You haven't given enough information to draw a complete schematic interfacing your 555 circuit.
    Heck, I don't even know anything about the timeclock.

    The ratchet relay is the key to toggling directions with each power impulse it receives.

    Picture a retractable ballpoint pen. Each time it is pulled in it switches. Also remembers (in or out) state mechanically.

    A complete solution, shown in last picture, is one ratchet/impulse relay for changing directions, and one time delay relay for setting run-time.

    Both can be controlled by 220vac directly from time clock.
    No other power supply or circuitry needed.

    It could also be ordered with a 12vdc coil allowing it to swap directions with each output impulse from 555.

    Electronic designs will get out of step upon power outages, unless there is feedback.
     
    Last edited: Jun 23, 2014
  19. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    Inwo thank you for your reply. I am using a 555 circuit that I received from this site over a year ago . Unfortunately the link to the circuit no longer exists and I don't know how to post the schematic that I'm using. Basically the circuit allows me to alter the time the 12VDC relay is activated from 1 second until about 30 seconds which allows me to control the amount the blind is raised or lowered. The time clock is a 220VAC narrow unit with the on/off contacts independent of the supply voltage. The time clock will not give a pulse but can be switched on for a minimum time of 15 minutes which is OK as I've tested it out and the circuit works fine. The problem I have now is how to change the direction of the 220VAC blind motor. The whole idea is that the blind will raise up automatically in the morning to a predetermined height and lower back down in the evening. If you can advise me how to post the circuit diagram it will possibly explain things easier, thanks, boatsman.
     
  20. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Below the Quick Reply box Click 'Go Advanced'. Scroll down. Click 'Manage Attachments'.
     
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