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Automated Sliding Door

Discussion in 'General Electronics Discussion' started by rbjarema, Dec 2, 2013.

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  1. rbjarema

    rbjarema

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    Dec 2, 2013
    I am new to this forum and just starting to get into the electronical side of things.

    I would like to make a sliding door that automatically opens and closes at set times. For example I would like to have the door open at 8 in the morning and stay open until 8 at night when it closes. I would like this to repeat every day of the week.

    I am currently looking at purchasing a 12v DC motor. With this I believe I will be able to perform CW and CCW rotation out of it. I have looked at putting limit switches at each ends of the door to stop it when it becomes fully open or closed. I also read up on putting a 3 pole relay in so the rotation direction will change when it hits the limit switch. But the issue is that will cause it to be continuous back and forth, in which I am looking for it to start/stop then start/stop.

    I appreciate any advice and if this explanation is not clear let me know.

    Thanks,
    Bob
     
  2. duke37

    duke37

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    Jan 9, 2011
    I think this can be done with three relays.
    One to turn on forward and latch, limit to turn off
    One to turn on reverse and latch, limit to turn off
    One to change over the motor polarity, connected to either forward or reverse relay coil to define direction.
     
  3. rbjarema

    rbjarema

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    Dec 2, 2013
    Thanks for the reply Duke. I know this is going to sound dumb, but am I looking at writing code or using something like Arduino for this to work.

    I was hoping that I could use a store bought timer, like a lawn sprinkler, and add in some limit switches and relays. After doing some more research I dont think it is going to be that easy though??
     
  4. duke37

    duke37

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    Jan 9, 2011
    I am sure it can be done with relays and a timer. It would be simpler to use a timer with two outputs if they exist, to activate open and close.

    If you go the Arduino route I cannot help. It is 30 or 40 years since I programmed a microprocessor.
     
  5. KMoffett

    KMoffett

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    Jan 21, 2009
    You didn't say anything about how this door is to be used...for people?...for chickens?
    You might want to think about a safety mechanism/circuit to prevent someone of something getting stuck in the door as it closes.

    Ken
     
  6. rbjarema

    rbjarema

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    Dec 2, 2013
    The door will be used for animals and will have it close at a slow enough speed. The animals will have plenty of time to move if they are in the way and feel the force of the door.
     
  7. rbjarema

    rbjarema

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    Dec 2, 2013
    I have come across a timer that is TORK DTU40. I have been reading up on it and it looks like it might do the trick. Below is a link with all the different wire configurations for the timer. I was looking at the one configuration that allows one heater to be on and one heater to be off. The problem I see is that it shows 240v supply which I dont have. Do you think this could be made to work with different configurations than shown??

    http://waterheatertimer.org/How-to-wire-Tork-DTU40-timer.html
     
  8. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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  9. rbjarema

    rbjarema

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    Dec 2, 2013
    Kris,
    Thanks so much for the reply. I was really hoping that this would work. I do have a 12V DC battery currently. Still looking for a 12V DC motor and suggestions on which limit switches to buy. If you could draw up a diagram I would greatly appreciate it.
     
  10. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    OK, here's my suggested connection diagram.

    [​IMG]

    I hope you can read it!

    AC mains comes in on the left, and feeds the DTU40 timer and the 12VDC power supply, which provides 12VDC for the motor. The DTU40 accepts 115VAC and 230VAC.

    The timer must be programmed so that its output is ON during the time that you want the door OPEN, and OFF during the time that you want the door CLOSED.

    The 12VDC output from the power supply is fed to the motor through the two changeover relay contacts in the DTU40 and the two limit switches. There are two separate paths.

    During the time that the door is to be OPEN, the timer is ON, so its "C" (common) terminals are connected to its "NO" (normally open) terminals. The positive output from the power supply enters the timer on the "C" terminal of the right hand connector and emerges on the "NO" terminal next to it. It then flows left and down to the negative terminal of the motor. Therefore the motor turns in REVERSE. The other side of the motor connects through the FULLY OPEN limit switch, back to the "NO" connection on the left hand connector, out on the "C" terminal and back to the negative of the power supply.

    In this state, while the door is not fully open, the FULLY OPEN limit switch is closed (short circuit) and current flows. The motor turns in the REVERSE direction and OPENS the door. When the door reaches the fully open position, the FULLY OPEN limit switch opens (disconnects) and the motor stops.

    At the other end of the day, when the door is to be CLOSED, the timer is OFF, so its "C" terminals are connected to its "NC" (normally closed) terminals. The positive output from the power supply enters the timer on "C" of the right connector and emerges on "NC" on that connector. It flows down and right, and through the FULLY CLOSED limit switch, to the positive terminal of the motor. Therefore the motor turns FORWARDS. The other side of the motor connects back to "NC" on the left connector, out on "C" and back to the power supply negative.

    In this state, while the door is not fully closed, the FULLY CLOSED limit switch is closed (short circuit) and current flows. The motor turns in the FORWARD direction and CLOSES the door. When the door reaches the fully closed position, the FULLY CLOSED limit switch opens (disconnects) and the motor stops.

    Unfortunately, that description is a bit confusing because of the words OPEN and CLOSED being used to describe both the door position, and the state of the limit switch contacts.

    The limit switches need to be arranged so that the contacts open (disconnect) and break the circuit when the door reaches the limit of its travel in each direction.
     

    Attached Files:

  11. rbjarema

    rbjarema

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    Dec 2, 2013
    WOW, Thank you so much!!

    One more question that might sound dumb or I may have forgot to mention is that this application is going to be off grid. Is it possible for me to supply the 115VAC thru batteries and inverters?
     
  12. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Yes you could use an inverter, but it would be simpler to find a timer that operates from 12V DC (or whatever DC voltage you have). It needs to have two changeover relay contacts for its output, like the DTU40.

    You're welcome :)
     
  13. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Re selection of limit switches, something like this would be suitable from an electrical point of view; you need to determine whether it's suitable mechanically.

    http://www.digikey.com/product-detail/en/V-10G3-1C24-K/SW1068-ND/369917

    Microswitches are also available with rollers on the actuator lever. That might be more suitable for you. Digikey have a huge range of microswitches at http://www.digikey.com/product-search/en/switches/snap-action-limit-switches/1114207?stock=1. Use the selection filter to narrow down your options. Go for one that's rated for at least a few amps.

    Regarding the motor, I don't have any specific suggestions. You could try robotics web sites. You may want one with built-in gearing.
     
  14. rbjarema

    rbjarema

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    Dec 2, 2013
    I am having a difficult time finding a 12V timer that has two changeovers. Like you said this would be the simplest solution instead of running an inverter. I was wondering if it would just be possible to have two timers set up. One timer would tell the door to open and the other tell the door to close.

    If I did two 12V timers.....
    1. Does each timer need a 12V battery?
    2. Can I still use one motor or would I need two, one for each timer?
    3. I have no clue how to wire it up.

    This is the timer that I was looking at.
    http://www.gandermountain.com/modperl/product/details.cgi?i=413181
     
  15. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    There is no need for a second motor. Any control scheme can be connected to a single motor - all you need is an external relay, or relays, to provide the changeover contacts.

    If you use two timers, they could both run off the same battery. This could be the same battery that powers the motor.

    There's not enough detail on that timer to tell whether it's suitable or not, but I don't think a single one will do it - it's designed to time "feed times" with durations up to 30 seconds and I think it only has one output.

    I've been thinking about this project and I realised that we have to consider what will happen if the door gets stuck for some reason. With the arrangement I drew up, if the limit switch isn't reached, the motor will just keep running. This could damage the motor or the mechanical parts of the system, and it also wastes power, which is important for a battery application.

    I think it would be better to control the motor from one output that activates in the morning, and a second output that activates in the evening, but the outputs only activate for, say, one minute. The alternative would be some extra timing devices to make sure the motor doesn't run for too long, but the first idea is simpler.

    I haven't found a timer that has two separate outputs that can be configured to pulse one output on for one minute in the morning, and pulse the other on for one minute in the evening, but you could use two of these generic timers:

    http://www.ebay.com/itm/LCD-Digital...-Time-Relay-DC-12V-16A-USA-Ship-/321127095779

    I'm really hesitant to recommend anything that's cheap and Chinese and sold on eBay, but it looks like it would do the job. You would use two of these, powered from the same 12V DC battery. One would be configured to turn ON for one minute in the morning, and the other would turn ON for one minute in the evening.

    Those timers have just a single normally open output contact, and you would need to drive a relay from each of them to provide the extra switching needed to reverse the motor. I assume you will want these relays to be panel mounted, with screw terminals for connections. Here are links to a relay and a panel-mount socket on Digikey, so you know generally what you're looking for. The relay and the socket are NOT COMPATIBLE with each other; I can't find a suitable relay with a compatible socket on Digikey! These are just to give you an idea of what you want. You will need two of each.

    Relay: http://www.digikey.com/product-detail/en/XT424012/PB1194-ND/1841562 (around USD 6 each)
    Socket (for DIFFERENT type of relay): http://www.digikey.com/product-detail/en/27E487/PB642-ND/678275 (around USD 7 each).

    You should be able to get suitable relays and sockets from a local electrical supply company. The relays need to have a 12V DC coil and DPDT contacts. The contacts must be rated for 12V DC or more, and several amps - I suggest at least 5 amps.

    These relays can be controlled from any timer or timers that have a relay contact output with two pins or more. I suggest you look for a good quality timer that can turn ON for one minute at a programmed time of day, and get two of them, or ideally, a single timer with two outputs, that can turn each one ON for one minute at different times of day.

    If you can't find anything, you could buy two of those units on eBay that I linked to. I don't recommend eBay products generally because they're often poor quality. Buyer beware and "your mileage may vary".

    Actually, two of the Wildgame Innovations TH-DT timers you linked to would probably be suitable, as long as the door doesn't take longer than 30 seconds to open or close. They are about three times the price of the eBay units though. Your call.

    One last thing I forgot before. The motor should have a diode connected across it, to suppress the voltage surge that it will generate when it's turned off. Without the diode, this voltage surge can cause arcing in the contacts of the relay or the limit switch, which can damage it over time. I will include a diode when I draw up a new diagram, once you've decided on what timer(s) to use.
     
    Last edited: Dec 4, 2013
  16. rbjarema

    rbjarema

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    Dec 2, 2013
    I would like to stick with the Wildgame timers only because I know the quality of them and can purchase them in store. I know I have been asking a lot from you so no rush on when you can get a drawing with two timers, one motor, one battery.

    I hope not to complicate things, but if I could use a linear actuator instead of a motor would the set up be the same? Trying to see if it could simplify things.
     
  17. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    OK, let's stick with the Wildgame timer. You'll need two of them.

    If the linear actuator consists of, or works like, a motor with a worm or similar gearing system, then yes you should be able to use it. It will save you from having to build the gearing yourself.

    In other words, if you can apply 12V DC to it to make it extend in one direction, and 12V DC with opposite polarity to make it extend in the other direction, and it moves at a suitable speed, then yes. Do you have a specific linear actuator in mind? I'm not familiar with them myself, so I can't suggest anything.
     
  18. rbjarema

    rbjarema

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    Dec 2, 2013
    Don't have any actuators in mind at the moment. I was just sitting here thinking of other options that might work with this. This might help eliminate the limit switches. I would just need to find an actuator that has the same stroke length as the opening for the door.
     
  19. duke37

    duke37

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    Jan 9, 2011
    You cannot put a diode across the motor if it is turning in both directions, you could use a couple of zener diodes back to back.

    Have you thought of a scrap electric car window?
     
  20. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Right.
     
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