Modifying RF remote control

Discussion in 'The Projects Forum' started by ecjohnny, Oct 9, 2008.

  1. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
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    Hey guys i have a RF remote control that i am think if it is possible to modify it into a sort of a RF repeater.

    Here i wish to short the receiver(a relay switch) to the transmitter switch.
    But i have a power supply concern. Both the Tx and Rx runs on 12DC.
    However, the transmitter uses a small 12V DC alkaline battery.

    Description : Transmitter - 27A 12VDC Alkaline battery
    Receiver(which is written on top of the relay)
    12Vdc
    NO = 20A
    NC = 12A 14VDC
    7A 120VAC

    So is is possible for me to use a 27A 12VDC Alkaline battery to power up the Receiver?

    if i short the receiver relay NO and GND to the Transmitter switch, will it work?
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Presumably the receiver controls the relay, and the relay controls some load. The specifications you give for the relay contacts (i.e., load carrying ability) have nothing to do with the power needs of the receiver.

    Second, when you say "27A" battery, is that amp-hour or is it some other measure of the battery size. A 27 amp-hour alkaline battery would be fairly big.

    John
     
  3. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
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    Sorry i just found 27A is just another name for the battery. So just single 12V battery.

    i have attach an image to the link below of the rough connection that i am going to connect. i just wanna know if i can use the 12V battery to power up the relay and supply to the transmitter as in the connection.(see image below)

    So the modified TX and RX together form like a simple repeater.
    The process : TX1 --> RX1-- activate--> TX2 -----> RX2

    RX1 and TX2 together will be like a repeater.

    can this be modification be done?



    [​IMG]
     
  4. jpanhalt

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    Have you considered how you will store the signal in RX1 during the period it takes to activate the relay and re-transmit? How will you prevent RX1 from receiving the signal from TX2?

    John
     
  5. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
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    RX1 and TX2 are of different address (coding). So basically it just trigger another transmitter of different address.

    So can the circuit work if i connect it that way? the 12V battery is sufficient for the connection? ( see my previous post picture)
     
  6. jpanhalt

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    Your previous picture does not load when I access the site. Can you re-attach it? John
     
  7. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
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  8. jpanhalt

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    Jan 18, 2008
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    I don't understand that schematic. You have com and and the NO contact tied together, but you don't show where the +12V connects to the contacts.

    BTW, your battery is drawn reversed. The shorter line is the negative terminal. You can think of it as an arrow pointed toward the ground, just like the common symbol for ground.

    John
     
  9. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
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    Opps.. thanks .. i draw the battery in the wrong direction. That drawing is not a schematic drawing. the +12V is connected to the battery.
    And by connecting NO and COM together and connecting the COM to the transmitter's battery side of (+) will produce a +12V when the relay is being activated? sorry i have not use relay for some time.. a bit rusty.

    i go read up more.. meanwhile is it possible for a dry contact relay to use a 12V alkaline battery?

    Thanks.
     
  10. jpanhalt

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    You could do it like this:

    [​IMG]

    John
     
  11. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
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  12. jpanhalt

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    Yes, assuming the red wires at NO and COM near the relay that cross are not connected at the crossing point.

    John
     
  13. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
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    yup.. thank a lot buddy.

    Does that mean the relay does not matter the current? as long as the voltage is 12 DC whether is it from a battery or a 12VDC power adapter?

    Also the picture below shows my receiver. is the coil there the antenna? is it possible for me to solder another antenna on it to increase the range?

    Sorry if it sound dumb... i don't know much about antenna.

    http://img366.imageshack.us/img366/182/antennasp2.jpg
     
    Last edited: Oct 9, 2008
  14. jpanhalt

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    Jan 18, 2008
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    Relays do require a certain amount of current in the coil to work. The spec. sheet will tell you how much. Your battery or power supply is probably adequate for it. Just test it to find out.

    John
     
  15. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
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    Thanks i got it work.. but the range is pathetic. i will require tons of repeaters.

    is there any ways i can modify it in the circuit so the range will go even further?
    Maybe like changing the antenna?
    i have heard of RF remote going as far a 2KM or more. How do 10m RF remote different from them? Maybe i can change the components?

    Thanks i really need a good RF remote control. i seriously need to penetrate walls. i am doing a hotel project.

    Or anyone here have knowledge in making one that would go VERY far out?

    Any other suggestions are welcome.
     
  16. jpanhalt

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    1) The range will be dependent on the TX and RX, not on the way they are switched. Therefore, changing the design shown in the last few posts will not help.
    2) Reception distance is controlled my many factors. Transmitter power and receiver sensitivity are important. If you start with a pair that has only a 10 m range, you are most likely stuck with something that has very short range. Modifying it for greater range would require knowing a great deal more about both units and perhaps a complete redesign.
    3) Every nation has laws regulating RF communications. Modifications to increase the range to several km will certainly come up against those laws.
    4) Have you considered using existing wiring (like telephone) and putting your control signal on top of the existing signal(s). For example, DSL goes on the same lines as telephone.

    John
     
  17. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
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    can you explain more on 4) how can i use it to transmit/receiver? Like how can plug a receiver into the telephone jack and transmit(wire) to my destination? Do you mean that?
     
    Last edited: Oct 16, 2008
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