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Thread: need some help with a relay

  1. #1
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    need some help with a relay

    total relay newb here... so pardon my ignorance. I've done some searching on the subject, looked at the datasheet, but am still a bit perplexed as to which pins to connect.

    The relay is a SY- 5 -K. Link to datasheet

    I'm going to take a leap here and say that I should connect the positive to pin 2, negative to pin 9, and the switch that I want to operate to pins 10 and 6. Am I correct in this? (going by the diagram on bottom of page 4 of the datasheet)


    thanks

  2. #2
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    ok,...tested that and it works... however now I'm stuck at a part that confuses me. I'm attempting the one-shot circuit as depicted in this post... I got it to work... once. I didn't think it was quite literally a one-shot deal...I figured that after the cap was discharged it would function again. I'm going to mess with it some more, but anyone have any tips on why it would work once and not again (even after I drain the cap).

  3. #3
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    no one? I'm stumped here. I've tried different values of caps, resistors, and the most I can get the circuit to do is energize the cap, and then watch an LED bleed off the power after the main power is cut so the cap is drained.

  4. #4
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    draw out how you have this circuit made. IS the LED constantly connected? DOes the LED light immediately when power is turned on? If so this may be the problem. With a resistor, a cap, and an LED in Parrallel with the relay coil. You may be dropping voltage too much to turn the relay coil on. Although the circuit it quite simple and easy it probably isnt the best way to do it. Try looking up 555 timer circuits, they are easy to build and will do what you want and be both dependable and pridictable.

  5. #5
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    no, the led isn't connected in the circuit at all. I apply power, nothing happens, disconnect the power and touch the leads of the led to the cap and can watch it drain.

    I will look in to the 555...I may even have one somewhere here

  6. #6
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    ok, afte some tinkering and troubleshooting with this thing, I finally got it to work like I want...partially.

    I have 2x3300uf and 2x2200uf in parallel to give a 2-3 second hold time on the relay. I also have an LED wired into the circuit to bleed off the caps once the power is cut.

    Circuit diagram below:
    [IMG][/IMG]

    now, what I'd like to do is have this relay trigger another which turns the device OFF when the power is cut...this I'm not sure of. I'm going today to pick up another couple relays and a timer, and I'll draw up a diagram of my idea, but anyone else done something like this?

  7. #7
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    no one? 170+ hits and no one knows? dang.

    Well, here's basically what I need - and I have half of it.

    I need a circuit that will attach to the switch on my bluetooth GPS receiver and close the switch for 2 seconds when the carpc is powered on. I have this part. Works perfect.

    the part I don't have, and can't get to work, is a circuit that will close the gpsr switch for 2 seconds when the carpc shuts off. Similar to the Delayed Off circuit in the schematics sticky.

    So at start, relays hold switch closed for ~2 seconds, then during normal operation relays are open, and at shutdown, relays hold switch closed for another ~2seconds.

    Can anyone help me with such a circuit?

  8. #8
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    Here try this and see how it works.
    Name:  PO CIRCUIT.JPG
Views: 4673
Size:  46.7 KB

    You will have to play with the cap and resistor values to get your required time delay of 2 seconds. I suggest you hook an LED to the output at first and time the LED till you get what you want. There is a formula for figuring time delay out but I am not good at math, nor do I know the formula so I always just use trial and error till I get what I want.

    Have fun! Let me know if it works.

  9. #9
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    awesome thanks! I've been searching around the internet and haven't found quite what I'm looking for, so I started to try to combine some different circuits to get what I wanted but my knowledge on the subject is limited anymore (last time I was REALLY into this level was almost 10 years ago...and when you don't use it...you lose it -at least I did anyway )

    I'll have to order the transistor b/c there are really no decent shops around my area. Radioshack is worthless here anymore, and that's about it for electronics "parts". I salvaged the relays from an old modem, all the caps from old motherboards, and also have voltage regulators, flip flops, nand gates, uarts, hex inverters, etc...but don't think I have any transistors. So off to Mouser I go

    and to be quite honest...since there were no posts in response, I sort of gave up on the idea and just added enough capacitance to drain off in the same amount of time that it took the bluetooth gpsr to timeout and shut itself down (30 minutes).

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