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Transformerless power supply with only Live wire

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Ibob, Apr 20, 2013.

  1. Ibob

    Ibob Member

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    I see your point MrAl, and you have right.
    The reason I didn't test it yet is because I will need to desolder as I cannot find such diac for the time being.
    Second reason is I didn't is because I didn't received explanaition how it will work.
    I would test something if I understand it.
    Here don't get me wrong - the problem is maybe my lower knowledge.
    When home, i will post the circuit I've tested.
    If you are still interested to help me.
    Cheers,
    B
     
  2. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    I'd like to see you get this working. It's best though if you post any circuit changes right away and let me know what you did. Since you tested this somewhat already then we are one step ahead.
     
  3. Ibob

    Ibob Member

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    Hi,
    This is the last circuit I've tested and now on my breadboard.
    image.jpg
    It is working. When I press a button the bulb goes ON, when I tap it again - it goes OFF.
    BUT, ...
    1) The voltage of the power circuit when bulb off is 11.7V - great.
    2) The voltage measured at the input of 555 IC when bulb ON - 5.7V - for the 555 ok but for the receiver?
    3) The voltage measured at the input of the MOC3052 is only 1.06V - at the minimum?!

    I am afraid that the RF receive wouldn't power with that voltage. I am not sure about the Current.
    I am afraid also not to blow up again the optocoupler, therefore these values of the resistors.

    Maybe some of the resistor values are too big?

    Now I have 2 LEDs ... One is just showing 12V supply. The other one is lighting when signal from the 555 IC.
    Actually I would like to have only one LED, which to illuminate when the bulb is OFF. :) ... but only if that will be safe enough.


    Unfortunately I will get the receiver after 8th of MAY as the Customs will not work by then - there are a lot of holidays now here.
    When I have it I will try to bypass the relay and to use directly the signal to drive the MOC3052. This will save me space, relay-click noise, and would require less power to operate, am I right?


    Cheers :)
    and looking for your comments...

    p.s. The buzz noise... is comming from the TRIAC, isn't it? Any ideas how to easily avoid it? The same noise is comming from the PIR sensor.

    Last but not least... when 230V power applied, the bulb is switched ON/OFF randomly. Ones ON, sometimes OFF. I will need to add elements to reset the 555 IC.
     
    Last edited: Apr 30, 2013
  4. dave

    Dave New Member

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  5. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello,


    You can try adding the diac between pin 4 of the optocoupler and the 500 ohm resistor. That should boost the voltage when the bulb is off.

    If you are not getting the kind of switch action you want then yes the 555 circuit will have to be modified.
     
  6. Ibob

    Ibob Member

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    I've got the remotes! Awesome!
    Tried your proposal with the diac but the same result.
    Tried also with a cap before it - the same.
    However when I play with the Value of the resistor connected to the input of the optocoupler I was able to achieve 11.7v when bulb off and 8 v when bulb on. That's 2.5k. When i press the manual button all works fine, but when i trigger the receiver, the relay closes and the voltage goes down to 6v, until the relay is closed.
    In general it works but the current or the voltage is not enough and the relay goes off even with the remote button pressed down and the bulb starts blinking.
    If i hook it to battery all is good.
    So now i have 2 options:
    1. Get rid of the relay and use the transistor that drives the relay;
    2. Increase somehow the voltage or current (not sure which one) when bulb is on (when triac is on)

    What do you suggest?
     
  7. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    I did not know you had the option of using just the transistor rather than the whole circuit with the relay too. The relay would use quite a bit of current so if you can get rid of that it's better.

    I need to see the whole schematic now that you are currently using. If you take too long to reply here i have to go over the circuit again anyway because by the time you reply i've looked at 20 other circuits and worked with 50 other equations of different kinds, so i have to refresh on your circuit. It's not a problem really if you take a bit longer to reply, but then i need time to refresh too and rethink what we were doing :)

    This new idea with the transistor is a good one, and you've come up with so many good ideas for this project im a little surprised you havent figured out how to do it already. So let me refresh you on what we are trying to do here. It's actually not difficult to understand.

    A relay is turned on with a voltage, and once turned on it would be kept on by keeping the voltage supplied to the coil. A triac on the other hand, does not turn on and stay on, but rather has to be turned 'back' on EVERY half cycle. Now normally this would happen right after the zero crossing of the power line sine wave. The triac turns off automatically as the sine goes through zero, but then is starts to increase again (opposite polarity) we have to turn it back on again. If we turn it back on immediately after the zero crossing however, then we dont see any voltage across the triac. So what we need to do is delay the turn on of the triac so that we can extract some energy from across the triac BEFORE it turns on. For example a delay of 1ms would mean the voltage shoots up for that 1ms period, then the triac is turned on the voltage goes down to only maybe 1 or 2 volts (which isnt enough). So the only goal is to trigger the triac after some small delay after the zero crossing. A diac does not turn on until the voltage reaches some set limit (like 20v) so that means the triac wont turn on right away, which is what we want. But there are other ways too such as using a small value capacitor and resistor because the introduces a phase shift which is similar to a delay.

    So hopefully that will give you a little more insight.
     
    Last edited: May 9, 2013
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  8. Ibob

    Ibob Member

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    Hi MrAl, hi all,
    Here you can watch what i have made so far:
    http://youtu.be/fqNeXrMJf-k
    Here is the circuit:
    image.jpg

    What's new from the last time:
    - 2nd cap added before the rectifier in order to gain more current;
    This is what i have read and indeed i can tell it is better. Actually i should get a new bigger cap like 225K = 2.2uF.
    - RF receiver connected to the power supply, relay contacts in parallel with the wall button.
    As you can see the wall button is going great job, the relay also triggers quite good when bulb off, but no power to trigger back (and fast) when bulb on. Some times, however as you can see in the video it does.
    - you can check the circuit of the relay trigger transistor i have analyzed looking at the receiver.
    I'd like an advice on how to get rid of the relay and "press" that wall switch with the receiver's transistor (btw SMD type). But i am not sure it will work as there will be some potential coming to the input of the timer 555?
    At least can i substitute the relay then with e.g. optocoupler or MOSFET?
    - Voltage when bulb off: 12.4v
    - Voltage when bulb on: 8.16v
    - Voltage when relay coil on: 7.15 - at this moment i think there is not enough current. Btw how and where to measure the current in this case?
    - the 500 ohm current limiting R in the supply is generating too much hot! Should i get more powerful like 5w or?

    Link to the relay datasheet:
    http://www.100y.com.tw/pdf_file/29-SRD-RELAY.pdf

    So I think that the relay is drawing too much current and if i find a way how to substitute it but at the same time the input of the 555 timer should not be compromised then i will be ready for production :)
     
  9. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello,

    You changed the circuit again, drawing those two caps in a manner that looks more like a network than just two caps in parallel which is not as clear.

    Also, there's no clear way to see how the opto turns on because pin 2 goes to ground and there is no clear path for a positive current to flow through the IR diode. So it appears from the schematic that there is no way for current to get through the IR diode, and the video does not show that part of the circuit very well.
    Perhaps take some pictures, and check that opto IR diode circuit.
     
  10. Ibob

    Ibob Member

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    Those 2 caps are in parallel because I don't have bigger and single cap. As far as I know the capacitance total is equal to the capacitances in parallel, so I cannot get your remark about the "network".
    I've made 2 small changes in the 555 cuircuit being the following:
    - i skiped to draw the capacitor connected to ground and to the button (now it is shown)
    - i have connected the ON led to positive (it was in series with the optocoupler before)
    - replaced the 12v zenner with 15v zenner.
    Nevertheless the circuit is still working as shown on the video and the voltages I am measuring when bulb ON and when relay coil on are the same as mentioned in my previous post.

    If you overcome the fact i am changing the circuit can you be so kind to advise on the questions i have listed in my previous post, especially the one how to trigger the 555 with something less powerful than the receiver's relay?
    Thanks in advance.

    image.jpg

    Just saw one mistake: the ON led read as OFF led and the OFF led read as ON led.
    Apologies..
     
    Last edited: May 12, 2013
  11. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello,

    No i wasnt disputing that the caps are not in parallel, i was disputing the way they were drawn, that's all. The way they were drawn not the way they are connected. If they were drawn better their function would be simpler to see right off. I drew the circuit with the caps shown better, but you discarded that.

    I thought you were going to use the transistor that drives the relay, but i see now this isnt so simple because the transistor of the RF is connected to line through the bridge rectifier. So how about using a lower current (coil current) relay?
    Or, change the 555 to something else which can trigger with a positive or ground signal rather than a relay (or switch) contact closure. Im sure there are lots of other ways to do that. Then the transistor of the RF unit can drive it directly.
     
  12. Ibob

    Ibob Member

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    Hi,
    Ok about the caps.
    I thought the same about the relay. To substitute it with some low current one.
    I will investigate what kind of low current relay I can get here and will post the results when I test.
    Thanks.
     
  13. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Well one more idea is to use an opto coupler with an LDR output rather that transistor output. The LDR is not polarity sensitive. If you cant find one, you might make your own with a white LED and LDR in an enclosed tube. If the LDR resistance is too high even when the LED is on, then you might modify the 555 circuit a little to be able to work with a higher impedance 'switch' so it will work with the real switch as well as the LDR (Light Dependent Resistor).

    The only real design challenge is your 555 needs a non polarity sensitive switching action. If that was changed this would be simpler.
     
  14. Ibob

    Ibob Member

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    Hi MrAl,
    I find your idea as brilliant!!!
    I've started investigation on how to acomplish that.
    Also I have few LDRs arround taken out from different equipments.
     
  15. Ibob

    Ibob Member

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    Ok, I have made the optocoupler with LDR!
    White LED, LDR. The LDR has 2M ohm resistance when diode off and 0 when diode on.
    Now how to substitute tge relay? Just to put the optocoupler made instead of the relay and with 1k R in series, removing the diode across the relay coil as well?
    image.jpg
     
  16. Ibob

    Ibob Member

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    Or even better, maybe I can avoid the transistor of the receiver also and connect the LDR optocoupler right after the R, before the receiver's transistor... ?
     
  17. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello again,

    When you say that the LDR has 2M resistance when the LED is off and 0 resistance when the LED is on, that's not enough information yet. We need to know what the min current is for the LED that will provide enough light to make the LDR go down to a low enough resistance to drive the circuit properly.

    You can make a quick table by driving the LED with 100ua, 200ua, 400ua, 800ua, 1ma, 2ma, 4ma, 8ma, and taking resistance measurements with an ohm meter of the LDR for each of these LED current levels. That will give us a good idea what we have there in your home made (cute ha ha) LDR opto coupler.

    Alternately, you can do the following. Connect the LED side of the new opto to the transistor collector in place of the relay coil but also use a 150k resistor in series with the LED. Try the circuit, and it probably wont work yet, so lower the resistance slowly until you find the point where it just begins to start to work. Figure out the current by measuring the voltage, then double that current level which requires lowering the resistance more. Once you have that setting it should work ok, but it would be nice to see the curve too as the above tests show.

    It's probably better to use the transistor rather than just the resistor in the RF module but dont forget to disconnect the relay coil by cutting at least one lead.

    LATER NOTE:
    I hope that is not black electrical tape around that home made LDR. I think it's cute and a good idea that you made your own, but electrical tape comes off after a while sometimes so i would not trust it, and if any light gets inside it will activate the LDR and screw up the switching action. Maybe some epoxy to enclose them, then covered with aluminum foil, then another layer of epoxy. You might have a better idea here.
     
    Last edited: May 14, 2013
  18. Ibob

    Ibob Member

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    SOLVED!
    Big THANKS to MrAl! Respect!
    It didn't work well with the LDR. It was triggering the bulb on but never off?!
    I am not sure why...
    So I used a IC Reed relay and just substituted the RF relay.
    You can see video on the prototype:
    http://youtu.be/I0CsAzSXdEM

    However I can still observe 2 issues:
    1. The current dropping R being now 10watt 540ohm is getting really hot!
    After 5 mins of work I cannot touch it for more than a second (mains disconnected);
    2. If you watch the video at the end of it, several skips can be observed. It happens sometimes the command not to be followed, or just a blink to be produced.
    I am suspecting the bistable 555 circuit, but ..
    Also tried with a cap 1000uF 16V connected in parallel to the supply before and close to 555 but it happens sometimes with it as well, maybe a bit less...

    What is different now on the circuit is that I've connected the pin 5 of 555 to GND via cap .1nF. But with or without it i see no difference.

    Any ideas how to improve the above 2 points?
    Cheers!

    P.s. sorry for the delay but very busy at work these days..
     
  19. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Where can i see the entire circuit the way it really is now?
     
  20. Ibob

    Ibob Member

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    image.jpg
     
  21. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi again,


    Here are the changes that will help the problems.

    1. Short out the fuse where it is now, move it to be in series with the N input line terminal. Make it a 500ma unit if you can but no larger than 1 amp.
    2. Change R560 to 330 ohms, at least 2 watts for now. We can probably get away with a 1 watt here.
    3. Remove C2, the 394k cap.
    4. Make sure the bridge rectifier is rated for at least 1 amp.
    5. Disconnect everything from the bridge rect (+) output, except the C5 cap (+) terminal.
    6. Keep C5 capacitor (+) terminal connected to bridge rect (+) output, but that's the only thing to connect the the bridge (+) output.
    7. Connect a 100 ohm resistor between the capacitor C5 (+) terminal and the zener cathode.
    8. Connect the rest of the circuit to the zener cathode (like the 555 etc.).
    9. Redraw the circuit and post here.
    10. Test.

    The above changes will help it work better and also make it safer.
     

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