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Thread: 5V regulator issue please help

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    Default 5V regulator issue please help

    I have wired everything according to EZs diagram except I left the main switch as is on the negative side of the battery in 3x AA box from madvapes. Now when I flip the main switch from off to on, I hear the atty begin to burn slightly, not enough to produce good vapor, but enough to get hot and the regulator gets hot too. When I press the horn switch, the atty fires at the expected 5v but ive got to flip the main switch off to get it to stop. Ive got a few of these 378R05 regulators with control pin and tested them all on the breadboard with same results. I am using 470 ohm resistor, as indicated by the diagram. Anyone not having this issue, or is that how this is supposed to run?

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    Forum Supplier ECF Veteran BuzzKill's Avatar
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    you must have something wired wrong , go over it line by line to make sure it is wired correctly !
    can you post the circuit ?
    or a link

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    I have wired everything according to EZs diagram
    As Buzz noted you've made some subtle mistake.

    Is this how you wired it?

    "The farther backward you can look, the farther forward you are likely to see"

    Try searching...

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    My first guess whould be the OP read the pin numbers wrong on the regulator, sometimes it can be hard to tell if pin 1 is on the left or right.

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    ImageShack® - Online Photo and Video Hosting
    Sorry about the amateur diagram, kinda reminds me of guitar tabs
    Hopefully my error is obvious.
    Last edited by Solder-Meister; 05-30-2011 at 02:03 AM.

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    Your diagram and pin numbers look right. Must be an error in the wiring.

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    PV Master ECF Veteran WillyB's Avatar
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    We'll look at how it works, that my help.

    The 470Ω resistor pulls the Control pin to GND, disabling the output, The resistor keeps the connection from reading like a dead short and cuts the volts/current that the switch needs to handle. The CT pin (Vdis) only needs a few volts and ~20μA to enable the regulator. That's not much. Your problem has to here.

    Check with your meter at the output leg of your momentary switch when you turn on your master switch, there should be nothing/zero at this point. Maybe you cooked it a bit and it's leaking just enough current to kinda enable the reg.
    bepsage likes this.
    "The farther backward you can look, the farther forward you are likely to see"

    Try searching...

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    With cartomizer in place, main switch on, the atty is getting 2.33 volts. closing the momentary switch gives the atty 4.85 volts. I tried using a fresh switch with the same results. Also, want to point out that these are the 5A horn switches from madvapes. I even took the liberty of throwing a 10uf 10v multilayer ceramic capacitor (pins 2 + 3) into the mix and it seemed to improve the situation because the atty doesn't fire as hard when the main switch is on.

    I also wired the circuit without using the control switch and it works perfectly; main switch on, 0 volts and 4.95 volts when fired. I'd really love to be able to use tactile switches which is why I'm pulling my hair out trying to figure this one out. I'm running out of ideas.

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    Quick question, kind of off topic. Do I need to worry about polarization with these ceramic capacitors? They are so tiny and there is no mark indicating poles.

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    Do what WillyB said and check the voltage on pin 4 when the momentary switch is closed and when it's open. Should be be zero when relaxed and battery voltage when pushed. If it's not, there's a problem with the switch circuit.

    It shouldn't work without the momemtary switch there so I don't really understand how it's working when you say it works without it. If you were jumping the switch, that would make sense.

    Possible you could be getting impedance or interference issues on the control pin by using long wires and a switch with large contacts like a horn switch. Try removing the switch and its wiring then jump pins 1 and 4 with a short piece of wire to see if that makes a difference.

    Data sheet says you don't necessarily need input or output caps, but just to make sure you're not getting some sort of wiring impedance or noise problem, you should try putting caps on both input and output right off the regulator pins 2-3 and 1-3. The data sheet recommends 47µF caps.

    If all else fails, try another regulator chip. Maybe that one is damaged or defective.

    When you do get it working, you'll need to use a 4.7K pull down resistor with a tactile switch. A 470 ohm resistor will result in too much current flow for most tactile switches.

    Ceramic caps are not polarized. You can connect either lead to the positive side. Tantalums and electrolytics are polarized and must be connected correctly.
    Last edited by CraigHB; 05-31-2011 at 10:00 PM.

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