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    Power Supply Design for timer application

    Dear all.

    I am looking for simple transformer less power supply design for one of timing application.i have an micro controller which is driven from 7805 regulator IC.

    Is there any recommended Capacitor based design ??

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    Re: Power Supply Design for timer application

    How much current? What input power is available? The 7805 requires at least 7 volts in to regulate to 5 volts, so we know you need at least that. How about just using a 9 volt battery?



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    Re: Power Supply Design for timer application

    Far more importantly, what does your timer control. Don't forget a transformerless supply has no galvanic isolation from the incoming AC power lines so it can't be connected directly to anything else.

    Brian.
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    Re: Power Supply Design for timer application

    Delete the 7805 and use the common 5V wallwort.
    They are cheap and provide isolation from the mains.
    Zapper
    Curmudgeon Elektroniker



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    Re: Power Supply Design for timer application

    there is loads of information on the net about capacitive droppers - don't forget they are all LIVE - i.e. at mains potential - so you need an opto or relay to interface any command signals to any thing TOUCHABLE by a person ...



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    Re: Power Supply Design for timer application

    I have below ckt for phase monitoring.previously i have used transformer based power supply design.

    Now i would like to use transformerless power ,with any of phase to generate 12V which goes to below IC.

    https://www.mouser.in/Datasheets/_/?...L78M05&FS=True

    Power goes to Single LED(Indication) and 2 potentiometer(10K or 200K)/ which is used for timing adjustment 24Vdc Relay
    assume these factor 5V 0.5A is requirement for MCU and LED.

    what care to be taken for this type of design.

    I have seen some design using Capacitor in series with Diode used. Is there any recommendation ckt.

    - - - Updated - - -

    people often uses these design:
    How it safe in design/ how isolation taken care.

    https://***********.com/capacitor-power-supply/

    - - - Updated - - -

    https://www.quora.com/How-can-we-eas...n-a-simple-way

    - - - Updated - - -

    Capacitive power supply design given below
    https://www.electronicsforu.com/elec...st-effective/5



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    Re: Power Supply Design for timer application

    Hi,

    Confusing informations...
    * You ask about a power supply circuit, but show a measurement circuit
    * you talk about 12V supply
    * then you talk about a 24V relay... Where is it powered from?
    * then you talk about 5V supply..
    * then you talk about 500mA for microcontroller and LED ... I'd expect only 1/20 of the given current.

    --> please give clear specifications and schematics, even hand drawn is O.K.

    5V x 500mA gives 2.5W --> for this high power a capacitive supply is not useful. It is useful maybe up to a couple of 100mW.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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    Re: Power Supply Design for timer application

    I have application for Timer/ Voltage monitor.
    In timer application , I have 4 pots / 1no 12V/24Vdc Relay/ 1 LED to be driven/1MCU. its single phase ckt.
    Assuming this 230VAC to 12V 0.5 or 24V 0.3-0.5A Current is more than enough.

    My second application 3 phase voltage monitoring.
    where i wanted to use one phase for Power generating 12V/24VDC with 0.3-0.5A
    In this application I am not sure about ckt attached and protection.
    If i used voltage trasnducer cost will be more
    if i use transformer cost will be increase and size of electronics also more
    I have some design using Voltage divider network using high wattage resistance but it not safe. What are care to be taken in this case'

    Alternate method are also appreciated.



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    Re: Power Supply Design for timer application

    You must understand the problem first. Three phase uses three wires so you cannot 'magic' an independent reference from them unless you use a transformer (or maybe more than one transformer).

    In the single phase schematics you have seen, the neutral is used as ground and the voltage from the line (live) is produced relative to it. With three phase you do not have a neutral so your only option is to use one of the phase lines as your circuit 'ground'. You can see therefore it is difficult to measure the voltage when one of the three is always zero. You can use capacitive droppers from the other two phases, each with their own rectifier to generate your supply voltage in the same way as a single phase supply does it but beware that the voltages will be considerably higher. Instead of dropping 230V RMS down, you could be looking at more than 400V RMS so the component ratings need to be that much higher.

    Also consider that the circuit 'ground' (0V or negative side of the supply) will be some 230V AC above real 'Earth beneath your feet' so you have to be extremely careful that no part of the circuit can be touched to prevent electric shock.

    Brian.
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    Re: Power Supply Design for timer application

    Quote Originally Posted by nayakajit87 View Post
    Alternate method are also appreciated.
    There is the optoisolator (optocoupler) method for monitoring voltage. Create expanded scale readings by installing a zener diode inline.

    Click image for larger version. 

Name:	3-phase delta 3 loads 6 led's 6 zener diodes (triangle layout).png 
Views:	2 
Size:	52.0 KB 
ID:	157778



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  11. #11
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    Re: Power Supply Design for timer application

    Actually I have 2 application
    1) Single phase timer which uses 240V AC input
    2) 3 phase voltage monitoring,

    1)IN single phase timer, I saw taken some power supply module from markets ,people using transformer and Bridge rectifier ckt.

    Usually i will take Power intergration readymade design if application demands. and cost doesn't matter.

    In this type application product cost ill be around 6-10$
    Thanks bradtherad for solution.

    2) IN case of 3 phase monitoring few people used above voltage ckt.

    I know transformer based design give isolated gnd & much safer in operation
    else of using voltage transducer is safer operation in such application.

    Here since i am looking for cheaper design for this application with safety i am asking safer ckts.



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