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running 230 V/50 Hz CLOCK in US?

Discussion in 'General Electronics Discussion' started by pupster, Aug 25, 2013.

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  1. pupster


    Aug 25, 2013
    I ordered a Philips HF3485 Wake Up Light w/ clock from Amazon.UK since it's sold out in the US. It runs on 230 V ~ 50 Hz. There's a fuse in the plug, and it's rated at 3 A, but I calculated the Amp based on the input voltage and wattage (100 W). It comes out to just under 0.45 A.

    I'd like to use the light in the US where I live. I know that some clock mechanisms are very sensitive to the frequency (50 Hz vs. 60 Hz). So, I was wondering if this "project" would work.

    1) Buy a 120 V 60 Hz AC to 12 V DC converter (car lighter socket)
    2) Buy a 12 V DC (car lighter plug) to 230 V/50 Hz inverter (modified sine wave, unless I find the clock needs a pure sine wave)
    3) connect the two of them


    Will this work?

    If so, what type of Amp ratings do I need for parts 1 and 2? I'll be sure that the inverter is rated for at least 300 W (3x the clock rating).
  2. duke37


    Jan 9, 2011
    I tryed to find how the clock works but without sucess. There are three methods that I know.
    1. Clock runs with reference to a crystal oscillator.
    2. Clock uses the mains frequency as a reference. This very accurate in the UK and if the frequency does drift, then it is compensated to correct clocks. I was told the best time to set the clock is midnight on sunday.
    3. Clock uses a radio time signal as reference.
    4. I have not heard of a GPS reference but it is possible.

    If the clock uses 1. then it should be possible to run on 60Hz
    If it uses 2. then your solution would probably work but the inverter would need to have a very accurate frequency.
    If it uses 3. then you may not have a suitable standard frequency transmitter available.

    I would try it on 60Hz at the right voltage and if it runs 20% fast, then go to your solution.

    100W at 12V = 9A
    300W at 12V = 25A

    The bulk of the power will be the used by the bulb which may not be fussy about frequency, certainly not if it is quartz - halogen, but it would be difficult to separate this from the clock proper.

    I have seen references to a method of making a 300Hz oscillator, locked to the mains and then divided down to 50 or 60Hz, driving an audio amplifier. This would unlikely to be suitable to drive a high power bulb.
  3. pupster


    Aug 25, 2013
    Thanks. I will try that. Question regarding the Amps...the clock will only draw what it needs, right? I.e. if I have a 300 W step up transformer to convert from 120 V to 230 V, the clock won't draw more amps than it needs, right?

    CDRIVE Hauling 10' pipe on a Trek Shift3

    May 8, 2012
    A decent 120VAC to 240VAC (yes it's not 230V) transformer might cost you more than the clock! I would also not rely on 12VDC to 120VAC converters to produce a clean or accurate 60Hz.


    CDRIVE Hauling 10' pipe on a Trek Shift3

    May 8, 2012
  6. pupster


    Aug 25, 2013

    Thanks. The model you're quoting is the now-discontinued US version. The UK versision is the HF3485/01 (not /060).

    Thanks for the thoughts regarding the quality of the power from an inverter. Hmmm...I really wanted the light, as it's the only Wakeup with USB (to play your own sounds) as well as a replaceable bulb. That's why I went to all the trouble to special order it from Amazon.UK. Total cost, including the shipping by a third party (I had to get a package forwarding company to forward the package, since Amazon.UK wouldn't ship that electronic device (for obvious reasons) to the US) was about $200, so I'm prepared to spend upwards of $300 to $400 to get it working properly....
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