Boost converter w/ Frequency Change

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Hi guys, I reccently aquired a turntable that is setup for European mains, so it runs on 220V with 50Hz. Over here the mains is (obviously) 120V with 60hz.

Do you know of any converters that will change the frequency as well as boost the voltage for a reasonable price?

I have worked with these sort of power systems before in class, only on a much larger scale. A TT wouldn't need much power, so I'm thinking a converter could be built from scratch for relatively cheap - but I may be wrong. If there are already designs out there, I would appreciate some help - pointing me in the right direction.

If feasible, i think building my own converter/supply could have lots of benefits including precision and ensuring that the TT gets a really clean power source. I figure I would need the following modules:

1. Rectification AC/DC
2. Boost converter for the DC voltage
3. Sinusoidal PWM (?) DC/AC converter w/ variable frequency

I am familiar with the first two steps, but unsure on the last step, approx. how much would a deccent DC/AC converter cost? Is it worth the hassle? I thorough enjoy doing these things so I wouldnt mind a bit of work. TIA!!!!
 
poobah said:
Check out Section 3.10 of the manual. It might be implying that all you have to do is flip some wires around inside. Wouldn't that be cool?

Maybe start a new thread with brand and model number in the title.

Plenty of Scots and Brits here.

;)

Don't think its that easy, but I will soon... I dont even have the TT yet, I'm just anxious to start on my new project and reading up on everything I can - Thanks a bunch.


P.S. I'm assuming a 3.3 Watt could be done relatively cheap??? I'm sure my mains is pretty dirty anyway, a power converter would probably be a good idea.
 
an RC oscillator will not be stable enough -- you need some basic digital (very basic) to do this -- if you can get a 1.638 MHz crystal divide down by 2^16 will give you 50 Hz -- you also pick off a 2^8 which gives you a 6.4kHz clock frequency with which to drive a switched capacitor filter -- there are some nice 8th order low pass filters from Linear Tech and Maxim to fit the bill -- when you use an LPF it gives you a very nice sine wave.

to precisely maintain the amplitude you could use a chip like the SSM2018.

jack
 
This is going to be a challenge for me since I've not learned ANY digital in class at all... but I've just read some stuff on crystal oscillators - there are some simple enough circuits out there, I will start on the frequency dividers and filters tomorrow. There are lots of threads and pages out there, but no one has actually gone through and built their own TT supply it seems. Everyone suggests quartz locking, but no one has done it so I suspect I am in over my head, but we'll see :smash:

EDIT:

I can't use 60hz for a 50hz Turntable.

Is there any component in spice that represents a crystal so I can experiment? It would make things easier on me I think.
 
Whatever you do, first throw away thy Spice crutches and walk on your own legs again.

Next, get yourself a pair of 4060 CMOS counters. Look for HEF4060 on datasheetarchive.com, there's a standard crystal oscillator circuit in the data sheet. With a 3.2768 MHz crystal, divide by 2^10 (first chip) and 2^6 (second chip) for 50 Hz square. (sorry jackinnj, you're off by x2)

Feed that to a simple low-pass filter (never mind switched-cap, 2nd order is plenty good enough to drive a motor!), then to a cheap chip amp - with one in bridge configuration, you can even run the whole show on a single supply.

If you're lucky, the motor will run on something much less than 230V anyway (my old Thorens turntable eats 18V AC from a wall wart, IIRC), so maybe the amp can drive it directly.

Otherwise, just use a cheap mains transformer in reverse. Add a couple watts to the trafo spec, especially if you use one built for 60 Hz.

Exact voltage isn't critical, it's a synchronous motor.

If you run the contraption on a car battery, you can call it a digitally crystal-controlled on-line uninterruptible sinewave power supply for high-precision rotary motion control applications ;-)
 
LoL... considering I have zero digital experience, I think spice might be a good idea.

I will work out a schematic and maybe someone can look it over for me.

I know what you're getting at frequency controls speed which is most important, and if the transformer runs at a lower voltage, but a high current the torque will still be there, but a higher current usually means higher temp in the motor - not good.
 
wine&dine said:
Whatever you do, first throw away thy Spice crutches and walk on your own legs again.

Next, get yourself a pair of 4060 CMOS counters. Look for HEF4060 on datasheetarchive.com, there's a standard crystal oscillator circuit in the data sheet. With a 3.2768 MHz crystal, divide by 2^10 (first chip) and 2^6 (second chip) for 50 Hz square. (sorry jackinnj, you're off by x2)


Must have been semi-conscious at the time.

CD4060 was used as a Baud Rate Generator -- remember your first Hayes Modem? You can pull the frequency one way or another by substituting a variable cap for one of the 20pF's shown -- or you could get fancy...the filter chip shown is a 5th order butterworth LPF -- Max280 -- there are less expensive chips which will do the same job.

An externally hosted image should be here but it was not working when we last tested it.
 
...and if the transformer runs at a lower voltage, but a high current the torque will still be there, but a higher current usually means higher temp in the motor - not good. [/B]


Not sure I understand you completely there - what I mean is that if the motor is designed for X Volts, get your output voltage there approximately (pot between filter and power stage), then leave it alone - don't bother to include a regulator circuit as maybe +/- 20% variation won't matter to the little synchronous motor. OK? Remember (also when picking your output stage) that you're talking about three watts only.
 
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