Help designing a circuit to power a 110V, 60 c/s clock in the UK

[Nickthedentist]

Hello,

A friend of mine is a Hammond organ fanatic (he has at least three!), and has just bought himself a 1930s Hammond clock from eBay.com to keep them company.

Naturally, it's designed for 110V, 60 c/s. The stated consumption is 2W.

It could be converted to quartz(!) or fitted with a period UK synchronous clock movement of course, but we'd both rather keep it original.

Assuming the movement's salvagable (no guarantees there!), I need to make up a unit to provide a suitable supply to drive it. There are semi-commercial units available at a reasonable cost, e.g. http://www.electric-clocks.co.uk/Fre...cyconvert.html, but I'd liket to have a go at a DIY approach.

Presumably, a 60Hz sinewave source running into an AF power amp feeding a "backwards" mains transformer would be a good starting point.

Has anyone here done this, please, or could anyone help with the design of a simple-ish 60Hz sinewave source?

Or is there a better way?

Many thanks,

Nick.

[Electronpusher0]

Many years ago the company I worked for made LVDT transducer amplifiers, ran off 50Hz mains, very low power.
One day they took an order from Sweden without first checking the testing requirements.
Long story short they needed it tested over a range of mains frequencies so I brought in my Mullard transistor amplifier and fed it into a reverse mains transformer to give 240V.
The input was a signal generator that could vary the frequency over the desired range. Worked a treat.
Something similar would work for a clock, the frequency would have to be fairly precise however.

Peter

110V isn't a lot for an amplifier using modern devices, saves the transformer. A simple phase locked loop from 50Hz could supply the 60Hz required with sufficient accuracy for the clock. The clock may well run happily on a square wave (voltage) making life easier.

[Hampus]

This seems to do what you are looking for:

https://sound-au.com/clocks/freq-changer.html

It is way beyond my knowledge so I can't say anything about the circuit except that it looks complicated

[jimmc101]

If you can handle AVR microprocessors then the circuit on this site could provide a simple solution with a suitably modified output stage.
I haven't tried it but it looks an interesting approach.
I confess I would feel happier with some capacity on the PB2 input to give some protection against possible miscounting caused by spikes on the mains.

Jim

[Buzby123]

Originally Posted by Hampus

This seems to do what you are looking for:

https://sound-au.com/clocks/freq-changer.html

It is way beyond my knowledge so I can't say anything about the circuit except that it looks complicated

I too thought it a bit over the top, and when I read this my confidence in the circuit dropped a notch -" I must point out that the complete project has not (at the time of writing) been built, ... "

[Radio Wrangler]

Originally Posted by Hampus

It is way beyond my knowledge so I can't say anything about the circuit except that it looks complicated

It looks reasonable and is designed around basic parts. It may look complicated if your definition is lots of parts. If your definition looks at whether it is straight-forward and splits neatly into separate sections which can be handled one at a time and is comfortable to understand, then it's simple.

So it could be a nice project to expand your knowledge with.

You could also use a DDS chip to make you an 10 bit sampled sinewave that would need less filtering. It would do all the division and enough of the filtering.
You'd need a little CPU to stuff data into it to set it up.

There are many ways, but it all comes down to a crystal oscillator being divided to the wanted frequency and then amplification and filtering (in either order)

David

[hamid_1]

I have the same problem to solve. Back in 2016 I bought a vintage 1970s General Electric AM clock radio for $3 from a charity shop in the USA. There's a video of an identical one here: https://www.youtube.com/watch?v=mkIcEGbrcj8

It's fitted with a Telechron synchronous electric clock movement which of course requires 60Hz AC to run at the right speed. I came across the same solutions mentioned previously. The commercially-made frequency changer is ideal, just plug and play, but at over £80 it's way more than my clock is worth. The Australian sound site looked promising, but the complete design is fairly complex and would take quite a bit of work to build, plus you'd have to design your own PCB first.

Now I've come across another solution which uses a PIC microcontroller to do the frequency multiplication and division, greatly simplifying the circuitry. I've attached a drawing of the circuit to this post. The main page for this project is here (scroll down to "50Hz to 60Hz sinewave converting inverter!")
http://www.romanblack.com/one_sec.htm

The (open) source code for the PIC is here: http://www.romanblack.com/onesec/ZE_SineConverter.htm

I think this is the best solution so far. The timing for the 60Hz output is derived from the 50Hz mains input, so your clock will be as accurate as the local mains supply. Over the long term, this is usually better than most quartz clocks. I reckon you can build it for less than £10 of parts, assuming you already have some suitable mains transformers. 240V AC - 12V AC transformers were quite commonly used with some ADSL and analogue modems, Christmas lights etc. as well as being found inside electronic devices such as portable radios / cassette / CD players. You'll almost certainly have something in your 'junk box'.

[broadgage]

A "plug and play" solution might be to purchase a small cheap power inverter from American ebay. Double check that the output is 60 cycles and 115 volts.
Power input is intended to be from a vehicle battery, but of course a 12/13.8 volt DC power supply could be used.

[turretslug]

How accurate is the 60Hz from a small cheap power inverter from American eBay? Unless it's based around at least a reasonably good crystal, it's likely to be close to hopeless for running a clock- a clock is sorely revealing of anything that isn't very close indeed to exactly its intended frequency and an inaccurate clock is a pain in the head and a liability. As hamid 1 points out, the public electricity mains is a more accurate long-term source than most common-or-garden crystals.

[emeritus]

My APC UPS can be switched to provide any combination of 50Hz or 60Hz, 120V or 240V output when running on batteries. I doubt it would be stable enough to run a clock long term but have no means of checking. Mind you, the daily drift might not be any worse than the variation in mains frequency nowadays that has been mentioned in other threads. The position of the sweep second hand of my mains electric clock relative to the Radio 4 FM time pips can differ by 20 seconds or more either way from one day to the next, athough there is no long-term drift from the average position.

[barrymagrec]

Many years ago (1976) I needed a 60Hz signal locked to the 50Hz mains for film sync purposes. I built a phase lock loop circuit using an LM 565 and a 7490 divider. I worked well but I don`t thinkl I still have the circuit. It was pretty simple though, I got the information from the National Linear applications manual.

Obviously it only produced a 5 volt TTL output but an amplifier to drive a clock motor wouldn`t be much of a problem.

[Skywave]

Originally Posted by Nickthedentist

Presumably, a 60Hz sine-wave source running into an AF power amp feeding a "backwards" mains transformer would be a good starting point.

Nick: I reckon your suggested idea has the merit of being relatively straight-forward and quite suitable for a D-I-Y approach.

A 60 Hz. sine-wave oscillator driving a moderate-sized low-frequency linear amplifier at about the 5-watt level, powered from U.K domestic mains, with its output fed to a smallish-sized transformer to step up its output voltage to 110-v.a.c.
A Wein bridge oscillator for 60 Hz. is where I would start. Should be quite simple to arrange using a cheap op-amp like a TL072.

Al.

[MikeM100]

A British pop group I once worked for took their own UK built and treasured Hammond Organ on a tour of the United States. On arrival they found it was hopelessly 'out of tune'. The reason being that it used a synchronous AC motor to drive 'tone wheels' to generate the notes.

https://en.wikipedia.org/wiki/Tonewheel

In the UK it operated on 240V AC 50Hz whereas in the States it was operating on 120V AC 60Hz.

I was therefore commissioned to quickly build an accurate 50Hz generator which I did using a using a National Semiconductor MM5368 IC and a 32kHz 'watch' crystal.

The 50Hz square wave output was fed to a band pass filter and an audio Power Amplifier that drove a 240V to 120V transformer in reverse.

The device can also generate a 60Hz signal as required for this clock application.