Inverter help needed.

[Deko]

A question for all you electronics gents. I have been asked to show my Fibre optic clock at a few events where there is no mains supply. The electrics on the clock consist of two LED drivers (switch mode), and one synchronous (240v) motor. My question is, will a small 12v to 240v inverter cause problems for the motor. As I understand these things the inverter is square wave output, ok for the LED drivers, but would the motor need a sine wave supply ???  Any advice will be most welcome.

Cheers Dek.

[Bluechip]

Well, young Deko .... Hmmmm ..

If it's something like this:

https://www.machinemart.co.uk/shop/product/details/010710400?da=1&TC=SRC-inverter

your motor will probably run fine, BUT ... one I played with [ not from MM but could well be a generic item ] the frequency is only somewhat 50Hz which is probably what you want ??

If it's pseudo-sine there will be harmonics which may well cause the laminations to sing a bit ?

If you look at the devices suggested for running off the inverter, they are all things which won't mind if the 50Hz isn't too accurate.

I once changed a Shuko[?]  socket for a 13A UK on one and it was scoped at close to 68Hz ...   

Once more it was not supplied by MM.

Dave

Edit .   Sorry, should be Schuko ...

http://en.wikipedia.org/wiki/Schuko

[Deko]

Thanks for the info Dave. Obviously it is the frequency that in this case determines the motor speed so if as you say it were to be 68hz rather than 50hz then the clock would be running very fast.

For the short time it would be on display this would not really be too much of a problem. What worries me is would it damage the motor in ANY way.

I bought the motor new about 10 years ago, when it came to final assembly of the clock I thought I would buy another the same, only to discover that they stopped making that model some years ago.

To fit an alternative motor would mean an almost complete rework of the clock, so as you can see it is a major concern

Cheers Dek.

[Bluechip]

What motor is it ???

I have a vision of a geared motor, bit like the uwave turntable motor ??

Dave

[Deko]

I haven't time to do it now, but I will scan the info sheet and post tomorrow.  Thanks again Dave.

Cheers Dek.

[Bluechip]

I haven't time to do it now, but I will scan the info sheet and post tomorrow.  Thanks again Dave.

Cheers Dek.

 

Dave

[Deko]

Hi again Dave,  Here is the info on the motor for what it is worth. Looks like it is a geared jobby, as there are various speeds available in the same housing. I chose this one because of it's nice compact size.

The only other info I have is a drawing with all dimensions shown, no electrical spec, or gearing info.

Hope this helps.  Cheers Dek. 

[John Rudd]

Dek,
Not sure if this helps you ......my son and made a clock using a stepper motor and 12 LEDs....driven by a pic micro ....the LEDs were for hours and the sweep hand minutes...all battery driven...no inverter needed just in case you change the motor..


But back to your orig....if the inverter uses a sq wave then as Dave says, the motor might sing a bit...maybe some sound proof material might help if its too loud...

[Deko]

Thanks for the reply John. The clock has been up and running for quite a while now with no problems. Like I said earlier, to fit a new motor of a different type would need a major rework, which I really don't fancy doing.
The only reason for wanting to use an inverter is to show the clock at an event where there is no mains supply.  Knowing very little about these things, I didn't want to risk damage to the motor for the sake of a few hours use at a show.
There is a thread about the clock on here in "General Crafts" under the title Fibre optic clock, and a (rather poor) vid near the end of the thread.  Thanks again John.

Cheers Dek. 

[John Rudd]

Just keep an eye on the temperature of the motor, if it feels too warm to the touch then you might have to think of another method for powering.....

[philf]

Hi Dek,

I think this is the right motor:

http://www.ebay.co.uk/itm/REPLACEMENT-MOTOR-4W-1-RPM-CW-DJ-DISCO-KARAOKE-LIGHT-LIGHTING-/261783348199?pt=LH_DefaultDomain_3&hash=item3cf380e3e7

£5.99 inc delivery!

I can't advise on using it with a 12v to 240v inverter but I have a 150w unit somewhere (I think in the caravan which is wrapped up for the winter). If I find it and have time I'll have a look at the frequency and see how it will drive a similar motor.

Cheers.

Phil.

[Deko]

Thanks Phil, that would be great. I have a fair bit of time to try and sort something out as the event is not until early July. I will now have a quick look at your link, then kip time.

Cheers Dek.

[philf]

Hi Dek,

I've retrieved the inverter from the caravan and have connected it up to a DC power supply and to a synchronous clock which has a seconds hand.

It must be running at slightly less than 50Hz because 5 minutes on the clock took 5min 4.45secs on my stopwatch so it's not too far out to demonstrate your clock. There were no untoward noises from the clock and no noticeable rise in temperature. I'll leave it running for a few hours.

The inverter is taking 0.5 amp at around 13.5v. It has a cigar lighter type connector so would need something rigging up to connect it to a battery. I've got it connected from my power supply with crocodile clips.

If you want to borrow it you're welcome. I'm sure we'll be coming down to the garden centre at Leighton on our bikes before July so I could bring it in my saddlebag. You'll have to supply your own car battery!

Cheers

Phil.

[Deko]

Phil, you are a star, I was beginning to have visions of trying to trail a mains lead 200yds across a field, or just not have the thing working.

I don't mind buying one if I know it will not damage the motor or be a waste of money. What make is the one you have ?, it sounds like it would be fine for the length of time I want to run it.

Cheers Dek.

[John Rudd]

Dek,
Summat like this?

http://www.maplin.co.uk/p/ring-automotive-12v-modified-sinewave-300w-inverter-with-21a-usb-a09lw


Probably get one cheaper on Ebay  390911203491 or 390586805375

[philf]

Phil, you are a star, I was beginning to have visions of trying to trail a mains lead 200yds across a field, or just not have the thing working.

I don't mind buying one if I know it will not damage the motor or be a waste of money. What make is the one you have ?, it sounds like it would be fine for the length of time I want to run it.

Cheers Dek.

Dek,

It's a Nikkai QM80. As John says, there are loads similar very cheap on eBay. Mine was from Maplin but a long time ago.

Which reminds me it's still running in the workshop!

The offer's still there if you don't get fixed up.

Cheers

Phil.

[Deko]

Thank you Phil and John.  Now I know that one of these things is unlikely to do any damage to the clock,

and the fact that I now know where to get a new motor like the one I have, I will no doubt treat myself to one.

Phil, you are most welcome to drop in for a brew anytime, no excuse for a visit is needed.

Cheers Dek.