A 12V *AC* power supply

[avraham rosenberg]

2010/7/13 Shachar Shemesh <shachar at shemesh.biz>

>  Hi list,
>
> I bought a USB connected logic analyzer for too much money (not that much).
> When buying, I did a mistake and not thought through the issues, and bought
> from a US supplier without telling them this needs to be a 220V country. As
> a result, I got an external power supply that is 110V, which outputs 12V AC
> at 1000mA (why they do not write "1A", I do not know).
>
> To my shame, I actually bought a universal DC supply without noticing that
> it's AC I need, and started a support call with the company. They were very
> nice, and when we, finally, found out the source (I hope it is it), the guy
> said I could probably get by with 18VDC, but it would strain the capacitors
> (my math suggests that 15VDC is closer to the mark).
>
> So, does anyone know where I can get a 12V AC power supply? They are not
> exactly a commodity.
>
> Thanks,
> Shachar
>
> --
> Shachar Shemesh
> Lingnu Open Source Consulting Ltd.http://www.lingnu.com
>
>
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>
> Shahar, I have two suggestions for you:
1-220/110 converters "for foreign travel" consist usually of an
autotransformer converting 220V to 110V for use with small appliances. you
can feed your 110V power supply through them.
It's worth checking with an electrical tester which way to insert it in the
socket in order to get the voltage of the outputs at 0, 120 V to ground, not
110, 220V to ground, something that your equipmnent might no like. I have a
small on in my junkyard. Unfortunately the maximum output current or power
is not mentioned and it might be too weak for your needs.
2-Spot halogen bulbs working at 12V ac are pretty common. I would ask  lamp
manufacturers/merchands or buy one of suitable power and size. At this ratio
of voltages between input and output the converter is most likeky a real
transformer, with good insulation between the primary and secondary
circuits. This is readily checked with an ohmmeter.
Again, I have in my junkyard a (bare) unit, extracted from an old lighting
fixture, marked Pri 0-230V , Sec 0-12V 50 VA. It is clearly a real
transformer, and looks allright.
You can have any of them, or both, for the asking. I live in Jerusalem.
Cheers, Avraham
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