Need Thai Retail Source for Step-Down Transformer

[StoneSoup]

I urgently require six small step down transformers to convert Thai household current (220 VAC) to 12 VDC, 3.5 amps (42 watts). An exhaustive search throughout Panthip Plaza produced zero results - no one there could even suggest a source.

 

I require six units now. My demand may grow to several hundred units per month, pretty quickly.

 

Referral to a local Thai "off-the-shelf" source would be much appreciated.

 

Thanks,

Stone Soup

[lopburi3]

I would first check the Telephone Yellow pages as they usually list firms that make/sell this type of item. Don't have a current copy myself. Would think you would be interested in wholesale rather than retail.

 

A place that I am sure you can find would be the Banmoh Road area of the old city. This is the center of electronic parts - testing equipment/transformers and there are many shops selling these types of items.

 

Banmoh road is one block to the West (toward canal) from The Old Siam Plaza shopping center. Taxi driver should know as center for both electronics and diamond sales.

 

[StoneSoup]

OK, thanks much. I will ultimately need wholesale, but I need a couple samples as soon as possible - retail. I'll let you know what happens.

 

"Let the good times roll!"

Stone Soup

[StoneSoup]

Well, I did make my way to Ban Moh late afternoon on Saturday. 'Hell of a taxi ride from MBK to Bahn Moh, due to congestion in Chinatown, but once there, I found something similar to what I needed within about five minutes.

 

I never could find the 12 VDC at 3.5 amps that I really needed - the closest I found (and purchased) was 12 VDC, 5 amps. That may satisfy my immediate demonstration requirement (although it may also kill the lifetime of the circuits being operated).

 

So - if anyone knows of a source for 12 VDC, 3.5 amps, I still have an initial demand, and will likely have substantial follow-on demand.

 

Thansk again.

 

The Fighting Fish

[danish30]

Hi StoneSoup,

 

although it may also kill the lifetime of the circuits being operated

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It wont have any impact on the lifetime of your circuits that your powersupply can deliver 5A instead of 3.5A. It only means that the 5A supply is capable of delivering more power than needed. Usually it is a good idea to dimension a powersupply a bit larger than needed, of course depending on what kinds of circuits you are connecting.

 

Best regards,

 

Danish30

[StoneSoup]

Hi,

 

Thanks for your comments.

 

I am working with thermoelectric circuits, employing the Peltier effect. These devices are basically like small, flat-bread sandwiches that pump heat - basically from one ceramic surface (slice of bread) to the opposite (with a semiconductor material in-between). The distance between the slices is about 2 mm. Excess current can cause the pumping of heat to be too vigorous - raising the temperature of the "hot side" above the melting point of the solder holding the package together. I am also using "sandwiches" that use two identical ceramic plates at opposite ends, each 40 mm square. The "hot side" expands, and the "cold side" contracts. Too big of a Delta T, and the shear stress on the circuits between the plates can cause failure.

 

So - anyway, your comments are correct with respect to the electrical functioning of the circuits, but the thermal effects of excess wattage can cause problems. The circuits can carry more current than their rating, but it can be dangerous to the health of the materials involved.

 

This is really unconventional technology.

 

Thanks again,

Stone Soup

The Fighting Fish

[lopburi3]

I am working with thermoelectric circuits, employing the Peltier effect.

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I admit am of the tube (valve) generation myself but do not understand how a transformer rated to handle a higher current is going to cause a problem. The transformer is passive. The only difference is a larger wire. A 3.5 amp transformer probably could handle 5 amps for awhile - it sure would not limit the amperage; until it burnt out. In my knowledge the only reason to use a smaller transformer is cost/size related. But then NPN and PNP are new words for me. ::

 

[ALHOLK]

Hi!

 

I to am from the valve generation and tend to agree with you. However if the current is an issue I would rcomend a power supply with a built in current limiter. These existed already in the sixties when I attended a technical school. I'm quite sure we have them in abundance in the labs at the company where I work.

 

regards

 

ALHOLK