Determining correct AC/DC adapter for equipment

:My new family owns a large selection of light toys collected over the :years. Unfortunately, in many cases the adapter is missing. Now, we :also a cache of old adapaters of varying voltages, ampages (is that a :word?) and polarities - AC/DC and AC/AC. Without the benefit of manuals :and, in some cases, no information on the toy casing either, I have had :a few mishaps blindly attempting to match up adapters to toys (mishaps :involving the smell of burning component). :My question is, in the absence of the usual information (or a :multi-tester), is there a way to determine what adapter is required for :a particular toy/appliance? Maybe opening up the toy and calculating :something from the components used inside? :In hope :Dean

Usually the device has on it the power requirements, for example:

3v DC, 1.25 amp. In general you want your AC adaptor to provide the correct type of voltage (AC vs. DC, and they are usually DC), the correct voltage (if it says 4.5v for example, you want your adapter so designated), and at least the amperage (that's the word!) asked for. I too have a good collection of adapters gotten from here and there.

Another thing you usually need is for the connector to match up. Has to be basically the same thickness and reasonable length to make the connections.

I have one or two multipurpose AC adapters with switches to change the voltage and with multiple connectors to fit various equipment. They don't work with everything, but do fit a whole lot of stuff. Of course, they are kind of klunky (big), but they work. You can get them at Radio Shack, independent electronics stores and such.

Dan

If all else fails, I hook up a multi voltage unit and check the current being drawn. I set the polarity for maximum current, then increase the voltage to either a reasonable current if charging a battery or until the device works.

Many thanks for the reply, Dan. Unfortunately, my problem is that on so many of the devices that require adaptors there isn't even the basic voltage information indicated near the adaptor socket, or anywhere else. Is there a way I can determine a device's power requirements - voltage and amperage - just by examining the components inside? Or do I need equipment like a multi-tester or some such?

The current the device draws can be determined after setting the voltage. So if you have say a 1 amp supply with variable voltage that should work for most things. Start at the lowest voltage and work up until it operates normally. Capacitors are one easy way to determine polarity. A DC supply can be used where the original was AC in many cases, but not the other way round.

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*If work is so terrific, how come they have to pay you to do it?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Junk the ac output adaptors, because dc output wll work for pretty much all devices, including those dedigned to take ac, whereas ac will damage many.

Normally the v i and polarity are marked semi-invisibly near the socket, the info is shallowly moulded into the casing, so holding it upto the light usually reveals a fair bit.

Opening it and looking for a diode or capacitor will indicate polarity.

Start at lowest voltage, say 3v, and increase until it works.

You'll succeed in nearly all cases this way.

NT

Thank you all for replying, a nice consensus of information. I'll see how I get on.

AC adaptors are handy for home build projects. They tend to be higher output, like for like. So send any junked ones here. ;-)

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*El nino made me do it

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

For those items that also ran on batteries, you can calculate the needed voltage as # of batteries times 1.5. Batteries are DC. You might be able to trace the battery wiring to the jack to determine polarity.

or use a multimeter to find that one of the battery conections connects directly to one of the input jack connections.

NT

I have a large bin full of them. I'd let you have half, just to thin the herd, so to speak.

Alas, they're too heavy to ship economically....

jak

Flat rate envelope? :)