Need expert opinion...

mlm001

Hello,

I am using the Basic Stamp 2 on the Super Carrier board.· I would like to use the 12 VDC
line off of a drive power connector of a PC power supply, by changing the connector to match
the specs on the Carrier board.·

As you know, this is a switching power supply.· Not sure what the wallwart is.· Also not sure what the difference is...

Will this work?· Please let me know, I really don't want to fry my stamp.· My application of the stamp will be located inside a PC in the long-run, and I just want to make sure I don't need additional power input.

Thank You,

Mike Marshall

dandreae

The voltages are correct coming from the PC power supply.· The only problem is the current capability of the power supply is so great that we have had numerous customers who have damaged their stamps.· However, you can use a voltage regulator beforehand· and it will work just fine.

Dave

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Dave Andreae

Tech Support
dandreae@parallax.com
www.parallax.com

·

allanlane5

A "wall-wart" is an AC to DC adapter that plugs directly into the wall. It then sits against the wall, looking something like a 'wart', thus wall-wart. Typically these are small black boxes with a two-conductor cable that has low DC (or AC) voltages on it -- like 6, 9, 12 volts DC.

What is in the 'wall-wart' is typically a small transformer which provides the 120 volt to 12 volt step-down, and a couple of diodes to convert the AC to a DC (with lots of ripple). These units also have a current rating -- 300 mA, 600 mA, 900 mA, 1000 mA. Usually, in "open-circuit" (no current flowing) these units measure a few volts above their rated voltage.

In BS2 use, a "Linear Regulator" device is used -- like the 7805, or the 2940-5. This device regulates the rippled 9, 12, 18 volts DC into a clean 5-volts DC.

Now, a "switching" power-supply does its voltage conversion in a different way. The output of a 'switching' supply tends to be much 'cleaner' (less noisy, smoother voltage) than a wall-wart. You CAN run this voltage into a Linear Regulator to get the voltage step-down needed for the BS2. The "Super Carrier Board" already has a LM2940-5 Linear Regulator on board, so all you'll need will be a jack (5.5 mm/2.1 mm, center positive) to connect the 12 volts from your PC into the board.

You need to wire your 12-volt line into the "Vin" voltage, as that is the voltage that goes to the regulator. You MUST not wire it into the Vdd voltage, or you'll burn out your BS2. Connecting to the 5.5 mm/2.1 mm power connector is the easiest way.

mlm001

Thank You for both replies.· I will keep these in mind.



Mike Marshall