Regulated or unregulated powersupply

PeterH

I am a bit puzzled. Can I use any 12V DC powersupply for my BS1?
Until now I have only bought regulated powersupplies, but is that needed since there is a regulator on the BS1 ( Stamp 1 Project board rec C - that is )

Not a big deal but the unregulated supplies are a bit cheaper

/Peter

Mike Green

The Stamps have their own built-in 5V regulators, so you could run them off an unregulated supply. On the other hand, with an unregulated 12V supply, the supply's output voltage may be quite a bit higher than 12V, especially at the low currents involved. With 12V for Vin, the built-in regulator has quite a bit of voltage to drop and it doesn't take much current to be drawn from the Stamp to produce a lot of heat: (Vin - 5V) * TotalCurrentDrawn. An unregulated 12V power supply could easily put out 14V to 16V at a minimum at low current draws. You'd be better off in general with a 6V to 7.5V unregulated power supply that is rated modestly more than the maximum current expected to be drawn by the Stamp and anything else supplied by the power supply. For example, if your circuit can draw a maximum of 100mA, I'd use an unregulated 6V to 7.5V supply that can provide maybe twice that.

Phil Pilgrim (PhiPi)

Adding to Mike's comments, if the unregulated supply is being sold as a battery charger, it may also be unfiltered, which will lead to dropouts when the 60Hz cycle goes to zero. This could cause the Stamp to continuously reset.

-Phil

PeterH

Thanks for the replies. Fabulous forum !

I have to use 12V for the sensor which draws 15-30 mA from Vin.
Then I Only draw 7mA for the BS1 project board + 15 mA for LCD Terminal AppMod = 22 mA over the regulator

But I think you are both saying : spend the extra little money and buy regulated supplies.