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Donivan
05-08-2006, 02:47 AM
How much current does the Basic Stamp I Rev Dx board have available to outside components on its Vdd pin? I want to use this for a 5v Relay (about 90 ma) but can't find the specs of the on-board 5v voltage regulator.

Thanks,
Donivan

Chris Savage
05-08-2006, 02:52 AM
Donivan,

90mA is definately too much. Always try to use an external power supply to power devices like that. Especially inductive devices. Have the BASIC Stamp drive them through something like a transistor, not directly.

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

Jon Williams
05-08-2006, 02:53 AM
That's too much -- you should use an external regulator (always a good idea). I would also suggest driving the relay through a transistor for some isolation and make sure you put a backlash diode across the coil.

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Jon Williams
Applications Engineer, Parallax

Donivan
05-08-2006, 02:58 AM
I'm driving the relay through a Darlington array chip (ULN2803) which I think provides protection for said relay. I'll power the relay though some exernal power.

Thanks!

P.S. Do you know how much I can actually draw from Vdd without it being a problem?

Chris Savage
05-08-2006, 03:05 AM
Donivan,

This is a quote from our website knowledge base.

How much current can the BASIC Stamp microcontroller’s on-board regulator provide?

The built in 5-volt regulator on the BASIC Stamp 1 module and BASIC Stamp 2 module can supply 50mA of current if powered by a 12-volt source. The BASIC Stamp 1 module consumes 1mA leaving 49mA available to power external devices not including any devices connected to the I/O pins.

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)