Pull up/down resistors and current limiting resistors

Clint

Do you have to use pull up/down resistors and current limiting resistors for inputs on the BS2? (for example, when using a pushbutton for an input)

Martin Hebel

The pull-up/down is a necessity for any device whose input into the BASIC Stamp may be floating. Such as a switch when not closed - the input to the basic stamp is not defined, therefore the pin is floating and may be high or may be low or may switch between the two dependent on static charges. Other devices, such as many digital sensors, may only output a low when active, and would need a pull-up as well.

The current limiting resistor is not needed, but typically added a safety feature so that if an I/O connected to a switch is made an output by mistake, the voltage between the two won't damage the I/O.

-Martin

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Martin Hebel
StampPlot - Graphical Data Acquisition and Control
AppBee -·2.4GHz Wireless Adapters & transceivers·for the BASIC Stamp & Other controllers·

Clint

Thanks for the response.

I am thinking that for prototyping I would use the current limiting resistors but for production I would eliminate them. Bad idea?

Martin Hebel

It's a good idea. Once the hardware/software is all finalized, the possibility of incorrectly driving an I/O is much less. And as we know, it's good to keep production costs down.

I seldom ever use the current limiting resistors for inputs and have never had an issue.

-Martin

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Martin Hebel
StampPlot - Graphical Data Acquisition and Control
AppBee -·2.4GHz Wireless Adapters & transceivers·for the BASIC Stamp & Other controllers·