can Stamp give me -5V

kranthi

hi can stamp give me -5V and +5V instead of 0V and +5V using commands like HIGH or LOW.

thanks,
kranth

Bruce Bates

kranth -

The direct answer to your question is no it can't, as is. However, I'm sure one of the analog gurus here can show you a way to add a transistor or two to the output pin such that you could get that kind of output.

Regards,

Bruce Bates

Beau Schwabe

Bruce, you rang?


kranth,

Here is a simple level shifter that will do what you want (inverted).
In other words, you make the pin HIGH (+5) and you get -5V on the output.
likewise, you make the pin LOW ( 0V or GND ) and you get +5V on the output.

Keep in mind you need to generate a -5V source to supply the level shifter.
Let me know if you need help with that, and I can supply a schematic as well.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Jonathan

Kranth,

A quick and dirty way to get *close* to -5 is called a charge pump. Look on the web for "negative charge pump". You'll find plenty of schematics for it. Basically you use a couple of caps, a diode and a resistor. The circuit requires being pulsed at a fairly high rate, so if your Stamp is too busy to do it, then a 555 timer can be used.

This type of arrangment can't provide much current, and it is noisy. It is best for things like a - voltage for an LCD that requires it, for example. It is not as good for things like op-amp amplifiers, as it adds noise. It is cheap and made from parts you can pull from junk.

Jonathan

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www.madlabs.info - Home of the Hydrogen Fuel Cell Robot

PJAllen

With·a MAX232 you could have +10 & -10V outputs, from only a +5V supply.

Better yet, if you want to have -5V, there's the ICL7660, a CMOS "+5 to -5V converter", an "ideal' option.· www.jameco.com/wcstore/Jameco/Products/ProdDS/51174.pdf