Maximum voltage into stamp pin.
FORD
Posts: 221
What is the maximum voltage allowed into a stamp pin (bs2p24) ?
I know its possible to put rs232 voltage into a stamp pin through a resistor, but I would like to know the maximum practical voltage, and also is there a simple formula to set the resistor value for the voltage in.
(its not as simple as ohms law is it ?)
Reason is that I would like to detect 12 and 24 volts with a stamp, and if I can safely just do it with a resistor I will, otherwise I'll·put in an optocoupler, but its for a pcb which has already been made.
Cheers,
Chris
I know its possible to put rs232 voltage into a stamp pin through a resistor, but I would like to know the maximum practical voltage, and also is there a simple formula to set the resistor value for the voltage in.
(its not as simple as ohms law is it ?)
Reason is that I would like to detect 12 and 24 volts with a stamp, and if I can safely just do it with a resistor I will, otherwise I'll·put in an optocoupler, but its for a pcb which has already been made.
Cheers,
Chris
Comments
·· The optocoupler is the way to go.· The voltage input information can be found in the datasheet for the SX, which is at the link below.· I hope this helps.
http://www.parallax.com/dl/docs/prod/datast/SX48BD-Data-v1.2.pdf
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Chris Savage
Parallax Tech Support
csavage@parallax.com
The Absolute Max is 7Volts difference between Vdd & Vss, but a nominal +5volts is considered ideal for the BasicStamp.
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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········
Using a plain resistor doesn't give you much safety, though. If somebody inadvertently raises the line too high, it can still blow the BS2 I/O pin. Thus the recommendation for an opto-isolator -- those are much cheaper to replace.
Thats cleared that up for me. Thanks Allan for the explanation on the 1ma max on the protection diodes, thats cleared it up for me. Obvioulsy not much tolerance to just go selecting a resistor. Will go the opto way.
Thanks again,
Chris,
West Oz.