Rationalphi
New Member
Hello everyone,
I’m working on a project with a Motorola HC11-E9 micro controller. I will be connected to 4 of the AD channels and sampling a slow system (temperature, humidity, etc in a room).
I’ve read through a lot of the reference manual for this chip but most of what I could take away was that for my A/D pins I should just have a series resistor to limit the current into the pin under the worst conditions that could be found on the board. Which would probably be a short to 12V. I believe they said a 1K resistor should work to limit the current (<25mA) without causing leakage from going to high with the input resistance. They also showed a bypass cap for noise filtration which would reduce the available sampling time but with my system sampling once every couple seconds would be fast enough.
So to rather than continue to make a short story long....
Could somebody suggest a good method or components to protect/isolate my pins that won’t adversely affect the accuracy of my readings?
I would also like to protect my output pins and since I’m just using on/off control all I need is a pulse and I should be able to use an optical isolator if needed.
Could somebody suggest an isolating IC perhaps with 8 channels or so for this portion of my system.. if such devices exist.
Thanks in advance!
I’m working on a project with a Motorola HC11-E9 micro controller. I will be connected to 4 of the AD channels and sampling a slow system (temperature, humidity, etc in a room).
I’ve read through a lot of the reference manual for this chip but most of what I could take away was that for my A/D pins I should just have a series resistor to limit the current into the pin under the worst conditions that could be found on the board. Which would probably be a short to 12V. I believe they said a 1K resistor should work to limit the current (<25mA) without causing leakage from going to high with the input resistance. They also showed a bypass cap for noise filtration which would reduce the available sampling time but with my system sampling once every couple seconds would be fast enough.
So to rather than continue to make a short story long....
Could somebody suggest a good method or components to protect/isolate my pins that won’t adversely affect the accuracy of my readings?
I would also like to protect my output pins and since I’m just using on/off control all I need is a pulse and I should be able to use an optical isolator if needed.
Could somebody suggest an isolating IC perhaps with 8 channels or so for this portion of my system.. if such devices exist.
Thanks in advance!