Hi folks,
I have what I think is a basic question but I've not been able to find an answer on my own and haven't been able to come up with the answer otherwise on my breadboard, I'm also a network/systems/software/database engineer type but not a hardware or electrical engineer though I'm learning.
I have a series of 12V .4mA circuits that I want to connect both to the GPIO on a Raspberry Pi and to an ADC, instead of having the RPI constantly polling the ADC I'll use the GPIO transitions to/from "low" and "high" as a method to replicate normal interrupt behavior. The RPI GPIO are 0 - 3.3V with 0 - 0.7V being the range for "low" and 2.4 - 3.3V being the range for "high" while the ADC channels are 0 - 2.5V.
Each of the circuits in the diagram are the same, we can disregard the purple lines with resistors. Using the bottom most circuit as an example, the one showing R11, R12 & R13. R11 & R12 are being used as a voltage divider to sufficiently and proportionally reduce the incoming circuit from 12V to something less than 3.3V; by my calculations with these at 1% tolerance Vout here should be 3.268V. This Vout is routed to the corresponding RPI GPIO which is the portion of the circuit exiting the diagram to the left. This Vout is also "tapped" by the circuit where R13 sits and this tapped run terminates to the corresponding ADC channel.
The issue I am struggling with is how to proportionally reduce the voltage at this point though I suspect I need another voltage divider to pull the 0-3.3V value into the 0 - 2.5V range. Secondarily I'm wondering if there is a better or more appropriate method for doing this given that eventually I'll have this built into a PCB.
Appreciate the feedback and guidance.
I have what I think is a basic question but I've not been able to find an answer on my own and haven't been able to come up with the answer otherwise on my breadboard, I'm also a network/systems/software/database engineer type but not a hardware or electrical engineer though I'm learning.
I have a series of 12V .4mA circuits that I want to connect both to the GPIO on a Raspberry Pi and to an ADC, instead of having the RPI constantly polling the ADC I'll use the GPIO transitions to/from "low" and "high" as a method to replicate normal interrupt behavior. The RPI GPIO are 0 - 3.3V with 0 - 0.7V being the range for "low" and 2.4 - 3.3V being the range for "high" while the ADC channels are 0 - 2.5V.
Each of the circuits in the diagram are the same, we can disregard the purple lines with resistors. Using the bottom most circuit as an example, the one showing R11, R12 & R13. R11 & R12 are being used as a voltage divider to sufficiently and proportionally reduce the incoming circuit from 12V to something less than 3.3V; by my calculations with these at 1% tolerance Vout here should be 3.268V. This Vout is routed to the corresponding RPI GPIO which is the portion of the circuit exiting the diagram to the left. This Vout is also "tapped" by the circuit where R13 sits and this tapped run terminates to the corresponding ADC channel.
The issue I am struggling with is how to proportionally reduce the voltage at this point though I suspect I need another voltage divider to pull the 0-3.3V value into the 0 - 2.5V range. Secondarily I'm wondering if there is a better or more appropriate method for doing this given that eventually I'll have this built into a PCB.
Appreciate the feedback and guidance.