Digital Capacitance meter using microcontrollers

[virdip]

Hey friends, I am trying to make a digital capacitance meter by using a HSC08 microcontroller chip (MC9S08QG8). Unfortunately this is one of those courses where one doesn't know anything because of lack of pre-requisites. Anyhow (enough complaining) what I have been trying to do is the following:
Connect the 555 timer to the IRQ pin of the chip. The 555 timer circuit has the unknown Capacitor attached to it. Now I am trying to measure the number of signals over a 7.5s period. I understand that I need an interrupt service subroutine to count the number of signals for this duration. However I am not sure how to control the count timing. I have been trying to use a delay subroutine such that the IRQSC register is set for counting in cycle of that delay.

 

[berkeman]

Hey friends, I am trying to make a digital capacitance meter by using a HSC08 microcontroller chip (MC9S08QG8). Unfortunately this is one of those courses where one doesn't know anything because of lack of pre-requisites. Anyhow (enough complaining) what I have been trying to do is the following:
Connect the 555 timer to the IRQ pin of the chip. The 555 timer circuit has the unknown Capacitor attached to it. Now I am trying to measure the number of signals over a 7.5s period. I understand that I need an interrupt service subroutine to count the number of signals for this duration. However I am not sure how to control the count timing. I have been trying to use a delay subroutine such that the IRQSC register is set for counting in cycle of that delay.

You can use one interrupt to just bump a counter variable (the pulse count) and return. Use a second interrupt to trigger on the expiration of the 7.5 second timer. That ISR disables the IO counter ISR, calculates the capacitance for display or whatever, zeroes out the IO counter variable, and re-enables the IO ISR.

 

[Mene]

I applaud your efforts to create a digital capacitance meter using microcontrollers. It shows a great curiosity and determination to learn new skills. However, I would recommend doing some research on the basics of microcontrollers and electronic circuits before diving into a project like this. It will not only make the project easier, but also give you a better understanding of the concepts involved.

In terms of your current approach, using a 555 timer and IRQ pin is a good start. However, I would suggest looking into other methods of measuring capacitance, such as using a frequency counter or a charge/discharge circuit. These may provide more accurate and reliable results.

Additionally, as you mentioned, setting a precise timing for the count is crucial. I would recommend using a timer interrupt instead of a delay subroutine, as it will provide more accurate and consistent results. You can also use the microcontroller's internal clock to control the timing of the count.

Overall, I encourage you to continue learning and experimenting with microcontrollers and electronic circuits. It may take some trial and error, but with persistence and the right resources, you can successfully create a digital capacitance meter. Good luck!