Arduino Interrupt Tute

Hi All,

I’m sure I’ve seen this around.

I need to write up a little routine to test the water preloading on my wicking bed project.

I seem to recall a tute on Arduino interrupt procedures but maybe I only dreamt it!

Is there such a tute?




Hi Gerard,

We have a section in our Arduino Online course, you can check it out here: Arduino Workshop - Section 5.4 - Interupts

If you have any other questions let us know!

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Thanks Liam. I’ll post up the hardware/ software when done. I think it’s an interesting design (if I do say so myself!!)


Hi Gerard,

We’re keen to see it! I’t been really interesting seeing your occasional update on the forum :smiley:


Apologies for the silence, there’s been a lot going on down here in Macedon!

Below is a more detailed look at the 40103 operation. I made some changes as I didn’t fully understand how the 40103 works.

I made U7 just a down counter that preloads to max count each time it gets a RESET. When the counter decrements to zero, it restarts at a count of 256. Why did I do this? Well, we measured the clock at U4D to determine how much water flows for a count of 256 pulses. It turns out that 1 litre is about 248 pulses of the transducer. So we kinda figured that a minimum flow into the wicking bed would be 256/248 litres…a bit over a litre.

U8 is preloaded with the correct amount of litres that we want to add to the bed. A count of 256 here means adding 256 litres. Something we don’t foresee happening. So the value will be much less than that.

The arduino turns the water on (U5B/8) and pre-loads U8 with a value we reckon will get the right amount of water into the soil. Then the counter decrements via the water flow sensing transducer. When it gets to a count of zero, pin 14 on U8 clears U5B and the solenoid turns the water off.

The 40103 is a pretty handy device and is pretty flexible.


I finally got the Wicking Bed PCBs made.

Looks good as they work like a standard Arduino.

The slave does all the grunt work. I have tested all the various parts but not as a whole yet. That explains the missing ICs.

The Master is basically a reporting/monitoring device with not much on it.