Renegade Red Currant Bush

My red currant bush just doesn’t behave like it’s supposed to according to the books. Again this year it’s flowering on 1 year old wood and there are very few flowers on the 2 and 3 year old wood:

The party is clearly on the 1 year old top shoots, and not much is going on below on the older wood:

The numbers on the picture below is the age of the wood:

But what the heck – I bet the fruit is just as good if we can get to it before the birds.

Soil Moisture Sensor Circuit Explained

Update 2011-09-05: I have created a new blog about electronics only – check it out here: Electronic measurements, NSLU2 and soil moisture sensor

The 1-wire soil moisture sensor circuit I use in my garden is designed by Eric Vickery from http://www.hobby-boards.com.

(c) 2006 Hobby BoardsĀ  Designed by Eric Vickery
Title: Moisture Meter 3
Rev: 3
Date: 10/27/2006 06:11:30p

(Click the picture for a larger version.)

Here’s a bit of explanation on how the humidity sensor circuit works.

The circuit is connected like this:

and the circuit works like this:

  1. Watermark sensor gets wet
  2. The time constant of oscillator IC 555 changes
  3. 555 IC oscillates faster and its supply current goes up
  4. Current in resistor R2 goes up causing the voltage across R2 to go up too
  5. The value of the current register of IC DS2760 changes
  6. Current register of IC DS2760 is read via 1-wire network

In my case I got the following values during calibration. I let the Watermark sensor dry in the wind and recorded the current register value, and afterwards the sensor was soaked in a bucket of water:

Dry = -0.2368
Wet = -1.400

These numbers form the 0 and 100 % limits of my soil moisture readings.