Monday, 16 June 2014

Problems with DHT11 Moisture sensor

I've recently been playing around with the DHT11 1-wire temperature and moisture sensor for my Arduino, and you may have seen my posts on and my old blog.

Now as an update, the DHT11 has burnt out! I was starting to get fewer and fewer readings, getting a checksum and then timeout error from the arduino code I was using. Eventually I never got any returned values, so decided to take a look. After checking all the cable runs, etc, I then added the pull-up resistor that was recommended in some locations. But unfortunately still nothing. So I decided to prise open the little blue plastic package, and the problem was quite clear:

If you look, in the lower left corner of the small coil (?) you can see the burnt parts which seemed to have made contact with the lower circuit board (where the spare leg was) and caused this burnt look. I'm not sure how or why this happened though.
My best guess is a large amount of moisture gathered, condensed and the water droplet caused the short to take place and kill the sensor.

So I've now got a replacement DHT11 and trying to work out how to safeguard the next one against damage and how to better sense the moisture in the dryer without destroying the sensor too!

Saturday, 7 June 2014

Arduino Leonardo with ENC28J60

This is a very quick post, it's mainly to act as reference for me in the future!
When connecting an Arduino Leonardo up to the ENC28J60 cheapo ethernet adapter things are a little more complicated than with the other Arduino's

I've used them before with the Uno and it's straight forward. PIN conections are:

// PIN Connections (Using Arduino UNO):
//   VCC -   3.3V
//   GND -    GND
//   SCK - Pin 13
//   SO  - Pin 12
//   SI  - Pin 11
//   CS  - Pin  8

However, when you get to the Leonardo things are a little different, as the Leondardo has the ICSP header which you need to use for this connection.
The ICSP connections are:
//   MISO  VDD (+5v)
//   SCK   MOSI
//   RST   GND

So the connections are:

Pin Connections (Using Arduino Leonardo):
//   VCC -   3.3V
//   GND -    GND
//   SCK - SCK
//   SO  - MISO
//   SI  - MOSI
//   CS  - Pin  10

Then to init the library pass it the pin 10 like this:
ether.begin(sizeof Ethernet::buffer, mymac,10)

And it works! Hopefully this will help you out if you're trying to do the same, otherwise it's just handy for my ageing memory ;-)

Friday, 6 June 2014

New Blog

Hello and welcome to my new blog. I'm moving from my old geeklog blogging to this, mainly because others use it and I like the format and ease of not having to maintain it. One such feed is who is always entertaining and good to read up on the challenges of running a DSL/ISP these days and hits upon many issues and frustrations I do too through $job

I'll hopefully import all my older blogs into this soon, but bear with me.