3 replies to this topic

[Moskus]

During the easter my daughter and my sister were growing some garden cress. However, due to our lack of attention, they were constantly running out of water. And died, much to my daughters  dispair.

 

But that got me thinking. Why can't I use a Netduno to water the cress? I've already figured out how to measure the moisture, so that's not a problem (use 3.3V to an analog input, it's dry if it gets below ca. 40%).

 

And I got myself a small motor, like this: http://www.ebay.com/...984.m1439.l2649

... for water supply and I want to run it from my Netduino.

 

I'm not that good with electronics, so how can I achieve that using the simpliest method?

[hanzibal]

HI!

 

Assuming you will monitor the humidity and control the pump with a software on/off regulator or filter since it will take some time for actual humidity to stabilize so that reading are reliable.

 

The pump will need at least 600mA so I suggest you get a separate 5V power supply capable of maybe 2A that can source both the Netduino and the pump. You can then connect the pump via a MOSFET to a digital output of the Netduino to turn the pump on and off as part of regulation.

 

Btw, what about the pump, do you need it for taking water from a nearby pond or well?

[Moskus]

Hi Hanzibal!

 

I've been testing with crass on a bed of cotton, and the Netduino reacts quit fast to water being added, so I'm not so worried about that. I'm just thinking of submersing the pump in a bowl of water and connect it to a flexible tube.

 

MOSFET is news to me, but then again there's much electronics that would be. Is it the same as a small relay or something like that? Where can I get one (in Scandinavia )?

[hanzibal]

A MOSFET (abbrevation for metal oxide semiconductor field effect transistor) reacts to voltage as apposed to a regular transistor that reacts to current. A key feature is their ability to handle large current since they have very little internal resistance, there are MOSFETs that can handle 70A or more. They are available in any electronics store.

Here's how to wire an N-channel MOSFET to run a motor:
http://bildr.org/201...0n06le-arduino/

I'm sure these are available in Norway or else you can order from this swedish shop:
http://www.electroki...laritet.nch-v16

Surely, you can find a transistor to do the job and a MOSFET might be a little overkill but they are very versatile and will keep you on the safe side.