Kristoffer, By default the Digital IO pins only return a True for High (3.3V) or False for Low (0V). If you want to read varying degrees of voltage you'll need to use one of the Analog IO Pins. These will return a voltage between 0 and 3.3V that you could then use to determine the proximity from the device. There are a lot of examples in the forums as well in several of the books on Netduino to help get you started. Good Luck and keep us posted on your progress.

If I remember correctly, The Netduino will see anything higher than 1V as True and this might be where your trouble is. Can you configure your voltage divider such that when the sensor is not triggered your below 1V? Guys, can you help me out with what the true voltage threshold is for On vs. Off on the digital ports?

I'm in the process of building an Electric Homebrewing system and I am planning on using the Netduino as the process controller. This means I'll need to use the outputs from the Netduino to turn on and off 120V and 240V AC devices, mostly motors and heating elements based on temperature readings. I've built the control interface and have the temperature monitoring circuit and code working just fine, now I'm ready to build out the power switching circuits and add the code to control the power to the devices. I've purchased some nice T9AS5D22-12 30 Amp 240V AC board mount relays, but was wondering if this was overkill. I'm needing to power one 120V 15 AMP Pump and one 5500W 240V electric heating element. Could I get away with some heavy duty power switching transistors or would it be safer to stick with the relays? I've looked at the BrewTroller boards which are built for the Arduino, but can't quite figure out what they are using to perform the switching. Any ideas what would work best? Thanks

Nicky, Good Catch! I had to do something similar with my web server. All TCP/IP communications would hang until the Netduino would get an IP Address when the Netduino was configured for DHCP. Another thing to watch out for, is your app will hang if the Netduino is configured for DHCP and you are not connected to a network. I ran into that a couple of times as well.

Magpie, You are right about it being in the spirit of brewing your own beer. If I'm too damn stubborn to buy my beer off a shelf at the bottle store, why would I not make my own components. I appreciate the good advise. I do not plan on cycling the pump on and off, it will be on for 60 to 90 minutes when I recirculate the mash and then on for 20 to 30 minutes when I use it to push cold water to cool the wort. However I believe the heating element will be cycled on and off quite a bit as I try to maintain a constant temperature between two thermocouples during the mash which lasts for 60 to 90 minutes. During the boil the heating element will be on all the time which could go as long as a couple of hours.

This is a really good piece of work. Once you have it all documented it definitely should get posted to the WIKI. Thanks for sharing your idea!

You need to add a reference to SecretLabs.NETMF.Hardware.AnalogInput and that should get you what you need. Hope this helps.

Magpie, I actually had drawn up my original circuit based on that exact diagram, I guess I got a little carried away thinking that maybe I was being too cautious. But looking at the specs on the Brew Trollers, their relays are only handling 10A at 240V, so my 30A at 240V should be more than safe enough. Now I just have to spend a fortune on water tight connectors and all of the rest of the hardware. The money I spend on my toys is outrageous!

Did you try the usual methods to stabilize the voltages, like in http://highfieldtale...highfieldtales/ - connect aref to 3v3 via a inductor, use a (fast) capacitor between aref and ground and a "big" one between 3v3 and ground?

Stefan,

That is a really good article, I never realized how much noise was going on. Being pretty rusty with electronics do you have a sample schematic that shows what your final solution was to filter out the noise?

Thanks,

Jim Lavin

I bought several of the relays for SparkFun to do just what your talking about and they work fine for things like the fridge, freezer and pump motors. I wouldn't try to drive a Water Heating element with them though. I was searching for a good thermocouple/thermistor for one of my mod projects and found that Brewer's Hardware have several different types you could purchase that work OK. I just stay away from the temp probes for the Brewtroller since they use One-Wire support and right now the Netduino does not support One-Wire communications without dropping back to version 4.1. I found out that they have both Positive and Negative temperature coefficient temp probes so you might want to call them to make sure you get one that is a negative coefficient probe and then you can use any of thermistor code out on the arduino forums to read the probes. I've also posted a lot about my Netduino Brewing Projects out on my site http://diybrewery.com and am in the process of putting together a book on my projects. Good Luck! I'm looking forward to what you come up with.

Hello Bryan.
Here the answers:

• no, I'm not familiar with *that* project, although we're developing our own, which is similar;
• yes, you should able to interface easily with a Netduino just leveraging my Modbus library.

Hope it helps.
Cheers

Mario,

I have a couple of questions for you about your Modbus library. Being new to the whole world of Modbus, let me give you a little background as to what I want to do with it and maybe you can steer me in the right direction.

I'd like to use it to control my Electric Brew Kettle's heating element by setting the target temperature I want to reach and then read back the current temperature and whether the element is on or off.

As for setting the target temperature and reading the current temperature and if the element is on or off, I'm thinking I could use the ReadRegisters and SetRegister methods.

I've also been working on porting over the Arduino PID Library to provide a better control algorithm and would love to be able to set the PID settings, however they are all doubles and I didn't see anything in the Modbus spec that talked about sending doubles to a device, everything looks like integer values.

Any ideas on the best way to go about setting this up?

Thanks

You are running into switch bounce which is a common problem. You can get rid of it by using The time passed into the function to check when the last time the button was pressed and ensure you reject any interrupts within a predefined period of time. Below is an example I'm using for my Brew Controller, I will only act on the interrupt if it has been more than 200 milliseconds since the last time I acted upon it.

public static void EngageHeaterButton_OnInterrupt(uint data1, uint data2, DateTime time) 
{
  if (engageHeaterButtonLastPushed.AddMilliseconds(200) > time)
    return;
  // button press state received in data2
  // 0 = open, 1 = pressed
  if (data2 == 1)
  {
    PinManagement.heaterEngaged = true;
  }
  _displayHelper.DisplayText("Heater|Engaged");
  engageHeaterButtonLastPushed = time;
}

Hope this helps you out.

You are correct about the bounce being a voltage fluctuation. The other part is how the Netduino determines an edge change from low to high. As I understand it, The Netduino will look at voltages below 1.6V as a logic low and those above as a logic high. So if your trace isn't showing a pronounced bounce it could be that the signal is varying just enough to be seen as fluctuating from low to high causing the Netduino to trigger the interrupt multiple times. Hope that helps

After checking out the sourceforge project and Mario's ModBus library, I'm thinking of replacing the web based app on my brew controller with this. Should be great for an example on how to use both together.

Check out this thread. It should give you a good idea of how to play a WAV File. http://forums.netdui...-finally-works/ Cheers!

For the price Annabooks is selling it for, You could buy a Kindle reader and all the books for the Netduino and still have money left over.

I'm in the process of building a brewing controller that will be used to control an existing heating element used on an electric turkey fryer. My goal has been to mod the existing unit without replacing much of the existing parts. As the system is now, the heating element is turned on and off by a 12VDC relay. I've got this working quite well by using a normal IO pin and turning it on and off. What I would like to do is as the temperature of the beer gets close to my goal temperature use one of the PWM ports to change the duty cycle from 100% to 50% on down to 0% as I get closer and closer. This way I'm hoping to reduce the amount of temperature drift in the overall system. When I started playing with the PWM port and varying the duty cycle I noticed that the voltage readings were strange, at 50% Duty cycle I was only seeing 1.6 volts instead of 3.3 volts. Maybe this is because I am using a multi-meter instead of looking at it with an actual scope. Does anyone know what I should be seeing? Also, is varying PWM duty cycles with a relay a really good idea? I've read where it's not an issue with solid state relays but I'm uncertain about normal relays. Thanks

I spent some time this weekend putting together a shield for the temp monitor circuit. I used a piece of tri-board, cut it down to the size of shield and then added the components. Attached are a couple of pictures of it. Hope you enjoy!

Hey everyone, Thought I would share my latest project with everyone. I'm building a process control system for an Electric Brew System. So to help me vet out all of the functionality I've been putting it together a piece at a time. To start with I wanted a nice web based user interface that would allow me to configure and monitor the mash, boil and cooling profiles of the entire brewing process. So I started off with the web-based user interface and the temperature monitoring since that is probably the simplest part of the entire process. So the solution so far has been a cobbling together of several libraries: Thanks to Markus VV and his NeonMika.Webserver project over at http://neonmikawebserver.codeplex.com/ I had a really quick time of putting together a JSON based control interface that would allow me to configure the temperature logging parameters as well as monitor the temperature using a couple of jQuery plug-ins. All of the files used by the interface are stored on the SD Card. The initial load of the page is a little slow, but I'm pulling down about 20 files in all, along with live data requests to get the current temperature, the temperature history and the settings. I incorporated a NETBIOS Name Resolution library and NTP Client library from Nicholas3 over at http://code.tinyclr.com which allowed me to make the Netduino Plus reachable by name across the network while using DHCP as well as update the system clock without having to resort to adding a Real Time Clock. I also incorporated a JSON generation library by Wouter Huysentruit over at http://code.tinyclr.com to extend the NeonMika.Webserver to quickly send back my data in JSON format. The temperature probe I built was based on a ADA Fruit tutorial on how to interface the TMP36 Temperature sensor to an Arduino. I also placed a 1uF capacitor across the 3.3V and Ground as well as a 1mH inductor between 3.3V and ARef to help cut down on some of the noise I was seeing from the Ethernet port. My original readings were back and forth across several hundred millivolts when I was taking readings very close to each other and the great advice that the folks in the forums had about this problem really helped me to cut down most of the noise. You can find a great discussion on the topic at http://forums.netdui...ading-accuracy/ But just to be safe all of the temperature readings are based on an average of 100 reads, this really seemed to help smooth out the readings even more. I've attached a couple of screen shots of the User Interface and of the very simple temperature probe circuit and schematic. I'm in the process of building out a quicky shield and cutting up a project box so I can have everything in one nice to handle box about the size of a cellphone. Once I'm done with the construction I'll post some pics of the final logger in its case. Enjoy!

Hi Coding Smackdown,

It's possible to download the source of this project?

Thanks,

Ludo

As far as source code, I'm going to try and load it up on to codeplex this week. Issue with loading up here is that the file size is too big and I'd have to upload multiple posts and If I update it, you wouldn't have the latest.

But I'll definitely update this post once I get it up on codeplex. In the meantime, if you need it you can send me a message via the forums with your email and I'll send it to you.

As far as source code, I'm going to try and load it up on to codeplex this week. Issue with loading up here is that the file size is too big and I'd have to upload multiple posts and If I update it, you wouldn't have the latest.

But I'll definitely update this post once I get it up on codeplex. In the meantime, if you need it you can send me a message via the forums with your email and I'll send it to you.

I took a little time this afternoon and put the entire project up on codeplex you can find source code, schematic and eventually documentation at http://diybrewerytem...r.codeplex.com/

Enjoy!

It does not look to be available in print, I checked both Amazon and www.annabooks.com. However Amazon does provide a free Kindle E-book Reader for both PC and Mac if that helps at all.

I didn't see anyone else post about this, so I thought I would give everybody a heads up. A new book was released about the .Net Micro Framework called, Professional's Guide To .NET Micro Framework Application Development. I picked up a copy on Amazon on the Kindle for a decent price. It does include examples for the Netduino as well as other .NET Micro Framework devices. I wouldn't call it a beginner's guide, but its not that advanced either. It is based on a training program provided by Annabooks, they provide quite a few example programs to explain each section. So far, what I've read is pretty good for an intermediate guide. Here are the book details from the Annabooks web site: Professional's Guide to .NET Micro Framework Application Development By John R. Malin and Sean D. Liming The Microsoft .NET Micro Framework brings Microsoft’s embedded expertise to resource-constrained devices, allowing device makers to bring products to market faster and at lower cost. TCP/IP and Web Services for devices functionality makes the .NET Micro Framework a compelling platform for a new generation of smart, connected, service-oriented devices. Its compact footprint (as little as 64 kilobytes) and support for 32-bit embedded processors without an MMU help keep per-device costs low, and a managed driver model makes it easier to develop device drivers. .NET Micro Framework applications are written in C# using either Visual Studio 2010 or Visual® C# Express 2010 Edition. Professional’s Guide to .NET Micro Framework Application Development provides the most advanced treatment of the .NET Micro Framework SDK available. Over 40 hands-on exercises guide the developer through the tools and APIs available in the .NET Micro Framework SDK. Nineteen chapters cover the basic operation, hardware I/O support, basic networking, graphical interfaces, storage, and the final sample projects to tie the different features together. Example Visual Studio® projects are available for the most popular .NET MF platforms on the market. Table of Contents SECTION 1 – INTRODUCTION AND C# BASICS 1 WELCOME 2 DEVELOPMENT SYSTEM SETUP AND TARGET HARDWARE CHOICES 3 .NET MICRO FRAMEWORK OVERVIEW SECTION 2 – .NET MICRO FRAMEWORK SDK AND THE PROCESS LOOP 4 THE .NET MICRO FRAMEWORK SDK AND THE FIRST .NET MICRO FRAMEWORK APPLICATION 5 INNER PROCESS MECHANICS SECTION 3 – HARDWARE I/O 6 GENERAL PURPOSE INPUT/OUTPUT PINS 7 SERIAL PORTS 8 SERIAL PERIPHERAL INTERFACE (SPI) 9 PULSE WIDTH MODULATION (PWM) 10 ANALOG-TO-DIGITAL CONVERTER (ADC) 11 ETHERNET SECTION 4 – GRAPHIC USER INTERFACE 12 BITMAP CLASS 13 WINDOWS PRESENTATION FOUNDATION CLASS 14 TOUCHSCREEN AND INK SECTION 5 – STORAGE 15 FLASH STORAGE 16 EXTENDED WEAK REFERENCES SECTION 6 – PROJECTS 17 MIGRATE APPLICATIONS TO A NEW PLATFORM 18 ROBOT PROJECT: TRAXSTER II 19 ROBOT PROJECT 2: STINGER Hope everyone finds this useful.

Thanks Guys, I thought I had read that somewhere, but I wanted to make sure before I went down that path. Right now I'm trying to keep from making any changes to the fryer unit if possible. The only thing I've done so far was to re-route the wiring to my Netduino Controller, everything else I left in alone. Down the road if I need to have more precise control over the heating element, I'll look into replacing the existing mechanical relay with a Solid State Relay that I can use the PWM feature on.

I was wondering if anyone had a comprehensive list of Netduino Resources such as blogs, videos etc. Thanks