I had experimented for some time with a peltier based heat exchanger to cool beer from my kegs (home brewing), but after a few iterations, I felt the system would not be as compact as I hoped, and the peltier was eating up too much current (80W).  Here’s the unit  – heatsink, peltier, and big block of metal that would be placed in a water bath.  I have 16ft of stainless steel tubing that wraps around the block for the beer to flow through.  I had the unit in a bucket surrounded by expanding foam for insulation.   Ultimately, it was ugly.

I finally gave in, and decided to buy a dedicated fridge for the kegs instead.  I found a neighbor selling one of the right size across the street (very convenient).  He was the nth owner, and it was a commercial unit with a nice stainless steel exterior.  However, after getting it home, it seemed apparent that the thermostat was useless.  It would turn on randomly and off randomly.  I figured I could fix this, but my goal was to spend no money.  Also, the thermostat has this meal tube that goes into the wall of the fridge – and it seems permanently attached, so I wasn’t sure how feasible it would be to replace the thermostat if I had to take the entire thing apart to replace that tube.

After looking through my pile of PCBs that I could repurpose, I came across my Texas Instruments LauchPad that I picked up at ESC.

The thing that makes this unit amazing as compared to the arduino is that it costs $4.30.  The thing that sucks is that the target MCU is a POS and really didn’t have enough ram/flash for my liking.  However, after looking at the schematic, the IC at the top left of the picture caught my eye.  It’s a MSP430F1612, and it is used as a programming interface for the target IC.  Unlike the target MCU, it’s very nice and had all the features I wanted.  It’s powered off USB (5V) but has a 3.6V regulator onboard.  This surprised me a bit as this is the max voltage the MSP430s run at, with 3.3V being more logical, and what I would have expected.  Additionally, the header exposed 4 of the I/O lines which are used to interface (program) the target MCU.  This was the minimum I needed to implement a temperature sensor, a display, and to control a relay to switch on the refrigerator compressor.

I love how appliances have wiring schematics on them these days (though I had to remove the condenser coils to access it).

Both neutral and line voltage (120VAC) are present at the location of the thermostat, and a simple relay is sufficient to drive it.   Oddly enough, the lamp switch was present but unused in the fridge (so it was always on – was probably a design mistake as the door never made contact with the lamp switch anyhow).   Not surprisingly, the bulb was burnt out.

The relay replaced the thermostat (pins 3,4 in the photo).  And a wall adaptor for my old cell phone which presented a 5V USB interface was used to provide power.  It was connected to the BLU wire and the WHT wires in place of the lamp.

The schematic for the lauchpad is provided by TI, which was nice.  The header I interfaced was J3. If you look, you’ll find that pins 5.1, 5.2, 4.7, and 4.2 are all connected through R5 to SBWTDIO.  Setting all but one pin as an input, and using the output pin worked fine.  Additinally, pin 5.3 connectes to SBWTCK (with a pulldown resistor which we can ignore if we are driving the pin).  Finally, we have the a serial interface on pins 3.7 and 3.6.

The header on the top left (you need to add pins) provide the programming header for the MSP430F1612.  There might be some way to program it from the USB port, but as I had the programmer, it was fairly easy.

The interface I  built was super simple, but looked ugly as it was a mass of wires handing all over.  Here’s the schematic.

Starting from the top, an IO is used to switch a darlington which turns on the relay.  Again, I just used what I had lying around, and it was able to switch the relay at 2V, which was good.

I have a number of SHT75 temperature and humidity sensors lying around that require a clock and data line to interface.  Additionally, the data line requires a pullup resistor, but the MSP430F1612 doesn’t have any so an external one was added.  They have some horrible example code that I ported over and after a few tweaks I was able to get it to work.  One tricky bit is that the data line should never be driven high – when the code wants it to go high, set it as an input so that the pullup resistor pulls it up.  For some of the messaging, you need to watch that line and see when the SHT75 module pulls it low.

Finally, I got lucky and had an LCD with the SerLCD module from sparkfun mounted.     It lets you use a serial line to drive a serial interface, dropping the I/O line requirements from something like 8 to 1.

I recently got an Ultimaker which is cool, but the documentation sucks sucks sucks sucks for a commercial product.  I need to spend the rest of the day today taking apart the print head and which is encased in melted plastic to add some teflon tape to prevent the plastic from oozing everywhere.   In any case, I was able to print out an enclosure for the device, and for the most part, it works fine.  Not having any additional input lines, I have no way to adjust the temperature setpoint without pulling the board out and reprogramming it.  It’s currently set to turn on at 45 deg F and off at 40 deg F, which seems a reasonable temperature range for beer.  Here are some photos of the unit operating.

The temperature probe is taped to the back of the fridge.

Yes, humidity is pointless in this application, but I had enough space on the LCD.

It’s still a mess, and I would like to remake the enclosure so it’s a bit nicer and it fully hides all the wires.  Feel free to contact me if you want a copy of the firmware.

I had a simple goal, and that was to have a background thread receive some data and update a text field in an “Activity”.  There were plenty of webpages that attempted to describe how to do it, referring to explicit intents, to modifying the Manifest.xml file, and all sorts of other jargon – but no clear examples.  I came across dozens of posts from people trying to do the same thing I wanted to do, but no answers.  I spent about 4 hours trying to piece together a method that worked. 

Hopefully, this simple explanation will help someone..

If you want to send data from one thread to another you can do it through a messaging protocol, and encapsulate data in that message if needed.  One big complication is that the messaging can occur across applications, it can be directed at a specific target if you know it exists, or it can be ambiguous and you figure something will deal with it.  The messages can also invoke an application (“Activity”) to do something.

What I’m going to describe is how to send a message from one part of an application to another – with the typical goal being to send data to the active “activity” to display data or somesuch.

1. In the activity where you want to receive messages, you need to create a class within the activity class (I have no idea what the java developers were smoking to come with this idea) that extends BroadcastReceiver().  You then want to override onReceive() to contain the business logic.

public class ActivityClass extends Activity {

  private BroadcastReceiver mReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (action.equals("net.reza.SET_BATT")) {
            setBattery(intent.getIntExtra("value", 0));
        }        
    }
  };

  /* rest of your code */

}

In this example, I’m creating  mReceiver which is a BroadcastReceiver but I am modifying the onReceive() method.  In the method, I’m checking to see if the activity string is equal to “net.reza.SET_BATT”.  This can be anything.  There are some standards that are meaningless.  Use whatever you want.  I think it’s called an intent or intent-filter.  I’m going to call it a ‘tag’ for clarity.

2. You need to register that mReceiver is capable of handing the “net.reza.SET_BATT” tag.  There are a bunch of places to do this in your code.  I stuck it in the onCreate() method for the Activity class.

@Override

public void onCreate(Bundle savedInstanceState) {
  IntentFilter ifilt = new IntentFilter("net.reza.SET_BATT");
  registerReceiver(mReceiver, ifilt);

  /* more code */

A lot of the documentation said you need to modify the Manifest.xml file and stick it in there, but that was a mess and not obvious how to make it work.  Defining it this way is /much/ easier, and in my mind, much more manageable.  Why do java people love XML so much? 

And I have no idea why they call these tags “intent-filters” but they do.  Based on my code, you don’t need to bother with the action.equals() line, as the only time it will be called is if that tag is registered with registerReceiver(), and I’ve only registered that one tag.   But if you register multiple tags with the same BroadcastReceiver then you should check to see which one is being called.

3. You need to invoke that tag.  This can be done anywhere, as far as I know.  Even from another application.  In my case, it’s from a background thread that monitors the battery voltage by polling a device over bluetooth. 

public class BatteryMonitor extends Thread{

Context context;

public BatteryMonitor(Context y) {

  this.context = y;

}

 

public void run() {

  /* some code */

  Intent i = new Intent("net.reza.SET_BATT");
  i.putExtra("value", bat);
  this.context.sendBroadcast(i);

  /* more code */

}

Couple things here.  First, I still have no clue what a context is, who owns it, and how to use it properly.   I kept trying different things till it worked.  I passed the output of getBaseContext() to the constructor of the background thread, and that seemed to work.  I think some other options are getContext() and getApplicationContext(), so try those too.  Please post a comment if you know what’s going on.  

So we create an Intent with the same tag.  We can then stick extra data in there – in my case, I add an int. And then you call the sendBroadcast() method from the context object to make it go. 

I now need to go write some more code in C to cleanse my mind from all this gibberish…

I finally had a chance to assemble this PCB.  Alas, I ordered an SO8 package for a part accidentally and had to stick it on a daughterboard.  Will replace with the right part.  Designed to scan complex bioimpedance from 1k-100kHz and communicate with a handheld tablet over bluetooth.  I’ve moved away from the CSR ICs to using these packages as the BlueCore 3 that we were using became more expensive than these modules, and the modules are a lot simpler to solder.  I’m planning on moving to the BlueCore5 for future designs – can get power consumption down to <10mA (if you believe the datasheet) at 115kbps.

They just started the talks at the MH2011 conf. So far I think that there are a ton of interesting people here, but I’m a bit dissapointed with the first 3 talks. Ill be posting some more as the conference progresses.

These will go from 1kHz to 100kHz.  If you notice the big PCB, I made the VIAs have a teardrop shape – they look cool.  It’s based on my design for a fixed 50kHz device for impedance plethysmography that I use to measure respiration.  Fun stuff!

First, great simple way to prepare chicken/pork.  This cooks fast, gives juicy results, and tastes great.  First, the marinade – super simple – super fast.  Sriracha Hot sauce & Soy sauce.  I bought this organic kikoman soy sauce and really like it.

Add a bunch (I use about equal parts, but adjust to suite your taste) to meat (I like using the costco frozen tenderloins).

Just a few minute seems to work, because we will then fry it in some oil.  Doesn’t have to cover the meat.  The meat absorbs none of the oil, cooks fast, and is super juicy.  I also use the same method for pork cutlets.  I sometimes add an egg yolk if I want it to have more of a battered feel, though it’s not needed.

I have also decided I can’t stand canned beans anymore.  Ugh.  I’ve tried my hand at lentils (someone posted a recipe that sounded great and involved bacon, but it didn’t come out all that great).  So I hit up a local Indian grocery store and picked up…

That, 1/2 and onion, a tomato, and some lentils

and I have some simple and great tasting lentils.  Super cheap too if you figure the cost of ingredients.   It takes about an hour or so worth of cooking, but you can make bigger batches and save.  The instructions require a scale, which I had.  I like cooking with a scale more than the volumetric measures we usually use.  Seems more scientific

Finally top off with what I’ve found to be a veggie that I’ve not gotten tired of – microwaved broccoli with mayo.  

Super tasty, and if you cook the lentils in advance, less than 15 minutes from start to finish.

What ensued:

1. Panic.  I felt like I was the captain of a plane that was on fire.  I wasn’t dead but I had to do something.
2. I decided pursue all my options simultaneously.  These included
• call library to find relevant mathematical and psychological textbooks.  Probability of mastering (which was required) the new material in 48 hours: 3%. 
• Email various departments looking for a tutor to help with the material.  (10% success probability)
• Try to figure out a way to slice and dice my content such as the “it’s not going to work” condition goes away.  This involved asking for a number of people to help in a brainstorming session.

Of the three options, the third won out and 5 hours later, I had a 100% different presentation that utilized 20% of the material I started out with.  An additional 7 hour of work on the slides and I had a first pass ready.  4 hours of sleep later and a 30 minute drive – and I was back on campus working the written part of the project.  I found a tutor who offered to help and we covered the relevant material in no time.  If someone explains content at the right level, I can digest it very quickly.  For example, I love “The Darker Side” – it does an amazing job of explaining mixed signal electronic design.  He’s also the only good author left on Circuit Cellar’s payroll. 

In any case, the exam is tomorrow.  One thing I’ve learned though all this is about stress, both the theory, about my experiences, and my developed theories (one of which I’ll be presenting on).  And what’s amazing is that I’ve been able to control the physical manifestation of stress – I’m so much better at being able to deal than I was just 3 months ago.  I’m really not stressed about tomorrow, even though I should be. 

I think I’m going to start posting some details about the progress of my diet through the course of it as this sort of info might be helpful to others.   I had my 1st “bing” day yesterday, which is sanctioned by the diet.  I decided to try to go full bore and see how it effected me.  My breakfast consisted of:

• waffles
• fried chicken
• 2x sausage & egg sandwiches
• grits (didn’t like it, didn’t eat much) – how are these supposed to be eaten?
• 2x 16oz glasses of sweet tea

As good as it tasted, it made me feel horrible for the rest of the day.  I had a headache and my body hurt.  It’s amazing how bad sugar is for you.  The evening was filled with more goodness including crab cakes, bolgogi beef, chicken meatballs, pan-fried mac and cheese balls, shrimp with bacon, sausage burgers, beer, wine, bourbon.   The results:

Now, if the diet works, by Tuesday I should return to my post-binge weight.  Sarah and I went to Safeway (how I hate that place) and I bought more veggies than I ever had before in my life.  Trying to follow the paradigm of “use bag of frozen veggies” just didn’t cut it and I need to get some variety.  So for lunch I had two “slow-carb” burritos that consisted of a large piece of lettuce, layer of refried beans, garlic pulled pork from last week, sautéed green beans/onions/garlic/spring onions, peppercinis, avocado, and habanero salsa (finally found a safeway salsa that I liked).  And it was really good – I didn’t miss the bread at all.  

I’m really enjoying the cooking that I’m doing for this diet, as I’m usually too lazy to cook.  I’ve found it’s been a lot better on the wallet but a huge pain in the ass to clean up.  The dishwasher runs like 2x/day now. 

And tonight – safeway had a great sale on Dungenous crab  — so I’m going to try to make a crab salad with homemade mayo (all the stuff in the store had some sugar added).   I’ll probably add some bacon to it as well. 

The chapter that talks about the diet is essentially converted from this blog entry.  I’m not going to bore you with the details, but I’m trying to be a bit methodical about the progress and want to document it.  Essentially, it’s 4 meals a day of lots of beans (I never want to eat beans again after this).  He also stresses keeping the meals simple (read: boring) and the same.  He argues it’s simpler that way.  Unfortunately,  following that advice will get me disinterested quickly from the diet.  I need variety.  I just finished cooking the garlic pork dish from this cookbook I found online.   

Anyhow, I’m doing pretty well though I accidentally violated one of the rules and had some fruit juice.  And I’m drinking some whiskey instead of wine right now (thanks diQ for leaving that bottle behind).  But so far I’m on track to hit my goal of 20lbs in 30 days.  I’m also following a regiment of a ton of supplements that he suggests – 13 pills a day no less at a cost of $75/month for the supply.  Normally I’m not into that kind of stuff, but there’s something cool about the thought of hacking my body, so I’ll give I a shot.  Here’s the data, though I started right after finishing 3 days of my unintentional food-poisoning diet which I dropped 5lbs over 3 days.  I’m actually less now than I’ve been in years.  I’m going to start weight training again after I hit 170, but my body puts on muscle fast and I don’t want to see my weight increase (it’s a motivational thing).