PWM

For an upcoming modification to the central heating I need a controller capable of outputting a (standard?) 0 to 10V control signal.

Of course, this is a job for Arduino/Jeenode, and not for some store bough industrial controller.

Since the JeeNode works at 3.3 volts,  I set off to build an amplifier, using an LM358, wired to multiply the input by 3 times, which gives a nice and convenient range of 0 to 10V!

I am still in the process of building the circuit, but for this I needed to get the oscilloscope out.

Once I had the work on the breadboard ready I captured the following images, I thought they were nice.

I wanted to have both lines in the same shot, but my channel B is not working well, so I can only use one channel of the scope.

After I shot these, I proceeded to blow up an LM7805 (why does it have a different pinout from the LM78L12) and consequently blow up my old trusty JeeUSB version 2...I hope I can bring it back to life.

Just a short mention of what the project comprises: 0..10V controller for a 24V ventilator fan, and two Dallas 1820 measuring the temperature of the water flow (in and out). The motor will be controlled based on these.
Soon the circuits and protoboard pictures, later custom PCB's?

Dashboard once again

It's been more than a year since I last published about the dashboard. And that it because not much happened in that front.

Meanwhile, a friend gave me a tablet, cheap chinese thing, which I planned to use to display the dashboard in a visible place in the house.
The thing could even display the HTML5 and handle the AJAX calls and all, but it was unstable, sleep mode would spend the battery almost as fast as normal mode, slow to boot, bad touchscreen (resistive), and so on, and so on, so I quit on it, and consequently on the progress on the dashboard, as the experience while using it is, in my opinion, of great importance!

A few months later, my wife offered me an iPad, the new retina display model! so that rekindled my interest in the dashboard. I came back to iWeb, expanded the design a bit, and have spend a couple of evenings implementing the functionality...this is the result:

And for the explanation:

electricity and gas consumption: the pointers move, as the data is updated, and shake slightly when stable, to indicate that the thing is alive. The numbers are updated twice a minute.

House control: this interfaces mainly with the FHZ1000 part of the automation. It reads set, measure and desired temperatures, displays the measured, and makes the box green if the room is set for comfort temperature (even if it has not yet been reached) and blue for low temperature. The boxes turn orange is there is no reply.
The buttons for the awnings are toggle buttons: click to extend them and click to retract them, since the system has no idea of what their status is (they can be operated locally). They briefly blink through orange to give feedback that something happened!
climate limited: is a button to limit the maximum temperature to which any room can be set
holiday mode: should set all rooms to a low temperature and out of the standard program. this is the only button not yet functional (and therefore transparent).

Door events: list of the last 4 events on the RFID door.

System messages: reports errors on the system, like now, the weather station has stopped transmitting.

Agendas: list a few items (enough to fill the respective boxes) taken from google calendar. I have a google calendar for the house, where I put the garbage schedule, and other maintenance activities that need to take place.

Outside temperature: like the name says, displays the data from the weather station. Now it displays nothing, since the station stopped working - see system messages :)

And that is it! data is updated on timers, and the agendas on loading of the page.

There has been talk in the tubes about some mechanisms to update data in real-time. That should be the next development, but that might take another few years :) This is nice enough to show to my friends :)

AH! last but not the least, I found out that one can include some lines in an HTML page to make it a iPad app, so, by adding:

    <meta name="apple-mobile-web-app-capable" content="yes" />
    <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />

I can save the page onto the iPad desktop (is it what it is called?) and run it as any other app, without the safari address bar. Only the top bar with the clock and stuff is still visible, but that is even a plus, as it gives you a clock and iPad info!

I'll try to post a screenshot from the iPad soon!

Switch Box

This weekend I finally finished a project that has been on my mind for quite some time: a Switch box!

In a few words, it is a box of electrical plugs, each with its own switch.

A few months ago we changed our old CRT TV by a new flat modern HD thing, mainly to get rid of the annoying little decoder box that we were forced to use in order to see the channels that we liked that were moved from analog to digital, and, since we every night switch off all devices, in the hardware switch we made sure the new TV had such a hardware switch.
So when we come home, all happy with the new TV, and switch, we discover that the nice sound bar that came with the TV not only required a separate power supply (plug) but didn't have a real switch, that allied to some devices hanging around that did not have a hardware switch (DVD player) which required a unplug action, until I hacked a light switch on to the cable, I decided to make the following contraption.

 Under side

 Top side

It is a series of 6 plugs, just like an extension cord, but where each individual plug has its own switch, UK style. I then hid it under the furniture where the TV and all devices rest on, with the plugs nicely hidden under it.
I think these things should be sold in shops! As a side note, I did consider having a remote control for this, using a micro-controller and some SSRs,  but that would complicate it, both in terms of build time, and safety considerations.
I am also not sure I it will ever recover its cost in saved energy, but hey, if we account for the energy I save going around unplugging devices at the plug, it already payed it self off today!

I hope you can get a good idea of the result from the pictures!

 

Mounted in place

Another view of it in place

Small update!

It has been a while since I posted something here...the truth is, not much has happened in the electronics front.

The JeeTherm has been working flawlessly since I installed it, on the 15th of January, so that it over 2 months ago. During those 2 months, we had some serious cold coming this way, I measured -15C on my weather station! That is the lowest ever recorded here.

One interesting thing about this whole story of the efficiency of an HR boiler, is that, due to some graphics I found I limited the temperature setpoint of the boiler to 55 degrees, as this is the limit above which the efficiency decreases rapidly, thinking that, if it gets really cold, I could raise this limit, as it is all software anyway, and there was no need to recompile anything (on the JeeTherm the limit is 80C, on my PID controller implemented in PHP, the limit is 55C).

As the cold came and settled in, I noticed that the boiler, and the whole heating system was still able to warm up the house, and keep it warm, even in the coldest days! so I ended up never having to raise it! I was glad, I had days where the boiler worked nonstop, but down to a simmer. My energy saving correlation calculation also indicated that the gas spent was way below expectations, although the curve fitting was not done with any data in that kind of cold range.

What bothers me the most, is that I could never really find any good info about this efficiency story. In many forums you can find people saying that an HR boiler needs a 20C difference between feed and return to operate at optimal performance, but all the graphics I find of performance, none indicates such a difference, the efficiency being a simple function of the return temperature. Furthermore, if that is the case, then the boiler should be set to start modulating to try and achieve such a difference, but the behaviour I see with my boiler is that it modulates to have a 7C or 8C difference between feed and return. sometimes even 5C. I start to think that all that matters is the return temperature...and that one, I have it limited to 55C now!

Project finished!

This is it! The OpenTherm JeeNode/Arduino interface is finished! and all ready to roll!

The prototype had been working for almost two months now, and finally the boards arrived from fabrication, I think the result was worth waiting for, and worth doing it! I got three identical boards, so if I mess up one I can go on with the next:

Bare boards

Very simple, but very effective :)
I thien collected the components, whe to buy the optocouplers, and incorrectly bought the 4N35 instead of the 4N27 that the prototype used, but only realised after they were already soldered, so I tested it, and they work fine! crisis averted:

All ready for assembly

Mounted everything, both the JeeTherm, and a JeeNode v4 I had around still to be assembled, and put it all in the enclosure:

Assembled, and in the enclosure, attached to the JeeNode

Another view

Had to fiddle a bit more to get the screen fitting in the cover, and connected to the JeeNode:

All ready for action

Checked that it all worked, and got it connected, instead of the prototype. It is now running happily:

Talking to the boiler

I am quite proud of the final result, it looks good and well packed, and I tried not to cut any corners this time, took my time, and tried to do it patiently...very often I end up messing up things in the rush to get them finished.

It is now in beta test phase, if it works well for the coming days, then I will attach it permanently, now it is still floating :)

Already thinking of the next project!