Designing a General Purpose Heat Pump Controller

[AC_Hacker]

Originally Posted by doug30293

Is there a specific reason for not considering an off-the-shelf PLC? The Automation Direct Click series, for example, is available in a multitude of I/O configurations, it's stackable, software is free, and it is easy to program

Doug

Doug,

Thanks for your input.

Speaking only for myself, I think that the world-wide popularity and appeal of the Arduino IDE makes it a better choice, especially since there are millions of inspired youths all over the planet who are either competent with the Arduino IDE, or are well on their way to competency.

We are not only working to solve our local problem, we are also contributing to a vast pool of inspired enthusiasts, who, if we speak their language (Arduino, and eventually C++) may take what we do and create something beyond what we can imagine.

-AC

[AC_Hacker]

Originally Posted by NiHaoMike

The hardware for it is very simple. RS232/RS485 is just bringing the UART to a common 9 pin connector via a level shifter and is useful for far more than just VFDs.

I had already put the RS485 option on the 'wish list' on post #2

Originally Posted by NiHaoMike

PWM is just bringing a PWM pin to a screw terminal... with some sort of buffer circuit in between. Then add an active low pass filter (literally just a resistor, capacitor, and opamp) and you also have analog output. A little more circuitry and it will also do 4-20mA output.

We can put in the hardware first and worry about the software later. We can also add WiFi capability with a CC3000 module. You can simply leave the spot blank if you're not going to use it. It's common practice in hardware engineering to provision in as many features as the space and time allow. Also use the highest end processor that is compatible with the footprint during development, then downgrade for going into production. (For a one off, just keep the high end processor as its cost - a few dollars - is practically nothing as far as the total system cost is concerned.)

Who is going to do the circuit design, circuit validation and CAD work for these added features? And should it be in rev 1?

By the way, there is a general engineering equation that predicts the reliability of a system. It is useful to note that in the denominator of this equation is the term n (for number of parts) squared. This means that if you double the number of parts, you have reduced the reliability of your system by a factor of four.

-AC

[NiHaoMike]

For such low frequencies, you can simply breadboard the circuit to test it. There's not much to go wrong with a simple buffered PWM output and buffered low pass filter anyways.

For the network interface, maybe it would be easier to just put in a "TTL" level (unbuffered) UART header to hook up to something like an OpenWRT router to handle the actual network interfacing.

[buffalobillpatrick]

item "Provide for a startup delay of the compressor"

This adjustable (up to 10 minutes) Delay on Make relay works great & are pretty cheap on Ebay.

Would control delay of compressor SSR.

[jeff5may]

Originally Posted by NiHaoMike

For such low frequencies, you can simply breadboard the circuit to test it. There's not much to go wrong with a simple buffered PWM output and buffered low pass filter anyways.

For the network interface, maybe it would be easier to just put in a "TTL" level (unbuffered) UART header to hook up to something like an OpenWRT router to handle the actual network interfacing....

We can put in the hardware first and worry about the software later. We can also add WiFi capability with a CC3000 module. You can simply leave the spot blank if you're not going to use it. It's common practice in hardware engineering to provision in as many features as the space and time allow. Also use the highest end processor that is compatible with the footprint during development, then downgrade for going into production. (For a one off, just keep the high end processor as its cost - a few dollars - is practically nothing as far as the total system cost is concerned.)

I agree with this approach. If you want to control or read from this device, do it with one of these ways:

• UART/standard serial protocol
• USB (using arduino as a COM PORT, not a host)
• digital or analog pin (basic functionality)
• 1-wire interface (using a digital pin)

The main focus of this project is to make a unit that will perform the same functionality as your basic residential heat pump with digital thermostat or slave control. That being said, we can devise transparency and flexibility into this unit so developers who want exquisite functionality can take snapshots or xrays of the system to suit their requirements. We can include some registers or tables to monitor short-term and long-term data values and to provide a common location to read and write hardware states and maybe some error codes.

I am not opposed to adding extra modules to the controller. As long as the module is generic and widely available for cheap (like the CC3000 module), and will not interfere with the (basic) core operation of the controller, have at it. Start a thread, build a shield or module, make it work, include code that we can call from the basic module. If it proves worthy, we can include extra firmware to account for this device (if necessary) into the main sketch.

I realize there are a lot of tech savvy ecorenovators with a wide variety of specific skill sets that we will need help from to pull this project off. But this main module needs to be basic, cheap, and easy to assemble without expert skills. It needs to go together like duplo blocks. A lego block version would be too complex for some. The Technic or NXT/Mindstorm line version would definitely need to be an add-on shield or module.

As for downsizing the module, an arduino pro mini or pro micro 5 Volt module would have the same compatibility as a uno R3, without the shield pinout configuration. Getting much cheaper or smaller, we lose the USB port.

[buffalobillpatrick]

How about these flow sensors: $11

450 output pulses/liter

http://www.amazon.com/gp/product/B00...A1EX7LU0M6LM21

Product Description

DESCRIPTION:
Waterproof, heat resistance, pressure resistance, cold resistance
Easy to install
Frequency: F=4.8 * Q (L / Min) error: ± 2% voltage: 3.5-24VDC, current can not exceed 10mA, 450 output pulses/liters,
F=constant * units of flow (L / min) * time (seconds).
Flow range: 1-60L/min
Maximum current: 15 mA (DC 5V)
Working voltage range: DC 5～24 V
Load capacity:≤10 mA(DC 5V)
Operating Temp:≤80℃,Operating humidity:35%～90%RH
Allow compression: Water pressure >1.75Mpa
Insulation resistance: >100M OHM
Storage Temperature:-25～+80℃
Storage humidity:25%～95%RH
Output Waveform: Square Wave, output pulse signal
ROHS Compliant
Material: ABS Plastic
Color: Black
Cable length: approx. 15cm
INCLUDED:
1 x Flow Meter

Arduino - PulseIn

I have simple solid Arduino code using timed pulse for my CO2 sensor:

see 1st post in thread: http://ecorenovator.org/forum/conser...no-sketch.html

[jeff5may]

AC,

Here's a project page for the meter reader RS485 interface:
APMR by smakonin

It has been said the power industry is going to be using zigbee for its smart power meters with rf interface. Who knows for sure?

Power Meter

[stef110]

@ jeff5may

What do you mean by simple? don't you think that if we made a paper tutorial with pictures, then i think that the can solder there own print?

The arduino nano has his own usb port but the same pin layout as the mini pro. I used in other project it is easy to use.

stef

[AC_Hacker]

Originally Posted by jeff5may

...I am not opposed to adding extra modules to the controller. As long as the module is generic and widely available for cheap (like the CC3000 module), and will not interfere with the (basic) core operation of the controller, have at it....
...as for downsizing the module, an arduino pro mini or pro micro 5 Volt module would have the same compatibility as a uno R3, without the shield pinout configuration. Getting much cheaper or smaller, we lose the USB port.

I really like the idea of a basic unit with snap-together modules.

I mean if the basic unit can run my heat pump, and jeff5may's air conditioner conversion, that is just fine.

Then if you wanted enhanced functionality, you could snap on extra modules.

The Arduino expansion 'pin + socket = shield' configuration seems like a great way to go. It is already developed and has super-wide acceptance. It would also make it easy for other hackers to develop enhanced-functionality modules. I mean proto board that conform to the Arduino configuration are available from multiple sources right now... no need to create one.

I like it that some Serbian kid could go down to his local Radio Shack equivalent and get started, or some girl in Nigeria could buy some incredibly cheap clone from ebay, and get started, all by simply downloading our freely-available code.

* * *

But I think that having the ability to easily configure the GPC for different configurations is vital, even more important that Xbee or Wi-Fi or cell-phone connectivity (not that it is mutually exclusive).

I have a brain-dead ASHP in the basement, I need to make it work. I need a GPC...

I have a small, simple GSHP that can feed a simple hydronic floor, I need a GPC...

My ultimate system will be a hybrid system that could handle a GSHP and also integrate it into a system that included a ASHP. I need a GPC...

We have a build going on right now in The Netherlands, by stef110 that is intended to integrate a solar heating system with an ASHP. He needs a GPC...

ditto buffalobillpatrick, He needs a GPC...

Also going on right now is a guy in England, wsexton1 who wants to do a GSHP and employ two different compressors. He needs a GPC...

The air conditioner-to-domestic-water-heater hack has proven to be surprisingly popular. It would be more popular yet if there was a GPC...

I also have the suspicion that randen's 3-phase monster also needs a GPC...

This project may not be easy, but the moment is definitely upon us...

-AC

[Ormston]

Originally Posted by buffalobillpatrick

How about these flow sensors: $11

450 output pulses/liter

http://www.amazon.com/gp/product/B00...A1EX7LU0M6LM21

Product Description

DESCRIPTION:
Waterproof, heat resistance, pressure resistance, cold resistance
Easy to install
Frequency: F=4.8 * Q (L / Min) error: ± 2% voltage: 3.5-24VDC, current can not exceed 10mA, 450 output pulses/liters,
F=constant * units of flow (L / min) * time (seconds).
Flow range: 1-60L/min
Maximum current: 15 mA (DC 5V)
Working voltage range: DC 5～24 V
Load capacity:≤10 mA(DC 5V)
Operating Temp:≤80℃,Operating humidity:35%～90%RH
Allow compression: Water pressure >1.75Mpa
Insulation resistance: >100M OHM
Storage Temperature:-25～+80℃
Storage humidity:25%～95%RH
Output Waveform: Square Wave, output pulse signal
ROHS Compliant
Material: ABS Plastic
Color: Black
Cable length: approx. 15cm
INCLUDED:
1 x Flow Meter

Arduino - PulseIn

I have simple solid Arduino code using timed pulse for my CO2 sensor:

see 1st post in thread: http://ecorenovator.org/forum/conser...no-sketch.html

Those cheap flow metres are OK for a while, mine has started playing up after around 4 months use. The impeller wheel sticks, so far I,ve managed free it several times by turning the circulation pump to full speed for a few seconds.
Maybe i 'm unlucky and got a duff one?

Arduino is the perfect platform on which to build a controller.