Designing a General Purpose Heat Pump Controller

[AC_Hacker]

* Flash From The Past *

I ran into a post on the 'Manifesto' thread where a Norwegian EcoRenovator posted a quick Arduino sketch for a heat pump controller.

The poster's name is Ko_deZ and the sketch is HERE.

Best,

-AC

[takyka]

Originally Posted by AC_Hacker

I went back to find this post, because it had mostly passed without comment.

I think Steve is absolutely right in saying that "Safety circuits should never rely on software".

-AC

Professional systems pressure switches with hysteresis are used. Adjustable or fixed connected in series with compressor.
Here is an example:
http://www.emersonclimate.com/europe...PS3__35003.pdf
http://www.emersonclimate.com/europe...N_PS1-2_TB.pdf

On e-bay some:
alco ps3 | eBay

Measuring temperature and conclude to pressure from temp is no-go if safety is a concern.

T.

[takyka]

Originally Posted by AC_Hacker

Sounds interesting... More details please...

-AC

You have on the UNO one serial port connected to USB converter. When you plug it to computer, it appears like a serial port. A simple terminal sw(built into arduino or an external one) can be used as text display and your keyboard as input device to arduino.
To handle it from controller side is easy. Look into examples->communication-Serialcallresponse. in Arduiono IDE. Serial.* functions doing the trick.

You can connect to Arduino serial port (those are exposed to pin header)a bluetooth module if you don't like wires. You can establish and use serial connection via bluetooth to arduino same way like you would connect via USB.
here is a module as example:
JY-MCU Bluetooth Wireless Serial Port Module for Arduino (Works with Official Arduino Boards) - Free Shipping - DealExtreme



In this post, I described to Jeff5may my menu system to setup the controller:
http://ecorenovator.org/forum/39098-post5.html


T.

[AC_Hacker]

Originally Posted by takyka

You have on the UNO one serial port connected to USB converter...

T,

This sounds like an interesting idea hardware-wise. If I am envisioning it correctly, it would offer a user the option of using the USB output as a serial terminal for uploading sketches and also for monitoring output.

(* ALSO *)

It would allow the user who might already own a $300+ tablet that has bluetooth to add the USB > Bluetooth adapter such as you linked to, in order to run an advanced user interface.

I don't think we want the requirement of owning a $300 tablet to be a barrier to being able to build, program, run and modify a General Purpose Controller.

I think we want to keep our target audience as large as possible.

There must be a way that opting for the bluetooth/tablet interface could be easily accomplished, with regard to including the required code and libraries, etc.

One question, if you do have tthe bluetooth dongle installed, can you also easily revert to USB/keyboard + monitor if you wish to?

Best,

-AC

[jeff5may]

I'm still working on this sketch, and most of it actually works! It has an LCD driven menu where you will be able to set functions, modes, etc. When not in the menu, it will display the current mode and status. I left serial pins open on D0, D1 to communicate that way.

As far as comms go with the arduino, you can hook up just about anything to a dev board as long as you use the right pins. With the smaller boards, creativity and luck is needed to make it do what you want. For me, this is part of the appeal of this project. Sure, I could go buy something elaborate and do it easy. But what fun is that? I'm not at work!

As far as safety is concerned, I would never completely trust an embedded device for anything critical. The rig you put this in should have its own fail-safe built into it as a cardinal rule. If it absolutely must work or else, you should probably go get something that has passed multiple testing methods and has a diploma already. This one might not solve all of your problems, and may end up causing new problems instead.

[AC_Hacker]

Originally Posted by jeff5may

I'm still working on this sketch, and most of it actually works!

Way cool!!

Originally Posted by jeff5may

...If it absolutely must work or else, you should probably go get something that has passed multiple testing methods and has a diploma already. This one might not solve all of your problems, and may end up causing new problems instead.

I have a suspicion that if this thing works at all as a heat pump controller, we just might have a very large pool of beta-testers.

That's the thing about open source, if you make the hardware and software public, bright minds will find ways to make it even better.

-AC

[NiHaoMike]

Originally Posted by AC_Hacker

It would allow the user who might already own a $300+ tablet that has bluetooth to add the USB > Bluetooth adapter such as you linked to, in order to run an advanced user interface.

I don't think we want the requirement of owning a $300 tablet to be a barrier to being able to build, program, run and modify a General Purpose Controller.

I think we want to keep our target audience as large as possible.

There must be a way that opting for the bluetooth/tablet interface could be easily accomplished, with regard to including the required code and libraries, etc.

Much easier to use a Bluetooth UART adapter. It can connect to the UART pins and override the USB to UART that normally connects to those pins. Very easy to have it use Bluetooth with the module installed and USB without the module. If you want to dynamically switch between them, add a little logic to connect and disconnect the transmit pin on the Bluetooth module. Or use a microcontroller with more UARTs and use another UART for Bluetooth, but I can't think of a compelling reason to use USB and Bluetooth at the same time.

[AC_Hacker]

Originally Posted by takyka

Good move! You can't imagine, how much these helps to find the best COP.
Only thing, your simple controller is not that simple anymore!

T.

OK, I reluctantly ordered two flow sensors, and they arrived today.

Best,

-AC

[Ormston]

Just received 5 of these.

5Pcs IIC/I2C Serial Interface Board Module For Arduino LCD1602 LCD2004 Display | eBay

Solder them to the 16 pin header on a standard 1602 of 2004 LCD and use I2C to wright to the LCD using only SCL and SCA (A4 & A5 on uno).

Quick test and they work great with the correct library, found here:
http://arduino-info.wikispaces.com/LCD-Blue-I2C#v3

As they are addressable you can have 8 of these connected and still use the same pins for other I2C peripherals.

The ones i bought are just the interface board but they are available pre-soldered to the LCD

Had been put off using serial LCD's in the past as they sometimes use a completely different command set to direct connected LCD's. As far as i can see from a quick test these use exactly the same syntax as a normal LCD and you can even control the backlight (on/off) via software with no extra pins.

Steve

[AC_Hacker]

Originally Posted by Ormston

Just received 5 of these.

5Pcs IIC/I2C Serial Interface Board Module For Arduino LCD1602 LCD2004 Display | eBay

Good find. I also got a couple of them, only with mine, each included an unsoldered 2x16 LCD and the cost for each pair was lower by about 20% of your price... go figure!

Thanks for locating a proper library, that will come in very handy.

Let us know how your application of this I2C module progresses. I considered using this approach on my CO2 controller, but I had mine working before I could order this module.

I like the idea of I2C, as it used fewer pins, if pins scarcity becomes an issue.

Seems to me that if memory space is sufficient, and available pins are scarce, I2C is the way to go.

On the other hand, if pins are abundant, and memory is scarce, driving the LCD directly could be the best option.

When communicating with the LCD, via I2C, you need to include the LCD library and also the I2C library, right??

Thanks for sharing...

Best,

-AC