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Old 04-11-12, 11:29 AM   #1
Acuario
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Default Controlling a DC inverter machine

As I have just been given a Daikin split system which has a DC compressor I started thinking about how to control it.

The threads I have read have all focussed on using controllers from various devices and adapting them. This involves 'junking' the existing control system and starting from scratch building a DC motor controller. Has anyone succeeded in doing this?

I still don't know if the units I have actually function, that's still to test, but assuning they do I'm firstly going to try a different approach.

What would be wrong with gutting the internal unit and then using it in abox to control the external unit? The unit I have has 1 thermal sensor and the remote that signalls to the unit what to do. Why re-invent the wheel as far as the external unit is concerned?

So my plan is:
1. Get the unit working with the existing internal unit control board removed from the internal unit.
2. 'Crack' the control code - unless it is detailled in the service manual (that I'm hoping to get hold of). It signalls down 1 wire (certainly referenced to ground or neutral so I should be able to monitor it).
3. Build my own controller to manage the external unit.

Any thoughts/suggestions?

Nigel

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Old 04-11-12, 12:42 PM   #2
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I donīt know Daikin, I have mitsubitshi here in my house, but certainlly maybe the same. The comunication between the indoor and outdoor units itīs Serial. If you post the model of the Daikin you have we can look to find the service manual on the net itīs not diffcult.

Basically the Inverter can divide on several blocks:

-Power Filter and Rectifier
-PWM controller (compresor and fan)
-Logical and signal handling (uProcessor)

In my opinion itīs easy to try to get the unit working removing original electronics, and installing custom controller.
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Old 04-11-12, 01:15 PM   #3
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The models are:
External unit RXS71E3V1B
Internal unit FTX71EV1B

Compressor is 2YC63BXD
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Old 04-11-12, 01:32 PM   #4
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Diakin's units are some of the best on the market IMHO. They have a better reputation for reliability and their performance beats the Mitsubishi. The Fujitsu's are a little behind in reliability, it seems, but have very high efficiency in their RLS line of their Halcyon inverters. Diakin's are hard to get outside of internal HVAC distributors as they don't like the DIY community touching them.

With that aside, you are likely going to lose some efficiency by setting up your own control scheme and even moreso by building your own controller. They use a BLDC controller and if you really want to, there are people who have messed with this sort of thing on endless-sphere or you could get a BLDC controller from hobbyking but you might have a hard time getting one that won't kill itself or your compressor unless you know what you are doing.

If you want to modify the compressor control, your best bet might be letting the Diakin stock controls do their thing but trick their thermistors and other sensors to get it to do what you want.

Is there something wrong with the Diakin unit you received? Is it broken or missing control parts? I'm just trying to figure out your intent and what sort of control you are looking for since you didn't say it in your original post.
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Old 04-11-12, 01:46 PM   #5
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Default T-Run ??

There is a way to test a Sanyo CH2472 ODU. It's the T-Run jumper header.
I wonder if other brands have a way of running ODUs without the IDU connected.


(Note: T-Run/Test connector is in the center bottom of PCB).

I'm not sure if the T-Run maintenance switch would allow the unit to run
with all it's normal functionality, like defrost etc.

Here's some videos of T-Run operation.
NCL :: Sanyo chill mode test video by Xringer - Photobucket

Green slot :: R410A cleaning loop video by Xringer - Photobucket
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Old 04-11-12, 04:24 PM   #6
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As far as I'm aware the machine works. It was unmounted, covered in cobwebs and in a garage and I know nothing of its history.The present owner of the house inherited it. The previous owner (who I knew) was a bit of a hoarder of junk 'just in case...'. It's missing the remote control. I'm planning to connect it up to check it out before I go too far though.

I'm not planning to replace the BLDC circuit - why bother when it (I hope) works. More a case of 'hacking' the internal units control circuit to get the external unit to do what I want. Initially using the existing control which will, I hope, enable me to decode the serial data stream. Then build my own 'indoor unit' controller using a PIC or similar (maybe a Raspberry PI - now there's an idea, I have one on order....)

As and when I get it going then maybe I'll replace my Mitsubishi that is running the heating to the house as this unit has a higher capacity (the Mitsubishi is around 6Kw ish and a conventional compressor), or maybe not.. the fun is in getting it to work.

Nigel
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Old 04-11-12, 04:37 PM   #7
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I once read a thread on the web about controlling Mini-splits.. Can't find it now.
But, I did find something you might want to check out..
Minisplit Inverter communication standard
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Old 04-12-12, 03:16 PM   #8
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Quote:
Originally Posted by Acuario View Post
So my plan is:
1. Get the unit working with the existing internal unit control board removed from the internal unit.
2. 'Crack' the control code - unless it is detailled in the service manual (that I'm hoping to get hold of). It signalls down 1 wire (certainly referenced to ground or neutral so I should be able to monitor it).
3. Build my own controller to manage the external unit.
Acuario,

As far as I'm concerned, this project you have going is the holy grail of heat pump hacking.

Modern mini-splits have wonderful efficiency, rivaling GSHP of a decade ago, and getting an inverter mini-split to heat water for radiant heating is such a great fit. The only existing unit that does this is the Daikin Altherma and it is really expensive.

Additionally, from my point of view, breaking the code on the inverter compressors makes them candidates for ultra high efficiency GSHPs, which would place our hacker community right at the cutting edge of the technology.

I did look at Xringer's link below and it is an absolute treasure horde of great information.

I am in touch with some pretty high-powered electronics geeks here in my home town, so if you hit a dead end, there is abundant help available.

I really like what you are doing, attempting to get the maximum effect while leaving as much of the existing developed circuitry in place.

Lots of photos and detailed descriptions will help you get more help... and ultimately help others in their projects.

Good luck on this one!

-AC_Hacker
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Old 04-17-12, 09:32 AM   #9
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I'm making a bit of progress - here are some pictures to keep you interested...
The comms is based on RS232, runs at 1204 baud and is 8 bits, 2 stop bits, odd parity, LSB first, non inverted.

It uses a single signalling wire from a (I guess) custom device that superimposes the signal onto the mains supply - it looks like it has a transformer encapsulated in it. I'm not too concerned with it at the moment as I'm monitoring from the low voltage side.

There are 3 signals plus power to the device. One appears to be a clock signal, one connects directly to the cpu, one is coupled via a pullup resistor to the cpu - presumably data in/out.

In idle the internal unit senda frames of data, 3 per second; the external sends 3 frames as well. Each frame is different but the frames repeat every second.

I'm trying to analyse the frames to work out what they contain; so far it looks like a unit id or address (it does change) (2 bytes) a zero byte, 16 bytes of data then a checksum byte.

The interesting bit will be working out what the 16 bytes are!

I have borrowed a remote control so at least I can get the unit to do things :-)

Nigel
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Old 04-17-12, 11:36 AM   #10
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Default Not 1200 baud?

IIRC, in the posts I saw (many moons ago), the hacker set up a similar kind of data stream capture,
and then used the remote to change the temperature, one degree up or down.

That allowed him to find the location of the temperature bits/commands in the stream.
I think he did the same thing for finding the 'mode' command byte(s?)
and decoded the function of each bit.
Which bit equals Fan only, Heat or Cool etc.?. Seems like a lot of work.

I've surfed the web over an hour, trying to find info on the CadillacKid (aka) Christopher in Columbus Ohio.
I'll bet he has a bunch of data we would be interested in seeing..

Maybe he will Google up this page and come join the struggle.

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