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Communication Circuit In Inverter AC PCB Board

suyog

Apr 22, 2016
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Apr 22, 2016
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Hie Guys,

I am working in Inverter Air conditioner PCB Board. I am getting stuck at communication signal circuit which is coming from Indoor Unit to Outdoor Unit. Circuit coupled with 2K 5% 3W resistor , 14D618K mov capacitor which further connected with two pc817 optocoupler interfaced with microcontroller.

Can anyone help to figure the schematic or working of this circuit.

IMG_20200321_234731.jpg
 

Harald Kapp

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Nov 17, 2011
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Not with the scarce "detail" you've given.
How about, for starters, a model number and a description of the problem you are working on?
 

dave9

Mar 5, 2017
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I'm going to go out on a limb here and suggest that what you are stating is incorrect.

It looks like you have just pictured a power supply board that has nothing to do with indoor, outdoor unit communication, unless they happened to integrate that feature onto the PSU board, which I would assume is not the case unless it does not have additional circuit boards for the control circuits.

Indoor - outdoor communication is probably nothing more than an on/off signal, maybe not even a signal in the digital sense, nothing more than a pair of power leads going to a relay to power its coil.

Why are you calling it an "inverter"? Inverter typically means it turns DC into AC while I suspect your board is doing the opposite, taking AC mains and converting to DC for the logic and relay activation.

I may have assumed too much, just seeing that small area of one circuit board and not having any description of the problem.

FYI, one of the most common reasons why an outdoor condenser unit won't start, is a failed motor start/run capacitor. Certainly if it is relay activated, a bad relay or wiring is possible too, or a refrigerant leak can cause a freeze-up, or compressor could go out, etc.
 

suyog

Apr 22, 2016
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Not with the scarce "detail" you've given.
How about, for starters, a model number and a description of the problem you are working on?
Here I have attached full indoor pcb schematic. As I have understood rx and tx signal generated using AC line most probably pwm frequency of 50HZ.
fig-5 (1).jpg
Following circuit is communication Circuit in the indoor pcb which used to transmit and receive the data.
IMG_20200324_161424.jpg

Outdoor Unit also has same communication circuit as follows
fig-6.jpg
Communication circuit as follows
IMG_20200324_161352.jpg

I hope this would be clear picture. I would like to is it possible to use ac voltage for transmission. Thanks.
 

Sure

Feb 28, 2021
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Feb 28, 2021
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Here I have attached full indoor pcb schematic. As I have understood rx and tx signal generated using AC line most probably pwm frequency of 50HZ.
View attachment 47478
Following circuit is communication Circuit in the indoor pcb which used to transmit and receive the data.
View attachment 47479

Outdoor Unit also has same communication circuit as follows
View attachment 47480
Communication circuit as follows
View attachment 47481

I hope this would be clear picture. I would like to is it possible to use ac voltage for transmission. Thanks.

Sir how you get this Ac board schematic pls replay and help me I am ac mechanic
 
Last edited by a moderator:

HPB

Nov 7, 2021
1
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Nov 7, 2021
Messages
1
Hie Guys,

I am working in Inverter Air conditioner PCB Board. I am getting stuck at communication signal circuit which is coming from Indoor Unit to Outdoor Unit. Circuit coupled with 2K 5% 3W resistor , 14D618K mov capacitor which further connected with two pc817 optocoupler interfaced with microcontroller.

Can anyone help to figure the schematic or working of this circuit.

View attachment 47443

Hi Suyog,
Although my reply is several month old, will like to point out key components in the picture for the
benefit of others.

Opto couplers in the photo, feedback output voltage error in SMPS that drive low voltage circuits
eg the microprocessor and relays.

Indoor to outdoor communications is via a single wire to pin 3 of CN3 connector.
Opto PC851 is always on via TXD on microprocessor side, that way indoor unit
sends data by pulling low S(N-W) line via a transistor/Opto coupler. Outdoor unit sends data by turning off/on Opto PC851.

Data is most likely serial RS232 low baud rate upto 4800bps on a single wire.

Cheers,
HPB.
 
Last edited:
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