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Support Forum » Washing Machine VFD

March 24, 2012
by JMitchell
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Hello, my question is about how a motor VFD drive from a front load washing machine can receive and send data over one wire. There is 120VAC in,and the control circuit has only 3 wires marked VCC in (5Vdc), Data, and Gnd. I am assuming the VCC and Gnd supply power to the small MCU on the board, but how could it send data in two directions over the only remaining wire??(no clock signal) The wiring diagram indicates there is data in and out from the main computer board to and the VFD board. These little 3 ph motors would be handy in projects if I could figure out how to control them.

March 24, 2012
by Ralphxyz
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JMitchell, don't have a answer but suggest you might search the Nerdkit forum for "3 phase" and Google "AVR phase controller"

or the like.

Sure will be interested in your answers!

Ralph

March 24, 2012
by mongo
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One wire data transmission is fairly easy, especially if in one direction. It sounds like this is the case, where data is sent to the VFD but not back.

In bi-directional data communication, each item on the line has a unique address and it just sits there intently listening for its own address to do anything. Generally, there is a control code, an address code, another control code and then the data. The first control code is just announcing that the next set will be an address. Then the second control code (Which may or not exist) just tells the addressee what to do with the data and how much there is to read. Much of the time, it is polling for real-time data and the node that was asked immediately responds with its own data set, while the host listens and records that data.

March 24, 2012
by JMitchell
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In the schematic, it says "Data In/Out". There is a sensor on the end of the rotor that is likely a speed sensor, but I assumed that it would only be used within the VFD control board to maintain a given rpm, but it could be that the rpm goes back to the main CPU board.(??). This particular VFD and motor are from a regular domestic 5 year old whirlpool front loader. This model uses a belt with a tiny pulley on the motor and a 12" pulley on the drum. The motor is 190 VAC 3ph, 800W, rated to 17,000 rpm!! This very high rpm makes it not as useful as a regular speed motor, but the newer washers use "direct drive", so the rpm will be much lower in those. (I'll be watching out for one at the dump). I had stripped this washer before I realized that it had the VFD drive in it, so I can't really measure anything now on the board when running. Thanks for the help !!

March 24, 2012
by Ralphxyz
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Now that is cool I'll have to keep my eye out for a front loader washing machine.

How do you plug a 190 VAC 3ph motor into a 110 volt single phase domestic circuit?

Or is there an ESC (Electronic Speed Controller) converter that you are calling a VFD (Variable Frequency Drive?)?

Ralph

March 24, 2012
by JMitchell
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Remember 120VAC is not the peak voltage but the RMS voltage. The 120V AC wave is rectified and stored in a large capacitor. The 3 phase AC wave is formed from that higher voltage DC and the end is 190VAC. The ESC is done by adjusting the frequency of the AC. It is a really good way to control speed, but in this case I have to be able to tell the VFD how fast to run. Jeff

March 25, 2012
by mongo
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If the schematic states data in/out, then is follows with the polling theory. It can still work the same. A similar data transmission format would be RS-485 or RS-422. Check these out for a possible clearer explanation.

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