Author Topic: Classic 150 SL Serial Logic Voltage and Raspberry Pi  (Read 141 times)

singlebarrel

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Classic 150 SL Serial Logic Voltage and Raspberry Pi
« on: September 06, 2017, 10:16:57 PM »
I am attempting to set up a Raspberry Pi to monitor an off the grid cabin's various systems, and one of the big ones is the solar power, which is controlled by a Classic SL 150. After reading through the forum, it looks like all of the registers can be read via MODBUS through the one of the three serial ports (I'm assuming SLAVE/OUT). The Pi has a serial port (it's a Pi 3 so technically it has two UARTs) but I'm seeing lots of warnings about how the it only uses 3.3V logic voltage and connecting to anything larger than that will fry the Pi.

My Question is: does anyone know what the logic voltage for the Classic serial port is? The RS-232 standard support 3-15V, but if it's more than 5V i'm not sure how to handle it. (With 5V I can apparently use a logic level converter.) Or if I'm just missing something and making this way too complicated let me know  ;)

Thanks!

dgd

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Re: Classic 150 SL Serial Logic Voltage and Raspberry Pi
« Reply #1 on: September 07, 2017, 12:27:12 AM »
You should use a serial port for the Pi that uses a MAX232 or MAX 3232 driver and that will handle all the logic voltage levels. Complete rs232 serial boards with suitable ttl interface for the Pi are available on Ebay and cost peanuts. Buy several so you can blow them up with aplomb

dgd
Classic 250, 150,  20 140w, 6 250w PVs, 2Kw turbine, MN ac Clipper, Epanel/MNdc, Trace SW3024E (1997), Century 1050Ah 24V FLA (1999). Arduino power monitoring and web server.  Off grid since 4/2000
West Auckland, New Zealand

boB

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Re: Classic 150 SL Serial Logic Voltage and Raspberry Pi
« Reply #2 on: September 07, 2017, 12:35:35 AM »
Some of these single board computers have serial I/O as real RS232 and some have just the 3.3V or 5V logic
level signal that connects up to an RS232 driver/receiver.   These interface ICs invert the logic signal and also
have a built in voltage booster that operates from the 3.3V or 5.0V logic supply.  That is why they have
a couple of pins for a small capacitor  (usually 0.1 or 1.0 microfarad)

Here is one that will run off of either 3.3V or 5.0V supplies and convert RS232 level to UART logic level
and vise-versa.  They are pretty cheap too.   OR you might find a small and inexpensive circuit
board that comes with an IC similar to this part from maybe Sparkfun.com...

The IC....

https://www.digikey.com/product-detail/en/stmicroelectronics/ST3222EBPR/497-6531-1-ND/1865364

The board...

https://www.digikey.com/product-detail/en/BOB-11189/1568-1193-ND/5673779?WT.mc_id=IQ_7595_G_pla5673779&wt.srch=1&wt.medium=cpc&WT.srch=1&gclid=Cj0KCQjwub7NBRDJARIsAP7wlT-TS_eduaBwOAAq2qgvsiW6T131BJybOz9i1Fv0EuaWSxYxi3qiZIUaAiX-EALw_wcB


You can also connect those transmit and receive and GND lines (3 lines)  to a telephone cable to plug into the Classic's
comm ports like you are wanting to do.  The pinouts of course are in our MODBUS comm maual (kind of old)....

http://www.midnitesolar.com/pdfs/classic_register_map_Rev-C5-December-8-2013.pdf    (last page)

The Classic jacks are 6 pin but you only need a 4 wire cable with 6 positions...  Used to be available
at Radio Shack but I find them at second hand stores or buy the wire and connector and crimper
at Lowes or some other decent hardware store.  Ace too maybe ?

boB

K7IQ

singlebarrel

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Re: Classic 150 SL Serial Logic Voltage and Raspberry Pi
« Reply #3 on: September 07, 2017, 12:48:40 PM »
Thank you both for the replies. I apologize for any confusion but I'm a software guy and just know enough about hardware to be dangerous.  :)

So it sounds like I need to go: Charge Controller RJ11 -> MAX3232 -> Raspberry Pi UART.  Think I can run about 40 ft of signal wire between the Classic and the MAX3232?

Thanks again.

dgd

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Re: Classic 150 SL Serial Logic Voltage and Raspberry Pi
« Reply #4 on: September 07, 2017, 11:57:37 PM »
Thank you both for the replies. I apologize for any confusion but I'm a software guy and just know enough about hardware to be dangerous.  :)

So it sounds like I need to go: Charge Controller RJ11 -> MAX3232 -> Raspberry Pi UART.  Think I can run about 40 ft of signal wire between the Classic and the MAX3232?

thats it and 40ft no problem

http://www.ebay.com/itm/MAX3232-RS232-to-TTL-Serial-Port-Converter-Module-DB9-Connector-MAX232-3-3V-5VDC-/112260803163?hash=item1a2343ea5b:g:8gYAAOSwSlBYv9s5

Please post your code in rpi area once you get it working.. Thanks.

dgd

« Last Edit: September 08, 2017, 12:01:59 AM by dgd »
Classic 250, 150,  20 140w, 6 250w PVs, 2Kw turbine, MN ac Clipper, Epanel/MNdc, Trace SW3024E (1997), Century 1050Ah 24V FLA (1999). Arduino power monitoring and web server.  Off grid since 4/2000
West Auckland, New Zealand

singlebarrel

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Re: Classic 150 SL Serial Logic Voltage and Raspberry Pi
« Reply #5 on: September 08, 2017, 04:09:24 PM »
Please post your code in rpi area once you get it working.. Thanks.
dgd

I certainly will, but I probably won't have anything until February when I have access to the charger again.

sb