Relay Driver for External Amp/LPF

[Jack Generaux]

I am building a Munin Amplifier and have a LPF100 low pass board from HFProjects that I plan on using.  I have used it with an older MOBO/CCI amplifier but I am repurposing it for the HL2.  I orginally used a PCF8574 board but that has the wrong I2c address so I am working on an altermate mcp23017 port expander with two ULN2803s -- one for the LPF and the other for future expansion.  I am attaching a couple images -- the schematic and board layout.  I did it in Eagle because I am more familiar with it.  According the the datasheet, the mcp23017can be run at 3.3 volts but I dont know if any other precautions are needed?  Thoughts are appreciated.

73

Jack (W0FNQ) 

[Steve Haynal]

Hi Jack,

Looks like a fun project. You can use the 3.3V from the HL2 CN7 to supply the MCP23017. No need for a voltage regulator if it was just for this. Also, the MCP23017 will not be the first supported. You may want to use a MCP23008 and just one ULN device. 

73,

Steve

KF7O

[Jack Generaux]

Thanks Steve,

I will work up a MCP23008 version; might even squeeze it to fit a 5x5 cm board which would be cheaper from Elecrow.  The LPF100 has six 12v relays so that stlll leaves a couple extra lines with the 23008.  I used the voltage regulator because I had to bring 12 volts to the board from the Munin anyway and it make it more stand alone for other rigs such as my STM32SDR.  Also I plan to add another header so that some other relay voltage could be used.  It is a fun project -- a friend and I are each building a Munin.

73,

Jack

[Jack Generaux]

Working on the interface for my 100 watt LPF.  Board is populated and Arduino sees it at 0x20.  However, I am not seeing any i2c activity on CN7 of my beta 2 with Quisk, Spark, or Powersdr.  I see i2c activity on CN17;   Is CN7 enabled in firmware?  If so, am I missing some toggle to enable it in software.  I tried playing with Alex and Apollo toggles but could not see activity.  Thanks.

73

Jack (W0FNQ)

[Steve Haynal]

Hi Jack,

The I2C inteface on CN7 is not enabled yet. Maybe I can get something to you within the next few days.

73,

Steve

KF7O

[Jack Generaux]

Thanks, but no hurry -- don't put it ahead of anything else.  I have the ptt to figure out and other things before its ready for prime time.  In the meantime, I'll use an Arduino to switch it manually.

73,

Jack

[Steve Haynal]

Hi Jack,

Okay. I just ordered this demo board to properly complete and test that the CN7 I2C interface will work with a mcp23008. It should arrive this week.

73,

Steve

KF7O

[Graeme Jury]

Hello Jack,

I am starting to write a simulator for HL2 I2C output so I can test my filter switching. I have as you suggested an Arduino to furnish the I2C signals and am driving it via the USB port with a Qt5 app that I am writing so the band signals are selectable. Neither are complete and debugged yet but finished enough to produce switching signals. Let me know if you want the code so far as you can either custom it to your needs or cut and paste bits of code which may be useful for you. The whole job should be finished in a week or so if you want to wait. I have attached a screenshot of the Qt5 app.

73, Graeme zl2apv

[Jack Generaux]

Graham, 

I would appreciate getting a copy of the code and ultimately your finished version.  You are producing a far more elegant solution than where I was heading.  I spent a little time today messing with a 7-segment display to show which filter is selected and a simple pushbutton to rotate throough the selections.  Still have a bit of soldering left as well as the arduino code.  The attached photos show the i2c board and the LPF I am working towards interfacing.  My email is 9artus<<<at>>>gmail<<<dot>>>com.

73,

Jack (W0FNQ)

[Jack Generaux]

I cobbled together an Arduino controller to switch the i2c lines for a little MCP23008/ULN2803 board.  I ran the LPF-100 through the various bands and produced the attached graph showing the LPF performance.  As previously noted, I will be using this with a Munin 100 watt amplifier.  Still have T/R switch to develop.  

73

Jack (W0FNQ) 

[Steve Haynal]

Hi Jack,

Thanks for posting your progress. It looks like a very interesting project.

73,

Steve

KF7O