I did a little video of the progress of the amplifier control unit. I managed to get some basic functions working and after the video was made I also managed to get the rack unit to send data to the openASC box, which through a menu you can see the state of the amplifier and control it with the external keypad.
The ringing sound is from the gears, hopefully it will go away after I put some grease on them. Everything isn’t perfectly centered so I don’t want to put much tension on them.
Today I spent another 6 hours in the lab at work. I am now almost finished with all the electronics for the amplifier control. What is left to do is to add the attenuation for the power meter, fix cables between the PTT input and the control board plus some mechanical job. I need to make the plates that holds the stepper motors and I might make them out of thicker aluminum so that I can make a hole for the variable resistors which makes it impossible for them to turn around if the nut happen to get loose (from vibration or something). That way the positioning can not be totally off or fail (except if the pot gets bad but that is detectable). I will also need to spend some time in the lathe making knobs for the back of the stepper motors for manual tuning.
It feels good, now I need to clean my desk at work so I have some room to put the stuff up so I can write the firmware for it. Later I will extend the system by measuring grid current, anode voltage, anode current etc. The amplifier has got built in grid protection so I don’t need to worry about that.
I’ve been a busy boy and built a USB-dongle for the openASC bus. This dongle can be used to communicate straight out to the bus. I had a previous version of this that needed external 12v to be able to transmit, but I made a new version with improved bus filtering but the main new feature is a step up converted which makes 9v out of the 5v that the USB port supplies. That way it can operate on its own without an external DC supply.
I also did more work on the amplifier project. I mounted 2 pcs of small relay boards which will be used to switch the input filtering plus also the relays that switch the output PI-network of the amplifier. I found this to be the easiest way to solve the issue of switching 12/24v relays since the amplifier control board had ULN2003A drivers to drive these small 12v relays. I also soldered lots of cables, so now the control panel is hooked up to the micro controller and soon its time to actually start writing the code, not that much too do on the electronics. I need to add another relay board to be used to switch ON/OFF the amplifier, toggle HV etc. plus I will need to hook up the potentiometers used to position the capacitors of the PI-tank to the control board.
I have been working on a few things lately. First I have fixed a box for the input filter for the amplifier project. I have also removed some old electronics from a radio module and taken the 19″ rack box, which is planned to contain all the control electronics for the amplifier automation project.
I also did change the design a bit of the current openASC power meter pickup modules. They now have an 16-bit A/D instead of the built in 10-bit A/D, which will improve the resolution a lot. I also added a new frequency counter which will make it possible to detect the frequency a lot more accurate than before. I assembled the boards and will do some programming on them this weekend.
If this work well SG3P (SK3W) will come up and build a bunch of these devices for his station as well.
