Raspberry Pi Communicating With Arduino Uno

http://www.instructables.com/id/Connect-Your-Raspberry-Pi-and-Arduino-Uno/

Arduino boards are great to dedicate them to one function. In my immediate “use case” I want to have a control box that supplies power and has two knobs to control my remote antenna tuner. I might even add a little LCD to give feedback from the tuner – like what offset the L and C Stepper motors are at.

If I were to control the remote tuner from my laptop via wireless it would be all digital – but I kind of like the tactile feel of analog – not to mention the rotary encoder “knobs” would be right below my SPE 1.3K FA amplifier and K3 – so I could tune and watch their SWR meters. I wouldn’t need to know what the SWR is at the antenna tuner at all – its best to read it right at the amplifier – since that’s the whole reason I even have that remote tuner – to keep the amplifier happy.

SO – while I could do this with my laptop – with its built in wireless, if I do build a box with the encoders and LCD – it could be powered by a Raspberry Pi that talks to my Arduino – which would be out in the tuner box along with the two stepper motors, their driver boards, the Arduino, a wireless board and just the DC wires going out there to power it all.

If I were concerned about the WiFI getting fried by my Mod Bob running full juice – I suppose I could run a 60′ Cat 5 cable – I have to think about this, and this is what my Summer Project will be. I’m glad that this project offers some challenge and fill at least July with fun stuff to do.

One other thing that is super cool – Fritzing:

http://fritzing.org/home/

Its truly the antidote to the “DX Doldrums” . . .

 

Sainsmart TB6560 Stepper Drivers

While Adafruit has some nice driver boards for Nema-17 Stepper Motors, my Nema-23 motors have a higher current rating. This seems to mean that Arduino is my only option at this point. I’m more than fine with this since its a dedicated project that will sit in a box out back. Here is one of many decent video’s. He uses a 24v power supply, I will use a 12v supply that I already have, unless it proves out that I need more power.

https://www.youtube.com/watch?v=RakXequOrSY

I don’t need or want speed, but it will take some torque to turn the double inductor control on the Palstar BT1500A. I also want it to be precise – on 80M, the tuning is a little “sharper” than on 160 or 30M.

I also will need to go with wireless because while I am only using 2 wires to provide 12V to the Palstar BT1500A out in the box, I will need one wire in my rotator cable for the 5V + line (I think I can share the minus line), which does leave 5 more wires for control. Since I might just use my laptop to control the tuner – use GUI sliders and then save settings to memory, I only need to send the commands.

Here’s a nice wiring page:

http://www.instructables.com/id/How-to-wire-an-arduino-based-3-axis-CNC-machine/

OK – I think I will have just enough to at least get the motors spinning and get my code to do what it needs to. I’ve been told to get the Duemilanova Arduino board, but since I already have an Arduino Uno, I will start with that. I will also worry about screw shields and wireless later – after I learn the basics.

I think this project is the perfect “hello world” Ham Radio and Maker project. It is VERY useful and is complex enough to be a chalenge, but not so overwhelming that I was scared into just buying my way out of the project. I’m especially happy that I did go with the Palstar BT1500A – because several nights checking into the net on 75M at full power and all is well – much betterthan trying to force the poor KAT-500 to match the Mod Bob – it really needs this remote tuner at the feed with these large analog components. No sparks, no arcs or faults!

OK – next step: remote controlled automation!

The New KY6R Shack

The Palstar R30CC, Elecraft K3 and P3, SPE 1.3FA, Elecraft Kpod, switches and power supplies.

Awards include SWODXA DXpedition of the Year for VK0EK, 8BDXCC, DX Coffee Best Communication Award for TX5K, and DXCC Honor Roll.

Antennas are 20M home brewed yagi, DX Engineering DV-40-P 40M phased vertical array and the KY6R “Mod Bob” for 160, 80 and 30M. For RX on 160M I use the 40M phased array, the Mod Bob and the Wellbrook ALA1530LNP rotatable loop – in diversity mode.

To the right of this desk is my “maker space”. A true “man cave”.

Palstar BT1500A Schematic and My Switching Arrangement

I’m not exactly sure I understand how to read this schematic, but for all bands, the relay switching that I have going on is >50 ohms, LP or the UP position(Hi-Z) -which by default has the 65 pf engaged at the output – and then the Low C, where the larger 960 pf capacitor is taken out of the circuit. The resulting circuit looks like this:

Its pretty cool how the BT1500A uses two 40 amp contact relays to switch the capacitors either at the input side or output side of what is basically a balanced L circuit – that looks like a Pi circuit:

The inductors are uH . . .

As I was hoping, this tuner is PERFECT for this application. Its one of only a few times where this tuner being remote at the antenna is in fact, much better than a T tuner in the shack. It also explains why on 80M, the KAT-500 would match but I had to limit the drive so that no more than 200 watts was generated by the KPA-500. It would be fault city if I drove it more – so I knew the impedance at the antenna was probably quite high. On 160 and 30M I think the impedance is a lot lower – especially 160M, where the Mod Bob had a very low SWR even without the tuner – because it was basically a half wave dipole.

The other thing I’m learning is a bit more about antenna matching and the relationship of inductance and capacitance and reactance and resistance at the antenna feedpoint.

When you force a match, there will be losses, but to have a multi low band antenna that covers 160, 80 and 30M is no small feat. If I didn’t have a very good mono band antenna on 40M, this antenna would work fine on that band too.

I have a strong gut feeling that the stress that was on the KAT-500, or on any in shack tuner is not nearly as bad with this tuner at the feedpoint, nor do I think the current / balun will heat up as much. The KAT-500 is also an L tuner, but when I saw so many faults with the KAT-500 at that lower voltage, I knew at 1500 watts I needed a better solution, and I am VERY confident that I have made the right choice. At 500 watts and below, you can get away with a lot more, but I think its better to always design something that can handle high power, because you will know right away of your circuit or shack setup tries to run QRO and you have amplifier faults.

Now I am really feeling good about not just going out and throwing money at something like the AT-Auto. My gut feeling to try this “different” route is turning out to be a good thing.

 

Raspberry Pi “Happy Accident”

Just for fun, I decided to download Putty onto my new Windows 10 laptop and SSH into the little Raspberry Pi, as if it were a server. Holy smokes! Its IS a little server:

For whatever reason, and now I know its not even worth bothering with – the GUI stuff in Raspian (Pixel) just won’t load on my Raspberry Pi. That’s OK, because I don’t need that bloat anyway – this little guy is meant to be a slave to my Palstar BT1500A tuner and just make the stepper motors work.

And so – the happy accident is that Raspian Lite Jesse is exactly what I want and need.

Now, this is incredible. I downloaded an Android ssh client called Juice and am logged into my Raspberry Pi from my Android phone. Gee, now I know what all the hubub has been about these last several years. Heck I’m almost late to the game – heh heh.

OK – now I need to order a Nema 23 stepper motor driver for either the Arduino or the Raspberry Pi – but I am actually MUCH more excited about the Raspberry Pi than the Arduino. Its really cool to have such a choice though!

Remote Controlled BT1500A Part 3: All Wired Up

The tuner is mounted in its waterproof gasketed box and has been tested to make sure the SPE 1.3K can work with it. The answer is Yes.

I said “servo” in the video but meant stepper motor. Anyway, that’s the next big half of the project – getting the stepper motors working and installed. In the mean time – its easy enough to go out back and manually change bands. We don’t get rain until November, so I have plenty of time, and will take my time and learn along the way. In fact, besides checking into a nightly net of 75M, I have nothing going on radio wise – but do have 40 and 20M which just use the internal tuner of the SPE.

Onward – and this next few steps will be where I learn the most.

Field Day

Wow – I’m having a big ham radio and maker weekend. This is exactly what I have needed to re jump start my hobby. I almost stopped blogging because after I “made the grade” with Honor Roll and DX-pedition of the Year goals in the bag, I really thought that I was done.

A few years ago I tried to get into Arduino, but the little starter kit I bought sat mostly in the box after putting together a few little projects. At the time I was going to automate an old Ten Tec 238 Tuner, but got lazy and just purchased a Palstar AT2K for the shack.

Yesterday I almost “flinched” again and started to think about just purchasing a Palstar AT-Auto for the shack, but since it was $770 more than the AT1500A, and also wasn’t really the best circuit for the Mod Bob, I decided to stick with the AT1500A automation project. I decided to start the project seriously and get my butt out back and start building, and to also get my Arduino and Raspberry Pi development environments up and running (which I have done).

Just for laughs I decided to participate a little bit in Field Day, and 40M was so good last night I did some search and pounce and even with just 100 watts, I was working everyone from coast to coast. This morning KH6 is pounding in bigly. Its been a little bit of fun. I don’t care for contests, and will never go on a DX-pedition, but its fun to goof around in a contest every now again. Its a good way to check propagation and antennas.

I will be getting my SWODXA DX-pedition of the Year plaque tomorrow and will give Bob, KK6EK the coax spool “end cap” VK0IR and VK0EK commemorative piece that I made a while back. Bob and this spool of coax are the only two people / things that have been to Heard Island twice for these two DX-peditions, and both won DX-pedition of the Year. I only keep the awards that were significant – I don’t plaster my walls with too much stuff, and have more art than ha radio stuff on the wall, but the little space above my radio bench and desk is big enough for 4 awards. I’ll post a new shack picture tomorrow after the plaque goes up – and my shack has been recently been upgraded and looks great. I can do more with a bench of equipment that is much smaller than it used to be.

I’m very proud of these accomplishments because they took a lot of work, but I’m very happy that at this “turning point” I have a new interest that could lead to more big successes. I’m goal driven and also like to learn something new every day – that’s what my antidote for burn out is – and I’m feel re-invigorated with the new possibilities and projects ahead.