Wednesday, August 2, 2017

New 3D Printer Project

|My poor little 3D printer has been busy for the last week or so printing parts for its big brother.  The AM8 design is based on a bunch of mods to the Anat A8 copy of the Prusa I3.  There have been several different versions of parts created to build the AM8 by different people.  Just looking at the files, I was not able to determine which would work the best for my build.  I ended up printing several different versions of several parts and then will decide which version I wanted to use for my project.  As I stated before, the original AM8 design used 2040 Aluminum extrusion for its frame. I did not have any of that profile, but did have some 2020 and decided to go with that.  Because I did not want to redesign a lot of the parts, I will sister two pieces of 2020 to get the desired profile.  Unfortunately I did not have enough Aluminum extrustion, so I printed some 2020 profile out of ABS.
  
After 4 days of 18 hour prints, I had enough 2020 profile finished to build the pieces I need.  After Acetone welding them together, I was pleased with how they looked and also how strong they were.
After cutting them and the Aluminum extrusion to length, I started the assembly.  The combination of Aluminum and ABS profiles went together very easily, and fit with the other printed parts very well.  After trying some of the different versions of parts I printed, I came up with what will work best for my project.  Because of some of these choices, I had to design and print several additional parts.  


After assembling the frame and gantry, I am very pleased with how it looks and how strong it is.  The size is just right to sit on the file cabinet next to my computer desk.
Now I am waiting on several other parts to arrive to complete the assembly of the X axis and Extruder carriage.  After that I can start on the motors, and electronics.  So while I am waiting on them, I can work on the boards for the SNA Jr 2.8 that came in last week.

Tuesday, July 18, 2017

Building a new 3D Printer update 7/20/17

While I am waiting on the boards for the SNA 2.8 I decided I want to build a larger 3D printer.  When I designed the case for the new SNA, I was limited by the size of my 3D printer.  As I mentioned in one of my earlier posts, the main problem with getting a 3D printer, is that I now have another new hobby.  The largest things I can build with my printer is abut 6" x 6", and I would like to go up another coupe inches.  I looked around and found a clone of the Prusa I3 called the Anet A8 that would be the right size.  There are several kits on EBay that can be bought for under $175 including shipping.  I checked several of the user groups on Google and Facebook to see what users thought of these kits.  It looks like they are  basic machines, but with some  work and modifications they can perform quite well.  One of the 3D printing sites I frequent is Tom3d.org, he recently did several You Tube videos on building a I3 clone from scratch.  After watching them I decided to build my own instead of getting a kit.  Looking at some of these kits and mods, I found a mod called the AM8. This uses many of the Anet A8 parts, but replaces the acrylic frame with one made from 4020 aluminum extrusion.  I have many of the parts, and some 2020 extrusion that should work.  I was able to download the  files for all printed parts and several mods from thingiverse.com , now to print the parts.

Some of the parts can be printed in PLA, but most need to withstand more heat and need to be printed in ABS or PTEG.  My printer works well with PLA but I have had problems working with ABS.  Originally this printer only used cartridges, but a recent software hack of the firmware enables the use of bulk filament.  I modified several used cartridges to feed filament directly from bulk reels, and tried several things I had found on-line to help when printing ABS.  My printer does not have a heated bed, and that was the main limiting factor for using ABS.  I added a thin PEI sheet to the build plate, and found that if I put several heavy coats of hair spray on the bed I could get the print to stick.  
I also designed some simple 20 x 1 mm. discs that when added near the corners of the object being printed, helped hold the part down to the bed.   

Without the heated bed, there was still some curling of the part when it cools.  From what I found on-line it looks like it might help to increase the temperature in the build area.  I found that by simply placing a plastic trash bag over the printer, the temperature was increased enough to prevent most of the curling, and also seems to help with layer adhesion.

Now that the printer is working better, I am in the process of printing the parts I need for a  printer based onthe Anet A8 and several mods I want to incorporate in my design. 
I have finished some of the larger pieces, and find very little curling, and what is there is not on any of the mounting surfaces. The pieces are very solid, and show no signs of layer separation. Wonders what a trash bag can do.

Update 7/20/17


Looking at the instructions for the modified printer now being called the AM8, the aluminum extrusion being used is 20 x 40 size. I have some 20 x 20 extrusion so will be using that instead. I do not want to have to re-design all of the parts, so I will mount two pieces together to get the profile I need.  I do not have enough aluminum extrusion, so I looked on thingiverse.com and found some files for printing some of the desired  profile.  My printer only has a print height of 150 mm. so I have to print in sections.  I printed several sections along with some extension support  pieces, and Acetone welded them together.  The resulting piece was stronger than I had thought it would be.  I guess now I just have to print up a few more batches and put them together.  Then I can cut them to length and mount to the Aluminum extrusion.

Friday, July 14, 2017

Lets call it SNA Jr version 2.8 for now

I have been trying to get a 3.2" TFT 8 bit parallel interface display working with the STM-32 board, but have had several problems.  So I decided to temporarily go with the Nano version, and a 2.8"  display with a SPI interface.  I had much of this working previously, so that part should go along quickly.  The previous board had a lot of additional circuitry on board that had been giving me problems.  I did a simple layout with just the Nano , display with simple voltage divider level translation, Ad8307 log detector, and a Adafruit SI351 board.  I usually make my own boards, but saw an offer from a Chinese board house that I wanted to try.  The board layout was under the 10 x 10 cm. size they had on special, 10 boards for $5 plus about $14 for postage.  At less than $2 per board, I decided to place the order.   Generated a set of Gerber files, uploaded them to their web site and placed the order.  Three days later I got an e-mail notifying me that the boards had been completed and were being mailed that day.  It has been about a week now, so expect them to show up some time late this week.  

While waiting on them, I decided to work on the packaging I wanted to use.  I had designed several 2 piece clam-shell type boxes that 3D printed quite well.  I changed the overall size ,and added cutouts for the display and joystick.  I was also able to design in mounting posts for these components, and added a bezel for the display.  It took a couple minor design changes and test prints to get everything exactly as I wanted it. 

It is still a lot easier than making a design on paper, transferring to  a box, then drilling and cutting out all the holes. Then you hope you have everything right, or you might have to start over with another box.  



I like being able to just do the design, send over to the printer, and in a few hours grab it off the printer sitting next to my desk.  The wife also likes the fact that I do not have metal filings all over the place anymore.




Sunday, June 11, 2017

Multiple project update 6/11

I had a wonderful time at FDIM and a great visit with my daughter.  Now I am back and need to get working on some of the projects I had on the bench.  The two main ones were the Spectrum Analyzer and version 3 of the SNA Jr.  After looking at the two, I have decided to make a few changes to my original idea and go with a more modular approach.  I now plan on making one board with the processor, display, AD8307, and SI5351 clock generator on one board.  This will be able to be used stand alone as a SNA or with one of several other boards to provide additional functionality. This will only have square wave output, so will be more like Farhan's Sweeperino.  I will see if I can add the code so I can use his PC 'Specan' software as well  as use it stand alone.  I had planned on having relay switching under software control to change functionality, but will probably just go with  SMA connectors and jumpers to change functions.  This should more easily allow the unit to be built and test itself as you go along.  
I also found that I was quickly running out of memory, both SRAM and FLASh.  This pretty much means that I will defiantly have to go to the STM32 'BluePill'. I had previously gotten many of the libraries and routines working with the 'BluePill', now it should not take too long to get the rest of what I need working.

When I got back home I spent a lot of time catching up on the e-mail and posts for the groups that I follow.   I did get a couple e-mails  from  Tony G4WIF, and Nick G8INE with  information and pictures of the SNA Jrs they had built. Tony also sent me a link to his web site with a post he wrote about the SNA Jr. http://fishpool.org.uk/snajr.htm .  To think that Tony, who is a co-autor of  'Simple Test Equipment for the QRPer' built one of my projects is a great honor indeed.  Since Tony and Nick are both interested in the SNA Jr. III, I guess I will have to get back to work.

Thursday, May 25, 2017

FDIM 2017

Again this year I was able to schedule a trip to visit my daughter with a stop over in Dayton for FDIM.  I had a wonderful time, and got to meet many people that I have met on the air or through e-mail and on many of the e-mail groups I subscribe to.  The highlight was getting to meet and speak with Ashar Farhan.  His BITX and other projects have been an inspiration to me and countless other home brewers all over the world.  Because of the speed with which hotel rooms filled up at the Holiday Inn where the FDIM event was held, I ended up staying a few miles away.  I was not able to spend any time on Wednesday to get to meet anyone there.  

Thursday was pretty much filled up with  speakers presentations, but afterwards there was ample opportunity to meet and talk with many other people who are active home brewers. A bunch of  us had a chance to sit down and talk with Farhan as he showed and explained the circuitry in some of his projects he had brought with him.  Among them was his 'Sweeperino' , 'Specan', and the uBITX design he is working on finalizing. 

I have been having some problems with a knee for a little while now. And after the long drive up Wednesday, and sitting around most of Thursday it let me know that walking around the Hamvention would not be appreciated.  So I spent most of the day Friday at the hotel and took my wife out for dinner before I went over to 'Club Night'  and the home brew contest.  I had a short time to talk to some of the Club members at different tables and several of the others in the home brew contest.  I spent the next couple of hours doing demos and explaining the AD8307 power meter probe I had entered.  I had been hoping to get either the Spectrum Analyzer or SNA Jr. V3 finished in time, but had to go with one of my earlier project.  After the contest was over I had a better chance to talk to the other in the contest and look at their entries.  

I also met Dave  VE3OOI , and several other members of the Peel Amateur Radio Club in Brampton Ontario at their club table.  I had exchanged several e-mails with them after I posted building my version of the Norcal S9 Signal Source.    Dave showed me the version they had kitted based on my project for their home brew group. 

It is extremely gratifying to know that others think your work is of enough interest that they will go and build something based on what you had done. 
 He later sent me a a copy of the manual they had produced for the kit. They went into a whole lot more detail in their manual than I had ever considered for the kits I had put together for my club. I guess I will have to put more effort into my documentation next time. 
  
He also sent a picture of some of the 30 club members that attended their 'build a thon' earlier this year.  It looks like they have a very active group of home brewers.

My knee told me that it still did not want to do much walking around, so Saturday was much like the day before. That evening we went to the QRP ARCI banquet and had a wonderful time.  We listened to the presentation by Ashar Farhan about his history in Amateur Radio and the steps that led up to the BITX design. After that there was the awarding of the door prizes and the drawings for the KX2s and other main prizes.  Last the awards to the winners of the home brew contest.  I am pleased to say that I took the award in the Test Equipment, Construction Aid category with my power meter.

All in all it was a very nice few days.  Even though I did not get to go and wander around the 'Hamvention', I did manage to purchase a VNA kit from the Austin QRP group during club night.  That and my own projects should keep me busy for a while.  We will spend about another week up with our daughter then the long drive back home.  Then I guess I should get back to some of my other projects.



Sunday, May 7, 2017

Quick SNA Jr V3 update

With  FDIM only a couple weeks a way, I am hurrying up with the build and programming of the SNA Jr. version 3.   This uses a mixer and simple crystal filter to eliminate many of the problems with  with harmonics when using a square wave signal generator.  I have a bunch of 4.9152 Mhz. crystals that I had purchased for another project.  I use the SNA Jr version 2 and simple test fixture to match several in frequency, and having a similar response curve.
I put them in the new board and directly wired the output of the signal generator circuit directly to the crystal filter circuitry.  Then using some of the new software I am writing for the version 3 system, I checked the response curve of the filter.  I found it to have a 3db response of around 100 Hz. and an over all response of about 1.2 KHz.  Since I am running out of program space in the NANO, I also used the software to find the center frequency of the filter.  I will program this directly into the software instead of writing a calibration routine.  For not It looks like this should work OK. 

Using this signal for testing purposes, I added a pop up menu with additional functionality.  One option allows me to normalize the waveform after it is acquired, instead of having a separate normalized sweep like the version 2 software.  Another thing I added was a marker to display difference in frequency and amplitude between the marker and cursor.  This picture shows the response of the filter and the new software features.
I had added pads on the circuit board for several attenuators, but found that I am gong to be a little short on gain even with out them. I also found that with the single sided board I could not get the low level noise floor that I had with other power meter circuits I had built.  I am going to quickly make a couple changes to the board and etch up a double sided version.  Hopefully I can shield the AD8307 and get another 10 dB dynamic range in the power meter part of the circuit itself.

Thursday, April 27, 2017

SNA JR V3 Case UPDATED 4/30

I was working on the SNA  Jr. version 3 circuit board, and did something really stupid.  I had been checking linearity using several in line attenuators.  Just set the different values I was not using at the time down on the desk.  Then I sat the still powered up board down on top of them, there it was the "MAGIC SMOKE'.
I guess it is time to build a case for the boards, before I do something stupid again.  
I had  a design for the side panels I had used for other projects.  It has slots for a top and bottom made from circuit board material that just slide in.  It also has a board slot for holding the circuit board at the correct height in relation to the top. It was just a matter of changing some dimensions and printing them.  I also designed and printed simple end pieces with a lip to help protect the SMA connectors for RF in and out signals.

I wanted a bezel around the display, and something to cover the hole where the Joystick comes through the top panel. 
 After a little playing around with the design software, I came up with one that would do both.  I then decided to also add mounting posts for the Joystick to the bottom of the bezel. 

 This is the reason I bought a 3D printer in the first place.  No more looking for and trying different stand-offs or other bits of hardware to make some thing kind of fit.  Just design exactly what you need and then print it. It might take a couple of tries but, I can usually come up something that works and looks nice. The first try almost worked, except that I could no longer get at a connector mounted on the main board.  So I moved the Joystick mounting posts a little and change the orientation, and the second part worked just like I wanted it to.  


The display mounted to the bezel correctly,  and I have a lip on the bezel to cover the hole in the top panel for the display. The Joystick comes through the top of the bezel at the height I wanted, when screwed down to the printed mounting posts. 


This was so much easier and cleaner looking than my original attempt using standard length stand off hardware.  The chamfer I built in around the Joystick opening also does a nice job of covering up the mechanicals of the Joystick.


I stuck the display assembly on the SNA  Jr. circuit board, and loaded in a sample sketch to check the display and the Joystick operation. Everything works well and looks great. 








UPDATE 4/30/2017
I cut the opening for the display and Joystick in the piece of PCB material,I am using for the top panel. I mounted the bezel with the display and joystick to it. Checked how every thing fits, epically how well the main board and top panel fit in the slots in the side panels.  I think it will look nice when finished.  I need to do some sanding and painting on the top and bottom panel parts, but for now I can work on the software without worrying about sitting the board down on  anything again.


Now to get back to working on the software and finish putting all the parts in the cabinet.  I want to see how it looks with just the printed parts, or if I want to do a little sanding filling and touch up painting on them.  Will keep keep you updated on the progress.