Wednesday, July 16, 2014

Updating the FSR Endstop Controller Firmware

The FSR Endstop Controller board is built so you can flash new firmware onto the board, and I’m providing pre-built hex files on Github, which you can find here:

In this post I’ll describe how to download one of those hex files to your FSR board.

What you’ll need

Before you get started, you’ll need the following:

  • USB programmer. You can find more information about programmers on AVR Tutorial: Choosing a Programmer. I’m using a Pocket AVR Programmer. Both Sparkfun and Adafruit both have other programmers. In any event, you’ll need one that has a cable with a 6-pin connector
  • Arduino. I installed Arduino 1.0.5-r2. Even though you won’t be using this directly, you’ll be using the avrdude program included with the installation
  • Six-Pin Header

Adding the programming header

Solder in either a 2 by 3 pin header, or two rows of 3 pins as shown below. You’ll be connecting the programmer to these pins, and the board will also receive power from the programmer.

P5021907 Cropped_400

Connect the programmer

Plug your programmer into your computer, and then connect the cable between the programmer and the FSR board as shown. Note the direction of the cable coming away from the FSR board


Also notice that the green power-on LED is on once the programmer is attached, as the FSR board receives power from the programmer.

Running avrdude

The final step is to send the new firmware to the board. The instructions below are for Windows. You can find more information about using avrdude here: Starting out with avrdude. First, locate where you have Arduino installed.  The avrdude program will be in a folder under that location: hardware\tools\avr\bin\avrdude.exe. Copy this full location.

Open a command prompt and navigate to the location where you’ve downloaded one of the hex files. Then run this command (all on one line):

C:\Users\John\Downloads\Arduino\arduino-1.0.5-r2\hardware\tools\avr\bin\avrdude.exe -p t861 -c usbtiny -U flash:w:"FSR_Detector 1.3.hex"

You’ll want to substitute your actual path to avrdude for the one here, and you’ll want to use the actual name of the hex file. You should see progress information from avrdude while it’s downloading and then verifying the firmware. While the firmware is downloading, the green LED on the FSR board will be dark. It will come back on once the firmware starts running again.

Monday, July 7, 2014

Pegasus Touch First Impressions

I backed the Kickstarter campaign for the Pegasus Touch SLA printer, which I got for $2,250. At that price, and given the samples they were showing, I thought it might be a good deal. Of course, with Kickstarter, you never know. And I’ve been seeing grumbles on the forum from other people who have received their printers (or perhaps not).

I received my box a few weeks ago and finally had a chance to set it up this past weekend. The packaging was good, and there were no issues with broken parts. The box included the printer, a 1/2 liter bottle of clear resin, and the power supply. That’s it. No manual.

I downloaded the manual and software and setup the machine on my desk. My desk isn’t near an Ethernet jack, so my desktop computer is connected via Wifi. No problem, the manual indicated that I could print without a network connection, using a USB thumb drive. So I fired up the machine. A splash screen appeared, and then the screen went blank after about 10 seconds, and just stayed that way. Even after 10 minutes, it was still blank.

OK, perhaps that meant I needed to update the firmware first. But how to do it. I checked the manual again, and the manual said that “Ethernet is the preferred interface but USB PC connection (requires microUSB cable, not supplied) and WiFi (requires dongle, not supplied) are also supported.” So, I connected the USB cable, and after some fiddling to get the drivers installed properly on Windows, the machine showed up in my devices list. And now RetinaCreate (their software package for talking to the printer) told me that the printer’s firmware needed to be updated. However, I couldn’t find a way to update it.

Finally, I moved the machine to another location where I could plug it into an Ethernet wall jack. It booted, and I was able to update the firmware. It turns out the manual isn’t correct, and you need a hard-wired Ethernet connection, at least to get started. I haven’t tried it without, so I’m not sure what does and doesn’t work. However, I was able to print—yay!

First Print

I loaded a model into RetinaCreate that I’ve been working on for a while to stress test the printer. This is a small caboose in HOn3, and it’s just under 7 cm long. You can find more details in my previous blog posts:

Here is what I got after 5 hours (using 50 micron layers):


You can click on the image to see a larger version. Below I’ll describe more about what I learned. But first, here is what the 3D model looks like in Solidworks:

Full Body

And finally, here is what I had in RetinaCreate:

Retina Full Body

In case you caught that I had clear resin, the picture above is after spray painting the model with light gray, which makes it a lot easier to see what the surface looks like. Also, I hand-modified some of the supports after using the automatic support generation feature.

What I learned

First, I learned that this printer has a lot of potential for creating small models. Until I printed this model, I wasn’t sure it would live up to the task. Sure, the printed part will need some sanding to smooth out the curved surfaces, but so do models from Shapeways.

I also learned a lot about working with SLA printers, which is very different from working with FFF printers. The model is printed upside down, and that meant that uncured resin got trapped in various parts where I didn’t want any resin. As an example, look at the floorboards at the end of the caboose. In the printed model, they didn’t turn out very well. A lot of resin got trapped under (or above when printing) the floorboards, so there was a lot of goopy resin still in there when I took it out of the printer. The floorboards also didn’t cure very well. That may mean I need more support, or it could be a result of the goopy resin above.

As it turns out, the orientation I used was completely wrong. I’d always wondered why SLA printers tended to print parts at strange angles. Well, now I know—it’s to allow the uncured resin to drain out of the part as it prints, so you don’t end up with partially cured goop. Using clear resin probably doesn’t help, as any trapped resin can still receive some light. I really want to get some tinted resin to see what difference that will make, because the laser doesn’t travel very far into opaque resins.

After printing this part, I discovered that RetinaCreate has a button called Find Optimal Rotation that only appears when you have the object selected. I had not noticed that. Here is what it looks like when I use that option:

Optimal Angle

That’s a very different. I’m not convinced this is the optimal angle, but I’m going to give it a try.

Saturday, July 5, 2014

Building the Manual Pick and Place Machine

In my previous post (Building the FSR Circuit Boards)  I showed how we assembly our circuit boards, using a manual pick and place machine that I designed and built. You can also find videos on that post. In this post I’ll walk through building the machine.

You can find all the 3D files here:

Bill of Materials

  • 3/4 inch aluminum tube. I purchased a 6 foot length from Lowes for about $20 (
  • M3 x 12 screws (9)
  • M3 x 20 screws (4)
  • M8 x 30 bolts (12)
  • M8 x 50 bolts (3)
  • M8 nuts (10)
  • M8 washers (12)
  • 608 bearings (18)
  • LM8UU bearings (2)
  • Spring (1). I used a 2-1/8 inch long by 7/16 in diameter compression spring (with 0.032” diameter wire):
  • 8 mm diameter aluminum tube (I purchased this from a hobby shop)
  • Luer adapter:
  • Tetra Wisper 20 Air Pump:
  • Tubing for the vacuum pump (available at pet stores)
  • Suction Headers:
  • Assembly

    You'll need to modify the Tetra air pump to convert it into a vacuum pump. There is a nice article and video on how to do this here:$20.html

    Modifying the pump only take a few minutes.

    Building the X/Y Assembly

    Start by printing four of the Y Post parts, and then cut two pieces of aluminum tube about 18 inches long. You can make them longer, but I wouldn't go much shorter. A length of 18 inches will give you about 11 inches of movement along the X (left/right).

    Next cut two pieces of aluminum tube about 12 inches long (or longer). Using 12 inches will allow movement of about 7 inches along Y. Print two sets of Y Carriage, Bottom Rollers, and Bottom Roller Clamp parts. Use the M8 x 30 bolts and washers to mount the 608 bearings to the Y Carriage. The washers go between the bearings and the part, and the M8 bolts are self-threading. Add the 608 bearings, washers, and bolts to the Bottom Rollers parts.

    Place each Y Carriage assembly around one X assembly and then use the Bottom Roller Clamp with some M3 x 20 screws to clamp each Y Carriage assembly to the aluminum tube of the X assembly. This picture should help:


    The bottom roller clamps don’t need to be really tight. They’re to keep the top rollers in place when you lean your hand on the carriage.

    Now insert the two Y tubes into the holes of the Y Carriage and then mount to a piece of plywood. It's best to screw down one side first, with the screws centered in the slots so you have some room for adjustment. Then attach the other side, ensuring the assembly moves smoothly from left to right.

    Building the Pen Holder

    Print the Pen Holder and LM8 Cap parts. The 8mm aluminum tube slides through two LM8UU bearings. The tube will need to slide up and down smoothly, as well as rotate. I found I needed to sand the tube down a little to get just the right fit. Do this slowly, testing the fit frequently.

    Insert the 8mm tube into the two LM8UU bearings, and then clamp them in place using the LM8 Cap part, held in place by four M3 x 12 screws. At this point you’ll still be able to remove the tube.


    Insert two M8 x 50 bolts, as shown through the three holes. Add an M8 nut to the back of each bolt and tighten. Next add one 608 bearing to each bolt, along with an M8 washer, and put it up against the square tube, as shown here:


    Add another 608 bearing to each bolt, followed by an M8 nut. Hand tighten each of the three nuts evenly, ensuring that the assembly slides smoothly without any slop.

    Building the Pen

    Print the Pen to Tube and Spring Stop parts. Add the spring, then the spring stop (which has a slot on the bottom for the spring). Use an M3 x 12 screw to clamp the spring stop in place. Apply some pipe tape to the tapered part of the Pen to Tube part and then push it into the aluminum tube. Finally, push the air hose onto the nib. When you’re finished, it should look like this:


    Print out the Lock to Tube Adapter and Pen to Tube parts. Carefully push the Luer adapter into the Lock to Tube Adapter at the larger-diameter end. It should look like this (when you also have a needle in place):


    In the photo above, I’ve also added some pipe tape to the tapered part to help create a tight air seal. You’ll want to push this into the tube after the tube is in place. When you’re done, it should look like this:


    Optional USB Microscope

    I initially installed a USB microscope in order to help with placement, but I found it to be more confusing them helpful. The problem is that it’s looking at the part from an angle, so it’s actually harder to line up parts with the microscope than with your eyes (stereo vision really helps). My friend uses a pair of Optivisors and found they work really well. I’m near-sighted, so I just take off my glasses. But if you do want to install a USB microscope, I purchased this one:

    And the parts you’ll need to mount this microscope are Camera Cap Top and Camera Cap.

    Building the FSR Circuit Boards

    My friend and I have been busy building the FSR Endstop Controller circuit boards (you can find the entire discussion on the Delta Robot 3D discussion here:!topic/deltabot/2Nvtv4aicKk%5B1-25-false%5D).

    Most of the work involved in building these circuit boards is placing the tiny parts onto the circuit board. The smallest parts are 0603 surface mounted devices, which means they’re 0.06” by 0.03” in size. For the first few boards I built, I dumped the parts onto the table, and then used tweezers to put them in place, under a microscope. But it was very time consuming to flip over components if there were upside down or no their side. And I also had to check the polarity of the LEDs carefully.

    I did some research into pick and place machines and then ran into a manual pick and place machine: I really like what he’d done, but it was mostly made out of wood, and I don’t have much in the way of word-working skills or tools. I also ran into a nice manual machine that was $199 so I checked out their web site. They were out of stock, so I sent them an email. After about a month I got an email that they were in stock again, but now the price was $399: SteadyHands PnP. By this time I’d already built my own machine for about $50.

    I decided to make a machine similar to vpapanik’s machine, but using 3D printed parts. Here are some photos of my finished machine:


    You can find information on building this manual pick and place machine here: Building the Manual Pick and Place Machine.



    The process of assembling the circuit boards begins with adding solder paste to the circuit board. I created a solder paste stencil and jig, as I described in my post Auto Adjust FSR End Stop Detector. This time I created a stencil that allowed me to add paste to four boards at a time.

    Once the solder paste is applied, the next step is to place the components onto the solder paste. This is where my manual pick and place machine enters the picture. This video shows placing a few parts with my manual pick and place machine:

    My Manual Pick and Place Machine in operation

    After placing all the parts on the circuit board, the board needs to be baked in a reflow oven to melt the solder. This video provides a short introduction to using a reflow oven I purchased off of eBay. I paid $200 for this oven, and it had a flaw—inside they use masking tape in an area that gets rather hot, and causes the masking tape to off gas, producing a terrible smell. I found instruction information and instructions about this here:  T962A SMD Reflow Oven Fix/Hack.

    Using a T-962 reflow oven to melt the solder paste and finish the boards

    In my previous blog post, I wrote about creating a programmer to upload the firmware to these boards. This video shows using this programmer:

    Programming the circuit boards

    Finally, here is a longer video showing me placing the other parts on the circuit board:

    Longer video of the pick and place machine