Next Project: Sewing Table with Machine Lift

My beautiful and talented wife frequently uses her sewing machine ( as well as the even more frightening Serger, multiple needles and blades). Right now she has to carry it down from her crafts cabinet upstairs and set it up on our kitchen table. The light isn’t the best in the kitchen and moving the machine every time is less than optimal. We have an old desk in our dining room that we never ever use and so we thought perhaps we should get rid of the desk and make a sewing table that could also store both machines and the sewing tool box. The dining room has much better light and there would be no carrying the machine any more. ROCKLER makes a sewing machine lift mechanism that can be put inside a desk or table to make the machine rise up through the top and then disappear inside when not in use.

I’m working on the design now and am iterating on a design that will look like a nice cherry colored ( to match or dining room table and chairs ) sideboard when it isn’t in use. And in fact it could provide a surface to serve food or drinks from in the future when it is closed up. The front will have doors that use 270 degree hinges ( and the big one a piano hinge in the middle ) to swing away to opposite sides of the case to allow the operator's knees to go under the surface. There will be a removable panel in the top that will reveal the sewing machine and allow it to rise up to be either flush with the top or be as if it were set on the top.

We’ll have an adjustable goose-neck lamp that can be stored under the table when not in use and installed in a bracket towards the back of the table when it is being used.

There will be two full extension slide out shelves on the left of the knee opening to store the Serger and the sewing tool box respectively.

It will be on brass ball casters to allow it to easily be pulled out from the wall to make space for fabric to flow through the machine and they will have locks to keep the table from moving around while there is sewing going on.

There will be a big out-feed space for the fabric on the left to make it easy to manage large or bulky pieces.

I’ve got a rough idea of the cut-list and hardware required and I’m waiting for the machine lift to get here from ROCKLER so I can look at it’s requirements and make sure I know how I’m going to accommodate it.

If you want to see a similar project this is the video that led me to the ROCKLER machine lift hardware.

I’m also looking to source the wood from a vendor closer to my home since shipping lumber across the country is slow and expensive.

Here are some design sketches so far:

View fullsize

View fullsize

View fullsize

I’ll post updates as things get going…

Fixing, making's sibling...

Back when I was a software engineer I really enjoyed fixing bugs, my bugs, other people’s bugs, old bugs, new bugs, difficult to reproduce bugs, you name it. There was something about figuring out the problem, making the fix, closing the bug report and watching the tests pass. Very satisfying. And you could get into a groove and do hundreds in a row if you wanted to.

I was thinking recently about the fact that I’m a lot more likely to try to fix stuff around the house myself than I used to be. Part of why that’s true is I just have more time since I retired. But, a bigger part of it is that since I’ve been making more stuff of size and complexity I’ve got a lot more confidence. Also, some of the skills that I’ve had to learn to make things are also skills that are useful for repairing things. A good example is the seat cushion on my leather recliner in the living room. It is probably ten years old and the seat cushion foam had given up from lots of use. I had just done the upholstery for the Morris chair that I built and I realized that I could probably restore my recliner using the same skills. I ordered a replacement foam cushion from Foam Factory ( these folks are awesome BTW, fast, high quality, easy web site ) and then I gave the whole chair a nice conditioning with saddle soap. When the foam came I just extracted the old foam and got rid of it and inserted the new foam. Now the chair is like new ( actually better because I used a higher quality foam than the original manufacturer ).

And that’s another aspect of making and fixing intersecting, the tools and materials. Once you start understanding the what’s available for materials that are pre-processed ( I’m not going to get all the tools to cut 6” thick foam from raw stock for the few jobs I’d ever do…) you can do better fixes. And having a drill press and a band saw makes doing lots fixes simple and easy.

After looking at renting a power washer ( all the ones for rent looked like kicked shit ) I ended up buying an inexpensive electric one. I’ve power washed our decks ( I used to pay someone to do it) but also I realized that it would take all the pollen stains, lichen, mold etc… off our teak deck furniture. It does a great job, I am going to have to sand it a bit and oil it now but it looks great. My new found wood finishing skills and tools will come in handy.

I really like not wasting things just because they had some minor defect. I also like not having to find an negotiate with someone else to do the work. Rebuilding a couple of mountain bikes from the 1990’s into cruisers for me and my wife is a good example of this. When I tried to find a bike shop to do it they basically said I’d have to wait forever to get them to do it and why didn’t I just buy a new bike… They’re great bikes and there wasn’t anything important wrong with them but the system is set up to discard things and replace them, not maintain or fix them.

There’s also the peace of mind of not walking past something that’s sorta broken day after day and having that feeling of “I should really get that fixed…” sometimes for years. Now I can just fix it.

Robot Project: Audio In/Out, Cat Treat Feeder, Refining the Patrol code

Whenever we’re away for a long time we worry about our cats. There are people who come in to feed them, play with them, and change the cat box, but still we worry. Over the years I’ve developed more and more technological solutions to allow us to check in on them remotely. Now, before we go I set up multiple wifi cameras around the house, each of which is in a likely cat activity space. I can reposition the cameras remotely and they capture based on motion and save up a nice movie of all the activity broken down by hour. They have infrared cameras and so we get twenty four hour coverage. This works pretty well and reduce worry a lot.

There was only one gap in this system, sometimes the cats decide to be completely outside of the view of all of the cameras for many hours. Being an engineer I felt compelled to try and build a solution to fill this gap. I decided that I would build a robot rover that could do the following:

1. Autonomously roam one or more rooms of the house

2. Take pictures during it’s patrol and upload them

3. Record sounds

4. Play our voices calling for the cats and offering treats

5. Dispense treats

6. Allow me to take over and control it’s functions manually over the internet

The theory would be that while a robot would likely make the cats wary, something that sounded like us and dispensed tasty treats would make them get over that and come close to be seen on camera somewhat on demand.

Now that I have the robot assembled and I’ve figured out how to program it, I’ve been working on the patrol code. It is still a work in progress but I’ve managed to get ten probes into a room and not get stuck, I have some ideas on how to get to the next level. Along the way I’ve discovered some interesting edge conditions in the python api code, for example in some locations where they convert from degrees to a number of intervals from the wheel sensor they use integer math. Not in general a problem except when the division comes back as zero in which case the onboard controller takes that as meaning “turn on the motors until you’re told to stop” instead of “stop after some number of wheel sensor signals" So, every so often everything would be going well and then the robot would need to turn a small amount and it would just start spinning in place until it hit the code to go forward which at that point was in a random direction. There was a similar issue with the code to go forward a certain number of centimeters resulting in running right into whatever wall was in front of it.

I’ve got all of the safeguards in my code now to prevent those conditions now, and it has been interesting debugging both in the code and physical world. One of the mechanical things that I ended up having to fix was that I had originally mounted the servo on the front and the ultrasound sensor on the lower deck of the robot ( they didn’t say you shouldn’t and it was out of the way of the camera .) Turns out, that you don’t get full range of motion of the sensor on the servo because the circuit board hits the upper deck. More importantly for something that rolls around the floor it was easy for the low mounted sensor to miss things that would interfere with the top half of the robot. So, I moved it up to the upper deck. I just pivot it out of the frame when I use the camera.

I also learned that you shouldn’t operate the motors and take a picture at the same time, the ribbon cable ( not shielded ) for the camera runs right past the power circuit for the motors. There is a lot of RFI when they’re running and so you get some pretty funky images as a result.

Robot showing amplified speaker, microphone, and new placement of the ultrasonic sensor

I got a very cheap USB microphone dongle to use for audio input… bad idea… the gain on the device was terrible, it worked but the audio was barely audible over the noise. The noise was because all of it’s circuits were yes, you guessed it, right near the motor controller board. I ended up using a nice USB microphone via a USB cable clipped to the side of the robot, that worked like a champ and had enough gain to pick up a cat vocalizing.

I also got a tiny rechargeable amplified speaker to plug into the Raspberry Pi’s headphone jack and that worked fine. I got a 90 degree adapter to keep the wire away from the wheels and mounted it to the back with some double stick tape. Using the pygame module it is easy to play any audio file so we should be able to record ourselves calling to the cats and use that.

Design for cat treat feeder…

The final item is the treat dispenser, this is an entire project in itself. I have a design that I’m working on and I’ve created a prototype of the dispenser mechanism. I have been using components from the Lego Technic collection of parts. The great thing is that they have all kinds of shafts, bearings, gears, wheels, beams, etc… that are all compatible with each other. I’m not qualified to machine anything or even do a competent job designing something to be machined. So, these are a godsend and have allowed me to build the core mechanism of the treat dispenser and get it working. The power for the treat dispenser will come from two additional servos one on each side which will push a peg on a drive wheel, they are set 180 degrees apart. (see video for demonstration in the prototype) Fortunately the folks who make the robot provide a kit with an add on servo controller board that can control multiple servos and it comes with a couple of big servos that should work. It also has it’s own batteries and so it won’t be dependent on the robot’s power.

You can see the up and down action of the servo being translated to rotation to drive the belt.

I’m going to make the case for the treat dispenser out of 1/8” acrylic sheet and I’m going to have to cut these parts a lot more cleanly that the last one because I intend to glue them together. My Dremel has a straight cutting bit and a guide collar and I think that would work with the panel clamped firmly to a sacrificial piece of wood and pressing the Dremel against a guide fence. I’m going to be experimenting soon.

That’s where I’m at for the moment.