I love the idea of being able to safely switch ac power from a microcontroller. There are products like the powerSwitch tail from sparkfun that easily do this job, but I like to try to be as cheap as possible, so I’m trying to do it for half the price with the Belkin Conserve. This seems like it is just a relay built into a wall wart that is only activate for a pre-selected amount of time. Ideally it helps you reduce your energy use by only charging your phone for say, 3 hours, or by turning off your tv after you fall asleep.
I bought one thinking the relay was probably powered by a dc voltage, and then that I could activate it with a pin from the arduino. Maybe I would have to put in a mosfet or an opto isolator, but it wouldn’t be too hard. After opening it up, I realized that it was all AC and I’m at the limit of my knowledge. I don’t want to zap anyone or any thing, so I’m asking the internet as a whole: what can I do with this?
Here is a closeup of the front of the board,
Here is a closeup of the back of the board.
If anyone has any ideas on how to safely trip the relay from a microcontroller pin I would love to hear about it. If not, then maybe I’ll just let it do what it was intended to do. And then go buy the powerswitch tail.
It all came down to this…
When I assembled the extruder (makerbot mk4) the allen wrench that came with the kit never felt right. Regardless I tightened the set screws on the gear until the allen wrench felt like it was about to strip it, and then I went on my merry way. After watching my extruder not work for the last few weeks I finally:
1) rebuilt my hot end
2) put longer leads on the thermistor and nichrome so I could move the extruder board out of the way
3) put a light on my table next to the maker bot, and
4) noticed that the motor shaft was spinning but the gear was not!
So I disassembled the extruder, found the RIGHT sized allen wrench (1.5mm maybe?) tightened everything down, and I was on my way! It’s frustrating that it took so long to figure it out, but I’m so glad that I finally did. I spent the morning printing out an accessible wade’s extruder and playing around in skeinforge.
I wasn’t able to print out the small gear on the wades extruder no matter what I tried. It always ended up getting eaten by blob monsters. I eventually figured out how to use the multiply feature in skeinforge and printed out 9 of them. With no raft to boot! The no raft thing was only cool because I figured out how to do it, but in the end three or four of them broke free and were garbage.
That last pic is what I was really surprised with. I have never printed without a raft before, and I was really happy with how flat and smooth the surface was. One more thing pushing me towards building that heated bed!
Let’s give this a try!
Tonight I prepped 4 3ohm 10 watt aluminum resistors with in two parallel pairs with solid copper wire. I gave it 12 volts of juice and it got plenty hot quickly, so hopefully this back of the matchbook effort will pay off.
I don’t have the aluminum plate with me, so I only prepped the electronics. This is what they look like.
Then I realized that Hydraraptor is using 240VAC. That seems dangerous, and in one of his posts he mentions how one of his resistors failed and ended up melting a bunch of his circuit breakers. Yikes, that’s not for me.
My plan is to set this up on an aluminum plate with the stock thermistor from the makerbot kit. I’m still unable to print because of some extruder issues, but this is a good distraction while I try to figure that out. I’m also going to try building one with nichrome wire. IF it works as well then it’ll be lower profile than this resistor configuration.
Yesterday as a fun distraction I ran across the makerbot music page. Thankfully you don’t need an extruder in order to make music, so I dropped the lady Gaga “bad romance” gcode onto my bot and hit run. It was a good break, and it was great to feel like my makerbot is actually capable of doing something for a change. While it isn’t as cool as printing something out of plastic, it’s a much faster way to confuse and amaze your friends!
I recently bought a molded reprap prusa mendel kit from Metrix create space. They are a hacker space in Seattle, Wa. The molded kits cost anywhere from a third to half of what a set of printed parts cost because they take far less time to produce. One downside of the printing method is that parts will end up sloppier and require some more post processing.
Here is what the base looked like as it arrived.
Here is the other three parts, unprocessed.
The next picture is where you can start to see the disadvantages of this method. There is a lot of plastic on the bearing holder (purple) that needs to be cut away, and you can see the way that the miniscus on the big gear has made the entire gear cupped. I want to clearly state: none of those are deal breakers. This is a great deal, and even the RP parts require a fair bit of processing. I was surprised when these parts came in, but after thinking about it I don’t think I should be. They appear to be functional, and that’s all that really matters to me. As long as they last long enough to print their replacements, I’ll be happy!
I’ve only had the makerbot for a month now, but it’s refusing to print. Sigh. I know it’s a diy kit, but this little puppy only had three whistles printed on it before it rolled over, ready to die. Here is my thought process as I go about trying to fix it.
Symptoms: The extruder would no longer extrude. RepG registers 220 and the hot end seems to settle nicely there. The motor turns on but nothing comes out. I have a mk4 extruder and was in the process of printing a wade’s extruder when the symptoms started (do you think it got jealous?) If I grabbed the filament with pliers then I could push plastic out the tip, but it also squeezed out between the pfte insulator and the brass barrel.
My Diagnosis: After adjusting and re-adjusting the difficult pressure wheel on the mk4 I settled on the idea that the tip must be partially blocked or not hot enough. I took it apart and broke the brass barrel in two. Then I made a new barrel out of a bolt and bought a new barrel (two path approach!)
Here you can see that the nichrome wire has burned/melted the kapton tape. Is that normal?
None good. The stock barrel behaved exactly the same. It would flow, but weakly and only with considerable pushing on my end. The new hot end I made fared about as poorly. I tried to re-use the nichrome wire from the original hot end build, but at some point it had burned off its coating and this was very problematic.
1 – rebuild stock barrel/ptfe combo
2 – test resistance of nichrome on new barrel
3 – buy and build wades extruder
4 – use both extruders on mk4 setup to see if it is the hot end, then swap in the wades extruder to see if it is the motor.
I really enjoy building mechanical movements, and I am terrible at it. It is really difficult to build things that move without relying on expensive pre-built mechanisms. Thus I am always looking for cheap ways to design and build cogs, gears, and sprockets.
For gears it is tough to beat the online wooden gear generator at woodgears.ca. It lets you specify size and number of gears, and also lets you see how they mesh and tweak a bunch of variables. I usually print these to pdf and then import them as vector to illustrator. With this site you can build any number of compatible gears. They have rather large teeth because they are meant to be cut out of wood with a bandsaw, but they will work very well for low-precision work. There is also an inkscape plugin that generates gears as described here by MAKE.
One note on importing all of these files into illustrator. Illustrator has strange import prefs, and if you import a dxf that is in mm, and your preferences are in inches, centimeters, or anything else, then it will scale your drawing on import. Be careful. This is an easy way to mess up at the very first step.
Timing belt cogs are another deal entirely. There isn’t an online generator. There are a few python scripts that purport to build cogs, but they never seem to work right. One other way to do it is with blender and a plugin, but then you end up doing more 3d modeling than cutting.
To build one in illustrator you will need to know the belt you plan on using and the number of teeth you want the cog to have. You will also want to go to sdp-si and download an example any cog that uses your belt pitch. Set your units to mm in illustrator>preferences>units. Grab the dxf of that cog and open it up in illustrator.
More than likely you will see something similar to the image below. It has two example teeth showing the tooth spacing, but the entire cog isn’t drawn out as a time saving measure.
Before I get too far into it I need to explain that most bolts are made of hardened steel. To de-hardened them all you need to do is to get them red hot with a blowtorch and let them cool slowly. Here is a pic of me doing just that to two m6 bolts.
After your bolt has cooled, it should look something like this.
Start out with a drill press, a vice, some c clamps and a drill bit. Put the drill bit lightly into the drill chuck backwards. Lower the drill press until you can grip the drill bit in the vice (which should be sitting on the drill press table) Clamp the bit in the vice, and the vice to the table VERY securely. Release the chuck on the drill press. Now you are going to take the bolt that you de-tempered and put it in the chuck. I left the head poking out. That will make it easier to get a good straight grip on it. Tighten everything down and grab some machining oil. Continue reading →
Due to a long and strange twisting string of circumstances I recently ended up with a makerbot kit at work. I have a build video and a lot of info, but here is the first of two quick posts about my trials and tribulations with this little guy. This is more a question to the world, as I am having a terrible time finding answers for it.
I built the bot and printed a whistle within a few hours. Everything seemed copacetic. A few weeks went by (in which I got to go to nyc resistor and meet Bre) and I came back to the bot to print something. It was just not working right. It would extrude for a little bit and then stop, and I could force it to restart and then it would stop again. I’m not sure if the extruder was bad, or the tip was blocked, or the software was just messing up. I took apart the hot end to check for blockages, but I didn’t heat it up fully before disassembly.
Well, this happened. I had two wrenches, one on the shaft and one on the extruder tip. I was trying to unscrew the tip after drilling the plastic partially out of the barrel. And then the brass tore in two. I eventually hit it with a very hot hot air gun (not a hair dryer) and got the plastic to melt out and then I was able to unscrew it easily. So the moral of the story is to always clean out the tube before attempting to unscrew a hot end.
Then I ordered parts from makerbot, assembled the parts when they came in, and still had the same problem! My bot will print out the beginning of a raft if it is warmed up enough, but then it stops extruding and just wiggles around for a long time, not printing anything.
In possibly related news, both versions of the extruder have seeped plastic from above the fender washer. See a picture below. You can see a plastic piece that looks a bit like a leaf coming out of the left side of the washer. In my mind this means that my motor is pushing the filament according to plan and the tip must be blocked.
I just can’t see any reason why my brand new tip would be blocked when I could see light through it!
Well, I’ll put the answer here when I find it. I have a wade’s extruder and a new hot end on its way. Possibly those will fix it. Possibly not. I will also have an upcoming post on making a new hot end, and the Makerbot Cupcake making of video.
I have wanted to build a rotary turntable for quite a while. With it I can shoot 360 degree product shots, I can set the camera up on it and shoot panoramas. I can use it with my timelapse setup to put motion into a long shot. I also have an idea about trying to use it to build a masterlock picker!
There is a stepper motor connected to a sparkfun easydriver via an arduino (not shown) The motor has something like 1.5 degrees per step and it is geared down heavily via the rubber belt, so it is very precise.
I used a table saw to cut this notch. Not something that I would recommend for the faint of heart.
Here is the easy driver on the breadboard.
This shot shows the bottom of the board. I used a “lazy susan” bearing from Home Depot to keep the turntable rolling smoothly. One thing I did wrong is that it was mounted several times while I was sanding or grinding and I definitely got a bit of grit in the bearings. more info after the break