Saturday, June 29, 2019

3D Printable Wago 221 Lever Nut Mounting Blocks

I like to use Wago 221 lever nuts in place of screw terminals and have started replacing screw terminals in my 3D printers with them.  To that end I designed a few printable mounting blocks to hold single and multiple lever nuts.

The Wagos come in 2, 3, and 5 wire parts (221-412, 221-413, and 221-415), handle 24-12 gauge wire, handle 32A up to 450V, and have multiple safety certifications (unlike the much cheaper Chinese made knock-offs).  Full specs are available here.  When I first got them I inserted some wires and then pulled at them and was unable to pull any of the wires out. They really hang on tightly to solid and stranded wires.  All the wires will connect together in each block.  The 5 wire blocks are great for making DC power distribution blocks in a 3D printer, as I did in UMMD.

I have printed the 2x2 and the 221-415 mounting blocks using ABS.  The other blocks are based on the same dimensions so they should work fine.  You insert the back end of the lever nut as far as it will go into the mounting block, then press down hard on the open end and it will snap into place.  They fit and hang on tightly so there's little danger of the lever nuts coming out of the blocks, and even if they do, the bare wires are entirely enclosed within the lever nuts, so nothing is going to short.

Here's the 1x5 mounting block with a 221-415 block installed.

Yes, they're pretty small.

Here's the 2x2 mounting block.  It uses 2 screws to mount on a flat surface or t-nuts to mount on t-slot.

Here are two vertical mounting blocks that hold 4 of the 221-412 lever nuts.  The one on the left has an 8 mm tang that prevents rotation in a t-slot (so you need to use bed-only support material when printing) and uses a single t-nut to hold it in place.  I used that one to make bed heater and thermistor connections in UMMD.  The one on the right is intended for mounting on a flat surface.
The CAD file is easy to edit for any combo of lever nuts you want to make.  You can DL the Fusion360 CAD file for the mounting blocks here.

Thursday, June 27, 2019

3D Printed White Board Marker and Eraser Holder

I used to use Expo white board markers.  They were just awful.  Even when new, the lines always looked faded and some colors of the ink were very difficult to erase from the board, even with the spray-on solvent.

I recently bought a 5 pack of Pilot BeGreen V Board Master markers.  OMG what a huge improvement!  The colors and lines are solid, and they all erase cleanly and easily using my old Expo eraser, a paper towel, or a rag.  The markers are refillable, but the refills cost more than buying new markers if you buy less than 12 of the same color at a time.  If you use a white board, get some!  And before you ask, no, I'm not being paid to say this.

I needed a shelf to hold the markers and an eraser (Expo!), so I spent 5 minutes in Fusion360 and designed a wall-mounted holder.

The holder prints upside down without any support material.  2 small screws or double sided tape will hold it on a wall or on your whiteboard.
 The CAD file is located here.

And here it is, in green ABS.
I may redesign it for use with suction cups...

Thursday, June 20, 2019

Replacing a B&L Microscope Lamp with an LED

I've recently been restoring some old microscopes for an organization called "Milwaukee Area Science Advocates" who have been gathering them from teacher's closets where they have been unused for a long time.  Many of them just need a cleaning to get them into usable condition, and a few need parts to be swapped.  Eventually the scopes will be used to promote science education by letting kids observe live microorganisms with them.

A couple of the scopes I've been working on are old Bausch & Lomb units with identical illuminators that slide into a bracket under the stage.  The illuminators are nothing fancy- just a 15W incandescent light bulb in a bakelite box with a blue tinted filter glass that probably absorbs IR and prevents the specimens on the slide from drying up.

One of the B&L microscopes with the funky illuminators.

The problem I ran into was that one of the two had a burned out light bulb.  I'm sure someone has a big stash of these bulbs somewhere, but not anywhere I could find, and even if I managed to find one, how much will it cost, and what's going to happen to the scope when the bulb burns out again?

The light bulb used in the substage illuminator.  15W 120V.
The substage illuminator opened up.  The blue glass blocks IR and helps keep specimens on the slide from drying out.

The light bulb base and switch.

I checked into adapting the E26 bulb socket to a candelabra (E12) bulb, but all the E12 bulbs and LEDs I could find were too long to fit into the enclosure.  After spending a while searching a few other possibilities, I decided I'd have to solve the problem myself, taking the easiest approach I could think of- I designed a printed part to screw into the light bulb socket in the bakelite enclosure, that holds an LED and a resistor, powered by a 6V wall wart, using the original power cord minus the AC plug.

I know from previous experience that a single, 5mm diameter, white, 20 mA LED easily throws enough light for a microscope, even at high magnification.  So I started working on the design for the light bulb replacement.  I quickly realized it would have to be done in two parts- one that screws into the E26 socket in the illuminator and the other that will hold the LED and allow it to be aligned with the optical path in the microscope.

The Base

The first thing I needed to do was duplicate the E26 light bulb base.  It's 26 mm diameter, but what are the specs for the threads?  A few minutes research revealed that E26 lamps have 7 threads per inch - that's 3.63 mm pitch - ugh!  I couldn't find a 7 tpi thread built in to Fusion360, so I created it by making a helix and subtracting it from a 26 mm diameter cylinder.

I needed to make electrical connections between the LED and the lamp socket, so I added a hole in the side of the base through which I could lay a wire in the threads.  The wire makes contact with the bulb base threads.  The other connection is made by looping a wire through the bar on the bottom of the base.  When the base is screwed into the socket, the wire will touch the center contact in the socket.  It probably won't get UL or TUV approval, but it works.

The base rendered in Fusion360.  The bar at the bottom holds the wire to make electrical contact with the lamp socket.

The LED Holder

The original bulb socket is mounted horizontally so the LED has to be turned 90 degrees off the axis of the base to point it up the optical axis of the microscope.  I couldn't predict exactly where it needed to be located, so I made the LED holder position adjustable to allow for alignment with the microscope optical axis.  The LED holder just friction fits into a hole in the base that allows it to slide in and out and rotate.  It grips tightly enough that it should stay aligned once set, though a drop of glue could be added to ensure stability.

Here are the two pieces used to make the LED holder.  The cylinder on the left fits into the hole in the base (middle).

Putting It All Together

I tested the 6V wall wart with the LED and resistors to get the current through the LED to about 20 mA.  I ended up using a 270 Ohm resistor.  If you try something like this you'll have to test it to see what value of resistor to use- unregulated wall-wart's voltages can be all over the place with a small load like a single LED.  I attached wires to the LED, fed them through the hole in the LED mount, and then attached them to the base to make electrical connections.

The LED in the base.  The wire will contact the threaded part of the lamp socket.  The bottom contact is also made by looping a wire around a plastic bar in the bottom of the base.

I cut the plug off the illuminator's power cord and wired the wall-wart to it, screwed in the LED mount and it lit up.  Then I put it into the microscope to make sure the light from the LED was aligned with the optical axis of the microscope.  The LED can be rotated and slid in and out of the base so it is easy to position it.

The illuminator with the LED replacing the incandescent lamp.  The blue glass is not really needed because there's no IR coming from the LED so it isn't going to heat up and dry out the specimen being viewed with the microscope.
That's it!  A pretty simple project making great use of a 3D printer.  The CAD file for the E26 to 5 mm LED adapter is located here.

Friday, June 7, 2019

Milwaukee MakerSpace on Fox6 TV local news broadcast

I spend my Tuesday evenings (and usually Sunday afternoons) at the Milwaukee MakerSpace. Channel 6 TV in Milwaukee recently took a tour of the Milwaukee MakerSpace.
Link to the broadcasts on the Fox6 web site.
And another page with more video.

If you're too lazy to click the links up there, here's video they shot of some of the things that go on at the MakerSpace:

You can see "The Spice Must Flow" sand table is in this video:

If you're in Milwaukee and you want to take a tour, we're open to the public on Tuesday nights at 7pm for meetings and tours.  The MakerSpace is located at 2555 S. Lenox St. in Bay View.

There are a lot of great restaurants in the area, but if you're hungry before or after a visit to the MakerSpace on a Tuesday night, Cafe Corazon (top left corner of the map, a few blocks from the MakerSpace) has great $2 tacos - I highly recommend the pork pibil!  It'll be the best 2 bucks you ever spent!