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Re: Is the new Arduino Due compatible with RAMPS 1.4? - 11 years ago

Greetings all, From the schematic http://www.reprap.org/mediawiki/images/3/3f/Arduinomegapololushieldschematic.png The MOSFETs for the three heater/fan channels are part# STP55NF06L whose datasheet is available online at Figures 3 and 4 give the most relevant data. Figure 3 indicates that with Vgs = 2.5 volts, the Max current (drain to source) is just above 15 Amps. (2.5 volts is conserv

by Larry_Pfeffer - RAMPS Electronics

Re: Smooth rod tolerance, material and surface options - 11 years ago

Greetings all, Has anybody tried ceramic-coated rods instead of steel rods as the linear slideways for RepRaps? At a previous job, we had good luck using ceramic-coated Al rod, running in plastic-lined bushings; however, that was a *beefy* system with 1 inch dia. rods. In the US, ceramic-coated Al rods are available from among others, in inch sizes. Interestingly, there's relatively minor

by Larry_Pfeffer - Mechanics

Re: Teensy 3.0 Kickstarter - 12 years ago

Greetings all, I just got three Teensy 3.0 boards via kickstarter. Physically, they are truly teensy! (1.4 by 0.7 inches) So far I've been trying it out via the TeensyDuino software add-on (to the Arduino dev software) written by the designer of the Teensy 3, Paul Stoffregen of PJRC.com. The T3 software is still in beta, with some rough edges, however it's not bad now and rapidly getting bett

by Larry_Pfeffer - General

Re: Wrex 3D Printed Prosthetic "Magic Arms" - 12 years ago

Greetings all, I'm pleased to find that another reprapper had already posted the link to this amazing story. From what I can tell, the WREX uses rubber bands and provides a partial cancellation of the gravity load (of Emma's arms), so that her available muscle strength is enough for her to move her arms against the remaining gravity forces. If you re-watch the video, you'll see one of the rub

by Larry_Pfeffer - General

Re: Reprap Boston meetup in 2012? - 12 years ago

Greetings all, First off, thanks to Jeff for both organizing and hosting yesterday's meetup. Doing that was a real contribution. @all: In case you're like me and have problems putting names to faces, I was the repRap-less guy who collected the pizza money. I had stopped work on my repStrap about a year ago (for reasons I'd rather not air on this forum.) Seeing the tremendous progress

by Larry_Pfeffer - Massachusetts, Boston RepRap User Group

Re: Reprap Boston meetup in 2012? - 12 years ago

Dave, Since I don't have a RepRap or repStrap, but have helped build the electronics for a couple, If you're incompleteness is in the electronics, I could bring my test equipment and lend you a hand with that. Which version of the electronics do you have? Larry

by Larry_Pfeffer - Massachusetts, Boston RepRap User Group

Re: Reprap Boston meetup in 2012? - 12 years ago

Jeff, Thanks again for hosting this. I'll be attending, barring disaster. I wish I had my (partially built) repStrap, but I won't until property division in the divorce gets settled. Larry Pfeffer

by Larry_Pfeffer - Massachusetts, Boston RepRap User Group

OT: Making music with electronic hardware (AKA the _Imperial March_ outdone) - 12 years ago

Greetings all, Hope you're in a mood for a bit of tech entertainment. I'm sure many of you have heard of and/or heard of a stepper motor/electronics being checked out via playing the Imperial March theme from Star Wars. I've used that, and I respect and appreciate it. However, if you'd like to see an even more impressive adaptation of (not nominally musical) electronic gear used to play m

by Larry_Pfeffer - General

Re: Filabot: Plastic Filament Maker - 12 years ago

@Filabot, Can you say anything about whether and/or how you keep voids (AKA bubbles) out of the resulting filament?

by Larry_Pfeffer - General

Re: Grade 2 vs Grade 5 Bolts/Washers - 12 years ago

Greetings all, The grade of (steel) fasteners is a measure of their strength and how well they've been tested. Increasing grade means stronger steel and better testing. Mild steel (A36, as used in bridges, etc. has a yield strength of 36,000 lbs/inch^2); no plastic yet extruded by a reprap comes close, even allowing for heat-induced softening of the steel. Short answer: grade 5 won't hurt for

by Larry_Pfeffer - General

Re: Reprap Boston meetup in 2012? - 12 years ago

Jeff, Thanks for your generous offer to host the meeting. I can make either of those two Sundays (though I can't do the one between 02/18.) No strong bias for one over the others; so I'll defer to those with tighter schedules. Thanks again, Larry

by Larry_Pfeffer - Massachusetts, Boston RepRap User Group

Re: Reprap Boston meetup in 2012? - 12 years ago

Greetings all, This may be slightly off topic, but l think it's worth mentioning. IMHO, repRap is overdue to move from an 8-bit CPU to a 32-bit one, and can pick up significantly improved computation and I/O while doing so. Although the Arduino organization has announced a 32-bit, ARM (Cortex M3) based Arduino, the design isn't complete yet, and they're still unavailable. (The Raspberry-Pi is

by Larry_Pfeffer - Massachusetts, Boston RepRap User Group

Re: Reprap Boston meetup in 2012? - 12 years ago

Ross, Thanks for organizing a local meeting. I could make it on a Friday, and would like to see Artisans' Asylums new quarters anyhow. I'm unlikely to make it to a Saturday meeting, due to divorce/visitation issues. However, if my son is interested, we might be able to attend part of a Saturday meeting. If others were OK with it, I could also make it Sunday. Unfortunately, my RepStrap mat

by Larry_Pfeffer - Massachusetts, Boston RepRap User Group

Re: Home Polymer Recycling Unit To Produce Filament - 13 years ago

Ben, Regarding your polymer recycling effort: Great stuff, but *please* be careful, particularly when dealing with such a high-power cutting/grinding machine. Any such that can cut up milk bottles could -- if things go wrong -- cut up the operator or bystanders. Please consider the following design aspects carefully: Both static and dynamic balance of the cutting blades. Blade/sha

by Larry_Pfeffer - General

Re: Leaf Labs - MAPLE arduino alternative - 13 years ago

Greetings all, I have one of the first-generation leaflabs maple boards. I'm considering getting another (r5) real soon now. One of the things I like the most about the Maple is that leaflabs tools support both Arduino software (I think they forked the code, and substantially modified it to work with GCC for the Cortex M3 arch.) as well old-school/command line tools. Note also that the ch

by Larry_Pfeffer - Next Wave Electronics Working Group

Re: Home Polymer Recycling Unit To Produce Filament - 13 years ago

Greetings all, I tried running just the thin part of a two liter soda bottle through a supposedly high-power shredder, one that claimed to be able to shred CDs. That shredder didn't do very well on the thin, flexible bottle material, and I had to manually unjam it multiple times. I was finally able to shred up 100 grams or so of PET. I then attempted to dry it out, and then melt it. Apparent

by Larry_Pfeffer - General

Re: Wanting to do Mendal for my Dissertation but can't think of any new ideas, any suggestions? - 14 years ago

Here are a couple of ideas for your consideration: 1. (Analyze the key issues for) and design a granule-based extruder. 1.a Devise a practical method of measuring the flow rate of melted plastic out of an extruder's tip IMHO, this is a key thing needed to make a granule extruder work well for printing. For void-free rod stock, one can reasonably estimate the output flow, based on the speed a

by Larry_Pfeffer - General

Re: 32 bit Arduino for reprap $50 - 14 years ago

Greetings all, I have one of the first batch of leaflabs maple boards. FYI, I posted a how-2 for the original leaflabs bootloader and LINUX From what I understand, their newer boards with an updated version of the bootloader is considerably easier to get talking, and also supports Windows, LINUX and MacOS. leaflabs is local to me (Cambridge, MA), and they seem like a good bunch of people -

by Larry_Pfeffer - General

Re: Thermocouple without sensor board? - 14 years ago

@dazed.dnc, If you look at the voltages a thermocouple produces, at the temperature (difference) of interest, you'll see that it's only a few LSB of an Arduino's A2D resolution. The Wikipedia article, gives the following info on type K thermocouples: 41 µV/°C. For a temperature difference of 325 degrees C (25 deg C to 350), this gives 0.013284 volts (13 millivolts.) If memory serv

by Larry_Pfeffer - Reprappers

Re: Granule extruder/filament maker - some new thoughts - 14 years ago

Greetings all, Although a direct granule-to-part extruder for reprap would be very useful, I don't see that happening soon. Enleth's notion of a separate, stationary device to make 3mm diam rod has merit, and I think is a more achievable goal. Toward that end, I'll pose a question: Must a table-top rod-extruder use an auger? An auger would be nice (among other things, to get a

by Larry_Pfeffer - Mechanics

Re: Lathe Questions - 14 years ago

Jeff, If you need/want something done on a lathe, email me and I can either cut the part, and/or give you an intro. I don't think you'd have much luck using a wood lathe for brass. Maybe for small parts, but the speeds and the toolrest of a wood lathe aren't good for doing metalwork (and there's no cross-slide or threading.) Also, suggest you watch craigslist in the tools section. I see

by Larry_Pfeffer - General

Re: Water-bath printing - 14 years ago

Greetings all, Most of the "engineering plastics" I've worked with have densities around 1.4 g/mL. Most plastics will sink in water, unless they are foamed. A possible problem with such rapid cooling is that it may prevent subsequent layers from sticking to the already-printed ones. (I think that good layer-layer bonding results from the new layer just barely melting a very thin region of the

by Larry_Pfeffer - General

Re: $39.90 ARM Cortex M3 board with SD/MMC socket built-in, for Reprap? - 14 years ago

Greetings all, The same company offering this Cortex M3 board also offers a high (-er power than our current gen 3 or 4) stepper controller boards, the The documentation is thin (no schematic), so it's not clear yet to me whether one would need a '297 to provide an equivalent (to our current) step/direction interface. However, the price low enough that I'll probably include one in my next o

by Larry_Pfeffer - Next Wave Electronics Working Group

Re: 35mm film driven repstrap - 14 years ago

@mlagana, You may be hitting the driver chip's current/thermal limit. Most of the H-bridge chips with integral drive transistors monitor the temperature of the chip internally, and shut down before they fry themselves. Try adjusting the current limits (down), and see if that keeps everything cooler and happier. Given your motor's (torque) specs, you really should be able to run at a fraction

by Larry_Pfeffer - Reprappers

Re: FlatPackRepStrap: Anybody pursuing it? - 14 years ago

Michael, Thanks for the offer. I'm always appreciative of drawings, esp. with dimensions. However, since I'm still mored in my kitchen remodelling project, don't do this -- any faster/better than you normally would -- on my account. I expect to start generating plywood scrap pretty soon, and I'll see what I can put together with that material. (I stil like the idea of making sheet-metal/ply

by Larry_Pfeffer - General New Machines Topics

Re: Electromagnetic linear actuated beds? - 14 years ago

Google is your friend. "Sawyer motor" brings up many relevant hits. These are certainly doable, but making the platens will take some effort.

by Larry_Pfeffer - Mechanics

FlatPackRepStrap: Anybody pursuing it? - 14 years ago

Greetings all, The description of this group mentions "FlatPackRepStraps," but I haven't seen any activity specifically using this name. (Have I missed some threads on this?) The overall concept of making (the great majority of the) parts flat would certainly facilitate shipment of kits. Forrest's work has convinced me that using slabs of material (wood or otherwise) is a better way to make a

by Larry_Pfeffer - General New Machines Topics

Re: 35mm film driven repstrap - 14 years ago

@mlagana, Rotary encoders (whether optical or magnetic) measure rotation of an intermediate shaft, not the X,Y,Z motion; as such, they don't measure backlash. Of the others, there's been much talk, but (to my knowledge) no clear, "this one works to this resolution, and it costs this much." So, I see no great harm in experimenting with magnetics.

by Larry_Pfeffer - Reprappers

Re: 35mm film driven repstrap - 14 years ago

Greetings all, I've been thinking of a variation on this overall idea, that may be lead to better closed-loop positioning for a variety of repraps, whether they use a film-strip as a drive element, or not. Some background: Before going over to primarily digital recording, the (professional) film industry used "magnetic film" to record sound. This was film stock (16 or 35 mm, with the holes fo

by Larry_Pfeffer - Reprappers

Re: RS485 questions - 14 years ago

Oops! I see that the soic package is out of stock at digikey, but mouser has some in stock in soic-8: Or you could still buy a DIP8 version, (digikey shows over 10K in stock): put it on some perfboard, and tack on wires to connect. Tedious, but probably faster than revising the ckt to use a different chip.

by Larry_Pfeffer - Reprappers