No it isn't broken, indeed 20 years ago that would have been the way I would have done it. The only real advantage is that the FET solution is slightly easier to construct. It just seems a bit odd from my point of view to using such out of date electronics technology on a project which is otherwise pioneering. Or is it just that FDM is new to me and is infact old hat to an expert in fabrication?by nophead - Controllers
Yes looks like a very nice device, a bit more cost than TIP110 but you save a heatsink and it is indestructible. It should be a drop in replacement, you can either leave the resistor in series with the gate or replace it with a link. BTW, rather than two TIP110, the wiki recommends a TIP120 for 4A.by nophead - Controllers
Yes the latest heater spec is 6R which would be 2A when driven by a MOSFET, a bit less with a Darlington. On the subject of current, with the standard motors and firmware I think we are only about 0.8A per motor as only one phase is on at a time. I only mentioned 4A as that is the maximum the chip can handle if people want to use other motors. Not all PC power supplies would be able to power sucby nophead - Controllers
The parts I have used on my machine are BTS 134D Infineon HITFETs mainly because I have a bag of samples I saved for 10 years. They don't need gate resistors or back emf diodes. I have not found a source for these though.by nophead - Controllers
The type I had in mind was a 2-way one of these which is actually a 0.156" connector, Molex I think. It will take up a lot less board space than disk drive connectors. I like to use connectors the correct size and make my own cables so they are the correct length but I seem to be in a minority here. You have the choice of crimp and poke or IDC. Obviously the crimps are a lot bigger than 0.1" sby nophead - Controllers
I posted the wire guages in the other thread a while ago For 4A you need 24/0.2 cable which is slightly smaller than 18 AWG. I can't think of a 0.1" connector that takes that guage. I used a 0.2" connector I salvage from the inside of a PC PSU. Wasn't the previous connector a bigger pitch? Could you just use a 2 pin version of that and either space them appart slightly or turn them 90?by nophead - Controllers
I would be nice to replace the Darlingtons with FETs and get rid of the heatsinks. However, those FETs only spec the RDSon for 10V VGS. That would require another transistor for a driver. I prefer to use logic drive FETS with ESD, thermal, over current and over voltage protection built in. They are more expensive but give a single component solution to driving inductive and resistive loads. I thby nophead - Controllers
The quick answer is probably no. The target resolution of the machine is 100 microns. To get 10 microns step size with the same mechanical setup you would need to add 2000 step shaft encoders and modify the firmware to handle these and also generate PWM to do 10 times microstepping. Theoretically you would then get a step size of 10 microns but I doubt the machine would maintain any sort of accuby nophead - Tissue Engineering
Did you add the extra cap d0ubled and I recommended and did you do anything about the power connectors being too small for the required wire gauge?by nophead - Controllers
Well so far the cut a cross, rough up the hole with a grinder, JB Weld and bake in the oven method has held up for me. It's actually easier than soldering and JB Weld is required for the heater anyway so you are cutting down on tools and materials required. The only downside is that it takes 24 hours but if you do it as the same time as the heater then you have lost nothing. I will post on thisby nophead - Mechanics
It's something I should be able to do as I have a DSO and if need be access to logic analyzers at work. The only thing I don't have is time at the moment so I think Zach's suggestion of leaving it to the next version is a good one.by nophead - Controllers
Yes the JDM programmer is a bit weird in that is gets the 13V by taking some RS232 lines low and some high. That means PIC VSS is at a negative voltage so I think you cant do ISP programming unless the UCB is disconnected. Given that we have a proper RS232 level changer with spare channels and a stable 5V rail I don't think the JDM circuit is well suited to what we are try to achieve. Perhapsby nophead - Controllers
Zach, What was wrong with the original steel pipe design? It looked like a clever way to get stiffness. If you change to acrylic you might get away with it for FDM but it will no longer be any good for milling. It seems a shame to downgrade the design like that unless you have a good reason. I think a lot of people are also interested in owning a small mill. You can boostrap another step that wby nophead - General
Yes, but the design of Darwin is such that it can print things almost as big as itself so you only need to break the frame into pieces that are half the full span, you don't need to make them any smaller. The main advantage of RepRap is that you can print custom shapes rather than having to assemble things from stock items. Having said that, it would take a very long time to extrude somethingby nophead - General
4mm/s would be in the range of outputs speeds yes, but the input into the extruder will be around 25 times less if you have a 0.5mm orifice yielding a 0.8mm filament. I hate to disappoint you but I don't think the gearing of the motor will be low enough to exert enough force for extrusion.by nophead - Mechanics
Ron, Does this work in a different way, i.e. have you replaced the screw thread with the small gear wheel? If so, how fast does it extrude?by nophead - Mechanics
Or just a PDF or PNG, etc, out of Eagle would be enough.by nophead - Controllers
Nice machine and good to see some more fellow Python advocates.by nophead - General
emf, It should be possible to make it reliable without having to change the software. If you post a schematic of what you have I will have a go at integrating the roman black VPP.by nophead - Controllers
It will always be required to get the 12V rail in spec with a PSU that suffers from this problem. As Kyle says the PICS get a regulated 5V so the machine will run but the motors will get reduced power. Some PSU's may keep shutting down and restarting with no load on the 5V rail.by nophead - Controllers
I think I mentioned before: I think this is what we need to get a cheap reliable VPPby nophead - Controllers
You need to put a dummy load on the 5V rail to get the 12V rail up to spec. Cheap power supplies like these only have one main regulator. When there is no load on the 5V rail the regulator has to throttle back so much to keep it in range that the other rails end up low. A suggested load is about 10R resistor which will draw 0.5A and dissipate 2.5W, so it will get hot. If you don't have anythingby nophead - Controllers
Yes you can easily keep track of the pulses from a 204 line shaft encoder (816 steps) on a GM3 gearmotor with an MSP430 at 12MHz. I will post the code and details on my blog this weekend. You should also take a look at Forrest Higgs' blog atby nophead - General
There is also a proper tool for straightening the legs of ICs. They are supplied splayed so that they stay in the board when inserted by a machine until they are soldered. The production tool for straightening them for manual insertion is just a metal bar, the correct width, mounted on a plate with a pair of ball bearing rollers either side of it. You just slide the chip along the bar through tby nophead - Controllers
"if it works, it works!" Trial and error is not really a sound basis for designing electronics. If you design something which meets all the specifications and then test it you can have confidence it will always work. If you get something wrong it is not guaranteed to fail the test but it may do when you make enough of them to see the full spread of compenent tolerances or use it long enough to sby nophead - Controllers
I am not too familiar with AWG but the wiki says 22 AWG is 7/0.25 wire. I would normally use 24/0.2 for this sort of current which is between 18 and 19 AWG. If we are assuming a couple of amps per motor then the table below suggestes we need 16/0.2 wire at least which is 20 AWG. from : Typical specifications: 10/0.1mm (10 strands of 0.1mm diameter), maximum current 0.5A. 7/0.2mm (7 strands ofby nophead - Controllers
What type are the power connectors? They look a bit small for the current involved. I would have placed C7 above the regulator to get the track to pin 1 as short as possible. You could then move R2 to where C7 was. The pitch for the resistors looks too small. I would use 0.4". The picture of the 1.2 board on the wiki shows the only resistor half in the air because it does not fit the 0.3" footpby nophead - Controllers