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Re: ALTERNATIVE SOURCE FOR MAGNETIC SHAFT ENCODERS - 15 years ago

You can avoid missing pulses by either polling faster than the inputs change with a timer interrupt or have one or both of the quadrature pins on an input that can generate interrupts on both edges. I have used both techniques in the past and had no problems with absolute accuracy, it's just standard engineering. Whenever you see one input change you look at the state of the other to determine wh

Re: Extruder tips - 15 years ago

Well actually I made tapped knobs just the right size using my milling machine but I figured that the tension is not critical enough that you could afford to leave all the wingnuts you were not adjusting in the vertical position. I.e. at most one quarter turn away from the ideal position. I think then you would have room to spin the nut you are adjusting. I couldn't find any dimensioned drawings

Extruder tips - 15 years ago

To make the extruder less fiddly to put together and take apart again I would recommend putting shake proof washers between the nuts and the plain washers. Once you get the bolt finger tight the washer bites and hold the nut. That allows you to tighten them with just an allen key rather than an allen key and a spanner in the other hand. I would also recommend using wingnuts to replace the nuts

Re: temperature swinging - 15 years ago

Hot air rather than cold then.

Re: temperature swinging - 15 years ago

BTW, I think I have worked out why the RepRap extruder is thermally insulated. I think it is because it has a fan cooling the workpiece so the barrel needs covering to stop it being cooled as well.

Re: RJ-45 / RJ-11 / Premade Cables - 15 years ago

That is if your logic is sensitive to ringing on the edges, asynchronous comms is not. What will happen is that the signal will bounce up and down the cable a few times because it gets reflections from each end that is not matched to the characteristic impedance of the cable. Traveling at around half the speed of light it can bounce up and down this length of cable many times and will dissipate

Re: temperature swinging - 15 years ago

He does the A/D conversion by charging a capacitor through the thermistor and timing how long it takes. The erroneous values are caused by the timing measurement being interrupted.

Re: Testing a UCB - 15 years ago

There could be a short from the TX pin of the PIC to an adjacent pin. That way the loop test would work without the PIC fitted because the pin the short is to is no longer driven. However, you have tried two boards so you would have had to have made the same mistake twice. I am really grasping at straws here, I can't believe we have got so far, done so many tests, and not been able to narrow it

Re: RepStrap Tommelise - 15 years ago

All the 7.5 deg motors I have are 12V. I don't think they go much faster than two or three revs per second with CV drive. I have never come across low inductance ones but if they do exist that might be an idea. The type I have are known as tin can construction and are relatively cheap compared to the stacked lamination type. They have less torque and less accurate pole piece alignment.

Re: Testing a UCB - 15 years ago

The only explaination I can think of for that is that you are actually monitoring your mouse! Do you have a serial mouse on your PC? Does it happen with the HT window in focus when you wave your mouse about?

Re: RJ-45 / RJ-11 / Premade Cables - 15 years ago

I think you will find that at these sorts of baud rates all the reflections will have died down long before the mid bit position where it matters.

Re: Nichrome wire Ohms clarification - 15 years ago

Yes I too had been assuming 18W for 8 ohms as I use MOSFETs for switching but actually the UCB uses a darlington with a 2.5V max drop at 2A. If we assume a more typical figure of 1.5V then that reduces the power to: 14W @ 8R and 18W @ 6R.

Re: RJ-45 / RJ-11 / Premade Cables - 15 years ago

Sorry my comments earlier about 7m should have said 7ft.

Re: Testing a UCB - 15 years ago

So 12 characters in 5 minutes. Did they all arrive at once or one every 25 seconds or did they arrive irregularly?

Re: RJ-45 / RJ-11 / Premade Cables - 15 years ago

Electronic parts are always much cheaper in volume. My company gets Ethernet sockets with magnetics for 1$ / 1000 off and PHY chips for less than $2. I think once the projects reaches critical mass the RRRF will be able to take advantage of volume discounts to sell remarkably cheap kits fo electronics parts.

Re: Dead link for the opto-endstop - 15 years ago

Re: Nichrome wire Ohms clarification - 15 years ago

I think it started at 12 ohms, went to 8 and now 6. I made mine when 8 was recommended and it rapidly gets to 200C, and would get hotter if I left it on, and that is without any insulation, so I am not sure why it needs to be as low as 6. I think Forrest's Tommelise has 6 but that has a large plate at the top end acting as a heatsink as well as no insulation.

Re: RJ-45 / RJ-11 / Premade Cables - 15 years ago

1. If you coil up 7m or wire and place it anywhere near a stepper motor or DC motor I would not be surprised if you got comms errors due to it making a parasitic transformer. 2. More time consuming than making a few crimps and a much messier result. Feel free to put the video of the RepRap site if you think it will help anybody.

Re: Testing a UCB - 15 years ago

So a loop back through the PIC pins echoes OK but when the PIC transmits the data is corrupted? Other than a very poor ground connection between the PCOM and UCB I am starting to run out of ideas. Can you send a screen shot of what the garbage is when running emf's transmit test?

Re: RJ-45 / RJ-11 / Premade Cables - 15 years ago

Well it makes a bit more sense using a 4 pin connector to handle three signals but how do you buy them at the right length? The link Zach gave is 7m long. Making them yourself is no longer an easy option because you need an expensive tool and it is quite tricky to use. I made a video of how to put on a crimp and it only took me 1 minute 40 seconds even while taking time to explain how to do it.

Re: Testing a UCB - 15 years ago

I don't think the voltage on pin 11 is well defined with nothing connected so I don't that is anything to worry about. When connected to the UCB it should go to around 5V. So a loopback test in HT works but emf's transmit test fails. Are you sure HT is set to 19200 baud 8 bits no parity?

Re: Testing a UCB - 15 years ago

The polarity of small electrolytic capacitors is usually marked by a stripe down the side nearest negative connection. The board marks the plus connection with a square pad and a + on the silk screen. If you look at the picture in the wiki all the negative pins are those facing the camera. If the caps are wrong that could be your problem, otherwise it looks like the MAX232 chip is faulty. Measur

Re: RepStrap Tommelise - 15 years ago

The electronics isn't much more complicated you just need a more modern driver chip that does it all. If you go too modern then you run into leadless surface mount chips which gets you into solder paste and ovens. The main problem is that you probably need to go to a higher voltage supply so the cheap, off the shelf, PC supply is no longer an option as is the idea of running it from a single car

Re: Testing a UCB - 15 years ago

Have you checked the voltages around the MAX232 chip and the polarity of its capacitors?

Re: reprap.lib missing - 15 years ago

The library is here: I think I had to copy it to C:\Program Files\kicad\library to make it work. I am not sure if that is how it is supposed to be used.

Re: RepStrap Tommelise - 15 years ago

Yes it would need more torque with a belt. The studding gives a higher gear ratio so it requires less motor torque at a higher speed. Having said that stepper motor torque falls off with speed so more torque is available when using the belt, as the motor does not have to turn so fast. I would guess that frictional losses would be a bit higher with a studding drive. I think Forrest published some

Re: Universal Controller v1.3.0 - 15 years ago

"Power wiring too?" No you need thicker wire for the power.

Re: RJ-45 / RJ-11 / Premade Cables - 15 years ago

Yes it would useful if everybody that has had problems give a quick post recapping what problems they have had, or still have, regarding UCB PCOM interconnect and testing. Also if people who had no issues could also post we get an idea of the scale of the problems. We should also be able to put together a debugging flowchart that differentiates each of the problem people have encountered so far

Re: RepStrap Tommelise - 15 years ago

The main problem with stepper motors and studding is speed. To get steppers to go fast enough you need a high voltage constant current drive and low voltage high current motors (low inductance). The RepRap electronics is constant voltage drive into relatively high voltage motors so its not going to be very fast. Threaded rod drives use much bigger thread pitches than standard studding but are exp

Re: Universal Controller v1.3.0 - 15 years ago

2 hours? We are talking about 5 one pin cables so that is 12 minutes per connection. I can see why it would take more than a minute per pin which is 10 minutes in total. Double it for somebody with no experience.