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| PeterE builds a 3d Printer |
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| PeterE:
picclock, First of all, thank you very much for nice comments! I will pick up your tip on both the 5V load resistor placing, and to fit a terminal block on the outside of the PSU housing, very good ideas both of them! nrml, The answer to the choice of a PC ATX PSU instead of a CCTV/LED unit is simply that I didn't find one as I was looking around. The ones I did find cost way more than about 18£ here in Sweden and none was to find on flea bay currently, had I found one that would have been the choice. On the other hand, using the PC ATX PSU I automatically solved the mains switch and power receptacle matter. I wish all readers a happy new year with many interesting builds of all kinds! BR /Peter |
| PeterE:
Happy new year to all! :beer: Starting out this year with a question ... picclock; On your picture of the rear of the PSU I tried to compare your setup with what I understand from the description I use and my PSU. The white cable to the far right, what is that one used for? For the rest it looks like you have (from left to right): - Ground - +12V - Ground - +12V - +5V - Ground - +3.3V - PSU On - Ground - ?????? Quite similar to my setup which turned out as below: I made a small label strip beneath just as a reminder of which is which and I think you can see which will be which on mine. There are actually two different +12V outlets on my PSU at 20A each :headbang: so I don't have to divide one into two. Furthermore, I will enter the cables from within the box to the topside of the terminal block so the consumers will be let out from below. I think that will make it easier to keep the cabling along the bottom of the machine later on. I will of course fit the cables for the consumers before fitting the complete PSU to the machine to simplify connections. There is a difference between the two in that you have chosen to have a 3.3V connection point (orange cables) outside the box whereas the description I use does not include that. Is your choice just due to not wanting to leave the possibility out and that the mod is a general one, or anything else? Just curious to know before not including it myself. BR /Peter |
| PeterE:
Well thinking long and hard and looking at what the manufacturer had chosen as suitable, I found that two strands/cables were judged to be enough for 12V 20A. A quick check with the 24VOLT.eu site told me that it was quite OK. So I could use that as template for the rest of the setup. The site turned out to be quite useful and the link is here: http://24volt.eu/kalkylator_kabelarea.php. Click the UK flag to change to English. I also decided to include one single 3.3 V connection on the outside to be prepared for any circumstances appearing. Had therefore to change the label so the rear of the PSU now looks as follows: But it is not yet possible to put the lid back on - of course the load resistor for the +5V line was not in my store so have to buy it next week ... While waiting for that to turn up, it is high time to try to understand the electronics setup and with the following walkthrough of the bits I hope to get some feedback if I am off track so to say. The base is an Arduino Mega 2560: It is fed using the USB connector to the left at loading and setting up time. When done, the USB connection can be removed as the control board called RAMPS is to be fitted as a piggy-back board on top of the Arduino board. This contains the controls for stepper drivers, end stops, extruder heater, hotbed, etc. The USB cable is not required as we connect the two +12V lines to the lower left for the two circuits. Thereby the Arduino board below seems to be fed from the RAMPS board. at least it looked like that when inspecting the connections. Then add the SMART-adapter for he display board on top of the RAMPS board to the right. Now we can attach the display board with it function selector in the SMART-adaptor connectors (quite short cables between those - hmmmm). And finally, five small stepper driver boards is fitted on top of the RAMPS board. I placed one of the five in the upper row to the left. This is supposed to be a job to be done with caution as if the stepper boards are turned the wrong way there is a risk for the whole setup to blow, all the way from the Arduino and upwards! So, this is what I can see from just looking at the parts, is this correct? Is there a way to ensure that the stepper drivers are fitted correctly, I mean something particular to note at assembly time? Now back to think about the best place for the control display ..... /Peter |
| picclock:
Hi Peter E Happy new year to you to :beer: Your PSU looks very neat, certainly smarter than mine. I think the white lead is -12V, it was just put together as a general additional bench supply for various project testing. I have been running running temperature rise tests on my stepper drivers and you really do need a fan for cooling them. I thought I might be able to get away without as I'm using 24v but it won't work for reliable operation. My chips trip at 150C and without a heatsink on top I was reaching just over 130C chip temp with an ambient of 11C (measured with infrared thermometer on chip surface at 75C). Worst thing is this is for a single driver at 1.4A. So very much on the edge. The twin driver z axis will likely dissipate 3x as much driving at 1.3A each so for continuous use good heatsinking needed. I have designed pcbs for the drivers you are using but they were never expected to dissipate so much. Problem is if one stepper shuts down for only a fraction of a second print is ruined. So to sum up, forced cooling essential if you want good reliability. When you start testing, ensure that you have bed and head thermistors connected or Marlin will shut down with ERR MINTEMP but the screen will continue to show normal operation. I have flagged this as undesirable/misleading behaviour with Marlin who indicate that the message will be changed to show the system has halted. Good luck with your testing and further progress. Best Regards picclock |
| chipenter:
This will test your steppers and drives , match the baud rate and they shoud turn , I can't get my software to see my shield says my encoders are wrong , but they turn so I know it's correct . |
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