Weve hit a wall UPDATED 06/13/10 06/11/2010
I was hoping to have better news by now but it is what it is. Grbl needed to be modified inorder to get the stepper drivers to dance. There needs to be a moment of pause between the pulse that signals the step and the next pulse....or something. Im not a programing wiz like some. I enjoy it and I tinker with it but thats about it. With that said grbl will now accept single lines of g-code through cutecom and execute them perfectly. Thats great if you want to do a project one line at a time. The problem comes in when a script comes in to send the commands to grbl from a file on the computer. I suspect that the delay I placed in the grbl code is causing some timing issues and tripping up the program when lines of gcode are sent one after another. The result of sending a line of gcode through cutecome looks similar to this.
G1 X5.345 Y4.332
Then you can send another line and it all works like its supposed to. Now when the script does it it comes out looking like this
G1 X5.345 Y4.332
G1 X1.115 Y7.223
Grbl>>G1 X5.345 Y4.332
G1 X2.225 Y7.435
and it stalls. Sometimes the first line is executed. some times its not. Now with the same script and the reprap 1.3 firmware all codes are executed but somethings seem to be different. Normally I would expect G1 X7 to turn 7 times then G1 X5 to turn back 2 turns. At least thats how grbl worked. The reprap FW turns 7, pauses a fraction of a second and turns 5 more in the same direction. Im assuming this is a setting or just a difference in code that can easily be fixed. Ive Emailed the writer of grbl but Im not sure if I did a great job of explaining my problem or if he will be willing to help me out. Well see when he emails me back. As for now Ive come across a couple of other ideas to try and implement and I will try to continue to read through grbl hoping for something to pop out at me.
Ive been emailing back and forth with Simen the programmer of the GRBl code. Were working through the basics now. making sure Ive got all my grounds and playing with settings. Its not looking great at the moment. well my set up is looking fine so far but since it workes with the modified code to a certain point I figured the stepper driver was looking for a a little different signal. well see how it comes out.
Back to Where it Began 06/02/2010
We have not reached the point where this all started. November 3rd of 2008 I posted a video of the HobbyCNC pro board I built driving a stepper motor I found on ebay. It was the first check marks I got to put on the wall of my CNC list. Here is that video for reference.
The next day I fried the board and that was that. I took several months of trying to figure out what I was doing. What went wrong. Where to go from there. I eventually decided to start on the table since I couldnt destroy it so fast. Now, almost two years later I present you with the latest in Steve-O tech. Straight out of the hot plate, with the solder still solidifying (not really), a single RepRap stepper driver v2.3 driving that same stepper motor.
Here is the inside scoop on my choice of the RepRap driver board. Stepper motors are pretty high dollar. As they should be. the driver boards for them are high dollar as well. When I killed the HobbyCNC board it was going to be close to a hundred dollars to replace it. No way to fix it. Now schematics. Nothing. I figured it shouldnt be that way. So I set out in search for a replacement that was open source to I could test, repair, or modify the circuit. It also needed to be strong enough to handle the motors I currently had. The RepRap design turned out to fit the bill and I went with that. Ed over at EdsLifeDaily seems to have found a similar solution. with that said, there are tons of solutions out there for this same problem. Even more if you know how to design your own circuits. Feel free to contact me if you have any questions, need some direction, or just plain want to share your project with me.
So whats next? Well I still have to finish the table. It still needs a drive system. I also need to come up with a way to get drawings to g-code and then to the arduino. I may have stated it in the past but a friend of mine has volunteered to help out with finishing this up and no0w that I have a working stepper drive we can move on to the next check mark.
Last bit of parts!!! 04/22/2010
The last package of components arrived yesterday! Pretty exciting. I haven't really thought about the CNC over the time I've been waiting for the parts to get off backorder so I'm ready to get back to work. I still need to order some solder paste and pick up an electric skillet. I've checked around at the local thrift shops to see if anyone had one but I haven't found one. WalMart and Target both have one for about $20 so ill just pick one up from there. Finals are coming up so don't expect to see a huge amount of progress! On a similar note I talked to Ed over at EdsLifeDaily and he's found a new driver design that he's testing out. Make sure to check it out. That's all for now but Ill be sure to get to cookin on those PCBs in the next month.
Gifts from Afar 03/11/2010
Yeah! It took 2 weeks and a trip to the local FedEx to get these puppies but they look great. I have more of them than I need so if any one needs a couple, hit me up and Ill sell them to you. Im going to put a couple up on eBay to see how they do. Ive still got about 12 LEDs on back order at Mouser so its still a waiting game. Its always nice to get stuff in the mail though. Ive got a couple more things to gather before Im ready to assemble. Solder paste and a hot plate. i went by Goodwill to see if they had el cheapo hot plates...They dont but thats cool. Target has them for like 20 bucks.
I posted 9 in the ebay listing last night and sold 3 soon after posting. I also got a request to ship three to Canada so it looks like I might recoup some of the money I lost having to order so many. Heres the ebay link for those interested in ordering.
RepRap Stepper Driver V2.3 PCB
Now we hurry up and wait. 02/25/2010
Latest news in my quest to finish up the CNC is that I've placed the order for the PCBs. I had to order 21 of them to meet the minimum order but Id rather have done that than to have paid 70 bucks for just 4 of them. It turned out to be close to 140 shipped with a 2 week turn around. I figure I can put a couple up for sale on ebay and connect with people looking to build their own RepRap. In my opinion its cool what the RepRap team is doing but its abit unstructured. For the average builder, not being able to acquire the stepper drivers or the bare PCBs to make them would be a dead end. Especially if they looked around and found out how much it would cost to have them made.
Head on over to Edward Fords page and check out his project CNC. Ill be looking into the software side of what he has dug up when I start pulling my electronics together and testing them.
The first batch of parts arrived today! 02/18/2010
Its for real now. I just received the stepper drivers from digikey. Ive been emailing around for some quotes for the PCBs.....wait WOW the UPS just dropped off the rest of the parts from mouser while I was writing this post. Thats crazy. What perfect timing. Ok. so whats left? Lets make a list.
- Get the PCBs made
- Get a hot plate
- Get solder paste
- Figure out how to work with SMD
- Wait for back ordered parts from mouser
- Assemble, repeat, repeat
- Figure out how to get it all to work together.
- Cut some stuff out
After looking at some of those parts Im amazed at how small they are. Its taken me a long time to get to the point where I am willing to try SMD. I guess you look at how to after how to and the pictures give you a false sense of size. Well see how it goes after I get the boards made and come up with a hotplate. For everyone out there trying to get PCBs made, make sure you mention if your a student. One of the places I got a quote from offers a 50% discount. Unfortunately they were still higher than my lowest quote.
A bit of history on me and my build after the break.
Started the Ball Rolling 02/16/2010
Ok, I took the first step. I thought I had sourced everything to make the Reprap driver boards. I ordered all but one part from Mouser (11.58) and the driver came from Digikey (5.81). I ordered four sets of components so I could have enough to have one as a spare. Then I went to order the PCBs. MakerBot used to have the whole board assembled and everything for 30 bucks a piece but thats been discontinued. They used to have the bare PCB as well in this nifty red but it as well had been discontinued. I found another site selling the bare PCB but it turned out to be discontinued there as well. So I spent the spare moments of the day looking into "fab houses" (places that make bare PCBs). Sparkfun has one that comes out to be close to $70 for three boards and I found a larger company that could make 12 for not much more than that. Im pretty sure that Im going to bite the bullet and get the 12 and either sell them on ebay or on here if any one is interested. A parts list can be found in the Reprap link I posted in my last post. The drivers are run off of a computer PSU and can run up to a 2A motor. Just so everyone knows, I didnt design this circuit. Props to the Reprap community for all they have accomplished for the open source community.
Possible Motor Driver 02/13/2010
I think I may have come across a suitable stepper driver board that will provide the 1.75A that my steppers need. Some of you may have read about the reprap projects. Basically the reprap is a cnc that lays plastic down rather than cutting material away. After doing some reading I found out the reprap boards will handle up to 2A it looks like.