CNC machine - V 2.5 aka "BFC"
V2.5 is almost here, I'm still thinking on a nice name for it :)
For now a list of changes I have done since V2.1:
- upgraded motors to 200 steps/rev bigger motors
- designed a new version of the driver based on the well known L297/L298 combo with current limiting, and Enable/Direction/Step control.
- changed the way the rails are mounted on both Z and Y axis to provide better sturdiness
- rewritten the stepper control parts of the Arduino software, added G02/G03, replaced the original serial implementation with a smaller/buffered one.
- painted the thing black :D
I'm still in the process of putting it back together after the trip to Madrid, a process which took longer than usual since I tried doing some more improvements while having it in pieces.
Will update as soon as I'm finished with the above, hopefully tonight I'll be able to have the electronics back working/tested.
05-May-2010: Well I guess it shall be known as BFC
The guys who were in Madrid know what it stands for :D
I'm still struggling getting the drivers back in shape ... plane travel undid all the fixes I did in Madrid, and the poor quality of the PCB's is kicking in again... Never rush up when doing such things it will always end bad, trust me.
14-May-2010: Dead in the water
All my attempts at reviving the drivers failed miserably, that's it. I was contemplating rebuilding them from scratch but the cost of the L297/L298 based combo and the uncertainty of what actually caused them to fail after working quite well in Madrid made me reconsider my options and finally I decided to try a completely new design based on the well known (to me) ATTiny 2313 (yes again :D) and TEA3718.
TEA3718 is a constant current driver, which can control one phase of a stepper with maximum recommended values of 45 Volts and 1.2 Amps.
This means the following:
- two of them are required to drive for stepper motor - that's cool because they are dirt cheap, also keeps the thing modular
- no other power driver is needed, so bye bye L298 and your stupid pin layout ... I hate routing those things
- direct STEP/ENABLE/DIRECTION control is not possible, they use a different scheme - but that is OK 'cause I still like the idea of having intelligence on the drivers and the ATTiny 2313 is great for that.
- they allow controlling the current in the phase in three preset stages and by modifying the reference voltage for the drivers - this time I'm sure microstepping is definitely an option
- the PCB layout should be nicer with those ... well I need to start designing it to see that :P
- they do not mention it anywhere but I think if more power is needed those guys can be stacked the same as with L293
A datasheet for the TEA3718 is here: http://www.datasheetcatalog.org/datasheet2/0/01arhti9l9hj2y97o5s3wa25c0yy.pdf
So I'm waiting for new parts now, they should be here next Friday or so until then I'll play with my other little projects.
27-May-2010: Uuuuu goodies !
So the special Friday, the day the parts arrive came and gone ... no parts. They delivered them eventually on Monday but I could not start anything with them. At least I finally got a wire stripper :)
Well another week is almost past since then and things start to roll again, I finished a prototype PCB design for the new drivers last night, hopefully this weekend I will be able to build it and it does not smoke when I power it on.