[TinkerDJ]

Has anyone designed a driver with either the national lmd18425 or the allegro sla7051m, i have sets of both and was wandering if it is worth the time and effort to build a driver board for one of them.

[santiniuk]

I can recommend Alan's Picstep boards for the LMD18245 I.C's.

It uses a Microchip Pic16F628A and a handful of discrete components.
Works a treat.

Details at :-

http://www.fromorbit.com/projects/picstep/

Good luck.

[H500]

The 18245 is a better chip if cost is no issue. It is bipolar and support microstepping.
You will need two of them per motor.

I will be testing an AVR based chopper circuit similar to the 7051, shortly.

[TinkerDJ]

Yeah i found that out about the lmd18245 chips, i guess i should have looked at them harder. I think i will focus a design on the 7051 chips or go with one of the open source boards. For now i will stay away from a pic driven board. I would like to build a board per axis and then use a pic18f452 to control everything from the com port or usb if i get a chance but thats all later. Maybe next winter. As for now i just want to get some boards done for the new steppers i have. Build my bigger router and go from there. As it is bitterly cold out right now i am more interested in doing indoor electronics type stuff rather then outdoor wood cutting router building type stuff. Thanx.

[kfong]

Definitely go with the lmd18245 if you can afford it. The lmd18245 is much better at dissipating the heat. It has better specs and can withstand 6amp surges. It has a 12-15amp burst rating as well. Here is our designs, very reliable.

http://www.embeddedtronics.com/microstep.html
http://www.embeddedtronics.com/microsteppld.html

Not open source but the code is posted as well as the schematic, design is proven. Boards are professionally done and are available if you find it too much of a bother to layout your own.

Kin Fong

[BobLWeiss]

Yup like they said, the LMD chip is real nice. I built the PicStep boards and they are working great. Do a search on here for PicStep and you'll see what I mean.

[TinkerDJ]

Actually i just got some lmd18245 chips in the mail. Problem is in my infinite wisdom i only ordered 3. (chair) Well i will work on the 7051 board design for now. I designed a board last night for the 7051 chips. But i need to trouble shoot any problems before i make anymore. I've actually looked at both picstep board and the embedded board. Both are very nice designs. Basically i am looking at building a controller that uses the pic18f452 and then seperate boards per axis. What the driver chips or arangements will be i don't know. Basically i'm reinventing the wheel and hoping to learn how it all works in the end. One thing i need to look at is either building or buying a pic programmer. But for now i will work on the board layouts and try and get my small router to work cutting pcb's. H500 keep me apprised of your board design. I have only played around with pic micro stuff but i have heard alot of good things about the AVR's.

[BobLWeiss]

I have only played around with pic micro stuff but i have heard alot of good things about the AVR's.

I have used PIC's for a long time now and I am biased towards them. They have never let me down yet in terms of power and speed. Their website offers a wealth of knowledge and support is great.

[TinkerDJ]

My absolute favourite part of using pics is that they will give samples. I blew a pic with my last board design. So i need another programmer. I haven't even tried any AVR stuff yet. But the robot community seem to really like them. But i am keeping my options open and making a stable board that will work is mostly what i am trying to accomplish.

[pminmo]

Atmel is pretty good about samples also. Three years ago when I was looking to get back into micro's, I originally looked to go with the PIC's or an updated version of the 8751 family, then I got a hold of some AVR literature. At that time the PIC's only had 8 bit a-d's and the AVR's had 10bit a-d's. When I found BASCOM's 2K basic compilier was free with an integrated development tools, I went the AVR route. I've never looked back. There is one part of the AVR family I feel is missing, a 14 pin DIP part. You jump from 8 pins to 20 pins. For example, a simple unipolar driver with 4 ouput drive lines a step and direction input will fit their 8 pin parts, but if you want an input for enable you have to jump to the 20 pin part. There not expensive $2, but would like the smaller foot print.

Phil

[TinkerDJ]

Through some of the web sites there are plus and minus's for all the micro controllers, basically every manufacture has one. I'm not pro pic or anti avr just inexperienced. I do have some knoledge of C programming is there a C programmer for AVR, i have one for pic's.

[pminmo]

A good starting point for avr's:
http://www.avrfreaks.org/
Free compiler:
http://www.avrfreaks.org/AVRGCC/

Phil

[H500]

I fried my programming cable by accidentally connecting it with my non-isolated oscilloscope in place. Fortunately, my com port is still OK. I'll have to opto isolate it one day, just to be safe.

I just tried my chopper program for the first time and one set of coils seem to be working fine but the other is chopping at too low of a frequency with a very slow rise time. I suspect that the fets gates were damaged by the previous mishap. I will try replacing them tommorow.

The real test is when I test how fast it can step under load on my mill. I have 4.5v 1.4amp 110 in-ounce unipolar motors. The previous configurations (direct 5v and 12v resistor limited) has been totally unacceptable. So far, I'm optimistic.

[BobLWeiss]

I guess eveyone has their preferences, but back to the topic, I would looking to the LMD's because they will sample 5 of them to you also..that's how I built my PicStep. Since they are $14 a pop and you need 6 that's a nice savings.

Another good thing about PicStep is that I don't need to use a heatsink with them running at 1.5 amps each/24vdc. They don't even get warm.

[BobLWeiss]

I have some 7051's laying around too but haven't seen any schematics for them. Anyone have an example circuits for using them besides the one in the data sheet? I know they stressed using a star-ground layout with it but that's as far as I got. I am building another machine and would like to use these for that controller and compare it with the LMD's. I also have the 3977 chips but they require alot of components to make them work and a double sided board which is always a pain. They are so damn small too.

[TinkerDJ]

I have 3 of the lmd12845 chips, like i said i forgot i needed 6, payed 17.50 canadian for them, I will try and get more samples but national makes you pay for shipping. My intended purpose in the end is to have a serial driven controller board then run the 3 axis boards. I would like to be able to use a palm pilot or clone to control the whole works as a sort of console. But this is far away. Right now my main focus is on getting a board design down that works.
The criteria i am looking at:
1. Has to have the ability for serial control. - Pic controller of some sort.
2. Seperate drivers for each axis, conforms with Phils designs for the Open source project.
3. Drivers must incorporate chopper technology, no more ballast resistors.
4. Single sided boards are prefered but not maditory.
5. In the process teach me what i need to know for parts of my engineering classes.
So should i focus on the controller and worry about the driver boards for later or build the boards now and then work on the controller once i have working drivers?

[pminmo]

If you have working drivers, it would seem to make sense to me to work on a controller. What kind of software do you plan to use?

Phil

[TinkerDJ]

I have one working driver but it was only in my bread board and was not used to control an axis only run with my test circuit. Curently i am using Turbocnc, i payed for the code. I was thinking about using KellyCAM but i don't know whats going to happen with this software, as the developer looks like he has family obligations, which i can understand. So basically its kind of up in the air so far for what software i will be using. Have you heard of cstep from Luberth http://www.luberth.com/cstep/. Although this will only be good for running my small pcb mill, which before i really go any farthur i need to deal with a problem i have with the z axis. I have seen a few really good suites for running the mill but i haven't settled on anything yet. Price is deffinitly an issue as i am a student. Does anyone have any experience with the max232 chip? Or a comparitive serial chip.

[pminmo]

I've used the Max232, it makes a simple rs232 interface with a micro.

Phil

[TinkerDJ]

Did you have any problems making it work at all, i was going to use the max232 to communicate with the pic18f452. I need to make a programmer but i think i might try building an in circuit programmer.