[Sanghera]

Hi all,
I was looking at the embeddedtronics boards and was just wondering why they are 11 pin and if they support step and dir signals (I'm not sure if they are 11 pin, are they) Aren't they normally 25 pin? How do these drivers perform for those who have made and used them? Do these drivers have the thermal shutdown aswell, and do these have relays for home limit switches?
Thanks. :rainfro:

[ger21]

Most drivers really only need the step and direction pins, which is only 8 pins for 4-axis. On a 25pin parallel port, I think about 5 of them are grounds. Plug you're parallel cable into a breakout board (they offer one of those as well), and just take the lines you need to the driver.

[kfong]

Hi Sanghera,

I came across your post and would be happy to answer any questions, our board is based on the National Semiconductor LMD18245 3A, 55V DMOS Full-Bridge Motor Driver. It's a great chip with these features

DMOS power stage rated at 55V and 3A continuous
Low RDS(ON) of typically 0.3W per power switch
Internal clamp diodes
Low-loss current sensing method
Digital or analog control of motor current
TTL and CMOS compatible inputs
Thermal shutdown (outputs off) at TJ = 155°C
Overcurrent protection
No shoot-through currents
15-lead TO-220 molded power package

We have sold quite a few of the boards and haven't had any complaints. The boards are professionally made by a reputable board house with silkscreen and grounded pour. We developed the boards for our own use and have thoroughly tested it before releasing it to the public. We have quite a bit of experience in electronics, as you can tell from all the designs on our web.

The board is all through hole so basic soldering skills is all that's needed. No hard to handle surface mount parts. The LMD18245 has a better heatsink and is rated higher than the Allegro A3977(rated at 2.5amp at 35V). The performance is great. We have two versions. One is pic based and the code is online so you can delve into it. The other is CPLD base, the code is proprietary. Both are really fast since the pic is running at 20mhz. The CPLD is faster since it's all hardware based but I doubt if most people will notice, since it's usually the PC or the stepper motor that will determine the speed limits.

On the parts list we marked all the stuff that is optional. All those can be omitted if you are really trying to keep costs down or don't need it to be so fancy. For instance you can just solder wires instead of using the terminal posts. The drawback is it would be hard to service. If you use a large enough heat sink then they shouldn't need to be serviced if run properly.

Sincerely,

Kin Fong

http://www.embeddedtronics.com/

[Sanghera]

So your boards do come with a heatsink?? Also, so is this right, you made the boards so that you can program them by yourself or you can have them preprogrammed? Kind of Newbie at this so what is CPLD mean, don't laugh.
Thanks.

[Sanghera]

Oh yeah, also, I saw on your site that it says that your boards can be flash programmed to do full half 4 8 or 10 microstep, how do you accomplish this, is it difficult? I have basically no programming skills, but I might be able to learn this stuff?
Thanks.

[Sanghera]

Hello?

[arvidb]

CPLD = "Complex Programmable Logic Device". It is a chip that contains lots (and lots!) of simple logic gates (like NAND gates or NOR gates and stuff like that). When you program the chip you tell it how to connect these logic gates together to form complex combinational and/or sequential logic nets.

The program is not executed line-by-line as in a microcontroller (like a PIC), but instead it explains how the hardware should work. This means that a CPLD is parallell in execution, and can be extremely fast (100's of megahertz). You usually use a "Hardware Description Language" to program them - Verilog and VHDL are well known industry standards.

These things are quite cool - you can often download a "package" that implements a microcontroller inside the CPLD! Free development software can be found on Altera's homepage (www.altera.com). Altera and Xilinx are two of the largest manufacturers of CPLDs and FPGAs (FPGAs are similar to CPLDs).

Arvid

[kfong]

Thanks Arvid,

I don't always get around to the newsgroups and it's great that people contribute.

The boards we sell are just blank printed circuit boards, you have to supply all the parts. It is very reasonable in cost if you price all the parts from Digikey. There are parts you don't have to put in so it all depends on how inexpensive you want to go. The best part of building it yourself is you will understand more of the electronics that go into making a CNC machine and you end up with a better product that you can service.

These are very reliable boards and are professionally done by a good quality board house. The boards are used by us and by many others and I have yet to hear any problems with them. The LM18245 is a beefy power IC and well engineered with thermal overload protection. It has much better heat dissipating features than the Allegro A3977, a design we started out with, but it wasn't as rugged when we tested it, or handled the high voltages we wanted to use. In general, higher volts gives more speed while higher current gives more torque. You can run a stepper motor over the rated volts but not the over the rated currents. It's the current that will fry out your motors, so you need to set the current at or below what is rated. Depending on the wiring scheme. If you wire it in series, the current should be set at half the parallel ratings. Wiring a stepper motor in series or parallel gives you similar performances. Series is usually the choice to go with, you have less current needed and power supply won't need to work as hard.

Newer triple stacked motors are now available that run under 3amps and have 1000oz ratings. So you really don't have to find big old honking stepper motors for that large mill you wanted to make. These newer ones are smaller as well and spin a lot faster too.

If you wish to program them yourself and save even more money, you want the Micostep. It is a PIC16F84A based processor that can be reprogrammed numerous times. The micro has a 20mhz clock so it is very fast as well.

We sell a programmer board (Picmee or Pprog) and supply the hex code for the various step rates. So all you need to do is run one of the downloader programs we mention on our site and just download the hex code. No programming skills needed to change the step rates.

Hope this answers you questions and then some

My email is [email protected] if you need a quicker reply.

Kin Fong

[fyffe555]

Hi Kin,

An interesting product you have there. The 16f84a is pretty much obsolete now, I'm thinking of replacing with a 16f628 - any thoughts. Obviously the code would have to be modified to suit.

Andrew

[abasir]

Andrew,
The code change would be very minor, probably in the initialization section only. My homebrew uses the same chips LM18245 and PIC16F628. With F628 4MHz internal osc, my max step rate is about 25kHz (interrupt driven).

[kfong]

Hi Andrew,

Not a problem, we have done that as well. Just have a lot of pic84's left and they still sell them on the market. You will have to change the initialization so it's set for the chip. The code isn't chip specific.

Kin Fong

[philba]

I dont know if this thread is dead but I'll ask the question anyway.

The F84A design requires that you reprogram the PIC to get different microstep rates. Is this because the memory is too small to hold all the step tables? It would be great to be able to change a jumper to change the microstep rate. A 16F648 is pin compatible and has 4K of flash so it should be no problem if its a memory thing.

[kfong]

Hi Philba,

Yes it would be possible, but you would have to change the code as well as the hardware. Although it would be a nice feature and something we will consider in the future. In everyday use, you would only need one setting. We chose 8 microsteps, it seems to provide smooth step rates that seem like they are servo motors and not over tax the PC side. You can have higher microstep rates but most microstep motors cannot resolve that well. You also end up burdening the PC since, it's the PC that needs to create all the pulse steps in software. For faster movements you want smaller microstep rates, but then you loose out on the smoothness.

Kin Fong

[Just John]

Maybe I shouldn't post this but I got my hands on 6 Allegro A397SLB's. Can these be used with the above mentiond cards?
Thanks in advance.
JJ

[kfong]

Hi JJ,

No, it would not work. You need to use the LMD18245 drivers from National Semiconductor.

Kin Fong

Originally posted by Just John
Maybe I shouldn't post this but I got my hands on 6 Allegro A397SLB's. Can these be used with the above mentiond cards?
Thanks in advance.
JJ