Bipolar stepper driver with 4000 line chips and mosfets

shortbus= said:

Also by using only full steps of the motor, you are limited in precision of table movement to the pitch of your lead screw. Most CNC's use smaller steps from a driver chip to get more resolution in the table movements. Most driver chips allow 1/2, 1/4 and even micro steps to be made.

Click to expand...

My resolution is 133 full steps/mm, I think it is very much good resolution. I also read that full steps are more powerful than half or one-forth steps. So there is less possibility missing any step.

But I have not experience whether it is 'very much good' resolution or not. Because I did not make any cnc job yet. What do you think? Is it not enough good resolution. Can I have any problem in real time with this resolution?

shortbus= said:

Wouldn't this circuit be easier with a dedicated stepper driver chip? https://www.google.com/search?q=stepper+driver+ic&ie=utf-8&oe=utf-8

Click to expand...

That is what I am investigating. That link you provided is valueless- what dedicated driver chip do you recommend and please show a full circuit.
Besides the OP specifically asked about a design using logic chips.

shortbus= said:

Almost non of the CNC machines that use steppers use a Pmos in their drivers.

Click to expand...

What is the point of this statement?

shortbus= said:

The time and money that will be spent building and trouble shooting a DIY driver board will be, in the end higher than just buying the correct ready made circuit.

Click to expand...

This is another general statement which would apply to nearly all the inquiries on ETO.
We can all make 'wise' and sweeping statements, but it is doing that counts.

spec

crazybuoy said:

Yes, you are right. I also want the same. But I just want to specify which parts are well matched to my application.

Click to expand...

CB, Are you saying that I have been wasting my time and all along you are going to buy a ready-made unit?

spec

spec said:

Your best bet is to realise the logic with 74HCxxxx/ 74AHCxxxx logic chips. Then you would need a driver chip between the output from the logic circuit and the MOSFET gates

Click to expand...

You and other helpful members are really great here. I am here consulting about selecting suitable logic chip, driver, MOSFETs and other things, that is what I'm doing here. I really apprciate all members here.

Can I use **broken link removed** h.bridge after SN754410 or L298 as described above by Spec.

I want to adjust this H-bridge in L297/L298 by connecting it after L298. Replacing it with 8 diodes. Is it right way of use this h.bridge.

crazybuoy said:

I have checked the connections by opening motor's back cover,

Click to expand...

you may have damaged your stepper motor by taking it apart. If the back cover also is the one holding the rear bearing. If it just was a wireing cover then you should be OK.

crazybuoy said:

My resolution is 133 full steps/mm,

Click to expand...

What kind of a lead screw do you have that is that fine of pitch? Resolution of movement is the screw pitch divided by steps. A 133 step to 1mm movement would be ~0.0075mm pitch. Never saw any screw that fine.

spec said:

That is what I am investigating. That link you provided is valueless- what dedicated driver chip do you recommend and please show a full circuit.

Click to expand...

What the link was meant to show is there are stepper driver chips that can do what the OP wants much better than a L297/L298. With that combo the steps are limited to full steps, most DIY machines use "fractional steps" to get the needed resolution for the machine. Maybe that is all the closer he needs. But with the many ready made modules that are proven by the years of use in the DIY CNC community, at very low prices on Ebay and from other sources, it doesn't make sense to me at least, to go back into the "stone age" of DIY CNC.

Places like CNCZone forum, can give the OP a much better idea of what to do and how it is done for a DIYCNC. There is a reason why no one is using the L297/L298 any more, and haven't for ~10 years or more.

I use V-shape lead screw with 1.5mm pitch, motor has 200 steps per revolution, so 133 steps/1mm.

Is it suitable resolution?

shortbus= said:

What the link was meant to show is there are stepper driver chips that can do what the OP wants much better than a L297/L298. With that combo the steps are limited to full steps, most DIY machines use "fractional steps" to get the needed resolution for the machine. Maybe that is all the closer he needs. But with the many ready made modules that are proven by the years of use in the DIY CNC community, at very low prices on Ebay and from other sources, it doesn't make sense to me at least, to go back into the "stone age" of DIY CNC.

Places like CNCZone forum, can give the OP a much better idea of what to do and how it is done for a DIYCNC. There is a reason why no one is using the L297/L298 any more, and haven't for ~10 years or more.

Click to expand...

OK SB- thanks for the explanation.

spec

crazybuoy said:

I use V-shape lead screw with 1.5mm pitch, motor has 200 steps per revolution, so 133 steps/1mm.

Is it suitable resolution?

Click to expand...

As to resolution, only you can answer that, I have no idea what your trying to machine.

A "V" thread leadscrew is a poor type for a CNC, but can work. But you will have backlash in it, and it is not as efficient as other types, it takes more power to turn it especially under the load of cutting. In order of screw efficiency it goes - ball screw, Acme/trapezoidal(name for metric Acme) then "V" thread.

1.5mm pitch divided by 200 steps = 0.0075mm per step. Each revolution of your screw will move the nut and table 1.5mm, that is what pitch means.

Have you read anything on the CNCZone forum? To see what others are doing. www.cnczone.com/

crazybuoy , seems like your making the same mistake on leadscrews for your machine that I did when I wanted to make a DIYCNC. Trying to use a fine pitch screw thinking it will give higher accuracy. As a machinist for ~40 years at that time, but never running a CNC, I forgot all about basics of machinery. Thinking that the addition of motors and computer control to a machine meant other parts of the machine changed too. Then I looked and researched about CNC, and found I was wrong, they use the same large/fast pitch screws as a manual machine. I some cases even larger/faster pitches. Some even have two or more "starts"(number of threads) on the same screw. Take a Bridgeport mill for example. A manual mill has a single start .200" pitch and lead(lead means the movement in one revolution of the screw) screw. But a Bridgeport built for a CNC uses a double start .400", .200" lead.

The faster pitch screws in a CNC are needed to do two things.
(#1) to give more accuracy, the inaccuracy(and all machined parts are to a certain extent inaccurate). The higher accuracy comes from averaging out the two starts/threads of the screw. A single start thread would just have that inaccuracy and it would show up in the movement.
(#2) to have the table of the machine move faster between areas when not removing metal. This is one of the big advantages of CNC, rapid movement between areas of the part. A screw with a single start for a certain lead, has to revolve twice as fast as one with a double start of the same lead.

I guess what I'm trying to say is, using a fine pitch screw is not going give you the advantages you think it will.

Some of us like to see pictures of machinery

spec

spec said:

Some of us like to see pictures of machinery

spec

Click to expand...

If that was meant for me, I don't have pictures, I never built the machine. Have all of the steppers, drives for the steppers, linear bearings and rails, and the design. But was forced into retirement before building the body of the machine. Forced to retire because the company was moved to China, and the result was retire or lose the pension money.

shortbus= said:

If that was meant for me, I don't have pictures, I never built the machine. Have all of the steppers, drives for the steppers, linear bearings and rails, and the design. But was forced into retirement before building the body of the machine. Forced to retire because the company was moved to China, and the result was retire or lose the pension money.

Click to expand...

Yes. What a shame! I would have liked to have seen your machine. Ever since a kid I wanted a metal-working lathe and, when I was about 30, bought one that needed sorting. It stayed in the garage along with other machinery for 20 years and in the end I gave it all away having never got around to refurbishing/setting it all up.

spec

When still working I bought 3 lathes , a Bridgeport, a surface grinder and bandsaws, have Mig, Tig and stick welders. All bought used and at auctions. The problem with finishing a CNC and doing it right (making sure all things are square and plumb) is my machines aren't big enough. Really unless your doing production work, a CNC isn't practical. For "one off" stuff, by the time you write program and buy the needed tooling, you can have the job done manually and be on to the next project. Just finished up building a gasoline powered capstan/winch using a old electric winch that someone was throwing away, using the gearbox from it and making the rest. It will be used in my firewood cutting to pull trees closer to the truck.

spec said:

Some of us like to see pictures of machinery

Click to expand...

It is very rough at this time.