[tekno]

maybe you could use the transistors and zeners to run the optos

One thing to note is that they need to be driven pretty hard to get the stated speeds (ie: 50ma). I don't think a parallel port can put out that much current.

I'm thinking of using transistors and zeners instead. Not as safe as opto's but perhaps good enough for 30-50v supplies.

[pminmo]

Actually the open source designs are isolated via a 10K ohm filter network. While it's not the isolation of an opto isolator, it significantly reduces the likelyhood of an induced failure in the PPort.

Phil

[Ito-Brazil]

Well guys, we got it! The 4N25 Optoboard works fine! Thanks to Phil and Marteen !
I tested the speed today. at 16khz it works fine on TurboCNC.
Tomorrow i will test more speed, im trying to finish the mechanical parts too.
Even more close to have a good CNC.
I can send the Eagle files if someone are interested. It´s opensource, you can copy.
THANKS GUYS ! It´s amazing how simple movements on a stepper motor can make us so happy, hahahhaha !

[pminmo]

Ito,
Send the Eagle files to me I'll post on the website.

16KHZ, that's impressive. What kind of steppers?

Phil

[tekno]

Glad to hear

[Ito-Brazil]

16 Khz thanks to you Phil, the driver board is your discrete.
I´m using old printer steppers (when i sad old, think about OOOOOLD ones).
They´re big: 1.5A / 6V / 1.8 deg/step UNIPOLARs NEMA 32 size (NEMA size is about flange size right?)
I´m using a 2x6.8 Ohms/10W ballast resistor at 12V
I have other ones very big, 2.6V / 3.1A, that i will use when i construct a very large wood carving machine (i hope this year), so that´s why i made the Discretes).
I´m a CNC adicted now !!!!!
Thaks to Phil, Marteen, Tekno, thanks to all of you guys!

[macmiester]

I first want to say that I'm impressed. I have one question though and apologize that its being asked with no knowledge of your design, but have you tried a 4n26? The diode to diode configuration would give you several orders of magnitude increase in switching speed.

[Ito-Brazil]

I didn´t use the 4n26 just because i didn´t knew it before. I will search the datasheet right now and if it´s compatible (same pins as 4N25 ?) i can buy some to test it. I put the 4N35 on eagle files because eagle have no 4n25. Phil will put the files on his website soon. Take a look at the design:

[tekno]

I'll also look at the 4N26.... I was at Digikey looking but ended up more confused.

[Ito-Brazil]

Eagle files from versions 1 and 2.
I used 1k on resistor between optos and lpt, but you can use a 390 ohm.

Version 2 has all GND-OUT separated ; version 1 has all GND-OUT together. Tht´s the only diference:
IT´S OPENSOURCE, FREE TO BUILD, COPY AND DISTRIBUTE. ENJOY.
It´s the minimal i can do to thank everybody: do the same and help otherones.

[pminmo]

Ito,
For me thats what it's all about, one big world wide hobby group helping each other.

Phil

The eagle files are on the website:
http://pminmo.com

[Alkirah]

Hi, i'm new here and I'm planning to build a cnc drill for drilling pcb. Sorry for my bad english. I've been looking for diagram of the 3977 chips since I have 3 of these. I've only found png image for the copper for the board. I do think it have some problem with the board ... Just to be sure ... i'll post an image here. I've noticed that some of the copper way are touching ground on the picture ... I'd like to know if this is normal. I've marked them with green arrow. I'm wondering if you could send me eagles files if they are not the last version or a newer version png file . I've looked to phil's site and they aren't there too. Thank you

[pminmo]

which 3977, the sed or slp?

Phil

[Alkirah]

Hi phil, My chip is the SED, the one you have previously post on this thread. The 44 pins square ...

Thx

[pminmo]

Alkirah,
Send me your email address via the Zone here.

Phil

[slowboy]

A quick question regarding the chopper converter.

I built one using vero board as a test before making up some pcb's.

Once i sorted out the correct resistor values my stepper is working correctly.

Its a step-syn 5v 1.3a 1.8deg just for testing purposes.

The problem i have run into is that for some reason i can not set the voltage any higher than 12v. If i set it 25v, 36v it turns the chopper full on without any stepper motion.

Can someone please guide me as to what is happening here.

Thanks, Rob

[H500]

Rob, I'm not sure what you mean by "it turns the chopper full". By the way, if you're using the a3977, 36v is too high. You risk damaging the chip.

[pminmo]

slowboy,
Is the Zener keeping the low side 10V lower than the powersupply? i.e. if the power supply is 22V, the bottom side of the 10V zener should be 12V.

Phil

[H500]

Phil,

I was wondering if you are satisfied with the performance of the a3977? I'm thinking about doing a SED version so that I can put it on a home made board.

I also notice you use 2 schmitt triggers per input. Does that improve the noise immunity or is it just used for re-verting the signal? I like to use 1 if I can get away with it.

[slowboy]

slowboy,
Is the Zener keeping the low side 10V lower than the powersupply? i.e. if the power supply is 22V, the bottom side of the 10V zener should be 12V.

Phil

Hi Phil,

Yes the zener is 10v lower than the power supply. Without the stepper connected the IRF9540 runs just a little warm - as soon as i hook the stepper up it gets real hot real fast and thats with the motor idle.

Thanks, Rob