UCN5804 Final Word

[mbp]

Hi !

I am really a newbie. My electronics knowledge is pretty basic and i can say that my mechanics knowledge is null. So i don´t want to start considering that PWM stuff.

I have some UCN5804 around here, so i made a board with them, based on the "Nuts & Volts" article.

This All-in-one IC solution is the kind i love, but its limited output capabilities is a problem.

I searched the forum for ways to up its current output and find these articles:

http://www.cnczone.com/forums/showth...6&page=4&pp=15

http://www.cnczone.com/forums/showth...6726#post26726

I have doubts in choose the best solution, and in some concepts they discussed.

1) Which is best: Darlingtons or Fets.
2) The output protection. schottky or Zeners Diodes or Snubbers and the correct way to add them to the circuit
3) In the snubber solution, how to determine the correct pulse width to calculate. An example provided in one of these articles, they used 5uS.

So if someone have a schematic...

BTW, since UCN5804 is pretty rare now, i was thinking to add some protection to it. So, if i screw things up, at least this IC is preserved. But how can i acomplish that? I was thinking to add opto's to its output, but with the high frequency pulses expected, i think this will not work.
Any sugestions !!

Thanks.

[pminmo]

Actually the 5804 isn't too tough to get, yet. http://www.futurlec.com/ICSFOthers.shtml has them, http://www.alltronics.com/cgi-bin/category.cgi has them. You can get them on ebay all the time. Use n channel MOSFETS but you will have to invert the output.

[mbp]

I already have 9 of them. So i´m planning to build a 4-axis board and use the remaining IC as backup´s.
What I really need is a definitive schematic for a PCB with this ICs.
The other thread (above) they used a 7414 in its output to invert signals.. Is this the only way ? How 7414 deal with high frequency pulses ? Is there a solution to isolate the 5804 from the power Fets?

Thanks.

[pminmo]

with a 5804 there is not high frequency pulses unless you consider the step pulse rate high, which it really isn't. There really isn't a need for isolation oa larger magnitude than a logic gate will provide the 5804. The 5804 should be able to handle any logic failures. Actually a 74AC14 would be better driving some IRLZ44 or IRLZ24 or IRLIZ34 or STP16NF06L FETs would be a good combo.

[mbp]

Thanks Phil for the tips.

I looked my stuff here and found some 74HCT14. Any concerns in using them?
I have doubts about the diodes in drain/+supply. Which is best and how many amps it must be. Or is better to forget the diodes and use snubbers?

I'm planing to use a nema 23 stepper rated as: 3V - 2.4A/phase. Currently, to learn purposes, i´m using a 17PM from minebea. I don´t have the specs for this stepper, since this is a custom stepper from minebea for epson ( Newbie needs help on stepper specs !! ). I´m assuming specs from similar stepper from minebea (3v - 0.6A/phase).

As you can see, i need nothing more than 2.4A/phase. So i can use the Darlingtons or Mosfets aproach. In case of using darlingtons, i thought on TIP122 (5A). Or using Mosfets, i thought on IRLZ34.

What do you think is the best solution for me ?

Thanks.

[pminmo]

HCT and IRLZ34 will do just fine.

[Jeff Simkins]

I used to work for Sprague Semiconductors probably when the UCNs were released to production (ancient history). They gave out free samples then, and today they offer free samples of their new devices!

http://www.allegromicro.com/sf/970701/index.asp



The applications engineers can help you with any of your design issues,...just don't ask them to do it for you.

Jeff

[mbp]

Thanks Phil.

Thanks Jeff. About other IC from Allegro, I already looked for them in local farnell-newark, but they don´t have them. I think companies are not sending samples to Brazil. I´m not sure, but is something related to local policy. And import this IC is very complicated and expensive (60% customs taxes). But thanks, anyway.
Meanwhile, i will try with i got here.

Thanks.

[mbp]

As i said before, i´m a newbie. So i still have doubts on this.
The first sch is the original by our colleague Urgundiz.

In the second i circled the original connection of diodes. I´m not sure about its function. So if someone can explain, i will apreciate.

Is the third and fourth sch possible ?

Thanks.

[pminmo]

Looks like 1 and 2 are the same, the motor coil has a diode across it to clamp inductive kick, but it won't clamp max voltage, but it will in all practicality load it so it's not an issue. 3 will clamp it essentially at the supply voltage but won't current limit the diode current. 4 The if the diodes are tranisil in nature the transil voltage will clamp the max voltage.

[mbp]

So, what´s your recommendations.

Or this one is better then the previous. (sorry. did on paint). R - 10/12 Ohms C - .47uF

Thanks

[pminmo]

look at the outputs of this schematic:http://pminmo.com/l297unipolar/schematic.pdf

diodes are bzw04-48. use a 74AC14 and FQP13N10L mosfets

all available from www.mouser.com