Question About IC Connections (UDN2917EB - Stepper Controler)

The datasheet is a bit sketchy. Going to Allegro's site, I found that this is a discontinued item - not a good choice for a new design. I couldn't even find any App. Note papers for it. Their newer products are easier to use, and are better documented.

I would consider using a newer driver. You might find something you can use here.

I probably should not respond, since I don't know much about stepper motors and their control...........but I guess that hasn't stopped me in the past :)

First, the part you are looking at has been discontinued by the manufacturer, probably not a good choice for a new project.

Second, if I'm thinking correctly, this part is just the motor driver, NOT a controller. You will still need something to control your stepper, this part just gives you all the pieces you need to actually "drive" the motor, with some sensing and protection features. There may be some parts out there today that are integrated controllers/drivers that are more in line with what you need. Check out this part by the same manufacturer:

LINK

As I said, I'm no expert in steppers, but do work with a lot of different electronics related items, so just trying to share what I can. Good luck with your project.

Tom D.

AFTER POST EDIT: Mike beat me to some of the stuff, sorry about the repeat info. It never fails that someone else posts while I'm editing mine!

Thanks for the replies,

The reason Im using this IC is that Ive taken it from a printer, and I wanted to play with it while I wait for a newer chip that i ordered online to arrive.

Besides, from what I've seen, this sort of conections/inputs appear in other steppers IC's, so It cant hurt to understand them.

I guess I'll just wait for the new ICs (free from st website :) ) more questions to follow soon...

See my recent reply.

If you got it for nothing then play with it.....I have just posted a link for a .pdf with connection data.....and a lot of newer chips!!!

Hi,

It shows you're new to motion control, but I'm sure you'll enjoy this project.

Pins 5 AND 19 close the winding circuit and allow current to flow to ground thru RS, don't leave it open, use resistors of enough wattage for your motor and calculate their value according to the supply voltage connected to Pin 22, so you dont exceed 1.5A when Pin 1, 2, 23 and 24 are set to 100% current.

Pin 4 AND 20 measure the voltage drop across RS and let the chip compare it to a threshold in order to disable the drive if the current setting is exceeded.

Since you are going to control one stepping motor using both halves of the chip, accomplish the following:

Vref (pins 44 & 25), should be tied together.

Enable (Pins 27 & 42), should be tied together.

Phase (Pins 43 & 26) should be tied together.

Use the Phase input to select the rotation, then use the Enable input to turn ON the driver bridge, thus energizing the motor, and finally, use the Vref ANALOG input to control the speed of the motor.

You don't need to energize each coil of the motor, this chip takes care of that.

Please be aware that you need to connect a transistor array with sourcing resistors to some of your parallel port outputs, in order for them to function as rough digital-to-analog converter and use its output as a voltage reference (or speed command or velocity control/command, whatever you want to call it) AND connect it to Vref on your chip.

Yahlasit

Yahlasit, your statement "use the Vref ANALOG input to control the speed of the motor..." betrays the fact that you have absolutely no idea of what you are talking about.

This input controls the current applied to the motor windings. As anyone with the first idea about stepper motor control could tell you, the motor speed is governed by the input step rate. IT'S A STEPPER MOTOR, DAMMIT!!!

(Jeez.)

1.- Not all controllwers need an input step rate, if you just had an idea of what a speed follower is, would know that.

2.- You're wrong about the current control of this chip, it has a digital current control being adjusted by the combination of I0 and I1 form 0% to 100% in steps of 33%.

3.- Why the hell would you bother to use this chip, if you needed to take care of the phasing order, train of pulses and all? it wouldn't be of more utility than just a power stage ( if you know what that means).

4.- Vref Controls the speed of the motor, I know because I've used several like-featured chips to build stepper motor controllers.

I've been in the motion control and motor manufacturing since the 80's, I dare you to prove me wrong about the Vref input, just give a convincing argument. (now all will be expecting it from you). And the next time, son, read the datasheets first.

Yahlasit

GA from me for a great answer....

I'm glad you wasted your time on this one !

I take the blow, I learned about this chip, thank you (I guess the absolute winner is the OP), but I warn you; this is not the last time I'll be questioning about tech stuff !

Have a good day !

Yahlasit

Oh, and I'm glad you're older than me too.

Very gracious of you.

Question all you like - just try to come in with a little less ferocity, unless you're absolutely sure of what you're talking about.

Good night.

Usually (especially on chips from Allegro!! Like here for example) VREF controls the maximum CURRENT through the motor coils, so that the chip can be used on a wider range of motors......

Step speed/frequency controls the speed, more steps per second = more speed!!!

Direction controls the direction of the motor!!!

No wonder you signed on as a Guest!!!!

Please see the datasheet for the L297 step motor controller, which includes details of the L298 dual H-bridge driver, which should give you an insight into how these things work.

You need to look for the "Applications data sheet" from Allegro. This may help you further, see page 85:-

http://www.allegromicro.com/en/products/categories/Sanken/Motor_Drivers/Motor_Driver_ICs_h1-i02eb0.pdf

It appears to be technically a slightly older design though as it still uses external sensing resistors (probably for compatibility for the discontinued 2916), whereas the latest designs have dispensed with them mostly to my mind, not that I am a Bipolar motor expert, I tend to use Unipolar designs running at a higher current.....

I do feel that there are better and newer designed chips from Allegro, but that's only my opinion.....

If you are designing your own PCB, be very careful with the ground plane design......

With Allegro, if the data sheet is not fully informative, that usually means you need to find the applications data sheet.....

Best of luck....

Okay, so just confirming:

E goes to ground, and the voltage at that point is due to diodes/internal components.

Input Vref controls the maximum current in the windings, makes sense.

Sense senses the current trough an external resistor, in order to keep the max current in check.

ENABLE(i) sends current to coil(i) in the direction given by the input PHASE(i).

So, to complete one revolution->

ENABLE(1) PHASE(1) ENABLE(2) PHASE(2)

1-----------0---------0------------0

0-----------0---------1------------0

1-----------1---------0------------0

0-----------0---------1------------0

Lastly, Since i dont have 200 to 500 pF capacitors (for the current trigger), can I use 0.1 uF combined with Resistances that would give me an equivalent time constant?

This IC seems a lot more difficult to operate than the L298 (which is what i ordered). I'll give it a try now, hope it works..

Oh, and thanks for that pdf Andy, it does help to see all the external conections.

I can think of several chips far easier to implement, but not for free!!

For rotation, the ENABLE input should be tied low (connected to 0V). The PHASE inputs are:

Re: the capacitors - you should get away with 0.1μF - it probably won't be a problem at slow-ish speeds. It should certainly run to some extent or another, and I can't see that it could cause any damage.

For the L298, you need to provide the current control somehow - this is usually done using the L297 controller. ST chose to split the system so that the PWM for current control lived in the controller chip, and the driver was just that (an H-bridge driver).

Allegro have put the PWM in with the driver, which makes some sense, because when the L297/8 combo came out, micro's were a lot less capable and more expensive. The L297 took over the job of translating the step & direction signals into the drives for the two H-bridges.

With cheaper & more capable micro's, it's easier to dedicate 4 outputs (and a bit more fast processing power) for generating the individual phase signals.

How do/did you propose to do the current limiting with the L298?

For both the Allegro and ST chips, if you only want to go slowly you can forget the current limiting (connect the bottom end of the bridges directly to ground) - as long as you keep the supply voltage down to the rated motor voltage. You won't be able to drive quickly, but single-stepping will be fine.

The reason all this current limiting/PWM stuff comes in is that to drive quickly, you have to build up the current in the windings quickly; this can only be done with a (relatively) high voltage supply. With this voltage connected continuously, the motor would burn out.

Sorry - I'm rambling a bit here - but I hope you get the idea.

A nice ramble!! And true as well.....

I hadnt planned to limit the current, because i didnt know there was a need to(with this IC). Right now Im trying to get at least minimal control trough the L298, but I cant seem to get it working. I checked the input signals independently and they work, but the motor is not moving at all, neither does it 'lock' so clearly I must have messed up one of the other connections.

One thing that i find very confusing is Figure 6 on this datasheet. Are D1...D4 external? If not, then is each terminal of the motor coil effectively connected to the +Vs line? Or is it internally connected to the +Vs line?

re: fig. 6 - yes, the diodes are external. Please note also that fig. 6 relates to a DC motor - not a stepper.

What type of motor are you using? What are the specs (volts & amps etc)? What supply voltage are you using?

The more info you give us, the more we can help.