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Author Topic: l297 and uln2003  (Read 3037 times)
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i found this image on the internet

as discussed in here http://www.kerrywong.com/2011/09/18/a-unipolar-stepper-motor-driver/
well it seamed easy and i couldnt find a L298 at the store where  i got my components from. (
(l298 probably no longer sold in europe due to poison materials used in it, so i skip it)

the url mentions that this is not the most ideal setup of these two components some futures are not used here, i think they deal with better torque and speed. So i wonder using these two chips if people got something better ?

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I think that circuit is a general purpose driver for low power steppers - if the stepper were bipolar you would drive it directly from the L297 (but would need to add free-wheeling diodes, or perhaps substitute the L298D).  This circuit adds a ULN2003 to conveniently drive a unipolar 6/8 wire motor.  The L297 provides the step/direction functionality and only needs 2 pins to drive it (the ULN could be driven from the Arduino from 4 pins, but maybe you don't have 4 pins available).
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Well the uln2003, got more clear to me.
It as 7 amplified OUT signals, or hmm i gues it provides negative for the inner motor coils
as their center wire of the two connected coils of one side of the motor gets a + voltage.

its the LN297, that is more of a mistery to me, and i got the impression that it is not optimal used.

for example what does INh1 do and INh2 ?
there is also Sens vref and osc, EN and ctrl and Sync what do they do ?
those are not use or connected together here, but must have a separated function (or else why create a pin for it)
 

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ok well turns out there are a lot of data sheets about the l297  , i didnt found them at first because of a typo smiley-sad
still maybe someone could enlight on the Inh1 and inh2, i'm not sure how /when to connect them i think its for micro stepping or so

Sens as explained in the datasheet is also something i dont get, good understanding of if i try to translate it (i'm not english)
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the sketch above is mirrored the real pin layout of the l297 below and also the other just as a note while i work on the breadboard
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« Last Edit: August 04, 2012, 09:12:01 am by PGTBOOS » Logged

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well it seamed easy and i couldnt find a L298 at the store where  i got my components from. (
(l298 probably no longer sold in europe due to poison materials used in it, so i skip it)

The L298N certainly is still sold in Europe, e.g. at http://proto-pic.co.uk/full-bridge-motor-driver-dual-l298n/ and http://uk.farnell.com/stmicroelectronics/l298n/ic-bridge-driver-dual-298/dp/403295?Ntt=l298n.

The L297/L298 combo has the advantage that the pair supports current limiting (that's what the SENSE pins are for), when they are connected at per the example in the L298 datasheet. This allows you to use a higher voltage to drive the stepper motor, which means you can get faster step speeds.
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i understood from a friend that a darlington is also able to handle higer currents, i believe the normal uln2003 handles 20v max.
or do you mean something else, i was wondered too about these sense functions, must perhaps be able to do something more ?.
or... might it rather be a protection (ie if the motor cannt rotate for a mechanical reason, that the circuit wont get damaged

i'm wondering
.. alhtough the uln2003 would protect the l297 for such mechanical failures too i think, the driver electronics wont backfire.
which would happen if the l297 had no driver unit at all... perhaps the l298 needs a bit of protection too ?? perhaps as it might be designed for even much larger currents ? (it got a huge cooling fan)
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i understood from a friend that a darlington is also able to handle higer currents, i believe the normal uln2003 handles 20v max.
or do you mean something else, i was wondered too about these sense functions, must perhaps be able to do something more ?.
or... might it rather be a protection (ie if the motor cannt rotate for a mechanical reason, that the circuit wont get damaged

i'm wondering
.. alhtough the uln2003 would protect the l297 for such mechanical failures too i think, the driver electronics wont backfire.
which would happen if the l297 had no driver unit at all... perhaps the l298 needs a bit of protection too ?? perhaps as it might be designed for even much larger currents ? (it got a huge cooling fan)

A Darliington needs lower base drive current than a power transistor when switching the same current. The downside is that they have higher saturation voltage. With the availability of inexpensive power mosfets, Darlingtons are pretty much obsolete.

The L297 is not designed to drive a motor directly, it is designed to drive a L298.
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ehm i try to translate what you say.
so the darlington takes more current ..resulting in a faster battery drain.. am i correct ?
or do you mean that a transistor is typically a slower switch (mosfets are not linear like transistors)

i have about 8 mosfets too ..
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so the darlington takes more current ..resulting in a faster battery drain.. am i correct ?

The main disadvantage of a Darlington is its a higher voltage drop, which also causes it to generate more heat when you use it to switch a large current.
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i have small motors a diameter of 1.5 cm and a height of 2 cm, i have no details about them, but those dont look like they would run on 60volt.
Maybe 5, or 10 volt and not like 2 ampere i think. So i think it will work.

Just in case i might later try a l298 or variant  (as  i dont like that pin construction, a SN754410 is the same but better fits a breadboard).
Do you recommend particular diodes, I have heard fast ones are required for schemes that make use of a L298 or variant of it.. ?

Also while i'm new into this stepper thing, i've seen some samples of complete solutions inside IC's (driver and stearing scheme, all in one IC).
But some of those where no longer fabricated, perhaps do you know of what is new and good in this small stepper motor IC scene ?
I bett that fabricators create once in a while new chips for this that perform better.
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