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1  Forum 2005-2010 (read only) / Troubleshooting / Re: Motor Control with Encoder on: January 19, 2006, 11:12:57 am
Thanks for the replies   ;D

Daniel --> from what i understand of servo motors, if they are hacked for continuous rotation, you loose the ability to accurately control the position. After the hack, the pulse controls direction and speed.... Is that right?? (I've never actually tried it.)

Michael --> thanks for all those details. The problem you are having is exactly why I would like a solution that takes the work away from the Arduino board.

Everyone! --> what I am really looking for is a system that handles the encoder off of the arduino board. So that the board's brain power is not being sucked up. Also, I would like a system like Arduino, ie, disposable!! (i'm a dreamer!)

Also, i'm still really interested to know if anyone has some experience of using the arduino motor shield.

Thanks again guys!
2  Forum 2005-2010 (read only) / Troubleshooting / Motor Control with Encoder on: January 18, 2006, 08:50:01 pm
Hi,

I want to control a DC motor with a closed loop system  to be nice and accurate.

So far I have controlled a stepper motor using a bunch of components so that all the arduino board needs to do is pulse on one line for one step and control direction on a second line.

I like this kind of system, where the arduino board is not bothered with thinking about the inside of the problem. It can just send instructions. It would be even better if I could send some serial instruction like 'turn to 120 degrees'.

I'm interested if anyone has any advice or recommendations for closed loop motor control??

As always, I want a good system for cheap  smiley-wink

I notice on the Arduino site, there are plans for a motor control shield. Does anyone have any experience on building and using this shield? Does this shield deal with the logic of motor control or is that left for the Arduino board program to deal with??

Any advice would be great

Thanks /Jonathan
3  Forum 2005-2010 (read only) / Troubleshooting / Re: L297 stepper motor controller on: March 19, 2006, 05:04:23 am
I'm back!! - after 10 days holiday in Prague! and feeling fully recharged by tons of beef and dumplings!

Daniel - thanks for the pictures!!  smiley-wink

So, some more questions....

1. As discussed earlier, the schematic on the datasheet has loads of capacitors and some more are needed for the 7805. I can see what capacitance I need but I don't know what kind of capacitors to use?? does it matter??

2. You are using perf board, right?? This is probably a real dumb question, but how do you use perfboard?? Do you just solder wires on the bottom of the board?? Please share any perf board tips or advice!!

3.
Quote
The schematic for this is exactly the same as the one on page 14 of the ST datasheet, with the addition of an LM7805 regulator for the power, a few caps and a reverse-polarity diode.  
are the extra caps just the ones required for the 7805 and what is the reverse polarity diode doing??

Thanks a million / Jonathan
4  Forum 2005-2010 (read only) / Troubleshooting / Re: L297 stepper motor controller on: March 01, 2006, 08:38:15 pm
There is a schematic for using the L297 with a unipolar motor on the L297 application notes pdf (not the datasheet).....

http://www.st.com/stonline/products/literature/an/1734.pdf

its page 15, fig 22.

It involves a darlington array, 4 protection diodes and 4 AND gates.

I'm planning to try it once I get the L297/L298 working together nicely.

Allegro have some new ICs out for controlling unipolar steppers that do the job of the L297 and the darlington array in one chip. I contacted my local sales rep and got some free samples. I haven't tried them yet though. (i'm old fashioned, so I like to learn how to do things the hard way before I use the shortcuts!)

http://www.allegromicro.com/sf/97052/

---------------

Regarding heatsinking the L298....  If you plan to step your motor slowly, for instance just a few steps per second, will the IC still need sinking?? How hot does that guy get anyway??
5  Forum 2005-2010 (read only) / Troubleshooting / Re: L297 stepper motor controller on: February 26, 2006, 11:11:55 pm
Well, its been about 3 weeks since my last post on this thread and by now I should have got a working L297/8 circuit. However, the reality of live, with a job and a family, has meant no electronics fun for 3 weeks and zero progress.

However, I have managed to buy the ICs and now I have a little time i've met my first problem  >>>  the L298 doesn't fit onto a breadboard. Looking on the data sheet, it is described as a 15 lead Multiwatt package.

Is there an easy way to fit this IC to the b/b?? Or do I need to go some other way??

Thanks as always / Jonathan
6  Forum 2005-2010 (read only) / Troubleshooting / Re: L297 stepper motor controller on: February 04, 2006, 10:33:28 pm
I just checked the farnell site for the l298 and it is listed as no longer stocked?????

Any idea why that might be?? I'm worried that these chips are on their way to retirement!!

Is there some other setup which I should be investigating??

any advice would be nice!

jonathan
7  Forum 2005-2010 (read only) / Troubleshooting / Re: L297 stepper motor controller on: February 01, 2006, 01:29:56 pm
Well, I've certainly been finding both of your advice very helpful! so i would second that motion!

I'm planning to breadboard the circuit very soon, so I will post some pictures of that, and the final schematic that I use. After this, I intend to make a circuit using the l297 and the ULN2075B to control a unipolar stepper.

Also I have a nice working circuit that uses a TTL 74194 shift counter as the transalator. I'll post some picures of that too (under a different topic). I'm interested to compile a group of circuits to control both unipolar and bipolar steppers, that offer a range of price vs functionality options.

Just for the record...

Jonathan is in London, the capital of rain and tea!

(and i changed my user name to 'flat stanley' for those who remember my 'little accident' just after the London workshop!)
8  Forum 2005-2010 (read only) / Troubleshooting / Re: L297 stepper motor controller on: January 31, 2006, 12:35:36 am
Thanks Massimo!

just to be sure.... like this?



Also, i'm still wondering....

what is the use of the 5V / 9V Power output pins on the Arduino board?? If i remember correctly, when arduino is powered by an external supply (ie not USB), the 9V pin actually outputs the same voltage as the supply voltage. So, if I run arduino on a 12V power supply, don't I get the clean 5V and unregulated 12V that i need?

Regards / Jonathan
9  Forum 2005-2010 (read only) / Troubleshooting / Re: L297 stepper motor controller on: January 29, 2006, 09:47:34 pm
Daniel -> 'Throw in a few extra 100uF capacitors on both sides of the regulator, just to be safe.'

hmmm.... Like this ??



(which reminds me... what apps do you use for your schematics and PCBs?? I found tinyCAD and freePCB - Should I try something else?? Now back to the topic....)

What I don't understand is... what is the point of the 5V / 9V Power output pins on the Arduino board?? If i remember correctly, when arduino is powered by an external supply (ie not USB), the 9V pin actually outputs the same voltage as the supply voltage. So, if I run arduino on a 12V power supply, don't I get the clean 5V and unregulated 12V that i need?
10  Forum 2005-2010 (read only) / Troubleshooting / Re: L297 stepper motor controller on: January 28, 2006, 05:36:03 pm
Thanks guys!

I'm getting closer to actually trying to build this thing! Just a few more questions.....

I'm gonna start with this circuit....



I have a few simple questions....

1. Daniel - you recommended a 12V/2A power supply. I can only find basic AC adapters at maximum 1.2A. Could you give me a link to one like you recommend?? - I just didn't look properly - Forget this stupid question!

2. The diagram suggests using the L6210 which is a '2 schottky bridge motor controller'. This seems to be discontinued. Would you recommend another IC or is it cheaper to use seperate diodes?? Daniel suggested Schottky diodes. Can you give me a part number?? I have found so many different diodes. I don't understand how to select the appropriate one. Also, maybe I'm confused, but I was thinking, can I use the l293d instead of the L6210??

3. Daniel - you wrote 'Use an onboard regulator (7805) to provide nice clean power to the L297, and lots of bypass capacitors'. Does this mean that I need to use some capacitors with the 7805 or are they included inside the 7805?? If i do need to use the 7805 with some external capacitors, how do I wire it up??

4. Very simple one... Does 'Rs1Rs2=0.5ohms' mean that both resistors should equal 0.5 Ohms or that the total resistance of Rs1 and Rs2 should equal 0.5ohms??

Thanks for helping out a slow learning electronics geek wanabe! / Jonathan
11  Forum 2005-2010 (read only) / Troubleshooting / Re: L297 stepper motor controller on: January 27, 2006, 03:00:27 pm
Thanks Daniel! You keep coming to my rescue ;D

I am planning to try the schematic on the l297 datasheet. I'm glad to hear that this one worked well for you! I have a few questions about it....

1. As i am planning to control the l297 from the arduino board, can i just use 5V output from that to power the l297 or do you suggest an external power supply using the 7805??

2. In the schematic there is a .33 capacitor and 22K resistor connected to the 'osc' pin. What is their purpose??

3. I'm new to electronics. I will investigate tonight, but perhaps you can explain... what is a trimpot and how do i connect it to the vref pin?? How do I know when it is adjusted right??

4. Am i right that the l297/l298 setup is for bipolar steppers only?? If so, have you tried some other setup using the l297 with unipolar steppers??

If you can answer any of these questions, I would be very grateful! Thanks / Jonathan
12  Forum 2005-2010 (read only) / Troubleshooting / L297 stepper motor controller on: January 26, 2006, 10:17:54 pm
I have been investigating stepper motor control for the last couple of months. I've been looking at lots of different solutions and right now I think that using the l297 chip is probably the best balance of features, price and useability.

First, here is what I have found about this chip that might be useful for others interested in stepper control.....

some useful docs....

STmicroelectronics l297 notes...
http://www.st.com/stonline/products/literature/an/1734.pdf

STmicroelectronics l297 datasheet...
http://www.st.com/stonline/products/literature/ds/1334.pdf

my understanding and brief summary....

The l297 can create the control signals for bipolar, unipolar and variable reluctance stepper motors.

In all cases, you can digitally select full stepping, half stepping and wave stepping modes.

The motor takes one step for each pulse sent from the arduino board. Direction is decided by taking a pin HIGH or LOW.

The l297 has another important feature. It includes two PWM chopper circuits to regulate the current in the motor windings. ??? what does that mean?? well, i found this page...

http://www.micromouseinfo.com/introduction/steppers.html

It's a nice and easy going explanation on stepper motors in general and it includes this bit on chopper  control of steppers...

'To increase the torque at higher speeds, stepper motors are driven at several times their voltage rating. A designer might use 5 volt steppers and then run them at 12 or 14 volts. To avoid destroying the motors, the current through the windings is monitored and power is cut off when the current reaches a critical level. When it falls back down, the power is reapplied. This technique is known as "chopper drive" and it allows the motor to increase its top speed.'

So that kinda explains the functions of the chip.

I don't yet understand how to implement the chopper drive properly. Also, I have not yet tried any circuits!! but from reading and researching, I believe the following to be true....

If you don't want the chopper drive......

If you want to control a bipolar stepper, you can use the l297 with the l293.

If you want to control a unipolar stepper, you can use the l297 with the L702B or any darlington transistor array. I'm not sure if you would need a buffer.

If you do want the chopper drive......

If you want to control a bipolar stepper, you can use the l297 with the l298.

If you want to control a unipolar stepper, you can use the l297 with the ULN2075B

In all cases, you will need a few extra components to complete the circuit.

So, now I have some questions for you!

Does anybody have any experience using the chip?? or any good circuit designs for using it??

The chip has an input Vref. This is used for giving the reference voltage for controlling the Chopper circuit. Can anybody explain how to connect up this pin??

I would like to compile circuit designs using the l297 to control bipolar and unipolar steppers, with and without chopper control. I want to find the easiest possible solution for each circuit. smiley-wink Please post if you already have a good solution for one of these circuits.

I will now start trying some circuits, i'll post when I get one working.

Thank YOU!

PS. maybe I made some mistakes above. Please correct me! I'm just a beginner still!
13  Forum 2005-2010 (read only) / Troubleshooting / RX / TX always on on: August 27, 2006, 03:57:06 pm
I bought a batch of assembled usb boards

They seem to be working fine but when I power them from the power in, the RX / TX lights are always on. If I power by USB, they go off.

Any idea why???

Thanks!
14  Forum 2005-2010 (read only) / Troubleshooting / Re: Exotic Stepper Motor ICs!! on: February 26, 2006, 11:15:21 pm
The stepper motor lab is located in the Far East (corner of my bedroom! in central London).

Its a sophisticated setup!!
15  Forum 2005-2010 (read only) / Troubleshooting / Exotic Stepper Motor ICs!! on: February 23, 2006, 12:43:04 am
In my ongoing quest for true stepper motor control, i requested some ICs from Allegro and to my surprise, i just received them.

The problem I have now is that my few circuit making skills all require the breadboard and these chips don't fit!!

I recognise one, it is a 24-pin SOIC package.

The other one is wierd. Here is its web page ....

http://www.allegromicro.com/sf/97052/

Is there some adapter for using these chips with a breadboard??

Or is there some other good secret simple way to use them??

Thanks!!
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