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Author Topic: Need Advice  (Read 1846 times)

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Offline robojohnTopic starter

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Need Advice
« on: December 09, 2009, 11:33:21 PM »
Can someone advise me as to what kind of moters are used in 3 1/2 in floppy and how i can identify the wires.
?? PLEASE.

Offline waltr

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Re: Need Advice
« Reply #1 on: December 10, 2009, 07:19:09 AM »
If my memory serves correctly, the last time I looked they used a stepper motor to move the head and a 3-phase DC motor to spin the disk.

Do you have an opened floppy drive to look at?
If so can you describe the motor or post a picture?


Offline Soeren

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Re: Need Advice
« Reply #2 on: December 10, 2009, 09:30:59 AM »
Hi,

I'll second that, apart from the "3-phase" in front of the "DC motor", which is an oxymoron ;D

Btw. A head stepper from a 3.5" floppy drives can be used as rotary pulser (or a miniature generator), only the axle needs to pushed in by some arrangement.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline waltr

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Re: Need Advice
« Reply #3 on: December 10, 2009, 10:06:05 AM »
Yep, you are correct. I believe the proper term is "Three-phase brushless motor".

Offline robojohnTopic starter

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Re: Need Advice
« Reply #4 on: December 11, 2009, 10:12:54 PM »
Sorry Guys, As i,m new to all this i,m not really familiar with most of the jargon.

I am referring to the small motor that drives the R/R head. Mounted at the rear with a slide axle. Has 4 wires
" Red | White | Yellow | Blue".

The other motor has a 4 wire strip with no colors.

I want to use them to rotate a small servailance camera. But how to I'D the wires and drive it via computer.

I,v read some of the tutorials but there all full of jargon that only those experienced would understand.  ???
   

Offline waltr

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Re: Need Advice
« Reply #5 on: December 11, 2009, 10:45:20 PM »
The on moving the R/W head is a Bi-polar stepper motor. Google the term for lots of info on have they work and how to drive them.
The four leads are connected to two (really four but each pair are in series) coils. An Ohmmeter will sort out which wire pairs are connected.

I'm not sure of the motor with 4 non-colored leads. Can you describe what it looks like and what its used for?
Pictures would be great.

Offline Soeren

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Re: Need Advice
« Reply #6 on: December 12, 2009, 05:35:05 AM »
Hi,


Usually, the tiny stepper (R/W head) motor (the one with the long "spiral" axle) has got a flat strip with the wires etched in flexible PCB and the wired one is usually the drive motor.

I'll second the "snap a photo" notion.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline robojohnTopic starter

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Re: Need Advice
« Reply #7 on: December 12, 2009, 10:55:51 PM »
Thanks for your help guys.

I,v since come across a helpfull tutorial that explains it in laymans term which is what i needed.

You,s are correct on all counts. Bipolar stepper motor. The second motor is the same with flexible pcb wireing as described.

As i wish to control them directly via a pc would i need a microcontroller and motor driver or is a motor driver sufficient.  ???

Offline waltr

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Re: Need Advice
« Reply #8 on: December 13, 2009, 08:07:38 AM »
Now that you know what kind of motors they are look for circuits to drive them. There are a number of ICs that have most of the functions in them and would allow you to interface to a PC. Here is one such solution:
http://www.sparkfun.com/commerce/product_info.php?products_id=9402

The EasyDriver only requires a couple of line to control the Motor. These could come from a PC's parallel print port or the control lines on one of the seriel com ports (with level shifters).
This is just one example.

Do experiment with parts salvaged from old equipment.

Offline robojohnTopic starter

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Re: Need Advice
« Reply #9 on: December 13, 2009, 09:43:48 PM »
Unfortunately that link is temporarily of line.

However my thoughts where to use a H bridge such as the L297
Or To buy one pre built such as this one

    SFE easyDriver Bipolar Stepper Motor Driver $14.95 US
    http://www.robotshop.ca/sfe-easydriver-bipolar-stepper-motor-driver.html

Amazing of all the drivers. !You recommended the same one i was cosidering.

But i,m not sure if i can connect directly to a serial port.  What are level shifters??  Please explain.

I have lots of old drives and printers i can salvage motors and mechanical parts from. But how to salvage
the motor drivers ect. wouldn,t that be the holy grail.

Offline waltr

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Re: Need Advice
« Reply #10 on: December 14, 2009, 08:52:46 AM »
A little background: a PC serial COM port is RS232 protocol. Among other things it specifies signal voltage of +10V to -10V (approx). The Easydriver logic inputs require a 0 to 5V TTL level signal. Therefore the voltages from a COM port need to be shifter in their voltage levels from +10 to 0V and -10 to +5V (the logic is also reversed on RS232).
SparkeFun (site is currently down for upgrades) and others also carry level shifters. Some use a chip like the MAX232 (and newer chips) others use a couple of transistors. Check the tutorials here on SoR for more info (look for the serial port tutorials on interfacing the COM port to microcontrollers).
Next dig into the comm port interface to the OS on your PC. There are ways to set and read the COM port control lines (look up the RS232 protocol) such as CTS, RTS, DTR, DSR. You would not be using the 'serial' lines of the COM port only the control lines.

I've never looked hard for the motor drivers in old disk drives. They are there but may in integrated into a chip that does much more (like keeping track of the head placement, etc) so they may not be useful. Since the drives are trash it is worth while to trace the motor leads on the PCB to a chip then try to find a data sheet on that chip.


Offline Soeren

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Re: Need Advice
« Reply #11 on: December 14, 2009, 10:41:15 AM »
Hi,

A little background: a PC serial COM port is RS232 protocol. Among other things it specifies signal voltage of +10V to -10V (approx).
The "RS-232" which is correctly named EIA/TIA-232F (the F is the revision "number"), but you can still see people calling it RS-232C).
The voltage levels are specified with an open loop voltage of +/-25V, a transmission voltage of +/-12V..15V and a received side minimum of +/-3V.

That aside... The PCB in the floppy drive will contain the needed hardware, so it could be hacked to make a "free" interface.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline robojohnTopic starter

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Re: Need Advice
« Reply #12 on: December 21, 2009, 07:38:44 AM »
Hi

Apologies for my delay in replying.

I have read many of the tutorials, looked up other sources and learned quite a bit in regards to RS232 standards
level shifters, motor drivers, ect, ect.

But here is where i,m having difficulty.

RS232 has two lines for data transmission TX Transmit & RX Recieve which leaves only one line for Transmitting data.
Bipolar motor driver H bridges have 4 input lines for controlling the coils.

So how do i interface the RS232 Level Shifter with the motor Driver??

Do i need to use a microcontroller in between??  If so how would i control it directly from pc software without having to also program the microcontroller??

Also the $50.00 robot connects a serial cable directly to the microcontroller without using a max232 Or Level shifter.
More Confussion.

Offline waltr

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Re: Need Advice
« Reply #13 on: December 21, 2009, 08:09:51 AM »
RS232 or Asynchronous serial sends and receives data on the TX and RX lines, bi-directional data.
The L297 and most other motor driver chips are not designed to directly interface with serial data. In most cases a micro-controller is needed to receive the serial data and then set the appropriate motor control lines. Motor speed can be send serially to the controller which also times the PWM pules to the motor controller.

Now, most RS232 also have a number of 'control' lines such as CTS, RST, DTR, etc (look up the spec). So from your PC you could use these as parallel output/input lines but you will need to write low level code to access the COM port's UART.
Another way to use a PC is through the parallel printer port (LPT). Again your will need to write code to control the output lines on this port. This was a common method back in the 1980's the control home made devices.  Both are easiest if the PC is running DOS and not WINDOWS.


Offline robojohnTopic starter

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Re: Need Advice
« Reply #14 on: December 27, 2009, 08:06:47 AM »
Hi

Quote
The L297 and most other motor driver chips are not designed to directly interface with serial data. In most cases a micro-controller is needed to receive the serial data and then set the appropriate motor control lines

I have had some modest experience in programming with C & a little with C++ and i feel confident that i can write the routines needed to access the com port. but programming a microcontroller is a whole new world to me
which is why i am looking for a way to interface it without a microcontroller. 

Quote
Now, most RS232 also have a number of 'control' lines such as CTS, RST, DTR, etc

I was only thinking of the RX/TX lines, but this has given me an idea based on some of the circutes i have come
across in some of these SOR tutorials.

I will get it back to you to see what you think (If your interested that is). Just as soon as i work out the details.

 


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