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A few questions about schematic

by maverick99
Tags: schematic
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maverick99
#19
Nov6-05, 11:49 PM
P: 74
Quote Quote by berkeman
Sure, whatever. Real world verusus the lab.
Alright, cool. Thx for all the help. I will be sure to post results and pics once I finish it here within a month. That is, if I don't have anymore questions during that time
maverick99
#20
Nov7-05, 09:07 AM
P: 74
Well I'm back again. Since I have to order parts online, I have to wait a few days to work on the reciever/transmitter circuits. I figure I might as well make the stepper motor circuit while I have this free time. Could anyone supply me with a circuit in which I could do this?

The stepper motor is supposed to sweep 180 deg, back and forth. The first my professor gave me was the L298 Dual Full-Bridge Driver.
http://tinyurl.com/e42un

The other is the L297 Stepper Motor Controller.
http://tinyurl.com/bzokx

Edit: Here is the data sheet for the stepper motor
http://www.jameco.com/wcsstore/Jamec...dDS/213321.pdf
berkeman
#21
Nov7-05, 12:59 PM
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You're going to need at least a CPLD or a microcontroller to drive the stepper motor circuit & process the sonar returns. What is your strategy for that part of the circuit?
maverick99
#22
Nov7-05, 01:09 PM
P: 74
Quote Quote by berkeman
You're going to need at least a CPLD or a microcontroller to drive the stepper motor circuit & process the sonar returns. What is your strategy for that part of the circuit?
I plan on separating the two circuits. The stepper motor circuit will turn back and forth 180 degrees. Thats all it will do. I will have the transducers hooked up with long wires and mount them to something fairly sturdy to put on the motor to turn.
maverick99
#23
Nov8-05, 06:01 PM
P: 74
Could anyone supply me with a schematic for the stepper motor with the chips that I was given?
berkeman
#24
Nov8-05, 06:21 PM
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Quote Quote by maverick99
Could anyone supply me with a schematic for the stepper motor with the chips that I was given?
The link you supplied for the L297 has an Application Note link underneath it. It looks to be a pretty complete tutorial. Just click through your link and look for the Application Note link:

The other is the L297 Stepper Motor Controller.
http://tinyurl.com/bzokx
maverick99
#25
Nov8-05, 06:55 PM
P: 74
Quote Quote by berkeman
The link you supplied for the L297 has an Application Note link underneath it. It looks to be a pretty complete tutorial. Just click through your link and look for the Application Note link:
In that pdf files, what is the MCU?
berkeman
#26
Nov8-05, 07:02 PM
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Any general purpose microcontroller could be used. That's why I asked earlier in the thread what CPLD or uC you planned on using. You will need at least some logic to provide those control signals to the stepper driver. It would be a good idea to also have limit switches at the ends of your 180 degree travel, to help your uC do some sort of initialization routine after power up or other reset.

You can start off playing with the motor by just using switches to provide the input signals....
maverick99
#27
Nov8-05, 07:23 PM
P: 74
When testing the motor, do i need any current limiting components?
maverick99
#28
Nov9-05, 01:16 PM
P: 74
On the schematic that was given, what is the purpose of the 8 diodes? Would rectifier diodes work for the schematic?
berkeman
#29
Nov9-05, 01:38 PM
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Quote Quote by maverick99
On the schematic that was given, what is the purpose of the 8 diodes? Would rectifier diodes work for the schematic?
Look at the currents in figures 15 and 17 for your answer. Any diodes should work as long as they have adequate current and power ratings.
maverick99
#30
Nov9-05, 02:20 PM
P: 74
Alright cool, sounds good. I tested out the motor and got it working right with just a dip switch. I will need to program a chip to count the way i need it to, too. My question is, do i even need the l297 and l298 in the circuit? Couldn't I just simulate the dip switch counting with the programmable chip and have that going to the motor? If not, then what are the l297 and 298 doing in the circuit?
berkeman
#31
Nov9-05, 03:04 PM
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You could probably drive the correct waveforms from your uC into the power transistors that drive the motors -- might even get you extra credit in the project. You need to make the correct waveforms for the stepping and holding currents, but yeah, the uC could do that if you program it right.
Ouabache
#32
Nov16-05, 02:12 AM
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Quote Quote by maverick99
Why would I have to include a power source and voltage regulators on the final project assembly? Wouldn't it work fine if I just used the 5 Volt line from my power supply and used the other output for 9V?
If you did want to make a real world design as berkeman suggested, using a voltage regulator to step down a 9v supply to 5v is not hard. On the bench, you could determine how much current is drawn by your design and then decide if a 9v battery could work for the high supply..
Ouabache
#33
Nov16-05, 02:23 AM
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Quote Quote by maverick99
I plan on separating the two circuits. The stepper motor circuit will turn back and forth 180 degrees. Thats all it will do. I will have the transducers hooked up with long wires and mount them to something fairly sturdy to put on the motor to turn.
How will you mount the transducers so they will be turned by the stepper motor? Will transducers be on the same board as the rest of your circuit? I am trying to get a 3-dimensional idea of your final setup. Are you going to go with a circuit like the minibot one you posted at the end of #11 of this thread?
Ouabache
#34
Nov16-05, 07:56 PM
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How about the range of your Ultrasonic Design. The spec for the project is 25feet. Only one of the circuits referenced on this thread are rated for that distance.

SRF04 Ultra Sonic Ranger
max range is 3m (x 3.28 ft/meter) = 9.84 ft
Ultra Sonic Rangemeter
max range 3.6m (x 3.28 ft/meter) = 11.8ft
Sonar Ranging System for Minibot
max range 5-6ft
Ultra-Sonic Ranging Design
max range 10.7m (x 3.28) = 35 ft

If you did go with one of the other designs, is there a way to improve gain of the circuit?
Perhaps use more sensitive transducers?? (see below)
Scientific Technologies, Inc.
Sensors with range 25ft
NEMA6 Acu-trac
Sensors 8m (25ft)
maverick99
#35
Nov17-05, 04:41 PM
P: 74
I will most likely use the circuit that has a max range of 5-6 feet basically because I already ordered the parts for it. I will be building it tommorow so I will test it out to see how far I can get it to go. On a side note, I got my stepper motor working from the 2 chips that I was given. The question I have is how to get it to stop at 180 deg, because it just keeps going 360 deg over and over. I noticed that there is a clockwise/counterclockwise pin on it but it does absolutely nothing when I put it to Vcc or ground. Any thoughts?
Ouabache
#36
Nov17-05, 08:11 PM
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I'll just toss out some ideas as if I was in your design group and we were brain storming a bit.. I suspect you are using a microcontroller. How about programming it with a "lookup table" with each "binary input" equivalent to a "unit of angular displacement" (e.g. 1deg, 5deg.) Since you can count positive and negative numbers in binary, maybe you can use positive binary to translate 0 to +90deg and negative binary for -1 to -90 deg.

Berkeman had a suggestion of using limit switches at the ends of your 180 degrees of travel. I am guessing he means some sort of conductive pin to catch the rotor at the endpoints. With a conductive pin, it could trigger a switch (limit switch) to let your microcontroller know (closed circuit = voltage or logic level), that it has reached a boundary. If you used limit switches, all you would need is a counter to increment (step the motor), then when it reaches a limit switch, the counter could change to decrement, then when it reaches next switch, change to increment again, and so on..

I am wondering how you will mount your transducers & stepper motor (see my post #33 this thread). I am trying to get a 3-dimensional image of your setup..


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