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Topic: Need some help with a circuit (Read 3 times) previous topic - next topic

01i

#5
Nov 10, 2010, 07:19 pm Last Edit: Nov 10, 2010, 07:22 pm by 01i Reason: 1
This is what the circuit actually needs to do

3 x Arduino pins connect shift controllers 1 and 2.

Shift controllers connect to 4 H-Bridge Motor Drivers and also to GND through a 560 ohm resister (as per Dave Auld's circuit diagram linked earlier)

Motor Driver 1 connects to two small toy DC motors
Motor Driver 2 connects to two small toy DC motors
Motor Driver 3 connects to a 2 phase 0.90 degree unipolar/bipolar stepper motor
Motor Driver 4 connects to a 2 phase 18 degree unipolar/bipolar stepper motor

Toy DC motors control the basic movements of a maplin robot arm.

As per Christian Liljedahl's 'Simple Rotary Encoder with Arduino' guide

http://christian.liljedahl.dk/guides/simple-rotary-encoder

I'd want to add a 10-20k resister to one of the inputs to enable me to get a very basic understanding of how far the motors have moved.

The 0.90 degree stepper motor should operate in half (or even quarter) step mode, and controls the slow movement of the laser scanner

The 18 degree stepper motor should operate in full step mode, and rotates a turntable 360 degrees in 10 stages of 36 degrees

No connections are required for the laser, which has its own housing, circuit and battery.

The robot arm itself, can hold 4x D Cell batteries to power motors, although I'd ideally want to power via the Arduino's USB connection or a direct connection to the mains.

I also noticed that in Larry's robot arm hack, the motor controllers do not have connections to their enable pins. I'm not sure if that needs to be corrected

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4 x MINIATURE DC MOTOR

Based on searching through Farnell, the motor is the same dimensions as their two cheapest motors, and smaller than the cheapest '3.0V to X' motors. The motors themselves contain no marking to help identify the exact specs.

MOTOR, MINIATURE, 1.5-3.0V
MOTOR, MINIATURE, 1.5-4.5V


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1 x NANOTEC - ST4209S1006-B - STEPPER MOTOR, 0.9DEG, 2 PHASE

http://uk.farnell.com/nanotec/st4209s1006-b/stepper-motor-0-9deg-2-phase/dp/4743143
http://www.farnell.com/datasheets/20218.pdf (German)

* STEPPER MOTOR, 0.9DEG, 2 PHASE
* Coil Type:Unipolar / Bipolar
* Torque Max:15N-cm
* Current Rating:950mA
* No. of Phases:2
* Resistance:4.2ohm
* Inductance:4mH
* Rotor Inertia:35g-cm²
* Current DC Max:0.67A
* Current per Phase:0.67A
* External Length / Height:33.5mm
* Indexing Angle:0.9°
* Weight:0.22kg

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1 x NANOTEC - SP1518M0204-A - STEPPER MOTOR, 18DEG

http://uk.farnell.com/nanotec/sp1518m0204-a/stepper-motor-18deg/dp/4743192?Ntt=SP1518M0204-A
http://www.farnell.com/datasheets/59159.pdf (German)

* Coil Type:Unipolar / Bipolar
* Torque Max:0.35N-cm
* Current Rating:180mA
* No. of Phases:2
* Resistance:50ohm
* Inductance:9mH
* Rotor Inertia:1g-cm²
* Current DC Max:0.24A
* External Diameter:15mm
* Holding Torque:0.0035N-m
* Indexing Angle:18°
* Weight:0.01kg

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4 x TEXAS INSTRUMENTS - SN754410NEG4 - QUADRUPLE HALF-H DRIVER, 754410

http://uk.farnell.com/texas-instruments/sn754410neg4/quadruple-half-h-driver-754410/dp/9592997?Ntt=SN754410NEG4
http://www.farnell.com/datasheets/75370.pdf

* QUADRUPLE HALF-H DRIVER, 754410
* Motor Type:Half Bridge
* No. of Outputs:4
* Output Current:2A
* Output Voltage Fixed:39V
* Supply Voltage Range:4.5V to 36V
* Driver Case Style:DIP
* No. of Pins:16
* Operating Temperature Range:-40°C to +85°C
* SVHC:No SVHC (18-Jun-2010)
* Operating Temperature Max:85°C
* Package / Case:DIP
* Temperature Operating Min:-40°C
* Base Number:754410
* Device Marking:SN754410NE
* Driver Type:Motor
* IC Generic Number:754410
* Logic Function Number:754410
* No. of Drivers:4
* Output Voltage Max:36V
* Supply Voltage Max:36V
* Supply Voltage Min:4.5V
* Termination Type:Through Hole
* Interface Type:
* Line / Bus Driver / Receiver / Transceiver Type:

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2 x TEXAS INSTRUMENTS - CD74HC595M - LOGIC, SHIFT REGISTER 8-BIT, 16SOIC

http://uk.farnell.com/texas-instruments/cd74hc595m/logic-shift-register-8-bit-16soic/dp/1753517
http://focus.ti.com/lit/ds/symlink/cd74hc595.pdf

* LOGIC, SHIFT REGISTER 8-BIT, 16SOIC
* Shift Register Function:Serial to Parallel
* Logic Type:Shift Register
* No. of Elements:1
* IC Output Type:Tri State
* Logic Case Style:SOIC
* No. of Pins:16
* Supply Voltage Range:2V to 6V
* Operating Temperature Range:-55°C to +125°C
* SVHC:No SVHC (18-Jun-2010)
* Package / Case:SOIC
* Frequency:42MHz
* Input Current Max:80µA
* Logic IC Base Number:74595
* Logic IC Family:HC
* Logic IC Function:8-Bit Shift Register with 3-State Output Registers
* Supply Voltage Max:6V
* Supply Voltage Min:2V
* Termination Type:SMD

cr0sh

Have you even bought one of these arms, yet?

If you have, then you would notice something really quickly: The motor gearbox housings form the structure of the robot arm; they are integral to the design.

Some of the steppers you propose to use are larger than the gearboxes housing the motors on the arm itself (the arm isn't that big). Heck, the shafts on some of the steppers are larger than some of the gears in the gearbox!

You already say you don't have an understanding of electronics; this project is -not- a beginners project. Nobody has yet even managed to implement position feedback on this arm using the motors as-is (a requirement for the system you propose). You may be on a route to frustration.

Lastly - what is this "scanner" system supposed to do? Is using a multi-degree-of-freedom robot arm the best solution? If it is, and precision is needed, you are likely to find it better to purpose build the robot arm from scratch, and not try to convert something like this toy. If you must use something off-the-shelf, a commercial robot arm (while insanely expensive, even used) is going to be the better solution.

You need to, however, learn the basics of electronics, robotics, motor-control, feedback theory, etc - before attempting something this advanced. Otherwise you are going end up throwing a bunch of money and time at a project that is only going to end up frustrating you and your bank account...
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

01i

#7
Nov 10, 2010, 07:57 pm Last Edit: Nov 10, 2010, 08:08 pm by 01i Reason: 1
Cr0sh,

The scanner is using David Laserscanner software and calibration panels

I have the robot arm, and am keeping all motors in their housing except one, which will do the scan itself, and sit in a custom housing that replaces the gripper.

The other stepper motor is for a seperate turntable.

Mechanics, hardware modification and programming are not a problem, just perfection of the the circuit. I dont require huge amounts of info from the 4 basic motors, they are literally just to get close to the right position start position for the scanner from location readings previously taken.

I have already spent around £1000 on a cupcake cnc which can make my custom housing, £30 on the arm, and £350 on the laser scanner.

I now need to buy an Arduino, a large breadboard, the two motors and the circuit components. Buying an arduino and 4 motor sheilds is the alternative but with significantly more expense

TND

I bought this arm a while ago, also inspired by Larry's blog. But to reiterate what cr0sh said - serious position control with the arm in its standard, out-of-the-box configuration is almost impossible. In fact, I found out this year that my university bought this arm to see if they could do anything with w/regards to position control, and a few projects were done on it. The conclusion? The gear slip makes it almost impossible. If it is at all possible, it will require some serious, serious control techniques.

And you said it only has to be able to roughly (you should make sure you know your own definition of 'get close', by the way) reproduce locations... well you'll also have to find a way to make your control solution not let errors from gear slip become cumulative.

This is really not a beginners project.

And something I don't believe anyone's pointed out yet - when you were asked for a 'schematic', I think they were talking about a circuit diagram. Your breadboard layout is a kind of... abstract circuit diagram, I suppose, but as Grumpy_Mike pointed out, nobody's going to sit and decode that into a proper cct diagram for you, you need to do it yourself.

You've obviously invested a lot already, so good luck with it!
Tom

01i

I made a circuit style diagram first, thought the breadboard would be easier to read. I found some sources to improve it a bit.

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