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

01i

Hi,

I am intending to create an automated scanner using a hacked robot arm and the basic code written for Arduino by Lucky Larry (http://luckylarry.co.uk/arduino-projects/arduino-modifying-a-robot-arm/)

I need to modify the system slightly, so that I can improve the wrist motor into a 0.9 degree stepper (Nanotec ST4209S1006-B) and for the turntable an 18 degree stepper (SP1518M0204-A)

Adding the steppers means I'll need an extra H-Bridge (Texas Instruments SN754410NEG4) from the Larry circuit, and - I assume - a shift controller (Texas Instruments CD74HC595M)

I may include an LCD display eventually

I've made up a basic diagram of how I think the circuit ought to look, however I dont know enough about controlling power levels with resisters etc.

Could somebody help out by letting me know what I need to add to the circuit, or point me to an online circuit testing tool that I can design it with

Once complete I'll post design info, pics and code in here


Grumpy_Mike

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however I dont know enough about controlling power levels with resisters etc.

Not sure what you mean by this.
You can use a resistor to limit the current through a motor but that's about it. Mainly you would only use it when you are trying to use too high a voltage for the motor ratings. Otherwise you would use PWM to control the motor power and hence speed in a loaded motor.
See:-
http://www.thebox.myzen.co.uk/Workshop/Motors_1.html
http://www.thebox.myzen.co.uk/Workshop/Motors_2.html
and
http://www.thebox.myzen.co.uk/Tutorial/PWM.html

01i

I thought I'd pose the example a little clearer.

The following is a breadboard layout of my basic requirements. I am choosing to use three pins on the arduino, to power 4 DC toy motors and 2 stepper motors.

I have built a circuit that combines the use of 3 H-Bridge controllers to manage 5 DC toy motors in a robot arm from one source (luckylarry) and added in the shift controllers from another source (Dave Auld). I then added an additional H-Bridge to give me enough motor control.

x2 - Connects arduino pin 2 with the data pin on shift controller 1
x3 - Connect to the other x3 on controller 2, and arduino pin 3
x4 - Connect to the other x4 on controller 2, and arduino pin 3, I have also added a 560 ohm resister between this part of the circuit and GND

A - Connects the output on shift controller 1 to the data in on shift controller 2.

B to Q connect shift controllers to the input pins on the motor controllers.

Basically assuming that the two example circuits work, then my circuit should also work.

But if there are any other tweaks that could be added to make the circuit more reliable then I'd appreciate the advice.


Grumpy_Mike

Quote
I thought I'd pose the example a little clearer.

A schematic would really help, unfortunately what you posted is a physical layout diagram which is next to useless in seeing what the circuit actually does.
Quote
if there are any other tweaks that could be added to make the circuit more reliable

Look to add lots of decoupling to prevent noise resetting the arduino. Also add some diodes to stop motor back EMF.
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

01i

Mike,

I know nothing about circuits, other than the real basics.

I'm going to take a look at the link you just sent, and look into diodes too.

What exactly do you mean by a schematic? The voltages going through each part of the circuit? If so, that's what - think - I'm trying to work out.

Or do you mean information about operating voltages of the various components? If so, I have bookmarks to all of that information.

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