Making a machine that draws like a Seismograph/polygraph

Hi

I am a design student, and I need to make a mockup of a sort of Seismograph/polygraph machine. I need to build the mechanism that can draw a simple graph like what is seen in a lie detector(polygraph)/seismograph, on paper.

I bought the Arduino starter kit yesterday, and I am guessing that the servo motor included could function as the arm that draws, being programmed to take random positions going left and right.

I would also need a motor to run the roll of paper. As I have understood, the AC motor included can not run very slow. So I would need a step motor and shield right?

I am entirely new to Arduino, and does not have much experience with coding. Is it possible to get help with coding here, or to hire someone to do it possibly?

Thanks in advance.

-Anders, Denmark

The servo(s) can work as the pen arms, no problems here. For the paper feed you can use a stepper or you could use a gear motor with a high gear ratio

Thank you for your fast reply. I think i will go buy a stepper as well then, so I am sure that i have all the parts needed. A shield is mandatory to get the stepper to work with the arduino right?

Don't rush out and buy a stepper.

I reckon a continuous rotation servo would work very well and would be much easier to install and control. You can failry easily convert a servo to continuous rotation, or you buy them already converted.

Only go for a stepper if you need the precision that it provides. As well as the cost of a stepper motor you will need to buy a stepper motor driver board. And you will also need to buy some sort of driver board for a DC motor. With a servo, the driver is already inside the package.

...R

As well as the parts already mentioned, you will need a power supply that is capable of supplying the current and voltage that the motors require. Servos, like the one you have, run well on 5V and could require an amp or better to move a load's mass. The Arduino 5V or USB probably does not have the current capability that is needed.

Today I went out and bought these:

A Motor Drive shield L293D, and a stepper motor: http://www.mitsumi.co.jp/latest/Catalog/pdf/motor_m35sp_11nk_e.pdf

The motor runs according to the manual:
Rated Voltage
DC 12V
DC 24V
Working Voltage
DC 10.8~13.2V
DC 21.6~26.4V

So does this mean i will need an additional power supply?

Is the motor shield i bought much worse than the Adafruit etc.? http://www.adafruit.com/product/1438
Unfortunately my local store only had the other one in stock - as i understand it, it is a big advantage that you can connect an additional power supply to the shield itself, to avoid overheating?

Thanks!

yes you can use a old pc power supply ,, ;D
why use bigg stepper for a seismo ?? for paper feeding ?
servo can react fast and i think better for a arm to react on things ,,
butt a stepper is maybe more precise
but yes you need a power supply

sometime the shield powers the board , be aware of this not over voltage it ,,
there wil be a diode there then maybe separate for use external power for arduino and the stepper shield ,

i see 300mA(PEAK) motor LOL
i think you can run this without a shield ,, butt you need 10 v at least
so a small adaptor 12v 500mah wil be ok ,,
i do not recomend this shield ,,

andersaa:
Today I went out and bought these:

I think you are rushing ahead of yourself here.

The datasheet for those motors says the coil resistance is 25 Ohms and the Peak current is either 200 or 300 mA. For some reason it does not list the max continuous current which you would expect to be lower.

Using Ohms law 5v = 25 Ohms * 0.2 amps.

If you feed 12v or 24v into that motor using an L293 the smoke will escape. If you only use 5v the performance will be very poor.

That motor needs a proper stepper motor driver such as a Pololu A4988 or an Easydriver. See this Thread for more info. This is why I suggested that a continuous rotation servo might make more sense.

...R

You might also find an old tractor feed printer in a thrift store and repurpose it.