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My first robot

xarxexxarxex Posts: 3
edited 2009-05-20 22:36 in Robotics
Hi!

I'm building my first robot with the propeller chip, but I've only got access to a couple of 6v DC motors, which obviously won't run on just the voltage of a high pin-out.

I've been trying to boost my voltage with a couple of transistors and an outside voltage source to get my motors running. However, I've burned a few transistors on my way.

I'm wondering if someone can help me with a circuit to boost my pin-out voltage to the 6v i need, using 2 transistors per motor (Got the motors running, but only for a short while).

The transistor type I've got is C945P NPN, and there is no time to order new ones.

Comments

  • edited 2009-05-20 22:05
    Normally most of the applications that I know about, people are using servo motors that work on the idea
    of sending pulses to the motors or a specific length.

    That gives the greater control that is needed for many robotics applications.

    I hope that this helps, I know you want to use the current motors that you have but maybe at some point,
    a change of motors would be helpful?

    Anyway good luck with your first robot. I am thinking about building my first propeller based robot so I will follow
    your posts because many of the same questions will be ask by both of us.

    Here are the ones that I have had pretty good luck with, them and the tank treads make for a pretty spiffy looking]
    robot, but what I found out was that after just a short while the 2K memory capacity of the basic stamp was just not
    enough, so now I am in the market for my second stamp, and looking real hard at the spin stamp.

    Here is a link to some motors that run pretty well with my last set up.
    www.parallax.com/Store/Accessories/MotorServos/tabid/163/CategoryID/57/List/0/Level/a/ProductID/102/Default.aspx?SortField=ProductName%2cProductName
  • xarxexxarxex Posts: 3
    edited 2009-05-20 22:06
    Problem is I'm restricted to the DC motors I have. I won't be buying servos for this specific project.
  • Mike GreenMike Green Posts: 23,101
    edited 2009-05-20 22:13
    xarxex,
    Go to the main Parallax webpage and click on the Resources tab. You'll see a link to Nuts and Volts Columns. Click on that and you'll get to the Nuts and Volts Columns index. Download and read Column #6. This has a variety of suggestions for controlling motors with a Stamp. The same circuits and ideas work for the Propeller as well. The main difference is that you need a smaller base resistor for any transistor. Use Ohms Law (Voltage = Current x Resistance). Usually the current for a Propeller output would be 0.01A to 0.02A and the voltage would be about 2.7V (3.3V - 0.6V for the base-emitter diode) or somewhere between 150 Ohms to 270 Ohms. You absolutely need the diode across the motor as shown on the last page of the column.
  • xarxexxarxex Posts: 3
    edited 2009-05-20 22:36
    Eric at Sac State;

    Thank you, that document got me going by just flushing through the text.
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