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Controlling A DC Motor

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8-17-04

I was surfing the net one day looking for information about object oriented programming. I had been programming a few applications with Visual Basic and was interested in knowing what other languages were available for that type of programming. I entered ‘OOP’ in search box on Google and, naturally, it pulled up a long list of items to browse. About half way down the page, it caught my eye; OOPic (see the site here). After reading the few short lines, my interest was piqued, so I clicked on the link. Being an electronic gizmo enthusiast, the device was the hobbyist’s dream!

The device used a Visual Basic like syntax and had virtual circuits that were linked together by the software! I quickly pulled out my credit card and purchased 2 of them online for $39 + $10 for the programming cable and the 9 volt battery clip. I also downloaded the manual and the software, which are free. After receiving them, I proceeded to setup my lab bench for a quick run around the block with the OOPIC.

The device has a PWM (pulse-width-modulator) that is programmable, so I quickly set it up as a DC motor controller. Within 30 minutes, I had the device controlling the speed of a small DC motor using a 5K potentiometer as the controlling device. The OOPIC has an analog to digital controller as well, which is where I connected the 5K pot. The OOPIC transforms the value of the pot into a scaled value in which I used that scaled value in the software to change the modulation of the PWM.

I used a power output circuit that I designed. The output circuit has a 714 operational amplifier and a complementary paired set of power transistors oriented in a push pull configuration. The transistors were made by Fairchild Semiconductor and are the TIP121 and TIP126 darlington type. The output of the 714 was tied to the bases of the darlingtons with a 333 ohm resistor pulling each base to the rails and in between there were, in series with the 333’s, 3 1N4001 diodes. The output of the 714 was tied to the TIP126, 333 ohm resistor (I will include a diagram when I get the tools to illustrate the schematic properly).

I have setup the OOPIC in several different configurations since that time (back in ’97) and there are many more cool ways to experiment with the OOPIC for the future. I can’t wait to get the chance to build more cool devices with OOPIC!

 If you visit the OOPIC website, there are several more new types of OOPIC’s that offer different options than the original that I have.

A picture of the OOPIC board.

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