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| jarrin > Interests > Electronics > Motorized Armchair | |
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Milestone'd 5/21/2006 8:10 PM
After determining that the TIP102 transistors I had were insufficient for the task of driving a 24v 10a motor I ordered a handful of 2N6052/59 power transistors (in the durable TO-3 package). They're rated for plenty of amps but they also claim to be designed for "low frequency switching applications". Well, I intend on driving them with PWM at 20kHz. I hope that doesn't make their magic smoke come out. The first image here is eight of the power transistors on a prototype board. The four on the left will be for the left motor and the other four will be for... well, I think you get the idea. Since I'm only working on building one h-bridge right now I'm only going to work on half of the transistors. In the second image the power transistor board is upside down (on the right). Four 10k pull-up resistors have been soldered between the base and emitter pins of all transistors. Four 1k resistors connect the base pins of the power transistors to the various output pins of the first stage transistors. Additionally a couple of connectors have been soldered between common pins. the green cable go from the collector pins of the transistors to the motor. To
On the large breadboard on the left side is a PIC18F452 microcontroller. It's just running a simple little program that drives the motor in one direction at a variety of speeds (via PWM) then runs it in the other direction for a while. Eventually this mcu will do more elaborate work (converting the controls from a joystick into PWM commands for the motors). All in all I'm pleased. Now I need to focus more closely on the mechanical engineering side of things to actually mount this motor to a base and see how much load it can push. Arguably I should have done this first because I may need to scrap all the work I've done if I need to switch to a different motor. I suppose if I were any good at this I would have done that. Oh well. Next time! |
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