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Topic: Issue with 7809 1.5A Linear Voltage Regulator  (Read 442 times) previous topic - next topic


Hi Tom,

I'm viewing the voltage and current readings on the laboratory power supply. It's at 9V, and it jumps up to about 1.2A when the servo motors run. Sorry, I guess this isn't the exact layout, everything is actually connected to a single larger and better protoboard. I ran all of these motors with an Arduino program fine, and I was running it for several minutes.

The servo motors require more current than the stepper motors, seemingly. The stepper motors are each connected to an A4998 driver as shown in the image, which is why I have the logic voltage and ground connected to the Arduino. The A4998 drivers also have a current limiting knob. The power supply voltage and ground are not connected to the Arduino in any way.


I guess I should have also mentioned that I'm never running more than two motors at the same time with my programming code... It's always 1 or 2 motors at the time. And I didn't use capacitors with my 7809... whoops again. But I'm getting a buck converter from one of my professors to test out, so hopefully I can get it to work.


I have, in the past, used a design similar to the image. I have added in a diode to the ground pin of the 7805 to make up for the Vdrop of the transistor junction.. The diode will need to handle 1A. The transistor should be rated a bit higher then the Imax as well as the components feeding the transistor.

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