Install operating system for the CPU control temporary stop :(
2007 07 Jan

Now that the robot’s PC is operational I’ve decided to start with the H-Bridge hardware to drive DC motors that is controlled by PWM (Pulse Width Modulation) signal. Still need to make the interface between H-Bridge and PC, but at least I can check first if everything is going has it should. And I’m glad i did!

It seems that the extra battery that I’ve installed to drive the motors (6VDC 4.5Ah) is not working properly with the H-Bridge that I’ve implemented from H-Bridge Circuit.

botdream interface
(I’ve used this circuit because is simple to implement, cheap and controlled by Pulse Width Modulation signal, quite easy to control when using Microchip PIC)

This bridge uses Darlingtons transistors and will have some losses between 2 to 4VDC at maximum current. Since DC motors need 6VDC and my battery is 6VDC less 4VDCmax from circuit losses, I can’t use this circuit to drive the motors. I need to use MOSFET based H-Bridge …Scratching my head …. hum! OK, I got it!

Well, since my robot is already overload with to much weight I’ve decided to remove the DC motors dedicated battery 6VDC 4.5Ah and connect the Darlingtons H-Bridge to the main battery 12VDC 7Ah to see how it handles! I’ve made some tests by increasing a PWM pulse to control power for the DC motors to check for voltage / current / temperature limits of both circuit and motors.

Perfect! The motors are almost at their limits due to the excessive weight, but they seem to handle it well. The H-Bridge is also working nice and cool. For now I will keep this H-Bridge but leave a note to use MOSFET H-Bridge in the future connected to a separated power supply. This also will reduce the time that the PC can stay connected, because I’m now draining power from the main battery.

I have already 1st H-Bridge circuit completed but still need to finish the 2nd.

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