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Multiple power sources

glasoglaso Posts: 38
edited 2005-03-08 16:36 in Robotics
hello:

I'm building a robot but I need three power sources: 6v for the servos (via PSC), 9v for de BS2 and 12v for the motors (via Motor Mind C). Is there some way to use the 12v lead-acid battery as the power source for all the components. What components I need to generate three outputs (6v, 9v and 12v) from the battery without the risk of damaging either the BS2, the PSC, the MMC or even the servos.

I was thinking in voltage regulators, but I don't know how to use them.

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2005-03-08 14:38
    Linear voltage regulators are very simple to use. Put a capacitor on the input pin to filter the input ripple a little (batteries have NO ripple, but load changes may generate some noise), put a 10 uF capacitor on the output, connect the middle pin to ground, and you're good to go. As long as the input voltage is higher than (V_dropout + V_Out), you've got good clean power. Oh, and as long as the current through it is less than 1 amp. Oh, and as long as the power dissapated is not too high. But these conditions tend to be easy to take care of.

    The LM7805 has a V_Dropout of 2 volts, I believe. The LM2940-5 is a 'low-dropout' device -- 0.5 volts is V_Dropout.

    So, you can drive the MotorMind-C directly with the Lead-Acid voltage, put in a 6-volt regulator for the Servo's, and a separate 5-volt regulator for the BS2. The BS2 doesn't need 9-volts, you can supply 5-volts directly to the BS2 Vdd from an external regulator.

    Oh, and you can look at the BOE schematic for a simple Linear Regulator design.
  • glasoglaso Posts: 38
    edited 2005-03-08 15:50
    Thank you very much for your message Allan, it was very complete and clear. I have only one question: I have to use both outputs (12v and 6v) as if they were separate power sources? I mean that if I have to tie the ground of both output as if they were phisically different power sources?

    I will work on a diagram and I'll share it with you to receive your opinion.

    Thank you!!!
  • allanlane5allanlane5 Posts: 3,815
    edited 2005-03-08 16:36
    In general, there should be a single Ground for your project, which has all power-supply grounds tied to it. This insures that all voltages are referenced to the same Ground.
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