Electronics > Electronics

Anyone Use Power Saver Features?

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Has anyone ever tried to add power saver features to a robot? From what I understand, some motors (I'm mainly thinking about Servo Motors) tend to continue to draw power, even when they are not in use. So, why not just use a transistor or MOSFET, controlled by a microcontroller, to turn off the motor when not in use? It would decrease the reaction time of your bot, but it could greatly increase its battery life.

The same thing could be done for almost any part of the robot. For example, if it's moving forward, do you really have to have the collision sensors in the back of the bot on?

I seems simple to me, but I've never really heard much about it.

I think the reason it isnt common is A, most robots require everything to be on when they are used, and B, it just adds another level of complication to an already difficult task of building a robot . . .

Most often there are nearby power sources readily available so no need to save power.

Ive built like 20-30 robots and not one could afford to turn off a motor or sensor. I was once going to make one that went to self charge when its battery ran low, hence requiring me to turn off all non-essential stuff . . . but then I never got around to it . . .

But look into space robotics, like the mars rovers, they work off of solar cells so they require what you speak of . . .

If you are considering doing this, keep me updated, I am interested in stealing your ideas =P

I will probably do it my self. I think I will post the design for my robots legs latter today. I just wish I could actually start on it sooner ;(

I did a bit more research into the subject, and I think I found another way to save power. This time, it mainly has to do with a variable voltage regulator. I found this article, which basically shows you how to use them. It should be possible to use another MOSFET, controlled by a microcontroller, to switch between say 6v and 3v.

This can be useful if you just want your bot to mover slower, so you don't waist as much energy. Unfortunately, I have no idea how much power this can actually save since voltage regulators aren't 100% efficient, the motor efficiency is usually based on a curve, and the microcontroller will have to draw a bit more power to supply the 5v to the MOSFET.

Another disadvantage has to do with the added complexity of the circuit. Plus, you'll have to program your microcontroller to deal with the motor at those different speeds, which can almost double the size of your code, as well as use up a extra port on it.

Anyway, this coupled with the full on/off switch will give you a good bit of flexibility, but your looking at 3 ports (on/off, high v/low v, and signal to servo) just for one motor.

I recommend just not doing the power saving right now till you get the rest of the bot done. Keep your steps small.

You can always upgrade later  :P


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