Let's Make Robots!

How do you manage the power to those devices? resistors? regulators?

Ok, some of you may notice this is relate to the quadbot I am building now. Those LED strip just an example, not really going to put it on my bot to make it low-cheap toy looking. As a begennier I really do confuse about these electronic stuff.

Here are the questions:

  1. There are spots 1. 2. 3. in picture(postive red wire). What should I use to manage the power from 11.1v battery? I know there are lots of resisters or regulators like 7805, 7809 etc. Which I should use to insure I don't burn anything here?
  2. How if 11.1V or 5200mAh 30C battery is too heavy for robot and I decide to use 7.4v or 2000mAh battery? Is there a formula that I can calculate what batter I should use?
  3. You may notice I have a switch in positive wire. Should I seprate into 2 or 3 switchs for each device? Should I have switch on positive or negative or doesn't matter?
  4. Some folks here told me each servo I have in picture probably take 1amp per each. Does that means I need to keep servo shield has 12amp current? Is that means if I have 4 servos are moving at same time and the rest of 8amp are going to each active servo which cause 1.2amp current running into active servos? or it still only draw 1amp? 
  5. Sorry if I don't describe clear enough in any where or bad English, I will try to make it clear as possible in the future post.

Yep! very beginner stuff but it really confused me how to make a proper power management. Thanks for anyone who could kindly point out these questions or links.

LMR!!

 


 

Servo Shield:
http://renbotics.com/products/servoshield.php

LED strip:
http://www.gadgettown.com/smd-led-strip-car-flexible-light-bar-line-green.html

Servo 485HB:
http://www.hitecrcd.com/products/analog/standard-sport/hs-485hb.html

Servo 645MG:
http://www.hitecrcd.com/products/analog/premium-sport/hs-645mg.html

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Ok, just to make things clear:

  1. Any microcontroller and sensors need 5V (or 3.3V) that batteries do not provide, so they MUST use a voltage regulator, but usually that is already provided on the board. So you don't need to add anything, just plug the batteries in the power connector of the microcontroller board. Jut make sure the voltage does not exceed the specifications for that board. For example, the Arduino can get power from 7.2V up to 12V. The SSC32 board works from 6V up to 12V.
  2. Servos DO NOT need a voltage regulator. They are designed to use unregulated voltage in the range of 4.8V...6V. You can overvoltage standard size servos (NOT the cheap small servos!) for a more powerful output, but you should not exceed 7.2V...7.4V. There are special (digital ) servos made for robotics that work with 12V, but they are expensive. The boards that have servo connectors usually have a special power connector for the servos. The Servo Shield has one, the SSC32 has 2. Plug the batteries in those power connectors and it will work.

Is it clearer now?

Nice and clear~ :)  

I can't wait for my shield and give it a try.

I would suggest to use the 7.4V battery, as the servos support that voltage, but not the 11.2V. This way you don't have to bother with a voltage regulator, as the servos draw over 12 amps and you won't find such powerful voltage regulator, or it will not be cheap. It's cheaper to add a battery dedicated for servos and a different one for the Arduino and sensors than to use a switching voltage regulator for the servos. So use the 7.4V battery for the whole robot, if the servos still jitter and the battery gets depleted fast, buy a bigger capacity battery at the same voltage.

So it would be couple batteries on the bot eh? That should make it easier.

Yes, I think I am just gonna stay with 7.4V should be good enough. But I wonder how did SSC-32 could handle that many servos? Any idea how did they do the magic? (I saw there are some chips and regulator on this board.)

In the diagram below it shows using of 2 kind of battery but I actually have my hexapod connect with one 7.4V battery and it still works fine. I heard someone told me 1V+- should works OK...?

Looking at the schematic here it shows that the SSC-32 doesn`t regulate the servo power at all. It takes raw battery voltage from the screw terminals VS1 and VS2 to power servos. Terminal VL is where logic power comes from which does have a regulator.

The idea behind seperating servo voltage from logic voltage is you can stop any noise that might affect the chips operation.

Thanks for explanation~ I guess this is one of the problem to my board now that noise affect the operation.

1.

Depends on current draw and required voltage of the parts. A very simple regulator is 1 zener diode and 1 resistor but this can only supply currents in the range of 100mA.

At position (1) your Arduino has its own regulator so you just need to feed 11.1V into the DC input jack on the board.

At position (2) I would put a high power switching regulator at 5-7V for servos.

At position (3) a power resistor of about 100 ohm should do.

2.

Essentially, the capacity of the battery you will need depends on how much current the whole system will draw multiplied by the number of hours you want it to run for.

3.

Some folks like putting a switch at point 2 as well. This way you can turn the micro on and test other systems without the servos activating or the robot walking away from you.

4.

That is just at stall. You could try looking for the stall or loaded current draw of your servos. It may be in their datasheets. Or you could measure it.

5.

Your english is fine.

Thank you for detail answers, very helpful :)

According to 4th question; the servo shield I am using has 2 x 4017 Decade Counter DIP16. Do you think they are good to handle the power I need for servos or I need to make or buy one for it? If so, any suggestion or link I can get the " power switching regulator" you mention above?

The info about the servo shield:http://renbotics.com/products/servoshield.php

The 4017 are there to allow control of many servos with fewer number of pins. They won`t affect the servos running voltage or be affected by the input voltage so you still need to sort that out.

Hum.....I see! I really learned every little thing everyday. When the day I complete, all you great people has credit in it. ;)