Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: Conscripted on April 13, 2008, 08:17:01 PM
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Hello all. I'm going over the things I have for the 50 dollar robot. I've got a couple of 11.1v li-poly batteries that I'd like to use for this project. This is almost double the voltage of the ones in the tutorial. What issues is this going to cause me? What are my options? Can I just run everything through the voltage regulator?
Thanks
Bill
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you can use the 11.1v battery but since it's going through a voltage regulator at 5v 6.1v of the battery will be turned into heat and just waist the battery
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The voltage regulator will take care of dropping the 11.1V down to the 5V needed for the microcontroller (although I don't know what regulator is used in the circuit, so look at the datasheet to be sure). The problem you will have is for the servos, depending on their voltage rating. You don't want to run the servos off the microcontroller power supply because you will run the risk of causing the mcu to reset each time a servo starts up from the initial power draw, if the servo backfeeds any current when it is stopped or reversed you run the risk of burning out your mcu, and (without looking back at the tutorial) I am pretty certain the voltage regulator used in the circuit can not handle the current draw needed for two servos.
You can either get servos rated for 12V, which you might already have, or create a seperate powersupply circuit using a higher amp rated and higher voltage output regulator. Either way, seperate battery is adviseable.
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The voltage regulator I have is an nte960. I also have in my collection a 7805. Should I use both? One for the servo's and one for the MCU?I don't have a 6v battery pack. I guess i could go with the AA and 9v option but I don't think it will look as nice. How much current does a servo take? I've looked around a little but haven't found any specs on them. As an alternative I have one of these (http://www.barello.net/ANT/ant1.0/index.htm). Would that allow me to drive dc motors like a servo? I know it works with an r/c system. Should be the same right?
Bill
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I think the 7805 has a 1amp max current so you can use that for your electronics (mcu, etc). The nte960 has a peak current of 2.2A. Depending on the servos you are using, that might work. For instance, the Hitec HS-311 has a stall current of 800mA, so with two of them you are still under the peak in a stall condition.
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Thanks for the replies. The servos I'll be using is the Futaba s148. I've been looking for the current rating on them but have only been able to find the idle current. Where did you find that information about the hitec servo's?
Bill
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the hitec website?
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Here's a chart I found for different servos and their current draw. The chart is at the bottom of the page.
http://www.fly-imaa.org/imaa/hfarticles/electro/v11-4-44.html
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http://www.societyofrobots.com/actuators_servos.shtml#regulate
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7805 can give max of 1.5 A not 1 A so it would be enough for any servo or motor , you can use the battery but power wastage will be high so i reccomend using 2 12v motors instead..
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check the $50 robot 9.6v thread
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check the $50 robot 9.6v thread
yea this question has been asked a lot
anyone want to make a tutorial about switching regulators? ;)
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i just might have to.
later when i get some free time.
all these projects are killing me
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switching regulators are needed , need tutorial soon