Don't ad-block us - support your favorite websites. We have safe, unobstrusive, robotics related ads that you actually want to see - see here for more.
0 Members and 1 Guest are viewing this topic.
regulating power to servos is a big no no
a 7806 can withstand 1.5 ma current
I was shifting through some old junk yesterday, and came across a 9.6v rechargeable battery pack.
A regulator that can handle the servo current draw during a stall, with a decent capacitor across the regulated power supply for surges should be fine.
QuoteRegulating Voltage to a ServoAs you should already know, servos have a voltage rating. Go above that voltage and your servo overheats and possibly fries. So suppose you have a 7.2V battery and you want to use a 5V regulator to power your servos, is that a good idea?Short answer: No!Longer answer . . . it will work, but its a huge waste of battery power.So lets say you have your 7.2V regulated to 5V and the servos draw a total of 1.5A of current.Wasted power is:(7.2V-5V)*1.5A = 3.3WPercentage wise, its(7.2V-5V)/7.2V = 30.6%Thats the battery energy percentage wasted to thermal heat - almost 1/3rd!!!Speaking of heat, your voltage regulator probably has thermal shutdown, meaning that if it overheats it will throttle down current to your servos - meaning your servos will have lower torque and lower speed. If your voltage regulator doesn't have thermal shutdown, it will just fry instead (not a good thing).But if you still really really need to regulate for servos, get a switching regulator (like ~83% efficiency on average).
Regulating Voltage to a ServoAs you should already know, servos have a voltage rating. Go above that voltage and your servo overheats and possibly fries. So suppose you have a 7.2V battery and you want to use a 5V regulator to power your servos, is that a good idea?Short answer: No!Longer answer . . . it will work, but its a huge waste of battery power.So lets say you have your 7.2V regulated to 5V and the servos draw a total of 1.5A of current.Wasted power is:(7.2V-5V)*1.5A = 3.3WPercentage wise, its(7.2V-5V)/7.2V = 30.6%Thats the battery energy percentage wasted to thermal heat - almost 1/3rd!!!Speaking of heat, your voltage regulator probably has thermal shutdown, meaning that if it overheats it will throttle down current to your servos - meaning your servos will have lower torque and lower speed. If your voltage regulator doesn't have thermal shutdown, it will just fry instead (not a good thing).But if you still really really need to regulate for servos, get a switching regulator (like ~83% efficiency on average).
only pulling around 300ma per servo under normal use, 600ma at stall.
yes its 1.5 A , power wastage was always a issue but what can one do , the servos can withstand max 8v actually but for safety it is rated at 6v so without the regulator , we can say the servo bye bye
Two servos through a regulator rated for 1.5a should not put the regulator into thermal shutdown (assuming it has a thermal threshold built in that is), as you are only pulling around 300ma per servo under normal use, 600ma at stall. Granted if your servos stay at stall you might have problems, but if your servos are in a stall condition that long you have other problems anyway. So thermal shutdown is not an issue.Energy waste is a concern, but you waste energy whenever you put a regulator into a circuit, even for your mcu power. In an ideal world a battery that is rated at 5V would stay at 5V from full charge to discharge, but seeing as that isn't the case, we dump in 6V or 7.2V packs to power the 5V mcu, wasting energy across a regulator.At this level (meaning the hobby entry level robotics), you aren't concerned with the energy efficiency needed to get through a darpa grande challenge track on battery power alone, so you really only have one concern with running stuff of a regulator besides an mcu, and that is amperage rating. Which in this case in not really a factor given the regulator mentioned by superchiku and it driving only two (I would assume) standard servos.So that leaves me with one good reason to say "you can use a regulator to drop voltage to drive your servos." If you have a batterypack laying around, and you want to keep the $50 robot a 50 dollar robot by not having to purchase batteries, but instead a $1.50 regulator then it seems like a good choice.
thats why i said use a switching regulator. very little is wasted to heat. no matter what imput voltage
switching regulators will be hard to find.. i hope digikey has it.
national doesnt ship free for single users , its not worth paying 60 $ for shipping a 2$ chip
