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Topic: TowerPro 9g servo + P2N2222AG transistor (Read 2 times) previous topic - next topic

kf2qd



Thanks.  So, basically you should usually set the signal first, then turn on power.  This application involves 100-2000 servos, of which only about 5% are in use at any point in time.  So really my issue is power - I don't have enough power to control them all at once, so when I go "attach all servos; set all servo angles to init angle; power on all servos" they all just get stuck because none have enough power to move.

I'm initially just doing about 80 servos, so if I just got a bigger power supply then I could go with your suggestion and avoid the transistors.  The power supply I have at the moment is 1A, which can move about 20 at once, so 10A should cover it easily.  Might do that for the moment thanks.


Sounds like you need to look into multiple power supplies. I am assuming that these servos are distributed around some structure and multiple supplies would make for more reliability.

kaploink




Thanks.  So, basically you should usually set the signal first, then turn on power.  This application involves 100-2000 servos, of which only about 5% are in use at any point in time.  So really my issue is power - I don't have enough power to control them all at once, so when I go "attach all servos; set all servo angles to init angle; power on all servos" they all just get stuck because none have enough power to move.

I'm initially just doing about 80 servos, so if I just got a bigger power supply then I could go with your suggestion and avoid the transistors.  The power supply I have at the moment is 1A, which can move about 20 at once, so 10A should cover it easily.  Might do that for the moment thanks.


Sounds like you need to look into multiple power supplies. I am assuming that these servos are distributed around some structure and multiple supplies would make for more reliability.


You mean one 1A power supply per 20 servos?  For the 2000-servo version that seems expensive (even compared to the cost of the servos).

For full scale - still need to find a way to avoid idle servo power usage, as for this application it'd be far higher than active servo usage (40x).  99% of the time all servos will be idle; 1% of the time 5% will be in use.  So idle power usage is 4mA * 2000 = 8A; average active is 200mA * 2000 * 1% * 5% = 200mA.

The active servos may be fairly randomly distributed, so can't power them in groups.

Yep they're all mounted to the same structure - can't say much more on the application as it's still top secret :smiley-zipper:

kaploink


For full scale - still need to find a way to avoid idle servo power usage, as for this application it'd be far higher than active servo usage (40x).  99% of the time all servos will be idle; 1% of the time 5% will be in use.  So idle power usage is 4mA * 2000 = 8A; average active is 200mA * 2000 * 1% * 5% = 200mA.


Oops, I missed something there - can address the "99% of the time all are idle" by just turning off all the power supplies for that period...  Hmm.   :smiley-roll:  So remaining average idle usage would be just 80mA, less than the 200mA active average.

Can the power supplies you're talking about easily be turned on/off with the arduino?

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