I'm doing a project where I want to have a servo on 24 hours a day and I was going to buy a real powerful servo that might draw between 5 and 6 amps. I want to use an Arduino Uno
I searched through the forum a bit and I think I know how to do this, but have some questions.What I think is that I should get an external power supply and connect the power to the Vin input on the Uno and to the red lead off the servo. The ground from the power supply to the ground of the Uno and the black lead of the servo, and pin 9 (assuming I'm using the sweep example code) of the Uno to the Yellow (or whatever color) of the servo.
If all of the above is correct here is my question. What do you recommend for a power supply? I found this at Adafruit:
Which has 5V DC and up to 10 amps. If I used it would I cut the cable coming out of it and separate the power and ground wires and use those? Is there a better item to purchase where I could just plug wires into it without cutting anything? If any one has recommendations on a product I would love to hear them.
It looks like a solid power supply. The big drawback is that it's 5v, so you can't power the arduino via VIN. You'll have to connect it to the 5v pin which is usually discouraged. You may want to test it a bit and make sure it's really a solid 5v output, but it'll certainly get the job done as long as the voltage doesn't go above 5v. It's a switching supply, so it'll probably even stay cool while powering the servo. As for not wanting to cut the cable, you could always get a different connector that matches the one on the servo to stick on the end if it makes you nervous. Be careful, though, and make sure that any connector you use is rated for more than 10A just in case.
Which servo? Are you sure about its max current draw? Worth checking I think - measure
the motor winding resistance to determine the max stall current (which ought to be about 0.8
ohm for 6A at 5V).
For high current connectors the ones used for RC purposes on LiPo batteries and
so forth are cheap and compact.
I haven't purchased the servo yet, but was maybe going to try a Hitech hsb-9380 which is supposed to be very stable, lots of torque, well made and will probably (hopefully) last a few years. It requires 5-6 amps.
MarkT I will look into LiPo batteries. If anyone has any specific product recommendations I would love to hear them. It seems like this would be a common thing to do with an arduino and a servo, but I haven't been able to find a specific commercially available product. The Arduino Servo shields I've seen don't put out 6 Amps.
I think MarkT was suggesting the connectors normally used between lipo batteries and those servos, not the batteries themselves. They're rugged, don't come apart easily, and rated for high current.
On a side note, I just came across this thread when looking for info on that servo:
In post #10, Mike Mayberry claims to have hung a 10lb weight from the servo and found it's current draw to be only 0.23A. According to him, the stall current was just 1A. So you might not need nearly as much power as you initially suspected. That might be worth looking into further before buying the power supply.
Well that servo will generate 20+W of power at full speed (7 rad/s) and stall torque (3.3Nm), so
I think it can pull several amps happily. However it has regenerative braking so it can also pump
that back at the supply - I would recommend using a battery if you want to make use of
this feature. They recommend the "PAD" device if not to prevent the supply rail jumping.