So I have an Adafruit pca9685 controlling an HSB-9380TH servo and a MG-996R servo. I recently began learning about building robot so I apologize if these questions seem dumb. I literally spent a days trying to google for answers.

I have two 3.7V lithium ion batteries in series connected directly to the V+ and GND PCB terminal on my Adafruit. This should give me 7.4V directly.

So this setup works to control my MG-996R but my HSB-9380 isn't moving at all for some reason. I assume it's because the HSB-9380 is probably more power consuming I would expect. I can't get seem to get my HSB-9380 to work or even move. I suspect that li-on batteries are not strong enough to drive the HSB-9380TH and I need to switch to lipo batteries. The manual for my HSB-9380 says that the stall current is 2.3 Amps. Shouldn't lithium ion batteries be sufficient?

I'm running the MG-996R on 50z with a PWM range of 150-650. I tried running the HSB-9380TH on a range of 1100-1900 as well as on 150-650.

So I have a few questions. If you could answer the ones you know about, I would really appreciate it.

  1. Do you know why my HSB servo isn't working?

  2. How much current can a Lion battery output?

  3. Should I connect the battery directly to the Adafruit PCA-9380 or do I need to protect it with a resistor? Or do I need to connect the battery to a voltage regulator to the Adafruit PCA-9380?

  4. Can I connect a battery directly to the V+ and GND female connectors of a servo or would this fry my servo because there's no resistor preventing a short circuit? Would I need a voltage regulator or some other component in the middle?

  5. Is it safe to drive different servo motors off the Adafruit PCA-9380 or should I make sure they are all the same type?

  6. Is there a way to power the HSB-9380TH off lithium ion batteries. I prefer to use lithium ion because they can last longer than lipo.

  7. How much current can generic breadboard jumper cables transmit?

  • $\begingroup$ please ask one question $\endgroup$
    – jsotola
    Feb 10, 2019 at 17:28
  • $\begingroup$ you have included very little information that pertains to the actual problem .... we know which driver and servos you are using and what you are using for power ..... we know nothing about the controller, the program and the electrical connections between all of the devices .... for all we know, the components could still be in their cardboard boxes $\endgroup$
    – jsotola
    Feb 10, 2019 at 17:32
  • $\begingroup$ For #7, breadboarding wires are typically 0.6mm in diameter. That makes them about 22.5 gauge. Consulting a table tells us that these wires (assuming a single strand) will carry close to 5 Amps. $\endgroup$
    – Octopus
    Feb 12, 2019 at 20:13
  • $\begingroup$ Update: I got the HSB-9380TH to work by setting the PWM range to be 180-580. Apparantly the HSB-9380TH will ignore commands outside this range. I was using an Nvidia Xavier as the microprocessor. $\endgroup$
    – aztrorisk
    Feb 15, 2019 at 15:21

1 Answer 1

  1. Have you tried to connect the PAD supplied with the HSB servo the fifth picture on this page? It is not necessary but in the case that your battery is fully loaded it an cause an overload if you don't have a BMS in your circuit.
  2. This depends on the battery you are using. Usually they are given with a value in mAh which correspond to the maximum amount of mili-Ampere your battery can deliver during one hour. So if your system requires more than this capacity, the battery will last less than an hour and reciprocally if it requires less than this capacity, the battery will last more than an hour. This value is usually given on the battery datasheet.
  3. You should connect directly your power supply to the Adafruit PCA-9380 board as described in the schematics in the bottom of this page, but I would advise you to test each servomotor separately before testing all together (in case of failure you may not burn everything and you will be capable of isolating quickly a problem). A voltage regulator is advised in the case that your power supply is not very stable or if it delivers more Volts than the required ones, so you don't need it here!
  4. The first servo will requires the PAD mention in my answer of your point #1. The Adafruit board your are using does the following things: It is wiring the V+ and GND of your battery to the wires red and black of the servomotor. It links the GND of your battery with the one of your board sending the signal (usually yellow wire of your servomotor) to the servomotor. It converts the orders you are sending via the I2C protocol into PWM signals to each servomotor. You can do all of this with an Arduino board but it will requires that you directly use PWM pins instead of I2C ones (SLC and SDA), and a servomotor library to control it. So I think that it's easier for you to begin with the Adafruit PCA-9380 board! For the voltage regulator, see my answer #3, and no resistor is required at all!
  5. As long as they accept the same input power and are controlled by the same protocol (here it is a PWM signal) at the same power level (here I suppose that it is 5V...), it is safe to use the Adafruit board to control them!
  6. There is no limitations of the tech used inside the battery as long as you respect the maximum value of Volts that the servomotor can handle and that your battery contains the same amount or more in Amps to control it! Don't forget that your servomotor requires its PAD to be safe (see my answer #1)!
  7. See the comment of @Octopus below your question !

Have you also tried using a multimeter to check your circuit?


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