How to fix overheating

[Erebos]

Hi, i started a DIY (I found the scheme on the internet), but i replace the 9V battery with lipo 18650, 7.4V, 3000mAh, and i have a problem with overheating servo 2. (I mean a lot overheat). Can anyone please advise me on what to do? How can I fix it?

 

[Lucien Nunes]

The servo might be damaged. Are the connections correct? What supply current does it take? Does it overheat with the PWM input lead disconnected and/or when it is not moving?

 

[stevethesparks]

As both servo feeds are from the same origin, and only one servo is overheating, I can only suggest at this moment that the pwm output from the Arduino may be programmed wrong or suspect?

 

[Julie.]

Check your wiring, if correct swap the PWM feeds between the servos, if it's the same servo overheating it's wiring or faulty servo.

PWM is just a series of pulses that the servo interprets as a position so unless it's overloaded or wrongly connected it shouldn't make any difference.

If the PWM signal is disconnected yet it overheats it isn't an overload.

 

[Erebos]

The servo might be damaged. Are the connections correct? What supply current does it take? Does it overheat with the PWM input lead disconnected and/or when it is not moving?

I connected it according to the attached diagram. I tried to change the servo for another one but it didn't help. The servo overheats even when pwm input is not connected.

 

[stevethesparks]

What is the lower switch for?

 

[Erebos]

What is the lower switch for?

it's a DIY useless box. I wanted to make it for my niece to play with. You can see in the video what it is for

 

[stevethesparks]

If wired as shown it doesn't make a lot of sense, so can only reiterate what others have said and say check the wiring.
Have you tried swapping the pwm outputs for the servos, what's the chance you have two duff ones (unlikely)?
If you have access to a laboratory power supply where you can limit the current, this may be a big asset in avoiding any damage whilst in the testing stage.

 

[Julie.]

Probably should have asked the obvious first, but both servos are 9V suitable aren't they?

The connections shown show that 9V is directly suppled to the servos, normally servos are 5V, but can be 9, or 12V as well.

 

[plugsandsparks]

Interesting gadget, like it !!.

First i would check you are getting around 5V supply to the servos, there appears to be a dropping resistor to drop from 9V to 5V ish. If that is Ok, i would look at your programming for servo 2 and make sure it is as per instructions, you could try swapping the PWM lead over and see if it follows the lead or servo 2 is still hot. Do the servos move as per design or are they "jammed" or hunting ?

Let us know - would look to see it working

P&S

 

[plugsandsparks]

Probably should have asked the obvious first, but both servos are 9V suitable aren't they?

The connections shown show that 9V is directly suppled to the servos, normally servos are 5V, but can be 9, or 12V as well.

The servos are indeed 5V rated but it varies up to 6.4, i think there is a resistor up top to drop the volts ( i hope) - lol

 

[Julie.]

The servos are indeed 5V rated but it varies up to 6.4, i think there is a resistor up top to drop the volts ( i hope) - lol

Yeah, I think it's a pot, so it could be set to zero ohms, putting too much voltage if they are indeed 5V versions (which is the standard).

Looks a bad option to me, it would be better to use a proper 5V supply, or if they are small loads the regulator in the UNO - take the 9V supply direct to pin Vin, and the supply to the +ve of the servos from 5V

But if the design calls for 9V or 12V servos ...

 

[stevethesparks]

Probably should have asked the obvious first, but both servos are 9V suitable aren't they?

The connections shown show that 9V is directly suppled to the servos, normally servos are 5V, but can be 9, or 12V as well.

Good call

 

[Mike Johnson]

Are they Digital or Analogue servo's, most servo's where designed to run on a four cell conventional battery pack i.e. 6volts, these where inevitably changed for a four cell rechargeable pack at 4,8volts, most used a five cell pack to compensate for lack of speed and make up too 6volts, hot off the charger these where nearly always over 7volts, so I don't think the battery is the issue.

 

[stevethesparks]

@Erebos
Any progress with the overheating servo?