What limit for the characteristics of a servomotor can Picaxe have?

goom

Senior Member
The torque specification of a hobby servo is the primary determinant of the current drawn by it. You need to ensure that the power supply to the servo is adequate for the higher torque servo. The Picaxe simply provides the control signal to the servo which is of low current, and more-or-less independent of the characteristics of the servo.
 

hippy

Technical Support
Staff member
You should really design for worse case "peak in-rush current". If that is not explicitly specified then "stall current" would be the best guide.

For the servo linked to that is around 800mA stall current at 4.8V, around 1A at 6V. A battery or supply capable of 6V at 1A (1000mA) would seem to be sufficient.

The problem with some battery and supply headline specifications is they don't always mean what they appear to show. The maximum current may not be achieved at the stated voltage, or the full voltage may not be delivered at the maximum stated current. One needs to consult the battery or supply datasheet to get definitive details.

The higher the stated headline current, the more likely it will be to deliver the stated voltage at a lower current, and your batteries probably would be okay.
 

inglewoodpete

Senior Member
Hi again, my servomotor specification sheet appears in https://www.google.es/url?sa=t&source=web&rct=j&url=http://www.strikemodels.com/wp-content/uploads/VS-2-Servo.pdf&ved=2ahUKEwiCq6GVktXaAhVBDSwKHWEIDywQFjABegQIBRAB&usg=AOvVaw1Qpa2HIUY0aLg1dEJN0qWD. The batteries are 2100mA, 6V, NiMH.
If my servomotor requires 0.2 A, does that mean it requires a 200mA battery, or is the calculation another?
Thank you for your answers
You seem to have omitted the "H" (Hours) from the NiMH battery specification. So, your battery has a capacity of 2100mAH, not 2100mA.

A battery's capacity is specified in Amp-Hours or milliAmp-Hours: That is the current that the battery can theoretically supply in 1 hour and be totally discharged (IE 'flat') at the end of 1 hour.

So, a 2100mAH battery supplying a continuous current into your servo, which draws 200mA, would theoretically last for 2100/200 = 10.5 hours.

The word "theoretically" is used because a battery has internal resistance that generates heat as current flows through it; also it cannot continually supply a constant current as it gets closer to being totally discharged.
 

BESQUEUT

Senior Member
Hi again, my servomotor specification sheet appears in https://www.google.es/url?sa=t&source=web&rct=j&url=http://www.strikemodels.com/wp-content/uploads/VS-2-Servo.pdf&ved=2ahUKEwiCq6GVktXaAhVBDSwKHWEIDywQFjABegQIBRAB&usg=AOvVaw1Qpa2HIUY0aLg1dEJN0qWD. The batteries are 2100mA, 6V, NiMH.
If my servomotor requires 0.2 A, does that mean it requires a 200mA battery, or is the calculation another?
Thank you for your answers
No problem till 2A ! Green Discharge curve for NiMH 2000 mA
 

Danielpbt

New Member
Thank you for the correction. I have used a language perhaps somewhat informal, and it is convenient that everyone who reads this forum can analyze it in detail, and it is important that the content is sufficiently rigorous
I currently have 8 servomotors, therefore 2100/1600 = 1.31 hours in theory, right? The point is that I want to change them for more powerful ones, because they can not with the weight of the artifact
How much intensity do you recommend me to not have problems?
I'm learning a lot in this forum
Thank you for your answers
 
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