Can I know what is the starting current for 210:1 Micro Metal Gearmotor HP @ 9 V ?
I am trying to size my battery as mAh and as i know either we use stall current or starting current as 1.6 A are really high (I have 4 motors) so now I consider the starting current.
When a motor starts from rest, it briefly draws the full stall current. Stall current varies linearly with voltage, which means that the starting current at 9V would be approximately 9V*1.6A/6V = 2.4A.
Really I though stall current is drawn if motor is rotating and wheels are not ? and starting current depend on interanl resistance of motor but it is less than the stall current.
2.4 A for a motor is too much to size my battery according to that isn’t it ?? what to do you suggest and also I am trying to find a way to not let motor draw the stall current becasue I am affraid it will damage my motor driver (I am using baby orangutan 328 P) do you know one ?
Stall current is the current a motor draws when it is stalled (i.e. when the motor is not rotating). When a motor starts from rest, it draws the stall current until it starts rotating, at which point the current drops as the motor speed increases. You didn’t specifically say what battery you’re using, but you should not use a 9V battery for applications that require a lot of current, such as driving motors. If you haven’t seen this yet, I suggest you read through Jan’s blog entry about understanding battery capacity. NiMH battery packs are generally a good choice for controlling motors like this.
The Baby Orangutan can tolerate up to 3A peaks, so it should be okay with brief 2.4A spikes. However, if you stall that motor at 9V, it will quickly overheat the driver and trigger thermal shutdown protection. The Baby Orangutan is slightly underpowered for the motor your’re using at 6 V, and even moreso at 9 V. I suggest you use a lower battery voltage if possible (something closer to 6 V), and try to take care to avoid situations where the motor will remain stalled for extended periods of time. Also, note that changing directly from full speed in one direction to full speed in the other direction will cause the motor to draw nearly twice the stall current, so you should avoid writing programs that do that (e.g. program the controller to brake the motor for a short duration before changing direction). One way to avoid drawing the stall current on startup is to program the controller to gradually accelerate the motor.