Arduino Forum

Topics => Robotics => Topic started by: BreadEatingBoard on Dec 31, 2018, 01:48 pm

Title: Which Servo/Motor do I Need?
Post by: BreadEatingBoard on Dec 31, 2018, 01:48 pm
I bought an ultrasonic sensor, leds, a pi 3, and now I'm looking for some motors/servos to build a simple autonomous car able to drive forward, detect object, turn right, etc....

I've worked with SG90 Servos before and my lesson from that is: Never again.

Noticed MG995 are good and better than 996r's but the issue is that it can either drive 0-180° or just continually which will just cause trouble for the sensor and turning left or right.

Any1 able to help me with this?

MG995:
Operating speed: 0.20sec/60degree (4.8v); 0.16sec/60degree (6.0v)
Operating voltage: 4.8~ 6.6v
Gear Type: Metal gear
Current draw at idle 10MA
No load operating current draw 170MA
Stall current draw 1200MA
https://www.towerpro.com.tw/product/mg995/ (avoid Tower Pro, they're known for terribly manufactured servos)

Ultrasonic sensor:
https://www.electroschematics.com/8902/hc-sr04-datasheet/
Title: Re: Which Servo/Motor do I Need?
Post by: Northof49 on Dec 31, 2018, 08:36 pm
but the issue is that it can either drive 0-180° or just continually which will just cause trouble for the sensor and turning left or right.

Any1 able to help me with this?
What do you mean, it can either drive 0-180 or just continually?


In my experience, you are better off to run multiple sonic sensors and gather all the readings (near continuously), than have a car that is slow to react, and varies in its time to react to an obstacle because it depends on a single sensor that takes time to pan left and right.  When its looking left or right, it isn't looking forward, that not only creates a delay in reaction, but introduces an element of chance as to when the sensor turns towards the approaching obstacle.  Panning sonic sensors look cool, but create a severe limitation unless your vehicle moves extremely slowly.  If it moves rapidly, it could run into an object because it is looking in the opposite direction.