Respected Gentlemen, We are building a robot for IEEE contest and are running across an issue that I hope this community can help me us with. We decided to use (2) 12V DC motor for our drive train. The following is the spec of the motors: 12V Permanent Magnet =B7 All metal gears =B7 Weight: 7.26 oz (.454 lbs) =B7 200 RPM =B7 30:1 gear reduction =B7 Stall torque 194 oz-in =B7 Rated torque at max efficiency. 50 oz-in =B7 Speed under rated load 161 RPM =B7 Stall Current 3.3 Amps =B7 78% efficiency =B7 Current at rated load 730 mA =B7 No Load current 115 mA
When connecting it with the OOBOT40-3 we should theoretically have 127 variable speeds. We assumed that it's not going to be that way but at least expected a decent variability.
After doing an experiment - connecting the OOPIC to the motors and getting the speeds by using a tachometer, here are the results. OOPIC Speed vs forward motor speed.
60 - 83 65 - 93 70 - 102 75 - 110 80 - 117 85 - 123 90 - 129 100 - 137 110 - 147 120 - 153 130 - 161 140 - 162 150 - 174 155 - 187 160 - 188 (max)OOPIC Speed vs reverse motor speed.
60 - 84 65 - 94 70 - 103 75 - 110 80 - 118 85 - 125 90 - 131 100 - 140 110 - 148 120 - 153 130 - 161 140 - 162 150 - 175 155 - 187 160 - 188We are controlling the motors by using an H-bridge. The PWM frequency is 2 KHz.
Is there a possibility to gain some more variability without adding major components to the design since we are only 30 days away from the competition and the Profs are going to chew me out if I propose some gadget to be added.
Any help, comment, suggestion, will be really appreciated
Best Regards Sahim.