# help needed in Motor selection

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#### Chullaa

Hi guys!

i am working on a robot for a racing competition. so far so good i managed to run my first robot motor with micro Controller. now i need some speedy motors that can run. i am willing to use dc gear motor so that i don't need to apply breaks. (actually i am afraid that i would burn my mosfets with FAST electrical breaking, mechanical breaking is not an option). My robot weights about 2-3 kg and i don't know how much torque is required. but RPM should be around 200-250. plz help me out.

#### Prototyp_V1.0

Hi. Need at least to know how fast the machine is expected to accelerate. Also, are you free to select gear ratio? Should there be one motor for propulsion or more?

What electrical limitations do you have?

daat73

### daat73

Points: 2

#### Chullaa

i suppose i would be needing 1000 to 1500 meter per second speed. the acceleration should be fast enough (may be 500 meter/sq second). i don't know exactly. No i cant select turn ration because what i have searched in the market are very limited variety and i can't reach gear motor with good RPM (200 to 250).

However there should be two motor at back to speed up and change their RPM to turn round. A free movable wheel will be used in the front portion. I am limited to use less or equal voltage of 12V.

#### Prototyp_V1.0

i suppose i would be needing 1000 to 1500 meter per second speed.
No serious?
Shall you race against gun bullets?

#### Chullaa

oh sorry! i miss calculated my bad. It would be 30 -50 meter per second, if i am not wrong.

---------- Post added at 19:21 ---------- Previous post was at 19:17 ----------

further more i am going to use wheels 12 inches of diameter.

#### Prototyp_V1.0

I suppose you use a resistor that can be used when breaking at high speed. When speed gets down, you can apply a short cut through a second transistor to avoind burning the fet's. Disadvantage is you must use two fet's.

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