Timeline for DC motor - Transistor / Mosfet - Design
Current License: CC BY-SA 3.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 26, 2015 at 22:03 | vote | accept | aaa | ||
| Mar 26, 2015 at 19:31 | answer | added | Bruce Abbott | timeline score: 1 | |
| Mar 25, 2015 at 23:39 | comment | added | user16324 | Q4 is holding Q1's base voltage down preventing Q1 from turning on. Add a resistor between Q1b (which is connected to the switch) and Q4b. What value resistor? Enough to take (motor_current/10) or I'd choose (motor_current/20) from 12V - Vbe. (Ditto the other pair of transistors) | |
| Mar 25, 2015 at 22:02 | comment | added | KyranF | In theory (H bridges are inverting the supply through the motor anyway) it wont have a difference | |
| Mar 25, 2015 at 21:46 | comment | added | aaa | @KryanF Ah. Indeed, I might have flipped the battery around, tot try and see if that worked better. Probably forgot tot put them back | |
| Mar 25, 2015 at 21:37 | comment | added | KyranF | I think the schematics are wrong anyway, the batteries are upside down or something.. hard to see them though. | |
| Mar 25, 2015 at 21:35 | comment | added | KyranF | On the right design, the BJTs are wasting a lot of voltage. voltage is what the motors use sort of like a speed control. The voltage over the motor needs to be as much as possible if you want speed, so using as little as possible in the switching elements is important. Not only that, but the power dissipation is far less if you give all the energy to the motor rather than burning it as heat and lost voltage. | |
| Mar 25, 2015 at 21:32 | history | asked | aaa | CC BY-SA 3.0 |