--- In Electronics_101@..., "ppplll000999" <ppplll000999@...> wrote:
Has been looking for SIMPLE way to reverse hobby DC motors to reverse tank or ship turret once mechanical triggered (like by a contact switch). Has to be very simple because it is for tiny scale models :)
For robotics and other hobby devices, reversing is usually done with a H-Bridge although a relay will certainly work. Speed control is often handled by the H-Bridge as well. With the relay approach, there needs to be a separate speed control device - usually just a transistor or MOSFET.
Motor current determines WHICH H-Bridge as they are available from 1A devices like up to drives large enough for a locomotive.
Put your direction control signal on 1A and the inverted signal on 2A. Pulse width modulate the 1,2 EN pin to get speed control (or pull it high). Connect the motor between 1Y and 2Y.
Note that there are 2 other half bridges (or 1 full bridge) left unconnected above.
Be aware that even very small motors can exceed 1A at startup. You can add a clip-on heatsink if you have room. Otherwise, I recommend a PCB with a heatsink (just a large pad) under pins 4,5,12,13. The entire back side of a PCB and a bit on the front side will help.
Be aware of the voltage drops on the high and low outputs (Voh and Vol) - they are 2V EACH. So, at 1A, this chip will lose 4V and dissipate at least 4 watts. The package (free air) can dissipate only slightly more than 2 watts. This voltage drop also reduces the voltage available for the motor.
Google for H-Bridge, there are a lot of hits.
A relay and MOSFET can provide a better solution if there is room. The MOSFET will have almost no voltage drop and the relay is a solid contact.
Richard
