H BRIDGE AND BIDIRECTIONAL MOTOR CONTROL -1

H-bridge:: USING SWITCHES

-Such type of circuit can be used for both heavy and small applications preferably for wired remote  controlled bots.
-it is easy to make and very cheap.

We have two circuits:-
-one using SPST* press to on switches and
-the other using retractable DPDT* switches.











SPST (PUSH TO ON switches):-













Such switches turn on and connect one terminal to the other when pressed and returns to its position when not pressed.

   
                                








-Here in this circuit when switch s1 and s4 are pressed then motor will run in one direction and
-when switches s2 and s3 are pressed it runs in the opposite direction.


DPDT switch

                                     

(RETRACTABLE DPDT SWITCH)






-A dpdt switch is equivalent to two spst switch.
-It can switch two paths for the flow of current simultaneously in two different directions.

   following circuit can be used.

When you press the stick of the switch the motor will turn in one direction and in other direction when you press it down.
        Now, since it is retractable, it will come to the center when you leave it free. You can use two such arrangements to drive two motors of a wired robot.






H-bridge USING RELAY

A simple and relatively cheap h-bridge circuit can be made using relays. Advantage of such circuit is that it can be used for heavy applications.


The circuit diagram given below:

When switch s1 is pressed the motor runs in one direction and switch s2 is pressed it turns in the other direction. The switches are simple spst switches used above(h-bridge using switches).

You can use any spst relay in such a circuit as I have marked12volts both for motor and relay however you can drive motor with higher voltages also which extreme values will be decided by the specification of relay you are using. One more thing, the two pins of relay opposite to no and nc are relay coil pins which must be supplied rated voltage only and not more than that.

NO: normally open

NC: normally closed

When no key is being pressed then in each relay ,the point between relay coil pins remains connected with NO , when switch is pressed the connection which was existing in the coil in off state breaks and now that pin gets connected to NC. Thus one lead of motor gets +12v and other gets ground. Similar thing happens with other relay when the other switch is pressed.

Motor will not run when either you press none of the keys or you press both the keys.

The relays I used for this circuit is called sugar cube relay and can withstand currents upto 10A!