How to make an H-bridge

Step 4 About our circuit.

Our circuit includes an H-bridge made out of 4 SPST relays (single-pole single-throw) and 1 additional SPDT (single-pole double-throw) relay which will be used to switch between the 2-sets of 2 relays.

Okay.... so this is how it works...

Power from the battery is going to the 7805 voltage regulator where is converted to 5V. Power from the battery is also going to "Relay 1" and "Relay 2" where it goes to the motor (but we're getting ahead of ourselves).

The 5V power is both going to the coil of the SPDT relay and it is also passing through the the SPDT relay. So, when the switch is closed, 5V flows through the coil of the SPDT relay and 5V also is routed through the SPDT relay to the coils of "Relay 1" and "Relay 4" forcing them to close. This allows 9V to flow through "Relay 1" and "Relay 4" in a way in which the motor can spin in a clockwise direction.

In other words, when we close the switch connected to the coil on the SPDT relay, we are triggering the H-bridge to allow the motor to spin clockwise.

Therefore, if we want the motor to spin counter-clockwise all we would need to do is flick the switch in the opposite direction. This will change the path through which the electricity passes through the SPDT relay and in turn close "Relay 2" and "Relay 3" (and by extension open "Relay 1" and "Relay 4").

Comments

[colin55]

Simply flick the switch to reverse the motor and it creates a brake function.

[ijabi]

Hello colin:do you have any simple way to do h-bridge with mosfet(a Schematics by chance). thanks

[colin55]

There are lots of circuits on the web using MOSFETS in an H-bridge arrangement. These are generally high power circuits and you need to do your own research as there are so many designs.

[colin55]

There is a much-simpler way to reverse the motor using just one relay. Connect a double-pole double-throw relay as shown in the enclosed diagram. No other components are required! Just a switch to energise the relay for forward or de-energise the relay for reverse. Colin - TALKINGELECTRONICS.COM

[Deviantgeek]

colin55: then you would not be able to brake

[dagenius]

just add another switch from one of the wires that goes to the motor, and then no matter which way you turn the first switch, the motor will only spin if you have the second switch on.

[godfreyandthandi]

if you really need braking you can tie in a relay somewhere else to cut power.

[rip333]

use a center off DPDT

[colin55]

Of course you can make the project with a double-pole double-throw switch and not use any relays at all. The only problem is the motor is constantly turning in one direction or the other. The alternative is to use two double-pole push switches or 4 switches as shown in the following diagram. You need to push both of the forward switches at the same time. By pushing the reverse switches very briefly you will get braking when travelling in the forward direction.